Julien Dupuis
email: julien.dupuis@insa-lyon.fr

Erwann Fourmond

Virginie Mong-The

Oleksiy Yen

Mathias Nichiporuk

Nam Greffioz

Mustapha Lê Quang

Lemiti

O Nichiporuk

M Greffioz

N Le Quang

M Lemiti

Study of rear pecvd dielectrics stacks for industrial silicon solar cells

Keywords: Capacitance-Voltage Measurement, PECVD, Silicon-Oxide, Silicon-Nitride

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

INTRODUCTION

Reduction of the material cost share is needed to enhance the economic attractivity of the photovoltaic technology [START_REF] Agostinelli | 17 th NREL Workshop on crystalline silicon technology[END_REF]. One of the solution is to reduce the wafer thickness of crystalline silicon solar cells.

The standard aluminum back surface field (Al-BSF) induces mechanical constraint problems on thin wafers, typically below 180 µm-thick. This increases the breakage risk and may affect the production output. Al-BSF is also insufficient for surface passivation, since rear surface recombinations become of predominant importance in this thickness range. Therefore minimizing the aluminum coverage and developing new passivation schemes for the rear surface is one of the key points for decreasing silicon solar cell thickness [START_REF] Agostinelli | 17 th NREL Workshop on crystalline silicon technology[END_REF][START_REF] Janssen | [END_REF][START_REF] Romijn | Proceedings 22 nd European Photovoltaic Solar Energy Conference[END_REF][START_REF] Schneiderlochner | [END_REF][START_REF] Agostinelli | Proceedings 20 th European Photovoltaic Solar Energy Conference[END_REF].

A literature review tells us that three major cell architectures are currently under development to handle the rear surface passivation problem. They are mainly based on dielectric layers for passivation combined with aluminum contacts. The actual technology under study are: bifacial cells [START_REF] Janssen | [END_REF][START_REF] Romijn | Proceedings 22 nd European Photovoltaic Solar Energy Conference[END_REF], Laser Fired Contact cells (LFC; Fraunhofer ISE) [START_REF] Schneiderlochner | [END_REF] and industrial-Passivated Emitter and Rear Cells (i-PERC; IMEC) [START_REF] Agostinelli | Proceedings 20 th European Photovoltaic Solar Energy Conference[END_REF].

The dielectrics used for passivation often consist in SiO x :H (SiO) and SiN x :H (SiN) layers deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD). This technology is one of the most promising solutions due to its limited thermal budget needed for the deposition, its reasonable surface passivation capabilities [START_REF] Dupuis | [END_REF][START_REF] Dupuis | Proceedings 23 rd European Photovoltaic Solar Energy Conference[END_REF][START_REF] Hofmann | [END_REF], and the availability of the PECVD system, widely used for SiN antireflection. Although the PECVD SiO/SiN stack is reputed to be one of the best candidate to passivate the rear side of the cells [START_REF] Dupuis | Proceedings 23 rd European Photovoltaic Solar Energy Conference[END_REF][START_REF] Loozen | Proceedings 23 rd European Photovoltaic Solar Energy Conference[END_REF], the SiO layer dielectric properties are not yet fully understood. The effects of the Metal-Insulator-Semiconductor (MIS) structure that is present in the i-PERC and LFC structures are still under investigation [START_REF] Agostinelli | 17 th NREL Workshop on crystalline silicon technology[END_REF].

In the present article we used simulation in order to investigate the influence of the MIS structure and the dielectric fixed charge density on the cell efficiency. Then we determined the fixed charge density of the SiO and SiN layers by dark Capacitance Voltage measurement (dark-C-V) technique, modified to better meet the solar cell application. Lastly, solar cells based on the dielectric structures were processed and characterized by I-V, quantum efficiency measurements, infrared thermography and Scanning Electron Microscopy (SEM).

DESSIS SIMULATION

Parameters

The 2D simulation was performed using ISE TCAD DESSIS [START_REF]ISE TCAD Release 8.5 manuals[END_REF]. The cell parameters used for the simulation are detailed in the table I. To highlight the rear side influence on the solar cell efficiency, a high value of the minority carrier lifetime was chosen (typical of FZ substrate). The rear surface recombination velocity (SRV) is similar to the result recently obtained using PECVD SiO/SiN stack [START_REF] Agostinelli | 17 th NREL Workshop on crystalline silicon technology[END_REF][START_REF] Loozen | Proceedings 23 rd European Photovoltaic Solar Energy Conference[END_REF]. Two rear structures were simulated. The first structure is similar to bifacial solar cell: the contacts are present only where the dielectric layer is absent. The second structure is based on LFC and i-PERC cells: the contacts cover the whole rear surface including the dielectric layer.

For both structures, we varied the type of dielectric used on the rear side (SiO 2 or Si 3 N 4 ) and the thickness of the layer (100 nm or 500 nm). The dielectric permittivity of SiO 2 and Si 3 N 4 are respectively close to those of SiO and SiN.

Simulation Results

The evolution of the solar cell efficiency with the dielectric fixed charged density (Q f ) is plotted on the Figure I. Under high inversion or high accumulation, the cell efficiency is nearly the same. For all rear sides simulated, there is a Q f range where the efficiency falls deeply and which may correspond to high rear surface recombination rate. The carrier recombinations become maximal when the free carrier ratio of electron and hole is equal to the inverse of their respective capture cross section ratio: In the case of localized contacts, this condition happens when the dielectric has Q f near 1.5.10 11 cm -2 , independently of the dielectric thickness. When the contacts cover the whole surface, including the dielectric, we have to take into account the band diagram modification at the Si/Dielectric interface. The difference between the aluminum work function (4.08 eV) and the P-Type silicon work function being negative, the metal presence makes the energy bands of the silicon to bend to lower energy at the interface. The metal has thus a similar influence as a positive Q f on the band diagram at the interface. This explains why the recombination rate becomes maximal for lower Q f in the dielectric when the contacts are on the whole surface.

Moreover, depending on the dielectric constant and thickness, the influence of the aluminum may be enhanced. When the layer is thin, the metal is nearer the Si/Dielectric interface and the aluminum-silicon work function difference has a greater impact on the band bending. This effect might be stronger if the insulator has a high dielectric constant (Si 3 N 4 in this case).

Consequently, thickness and dielectric constant values can strongly affect the Q f condition for the maximal carrier recombination rate, as it can be seen in the Figure I. With a 100 nm thick layer of Si 3 N 4 , the cell efficiency becomes minimal when Q f is negative.

Conclusion

The simulation shows two important points. Firstly, an inversion layer on the rear side may not be problematic towards the solar cell efficiency, as it was also established by Mittelstadt et al. [START_REF] Mittelstadt | Proceedings 17 th European Photovoltaic Solar Energy Conference[END_REF]. Secondly, depending on the dielectric thickness and permittivity, negative Q f is not always beneficial for a field effect passivation on P type silicon.

CAPACITANCE-VOLTAGE MEASUREMENTS

To measure the fixed charge density of our PECVD dielectric films, we used the capacitance-voltage method (C-V). Two types of measurements were carried out. The standard dark-C-V was made by applying a voltage ramp from the accumulation to the inversion conditions, and back from the inversion to the accumulation conditions, in order to reveal a possible hysteresis effect.

From this first measurement, the flat band capacity (C FB ) is extracted. Then, we performed a second characterization by applying a null voltage during five minutes and slowly polarized the samples to the flat band voltage (V FB ). We called this method "weak polarization" (WP).

The WP method is more similar to the working conditions of the dielectric films on the rear side of solar cells than the standard dark-C-V measurement. The metal and the silicon stay indeed nearly at the same potential. This method can avoid traps charging effect when the MIS is strongly polarized, which may change the determination of Q f .

Experimental

Three dielectric layers and one dielectric stack were studied: a standard silicon nitride usually used as antireflection coating (SiN), a rich-silicon silicon nitride (SiNr), a silicon oxide layer (SiO) and a stack of silicon oxide cover by a standard silicon nitride layer (SiO/SiN). All these structures have been deposited on 2 inches Ntype monocrystalline wafers, (100) oriented. They have a 5 ohm.cm resistivity and a thickness of 280 µm.

The deposited layers thicknesses were verified by ellipsometric measurements and were contained between 40 and 50 nm, except for the SiO/SiN stack (40 nm of SiO and 25 nm of SiN). All these layers were elaborated in a direct PECVD working at 440 kHz and 370°C with ammonia (NH 3 ), silane (SiH 4 ) and nitrogen protoxide (N 2 O) as precursor gases.

After the deposition, the samples were annealed in a belt furnace from Photowatt. Next, aluminum plots were evaporated in order to form the Metal-Insulator-Semiconductor structure on all the samples. The rear contact was made with indium-gallium and silver pastes.

The C-V characterizations were performed with a probe station using standard dark-C-V measurements followed by the WP characterization (performed on a neighboring aluminum plot). The Q f determination was done from the flat band capacity value [START_REF] Nicollian | MOS Physics and Technology[END_REF].

Q f results

The fixed charge density results are presented in the Table II. Two values are given for Q f with the dark-C-V measurement. This is due to the hysteresis effect present in all the samples. This hysteresis is caused by electrons trapping and holes injection from the dielectric in accumulation condition (see Figure II). The opposite effect may also happen in inversion condition. This hysteresis effect is avoided when using the WP method. We will thus rely mainly on the fixed charges density obtained by this second method. Surprisingly, most of the dielectric layers exhibit negative fixed charge before and after annealing. This is even true for the standard SiN, reputed to have positive fixed charges [START_REF] Dauwe | [END_REF][16]. The detection of positive fixed charge may be caused by holes capture or electron release in the dielectric with the polarization when using the standard C-V measurement.

The Figure III highlights the behavior of the SiN layer with six consecutive measurements: the hysteresis effect is strongly reduced and the calculated fixed charge becomes clearly positive and superior to 10 12 cm -2 , as it can be found in the literature. The measurement reproducibility for the other layers is clearly better than for the SiN. The SiO keeps a negative Q f even after several dark-C-V characterizations. Nevertheless, more investigation is in progress to identify the type of traps responsible of the negative charge in the dielectrics.

Annealing the layers does not change the sign of Q f (except for SiNr) but strongly increase the hystereris effect due to trap formation in the dielectric layer near the Si/Dielectric interface. The layers seem to degrade more or less with the annealing, depending on their type. The SiO/SiN stack is one of the most stable structures. The Figure IV shows the dark-C-V curve for SiO, SiN and SiO/SiN after annealing. A smaller hysteresis effect is indeed visible for the SiO/SiN stack than for the other dielectrics. This is in agreement with Agostinelli et al.: they pointed out the thermal stability of this structure, even after successive annealing, due to its stable passivation properties [START_REF] Agostinelli | 17 th NREL Workshop on crystalline silicon technology[END_REF][START_REF] Agostinelli | Proceedings 21 st European Photovoltaic Solar Energy Conference[END_REF].

Conclusion

The C-V characterizations show that the PECVD dielectric layers may have negative fixed charges in their bulk. Moreover, the SiO/SiN stack seems more thermally stable in comparison with the other dielectric layers. Thus, it may be more efficient for an application on the rear side of solar cells.

SOLAR CELL RESULTS

Experimental

Multicrystalline silicon solar cells were elaborated, on 125×125 mm 2 wafers, 200 µm thick and with resistivity of 1 ohm.cm. SiO/SiN dielectrics stacks are deposited by PECVD on the back side. Three different SiO/SiN stacks thicknesses were tested: thin (65 nm), standard (500 nm), and thick (900 nm). The layers are opened by UV laser ablation (λ=355 nm) and covered with standard aluminum serigraphy before being annealed. A set of standard solar cells with a full rear side aluminum back surface field (Al-BSF) was also made in order to compare the efficiency.

Current-Voltage characterization

The electrical results (Table III) depend strongly on the thickness of the SiO/SiN stacks. The best results for the cells with a dielectric stack are obtained for thick layers, in accordance with IMEC results [START_REF] Agostinelli | Proceedings 21 st European Photovoltaic Solar Energy Conference[END_REF][START_REF] Ma | Proceedings 23 rd European Photovoltaic Solar Energy Conference[END_REF]. Minority carrier lifetime investigation shows that the improvement of the V oc and J sc is due to a better passivation effect, mostly caused by the reduction of the MIS effect and a thicker SiN layer. In fact, as we presumed in the simulation part, the Si/Dielectric interface is less affected by the aluminum coverage with a thick dielectric stack. It may also bring additional hydrogen to passivate the rear surface and the bulk of the substrate. The fill factor decreases when the SiO/SiN stack is thickened. In fact, for thick dielectric stack, the serial resistance of the cells can be 20 percent higher than for the reference cells. As illustrated in the SEM picture of the rear contact (Figure V), instead of having a thick Al-Si alloy as presented by Ma et al. [START_REF] Ma | Proceedings 23 rd European Photovoltaic Solar Energy Conference[END_REF], a cavity is formed under the dielectric layers and limits the contact between the aluminum and the silicon. When the aluminum begins to dissolve the silicon during the firing step, an insufficient viscosity might prevent the serigraphy paste from filling up the hole, and cause the silicon to be absorbed in the paste. An optimized paste and firing conditions, or larger laser point contacts, may be needed to avoid this phenomenon.

Spectral Response measurement

Even with increasing the dielectric stack thickness, the open circuit voltage stands below the Al-BSF reference. In order to investigate which factor may cause lower Voc, we carried out spectral response measurements. We performed two characterizations with and without a bias light to avoid a low rear passivation due to a weak minority carriers injection [START_REF] Dupuis | Proceedings 23 rd European Photovoltaic Solar Energy Conference[END_REF][START_REF] Mittelstadt | Proceedings 17 th European Photovoltaic Solar Energy Conference[END_REF]. A typical internal quantum efficiency (IQE) obtained for solar cells with a thick SiO/SiN stack is displayed in the Figure VI.

Although the additional bias light is less powerful than the standard solar spectrum, the comparison of the IQE in the infrared range proves that the rear passivation by the SiO/SiN stack is effective. The low Voc value may thus be ascribed to another cause. Note that the low infrared response does not disappear for thin SiO/SiN stack (65 nm) due to a limited passivation effect.

On the other hand, the cell with the dielectric stack exhibits a lower IQE than the reference cell on the whole spectrum. These results point out a homogeneous degradation affecting the whole current. In order to identify the source of the degradation we performed on the standard cells a laser firing step before the serigraphy of the contacts, in the same condition than for the "dielectric" cells. The processed cells show similar Voc and efficiency degradations as the cells with a rear dielectric stack. We may thus conclude that the Voc degradation is mainly caused by the laser step, which probably entails parasitic shunting problems. To confirm this hypothesis, we use infrared thermography to detect abnormal heating.

Infrared thermography characterization

By polarizing the cells in inversion, the infrared thermography is able to detect abnormal heating due to local parasitic shunting [START_REF] Kaminski | [END_REF]. Although the reference cells, without laser, do not show significant shunt, the cells with dielectric stacks exhibit several places where a high current is detected. The high majority of the heating sources are localized near grains boundary of textured gains, corresponding to the position of front side metallization. The Figure VII emphasizes the localization of the shunts in comparison with the corresponding front side (the picture was mirrored to make it correspond to the rear side). We note that the laser impacts are not directly responsible of the shunts because large surfaces exist without any abnormal heating. To explain the localization of the shunts, we may suppose that the texturized surface might be sufficient to concentrate locally the laser pulse, as it was demonstrated by Knorz et al. [20]. Then, when the laser hits the surface between two grains, the energy might affect the gain boundary integrity, by increasing the extended defects concentration, dissolving the impurity precipitates and degrading the front emitter. This phenomenon might be enhanced by the constraints occurring during the contact formation and also by the rear reflectivity in the ultraviolet range. More investigations are in progress to verify this hypothesis.

CONCLUSION

In the present article we found that the MIS structure and the Q f of the dielectrics used as passivation coating on the back side of solar cells can strongly enhanced the carrier recombination. The stack thickness, the dielectric constant and the Q f have to be carefully chosen to avoid high rear recombinations.

Q f was investigated in PECVD SiN and SiO layers with capacitance voltage measurement a global negative charge was found. Besides, with a reduced hysteresis, the SiO/SiN stack appears to be more thermally stable than the other layers.

Solar cells with SiO/SiN stacks were made. The solar cells efficiency depends strongly on the thickness of the SiO/SiN structures, with better results for thick stacks. The reasons of the medium fill factor and Voc are studied by spectral response, scanning-electron microscopy and infrared thermography. It was found that the serigraphy is not optimized for point contacts because it entails cavity formation instead of a good silicon-aluminum alloy in the hole created by the laser. Several parasitic shunts were also detected along the grains boundary. They seem to be caused by the laser impacts on the boundary which might degrade the front emitter.

  p) the electron (holes) density and σ n (σ p ) the electron (hole) capture cross section. Since σ n is about 100 time superior to σ p , p ≈ 100 n when the recombination rate is maximal[START_REF] Girisch | [END_REF][12]: the interface Si/Dielectric is thus in desertion condition.

Figure I :

 I Figure I: Evolution of the solar cell efficiency with Q f for SiO 2 and Si 3 N 4 dielectrics of two different thicknesses. The aluminum contacts cover the whole surface, except for the localized contacts case.

Figure II :

 II Figure II: Illustration of the influence of SiN traps which may create a hysteresis effect.

Figure

  Figure III: C-V curves for the SiN sample before annealing obtained by C-V measurement. The Q f evolution toward positive fixed charge is clearly visible.

Figure IV :

 IV Figure IV: Comparison between normalized dark-C-V curves for the SiO, SiN and SiO/SiN layers after annealing.

Figure V :

 V Figure V: SEM pictures of the cross section of a cell with a dielectric stack. The serigraphy was partially removed due to the cell cut.

Figure VI :

 VI Figure VI: Internal quantum efficiency of a cell with a 700 nm SiO/SiN stack, with and without a bias light.

Figure VII :

 VII Figure VII: Infrared Thermography picture of the rear side of a solar cell with a SiO/SiN stack (900 nm) (left). Mirrored photography from the front side of the same cell zone (right), with the shunt positions underlined.

Table I :

 I Solar cell parameters for the simulation.

	Substrate
	Substrate type & doping	P (boron) 1.10 16 cm -3
	Thickness	150 µm
	Minority carrier lifetime	240 µs
	Rear side
	Al-BSF doping & thickness	5.10 18 cm -3	5µm
	Contact coverage & material	12.5%	Aluminum
	Dielectric materials tested	SiO 2	Si 3 N 4
	Dielectric thicknesses tested	100 nm	500 nm
	Rear SRV	300 cm.sec -1

Table II :

 II Q f values calculated with the dark-C-V and the WP results. The blue (red) value means that the global charge is negative (positive). The value is black when the sign is not determined.

Fixed charge (cm -2 ) by dark-C-V by WP SiN -2.0.10 11 /+1.9.10 12 -1.5.10 11 SiN annealed -1.5.10 12 /+1.9.10 12 -1.3.10 11 SiNr +0.3.10 11 /+1.2.10 11 +0.6.10 11 SiNr annealed -0.2.10 11 /-1.8.10 11 -1.2.10 11 SiO -8.0.10 11 /-1.6.10 12 -2.3.10 11 SiO annealed -2.6.10 12 /-7.0.10 12 -1.3.10 12 SiO/SiN -1.3.10 12 /+1.1.10 11 -2.7.10 11 SiO/SiN annealed -0.2.10 11 /-1.5.10 12 -1.8.10 11

Table III :

 III Solar cells results for various SiO/SiN stacks thicknesses.

	Cells	V oc (mV) J sc (mA.cm -2 ) FF(%)	η(%)
	Al-BSF	591	31.68	74.2	13.77
	SiO/SiN 65 nm	573	29.04	74.0	12.21
	SiO/SiN 500 nm 582	30.34	72.7	12.72
	SiO/SiN 900 nm 585	31.33	71.5	12.97

ACKNOWLEDGEMENTS

The authors want to thank the Nanolyon platform staff for its technical contribution and the National Research Agency (ANR) with the French Agency for Environment and Energy Management (ADEME) for their financial contributions through the national project INFIME.


Katelyn Samson
email: katelyn.samson@rmit.edu.au

Social Learning: A complementary approach to managing water at the catchment scale in Victoria, Australia

Keywords: Social learning, integrated catchment management, multiple stakeholder processes, water policy, Australia

HAL is

BACKGROUND

The Australian landscape holds three million kilometers of rivers and creeks, at least 16 million hectares of nationally important wetlands and more than 1,560 estuaries. While these natural water assets underpin the wellbeing of Australian society, its economic development and unique biodiversity the ancient Australian landscape is in fact old, flat and salty. Currently, Australia is in the midst of a long cycle of water crises. The south eastern State of Victoria, specifically, is in its twelfth year of drought and is projected to become drier, endure more hot days and more storms (DSE 2004). Projections such as these serve to demonstrate that the relationship between Australia's water resources and its people is characterised by risk and uncertainty. As a result, significant community concern is emerging around the sustainability of Australia's water resources.

Blame for the current state of uncertainty surrounding Australia's water resources is being pointed in a number of directions. Those drawing from the pages of Australian history claim that since European settlement, over two centuries ago, serious mistakes in environmental management have been made while attempting to alleviate concerns over Australia's water supply. As such, they place primary blame on the direct transfer of 'European principles of land and water management to a completely different geographic setting' (Mercer et al 2007). The impact of these 'mistakes' can be seen today as Australia's precious water resources are being placed under increased pressure from growing demands for agriculture, industry and a highly urbanised population with rising expectations about quality of life, the state of the environment, and the maintenance of a robust competitive economy [START_REF] Pigram | Australia's Water Resources: From Use to Management[END_REF]. Others label Australia's Federal and State governments' performance in terms of water policy as 'fair to poor' and question whether the allocation of constitutional power between the Commonwealth and State governments is to blame or whether Australian citizens simply remain unconvinced that radical cultural change is required to conserve and manage Australia's water resources (Dumsday 2001).

Traditional policy responses prescribed to manage Australia's water resource dilemmas have included community-government-industry partnerships; community participation in water quality monitoring; integrated catchment management (ICM); environmental communication and education; social marketing; capacity building for individuals and local organizations; and market driven incentives and strategies including the establishment of new institutional arrangements for permanent water trading in many parts of the country. While these strategies have had some impact, they have often been dislocated, used in isolation, and inadequate to ensure sustainable water resources for the driest inhabitable continent on earth [START_REF] Pigram | Australia's Water Resources: From Use to Management[END_REF]Stafford Smith 2003). Several explanations have been offered to account for the limited success of Australia's water management strategies to date. Authors, such as [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF], suggest that one of the most significant barriers to the success of environmental policies is that it is commonplace for environmental policy 'ends' or 'goals' to be pursued with little or no consideration for the process by which the ends are met. In other words they do not take account of new knowledge and the dynamics of social and economic systems or make allowances for the future [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF]. Similarly, [START_REF] Lee | Compass and Gyroscope: Integrating Science and Politics for the Environment[END_REF] argues that policy systems that seek to produce a particular end result have little relevance to the pursuit of sustainable development. Additional arguments include the failure to include civil society in democratic decision making processes; and the failure of regulatory legislation to inspire environmental citizenship (Dobson & Bell 2006).

The limited success of legislation, policy and programs to establish a culture of commitment to sustainable water management and conservation in Australia supports the notion that it is not viable to aim for 'everlasting' 'optimal' institutional arrangements for sustainable water management. In trying to do so, Australia's institutional arrangements have neglected the dynamic nature of managing Australia's water resources. In other words they have neglected the fact that change is constant in social-ecological systems. For example, human use changes water resource systems; water systems themselves undergo change processes; and human needs and interests in water resources change. While the continuous adaptation of management practices is promoted as the means to ensure the sustainable management of water resources, the question of whether and how this ongoing adaptation can be facilitated must be addressed (Maarleveld & Dangbegnon 1999).

From the dust of these 'mistakes' a new paradigm for water management has risen. At its simplest level, this new paradigm is based around the principles of equity; efficiency; and diverse knowledge integration (Pahl-Wastle et al 2008). It rejects merely boosting supply as the way to address water demands and instead prioritises more effective management of available water resources. Within this new paradigm, reform of water institutions and organisations is high on the agenda of federal and state governments, which brings to light the important role that effective and adaptive governance plays in managing water resource dilemmas. Emphasis is placed on the integrated management of water resources and the devolution of water resource management to the catchment and regional scale. Additionally, water policy is scrutinised in daily media coverage and debated openly by concerned citizens [START_REF] Pigram | Australia's Water Resources: From Use to Management[END_REF], Pahl-Wastle et al 2008). Within this emerging paradigm, there is a strong case for enhancing social learning as a means for 'analyzing' and 'catalyzing' collective decision making in the management of Australia's water resources. This, [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF] suggests, can be complementary to existing policy instruments by introducing in the policy some aspects related to the decision-making process itself rather than the end result.

The social learning approach to sustainable water management at the catchment scale

The concept of social learning is not new. [START_REF] Woodhill | Sustaining Rural Australia: A Political Economic Critique of Natural Resources Management[END_REF] has described the way in which social learning was proposed by Dunn as the new paradigm for the social sciences in 1971; motivated by a concern for improved practice in economic and social development. Since then, general definitions of social learning describe it as a key cognitive process responsible for the acquisition of new knowledge by people being exposed to each other in a common environment. Conte and Paolucci (2001) suggest that many complex social phenomena lead to social learning; yet, imitation and social facilitation are highlighted as the most important. Today, however, social learning is increasingly viewed as another way of conducting public business 'alongside regulation, compensation, stimulations and the operations of the (free) market' [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF]. Social learning has also been promoted in recent years as essential for the management of 'complex' natural resource problems and a key process of adaptive management [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF]. However, when social learning is applied to or considered in the context of natural resource management (NRM), definitions such as the one above prove lacking.

In the context of 'good' NRM, [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF] neatly describes social learning as 'the process of collective action and reflection among different actors directed toward improving the management of human and environmental interrelations'. In this context, social learning does not happen by accident; rather, it requires conscious design and facilitation. Accordingly, [START_REF] Woodhill | Sustaining Rural Australia: A Political Economic Critique of Natural Resources Management[END_REF] proposes that social learning has two main concerns; 1) the ways in which different people or groups engage with each other to understand, contest, and influence the direction of social change; and 2) how society understands itself and its relation to the world around it. Social learning processes, therefore, allow societies to adapt their traditions, assumptions, beliefs, systems of social organization and approaches to problem solving in order to deal with external threats or achieve particular objectives [START_REF] Woodhill | Sustaining Rural Australia: A Political Economic Critique of Natural Resources Management[END_REF][START_REF] Woodhill | Dialogue and transboundary water resources management: towards a framework for facilitating social learning[END_REF]Bouwen & Thaillieu 2004;Maarleveld & Dangbegnon 1999;[START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF].

In 2001, the European Commission funded a multi-country project that aimed to investigate the socio-economic aspects of the sustainable use of water. The project title was SLIM, which stands for 'Social Learning for the Integrated Management of Water at the Catchment Scale'. The main focus of the SLIM research lay in understanding the application of social learning as a 'conceptual framework', an 'operational principle', a 'policy instrument' and a 'process of systemic change' (SLIM 2004;Ison et al 2004). The project ran in parallel with the implementation of the European Water Framework Directive (WFD) by all European Union member states [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF]in Keen et al 2005). The WFD, published in 2000, is a legally binding document that requires all member states to implement water management strategies that will achieve good overall water quality for European water bodies within fifteen years [START_REF] Steyaert | The European Water Framework Directive: How Ecological Assumptions Frame Technical and Social Change[END_REF]. The WFD has significant implications for social learning especially given the mandatory nature of public participation and demands for transparency in decision making [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF] thirty researchers from six countries in four European countries, namely France, Italy, the Netherlands and the UK. SLIM researchers studied social learning or determined the factors that enhanced or constrained the social learning process as a 'purposeful policy and praxis option' (Ison 2004[START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF]in Keen et al 2005). Evidence from the analysis of these case studies indicates that deliberate investment in social learning, or 'multi-stakeholder learning partnerships' at the catchment scale achieves the necessary change in individual and institutional behavior at the large scale. This, [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF] suggests, occurs due to the fact that the social learning approach 'provides a context for a dynamic decentralized process, and, in the case of large watersheds, for concerted parallel processes'. As such, SLIM researchers propose that social learning processes should be seen as complementary governance mechanisms [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF].

The SLIM research was undertaken in part as a process of co-learning between researchers and case-study partners and action research. The SLIM project sought to understand and reflect on the role that social learning processes played in the transformation of situations towards concerted action for sustainable water management at the catchment scale. While the study focused on one particular approach to social learning, namely the 'co-construction by interdependent stakeholders of a resource management issue and of ways to resolve or improve it' (SLIM Introduction 2004), the study illustrated the variety of ways in which an inquiry based around social learning as a complementary catchment management tool can be designed and undertaken.

The SLIM researchers engaged three methodological positions in their case studies. The first entailed 'researcher as observer', which is considered traditional case study research in the sense that it provides the researcher with the opportunity to reflect, understand and consequently learn. The second concerned 'researcher as facilitator' through the use of tools, skills, data and the involved others learning. The third methodological position involved systemic action research through co-research and revolved around 'co-constructing knowledge-in-action with stakeholders in a joint process with shared responsibility' (SLIM Introduction 2004). The SLIM researchers engaged a combination of these methodologies in each of the twelve case studies.

The final product of the SLIM project was a conceptual framework for 'organizing, analysis and action in situations of complexity, connectedness, controversy, multiple perspectives and uncertainty, such as water catchments' [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF]. The framework was developed by SLIM researchers so that others can understand and promote the use of social learning for integrated catchment management and more broadly for addressing 'complex' natural resources issues [START_REF] Ison | Traditions of Understanding: Language, Dialogue and Experience[END_REF]SLIM Framework 2004).

Applying the social learning approach for sustainable catchment management to Australia Today, key social learning thinkers in Australia suggest that the case for enhancing social learning in catchment management is built around the need for equitable learning partnerships between the combined expertise of communities, professions and governments; learning platforms that enable interdependent individuals and groups concerned with common environmental issues to meet and interact in forums to resolve conflicts, learn collaboratively and take collective decisions towards concerted action (Roling 2002 in Keen et al 2005); and a recognition that social change requires a transformation in our thinking and in the learning values that underpin learning processes (Keen et al 2005). Keen, Brown and Dyball (2005) highlight five key components of the social learning approach, which they describe as the 'braided strands' of social learning; these are: reflection, systems orientation, integration, negotiation, and participation.

The social learning approach to managing water at the catchment scale is particularly applicable to Victoria's commitment to integrated catchment management (ICM), which theoretically underpins the Victorian State Government's approach to managing Victoria's water resources. Table 1, below, summarizes the six principles that govern the way catchment management is implemented by Victoria's ten Catchment Management Authority.

Sustainable Development

Victoria's whole of catchment approach to natural resource management seeks to deliver social, economic and environmental outcomes for the community and reduce our ecological footprint.

Community Empowerment

Catchment management is a partnership between community and Government. Planning and implementation of natural resource management programs should maximize opportunities for community engagement.

Integrated Management

Management of natural resources should recognize the linkages between land and water and that the management of one component can impact on the other.

Targeted Investment

Government and community need to ensure that resources are targeted to address priorities and deliver maximum on-ground benefits.

Accountability

Those making decisions on natural resource management should be clearly accountable to Government and the community, both in a financial sense and for biophysical outcomes.

Administrative Efficiency

To maximize on-ground results catchment management structures should facilitate more efficient procedures and practices.

Source: DSE 2004.

In 2004 the Victorian Government, through the Department of Sustainability and Environment (DSE) released a White Paper titled 'Securing Our Water Future Together'. In an effort to ensure the future of Victoria's water assets, the White Paper set out a fifty-year strategy for the integrated management of Victoria's water resources. A number of 'Sustainable Outcomes' were identified within the strategy. This study is being undertaken to particularly contribute to two community-related outcomes identified within the strategy, namely:

• "Communities that truly appreciate all the services that water provides, that are able to make considered choices about how those services are delivered; and • Communities that have a stronger ethic of water conservation". (DSE 2004) While these community-related outcomes represent the 'human dimension' of water management (Pahl-Wostle & Hare 2004), their achievement depends on a number of factors that entail social learning for sustainable catchment management. Some of these include development of knowledge and understanding of water management issues; positive experiences that clarify and promote a water sustainability ethic, ethical discernment to integrate personal wishes and community needs in judgments about water issues, and commitment and skill to act, both individually and as part of a wider community [START_REF] Lee | Compass and Gyroscope: Integrating Science and Politics for the Environment[END_REF][START_REF] Fien | Social Capital and action competence in two catchment management groups[END_REF][START_REF] Woodhill | Dialogue and transboundary water resources management: towards a framework for facilitating social learning[END_REF], Keen, Brown and Dyball 2005).

METHODS

At its most basic level, this study is being undertaken to determine whether a social learning approach can help achieve these outcomes as a complementary management tool for catchment management in Victoria. In doing so, the study aims to contribute to the Victorian state government's agenda of ensuring sustainable water resources; and the broader agenda of social learning for sustainable catchment management by producing:

• Practical guidelines for ensuring that social learning complements other policy instruments and is integrated into a comprehensive approach to managing catchments sustainably; and • Practical guidelines for developing the organizational frameworks and training programs needed to ensure that local communities are effective participants in planning and decision making for sustainable catchment management.

The study is also seeking to identify the ways in which social learning can complement other policy instruments to encourage an integrated approach to managing water sustainably. It is analyzing the strategies for, and the drivers and barriers to, facilitating the kinds of social learning that can develop the understanding, commitment, ethical discernment and purposeful individual and collective action needed for successful public appreciation of the importance of water issues and catchment management needs. Additionally, it is evaluating the extent to which, and in what ways, enhanced social learning for catchment sustainability contributes to broader policy objectives such as building the social capital that underpins resilient and sustainable communities, and improvements in the conservation status of natural resources.

The Pennyroyal and Deans March Creeks restoration project has been selected as an ideal case study to investigate social learning as a complementary approach to water management at the catchment scale in Victoria. The Pennyroyal Creek and its major tributary, Deans Marsh Creek, are situated within the Corangamite catchment in south west Victoria. The catchment region covers an area of 13,340 km 2 and is populated by 330,000 people living within regional cities, coastal and inland towns, and rural farming districts. Important water assets of the region include the estuaries of the Great Ocean Road, which are considered some of the most diverse in Australia. [START_REF] Dse | Victoria's Catchment Management Authorities[END_REF]. The Pennyroyal Creek is considered the most connected Creek to the Barwon River, which flows into the Lake Connewarre estuary system, a wetland of international significance listed under the Ramsar International Convention. This study is being undertaken using qualitative research techniques. As an interpretive study, a phenomenological approach is being used to understand and explore the experience of social learning amongst stakeholders of the Pennyroyal and Deans Marsh Creeks restoration project. It seeks to uncover a deeper meaning of the phenomenon of social learning. This study does not rely on measurable variables, but adopts a more open-ended approach, allowing 'truth' to emerge through use of in-depth interviews and the analysis of personal experiences through narrative.

The method underpinning this research is known as 'enthusiasm'. The 'enthusiasm' method is an approach to case study research and involves listening to people, especially to their stories of the past and present, and provides them with the opportunity to voice their hopes and wishes for the future. As such, it involves creating opportunities for dialogue from which learning and personal, social and/or environmental change may result. Whilst relatively uncommon, the enthusiasm method has been successfully used and championed by researchers such as Ray Ison; for example during participative rural development projects in New South Wales (Ison & Russell 2000).

The 'enthusiasm' method is underpinned by the biological and theoretical understanding of the enthusiasm 'drive' itself. The key to using enthusiasm as a research method is that the researcher does not re-direct a participant's energy -rather it is the researcher's initial task to discover where a participant's energy lies. Ison suggests that this can be done by asking the 'right' sorts of questions. Some of these questions could include 'what do you want to do…?' or 'why are you involved with…?' or 'what is it you get out of this activity that you find satisfying?'. Ison recommends that engaging participants with this sort of conversation requires respect for the individuality of participants and acceptance that whatever they are going to say is valid. This, he suggests, is based on the notion that it is the god within a person that has to be respected. In giving the participants the opportunity to be actively listened to they will have the opportunity to tell the story of where their energy comes from, how they see it expressing itself and what they consider as obstacles to the manifestation of their energy. Underpinning all this is the ethical implication that research participants' have 'control of the process (Ison & Russell 2000).

The following features foster the use of enthusiasm as a research method:

• Active listening and cultivation of stories;

• Space for facilitated participation;

• Avoidance of imposed practices that enforce consensus;

• Collective responsibility, transparency, and rituals which create a sense of common purpose.

A case study is being used to inform this inquiry as it gives the researcher great opportunity for insight, analysis and interpretation [START_REF] Merriem | Case Study Research in Education. Ch.1 'The Case Study Approach to Research Problems[END_REF]. Three key research techniques are being used to collect rich, meaningful data in the case study. In-depth, unstructured interviews with open ended questions are being undertaken with approximately thirty stakeholders of the Pennyroyal and Deans Marsh Creek restoration project. These interviews allow the research participants to explore and explain their experience with the social learning process; and give the researcher the opportunity to understand the interviewees' experiences with the phenomenon of social learning and the phenomenon itself. Facilitation of the learning process in workshop settings engages research participants with opportunities for social learning. Observation of the social learning process allows the allows the researcher to reflect upon and make sense of the process of social learning through first hand experience and allows the researcher to judge whether a social learning approach is an effective complementary management tool for catchment management.

Relatively informal data gathering techniques are also being used. For example, casual conversations and incidental observations also provide a rich source of information to validate or provide a different perspective from interview responses and set the context of the study. Data collected in this way is building a picture of the role that social learning plays in contributing to the restoration of the Pennyroyal and Deans Marsh Creek. The case study is being undertaken in six clear stages. Table 2 below outlines the events of each stage, the data collection and analysis techniques and how the data is being validated.

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  , which necessitates what Williams (2001 in Ison 2005) describes as 'a joined up strategy' to bring all affected stakeholders together. The twelve SLIM case studies were undertaken by

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Table 1 : Summary of the Victorian Catchment Management Structure.

 1

  The lower reaches of the Pennyroyal and Deans Marsh Creeks have been channelized and are incised. The Creeks are affected by bank erosion as a result of bed incision and other factors such as riparian vegetation loss, willow infestation 1 , uncontrolled live stock damage, and fluctuating water quality. The restoration project is being managed by the Corangamite Catchment Management Authority (CCMA) and is being undertaken in partnership with the Upper Barwon Landcare Network, the local Water Authority Barwon Water, and local landholders.

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Table 2 : Case study stages

 2

Willows are listed in Australia as a 'weed of national significance'.

Thematic analysis Face validity

CONCLUSION

There is increasing concern associated with water security in Australia. While Australian Federal and State government's have implemented several new strategies that address water management, using market driven, regulatory, educational and incentive based approaches, none have adequately provided for true participatory and integrative approaches. The need to fill this gap and implement true participatory and integrative approaches to managing water sustainably


Caetano C Dorea
email: caetanodorea@hotmail.com

"Appropriate technologies" for drinking water supply in developing countries

Keywords: Appropriate technology, coagulation, development, emergencies, slow sand filtration, water treatment

"Appropriate technologies" for drinking water supply in developing countries

Caetano C.

INTRODUCTION

Health risks associated with drinking-water, particularly microbial, are a major concern in water treatment. Particularly in developing countries where resources for a minimally adequate and reliable water supply are many times lacking. Therefore, drinking water treatment and supply projects should make the most of the accessible resources by adopting the most adequate technologies available. The term "appropriate technology" is commonly used in the context of water treatment and supply in developing countries to refer to water purification techniques that can be implemented (sometimes), operated, and maintained by the beneficiary community.

Appropriate technology usually refers to situations where there is a relative stability and time for the involvement and capacity building of the local community (i.e. development projects). Locals are consulted on their preference of technology and factors such as locally available skills and resources are taken into consideration together with the cultural and environmental settings. However, in situations such as humanitarian emergencies an appropriate technology may refer to water treatment methods that can be quickly and easily implemented (usually by a foreign aid agency) in locations with limited resources (e.g. energy source, chemical supply, spare parts).

Three case studies are presented on use of appropriate technologies for water treatment in developing countries, varying from rural community slow sand filtration systems to chemicallyassisted emergency water treatment kits. Both successes and lessons learnt are illustrated in each case study from varied geographical locations (i.e. Sub-Saharan Africa, South Asia, and South-East Asia) and contexts (i.e. development and humanitarian emergency).

Multi-stage filtration

Slow sand filtration (SSF) has been well established as a biological process for drinking-water treatment that can achieve significant improvements in water quality. However, it is sensitive to influent waters of high turbidity. This limitation has the implication of hindering the reliability of the process in terms of continuity or negative effects on the biological activity. This shortcoming to SSF can be dealt with the incorporation of pre-treatment stages. Gravel (or roughing) prefilters are units filled with gradually finer graded media with varying bed depths (or lengths). They have been used together with SSF due to their effectiveness, simplicity, and reliability as pre-treatment, providing (together with SSF) a multiple-barrier system; otherwise know as multistage filtration (MSF) systems. Such a treatment approach relies on more than one purification stage (or barrier) during the treatment process progressively removing contaminants and consistently producing safe and wholesome water [START_REF] Galvis | Overcoming water quality limitations with multi-barrier concept: A case study from Colombia[END_REF].

Study area

The study area is situated in the communities of Nyabwishongwezi and Ntoma in northeast of the country bordering Uganda and Tanzania. The two multi-stage filtration (MSF) water treatment plants (WTPs) are located in a hilly terrain and utilize the river Umuvumba that runs through the boarder of Uganda and Rwanda. The Nyabwishongwezi WTP is a multi-stage filtration plant consisting of four parallel storage tanks followed by two parallel two-stage gravel (roughing) pre-filters and four parallel slow sand filter units. Choice of such treatment system was based on the inadequacy of groundwater as a source in terms of quality and quality (i.e. high iron content). This WTP was designed for a population of 18000, mainly returnees from the 1994 genocide. The neighboring Ntoma WTP was commissioned by a different non-governmental organization (NGO) shortly after the construction of the Nyabwishongwezi WTP. It is said to have been a "blueprint copy" of the Nyabwishongwezi WTP; mainly differing in the fact that the water is pumped from the river intake to conventional rectangular (horizontal-flow) sedimentation basins, in contrast to the batch (i.e. fill-draw) storage tanks of the Nyabwishongwezi WTP. This is followed by two-stage up-flow gravel pre-filters and slow sand filters.

Field visit outcomes/findings

Despite having no terminal disinfection, the finished water produced by the MSF system in Nyabwishongwezi was substantially better in terms of turbidity and microbiological quality in comparison to the polluted source water (Figure 1). The water quality assessment was done in conjunction with the plant operating staff that received water quality training during the first field visit to the system in 2002. However, some design/operational problems were also noted [START_REF] Bertrand | From Emergency to Development: the Nyabwishongwezi Water System[END_REF][START_REF] Dorea | Performance of a rural multi-stage filtration plant after its handover[END_REF], some of which could be simply remedied (e.g. floating outlets to storage tanks, drainage system for gravel pre-filter cleaning); while others would require a substantial investment (e.g. adequate intake structure, insufficient number of gravel pre-filter units). Subsequent visits to the Nyabwishongwezi WTP in 2003 and 2004 saw improvements with regards to the simple deficiencies. It was also noticed that the continuing operation of the WTP was being affected mainly by issues relating to the tariff system. There was a low revenue collection due to seasonally low water usage (i.e. rainy season). Notably, the tariff system (by demand of local authorities to comply with National tariff model) did not factor the depreciation and replacement of items (e.g. diesel pump). Moreover, by 2003, the increase in fuel costs, attributed to the events occurring in the Middle East, was already affecting the community's capacity to purchase diesel to run the pumps. A final visit to the system revealed that the Nyabwishongwezi system was not operational due to the breakdown of the pumps.

The Ntoma WTP shared as well many similarities in terms of design shortcomings that could have been avoided with consultation. Most notably was the choice of sedimentation basin. Conventional rectangular (horizontal-flow) settling basins require a constant flow in order to be effective. However, due to the positioning of the WTP and the topography of the region a constant supply of water would require a non-stop pumping regime; which is unfeasible for this type of rural scheme. Unfortunately, no information on the operation of this water treatment plant was available, as it is said to only have operated for the two days in which the implementing NGO was present [START_REF] Dorea | Performance of a rural multi-stage filtration plant after its handover[END_REF]!

CASE STUDY 2: EMERGENCY "CLARIFIER" IN INDONESIA Oxfam Field Up-flow "Clarifier"

The supply of safe drinking water during disasters can be compromised and is one of the top priorities in public health interventions that must be reestablished to prevent the spread of disease. When the speedy establishment of adequate water supplies is beyond the capacity of local authorities, emergency response and equipment from external relief agencies can often provide timely interim solutions while more durable long-term repairs are being planned. The Oxfam Field Up-flow Clarifier Kit is an emergency water treatment kit that is one type of treatment option deployed to emergencies in the event of disasters [START_REF] Dorea | Particle separation options for emergency water treatment[END_REF]. The Clarifier relies on the principles of up-flow blanket clarification and is driven by a single pump; requiring only fuel and aluminum sulfate, which are typically widely available. Detailed description and performance of the Clarifier is available elsewhere [START_REF] Dorea | Performance of an Up-flow Clarifier for Emergency Water Treatment[END_REF].

Study area

Following the Asian Tsunami of December 2004, two Clarifier units were deployed to the affected villages of Lamno and Meulaboh on the island of Sumatra (Indonesia). In Lamno, precoat (diatomaceous earth) filters were being used for emergency relief water supply. Yet, the effectiveness of these units was being compromised by the increasing turbidity of the source river, due to the approaching of the monsoon season. This prompted the installation of an Oxfam Field Up-flow "Clarifier" Kit to aid in the water production in May 2005 [START_REF] Dorea | Performance of an Up-flow Clarifier for Emergency Water Treatment[END_REF]. In Meulaboh a unit had already been installed, but required optimization and operator training.

Field visit outcomes/findings

Operator training was provided for the unit installed in Lamno before being handed over to the local Public Health Engineering. It was later reported that high turbidities could be effectively reduced to the recommended potable drinking water limits (i.e. below 5 turbidity units), as per Sphere Project (2004). Such unit was still running for more than two years when it was last visited in 2007. On that occasion it was noticed that the (unskilled) operators had been successfully running the Clarifier with only the training received when the unit was installed (Figure 2). The unit installed in Meulaboh was also visited and optimized. Operators there received training in field jar-testing for coagulant dose determination, as explained by [START_REF] Dorea | Simple improvements for emergency batch water treatment[END_REF]. Simple concepts delivered in the training proved to be effectively assimilated by the operators. A sign of this was that during a 103 day (unsupervised) period following the training, the logged Clarifier performance revealed that the treated water turbidity was always below recommended potable drinking water limits [START_REF] Dorea | Performance of an Up-flow Clarifier for Emergency Water Treatment[END_REF].

CASE STUDY 3: EMERGENCY BATCH WATER TREATMENT IN PAKISTAN

Emergency batch water treatment Batch mode emergency water clarification is usually carried out in storage tanks by adding the coagulant (e.g. alum) the incoming water. Once the tank is full, the water is left to settle; after which the settled water is then decanted, stored, and disinfected prior to distribution. Despite limited process control, turbidities in the hundreds can be reduced to what is considered to acceptable by the Sphere Standards, i.e. < 5 NTU. This is a simpler (in comparison to the Clarifier) and most common form of emergency water treatment [START_REF] Dorea | Simple improvements for emergency batch water treatment[END_REF].

Figure 1 :

 1 Figure 1: Improved water quality along MSF system (samples from: raw water, settling tank, pre-filter, slow sand filter -left to right).

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Figure 2 :

 2 Figure 2: Operator training on simplified jar-test procedures for coagulant dose determination.

CASE STUDY 1: MULTI-STAGE FILTRATION IN RWANDA

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Title of the paper -First name FAMILY NAME

Study area

In the aftermath of the October 8 2005 earthquake in Pakistan two rural filtration systems were visited in the Jehlum Valley region near Muzaffarabad (AJK, Pakistan). Both plants were similarly designed and operated by the local governmental water authority. Of the two, the Gahri Dupatta WTP was the worst hit; having its pumping station, settling basin and slow sand filters structurally affected. Further upriver, the Hattian Bala WTP was still operational relying on an undamaged slow sand filter bed. Both systems relied on river abstraction by pumping in to plants consisting of baffled hydraulic flocculators followed by conventional rectangular sedimentation basins and slow sand filters. Whilst the rehabilitation of the Gahri Dupatta treatment plant was being commissioned, the damaged settling basin was by-passed and alum-assisted batch emergency sedimentation tanks were used for the emergency relief efforts (Figure 3).

Field visit outcomes/findings

A few design issues were observed, particularly with regard to the choice of sedimentation basin and pre-treatment method for the slow sand filters. Similarly to what was observed in Ntoma, the location of the WTP on a hillside should have proscribed against the choice of settling basin. The electric pumps operated intermittently due to the constant power shortages experienced in the region (even before the earthquake). Such operating regime most likely would have caused the stirring up and carry over of previously settled particles into the slow sand filters every time the flow was started; thereby shortening the duration of the filter runs. In addition, the choice of an alum-based pre-treatment method was perhaps not ideal considering the rural settings and availability of other non-chemical pre-treatment techniques (i.e. gravel or roughing filtration). Anyhow, it was noticed that operators in both plants assimilated well the simplified jar-test procedures for coagulant dose determinations, as had been observed previously in Indonesia. Prior to the training sessions, the operators would add the entire daily coagulant "requirement" was added at once directly into the incoming flow of water in the baffled flocculator. Noting that the alum "requirement" was arbitrarily decided depending on the perceived color of the river.

6

SUMMARY AND CONCLUSIONS

The case studies presented give abridged descriptions of research/field work with appropriate technologies for water treatment in developing countries. In the field visits where rural supply schemes were encountered (Rwanda and Pakistan), the importance of proper design and adequate choice of treatment unit processes (e.g. sedimentation basin) is illustrated. Such examples of by-the-book designs are great, but only if they fit within the local context and can be properly operated as recommended by-the-book! In the context of areas with limited resources, coagulant-based water treatment processes are not viewed as appropriate technologies; such was the case observed in Pakistan. However, experiences also indicated that in extreme circumstances, such as in the aftermath of disasters, local (and mainly unskilled) operators can successfully operate coagulant-based processes. Noting that these were short-term measures only utilized whilst a supply of chemicals was available from the implementing aid agency. The main key to the successful operation of these systems in emergencies was the adequate training and capacity building of operators. Finally, another non-technical factor to take into account when selecting a technology is the cost-recovery of the running expenditure. This should include in the tariff system for the successful long-term operation of a water supply scheme.


Gemma Carr
email: g.carr@reading.ac.uk

S Nortcliff

R B Potter

Urban wastewater reuse for irrigated agriculture in Jordan: Soil sustainability, perceptions and management

Keywords: Perception, sustainable development, urban water, water management, water re-use

Jordan is a country with very limited water resources and urban treated domestic wastewater offers a valuable contribution to the country's water balance. Water reuse is particularly well-suited to irrigated agriculture, for which water is in constant demand. The physical characteristics of the water (high organic content and solute loaded) mean that suitable soil management strategies, such as periodic leaching and nutrient management are required to maintain soil productivity and prevent the accumulation of plant toxic solutes. The effect of water reuse on soil sustainability was investigated by means of soil sampling and analysis combined with interviews with farmers and organisations involved with water reuse. The results reveal that the perception and knowledge of the water is important in the process of decision-making as to the relevant management strategy to be applied. The research stresses that maintaining soil sustainability when reusing water is imperative for agricultural development in Jordan and is achievable through water management both on and off the farm.

INTRODUCTION

Water scarcity is a growing problem across the world as greater pressure is placed on the available water resources. Rising populations require more freshwater for drinking, domestic uses and particularly for food production. Irrigated agriculture is essential to sustain the increasing populations and in arid and semi-arid lands it commonly absorbs a majority share of the freshwater resources. The countries of the Middle East are facing some of the greatest water shortage problems in the world. The available resources are significantly lower than the potential demands placed on them by industry, agriculture, tourism and domestic uses. Jordan, at the centre of the Middle East, is one of the most water scarce countries of the world. With only 497 cubic metres per person per year (FAO Aquastats, 2008) it is well below the official criteria for water scarcity of 1000 cubic metres per person per year [START_REF] Winpenny | Managing water scarcity for water security[END_REF].

There are three principal ways which water scarcity can be alleviated. Firstly, through the development of new resources via the construction of dams, desalination of sea water or by exploiting deep groundwater resources. Such schemes typically involve hard engineering and technological developments and tend to be expensive. Secondly, the aim may be achieved through water demand management which aims to lower the demand for water by encouraging water saving devices and reducing water use in the home, in industry and in agriculture. The third approach is by reusing urban domestic wastewater after it has been treated. Treated wastewater is particularly well suited for agriculture as it often contains significant quantities of plant essential nutrients like 8th World Wide Workshop for Young Environmental Scientists WWW-YES-2008: Urban waters: resource or risks? 13-16 May 2008 nitrogen, phosphorus and potassium. The strong psychological aversion to reallocating used water to domestic needs also drives the use of treated wastewater for irrigated agriculture.

In Jordan water reuse is taking place on a grand scale. 65 per cent of households are connected to a central sewage system (Water Authority of Jordan, 2007) which means that about 80 million cubic metres (MCM) of wastewater are produced annually [START_REF] Vallentin | Agricultural Use of Reclaimed Water -Experiences in Jordan[END_REF]. This constitutes just under 10 per cent of Jordan's 850 MCM of renewable water annually. The majority of this is produced at the Khirbet As Samra treatment plant located 30 km east of Amman (the capital of Jordan). Figure 1 is a schematic diagram showing the domestic to waste to irrigation water pathways in north-west Jordan. It shows that the majority of the wastewater coming from Amman is sent to the Khirbet As Samra treatment plant. After treatment the water is released to the Zarqa River, where it flows down to the King Talal Reservoir. From the reservoir it is then released as required to be used for irrigation in the Jordan Valley (a major agricultural area). The use of the water is split between that consumed directly around the treatment plant and that used indirectly (after significant transportation and the seasonal addition of natural surface runoff) in the Jordan Valley. Water has been reused successfully in Jordan for several decades and the aim of this research is to investigate the sustainability of this practice in terms of both the effects on soil and the ability of people to manage and mitigate these effects. Water management is increasingly emphasising the importance of an holistic and interdisciplinary approach to overcome the water challenges of the 21 st century. The need to incorporate social considerations alongside technical planning is frequently discussed, yet in reality it is often limited or lacking. This research seeks to emphasise that combining approaches from the social and physical sciences is potentially rewarding in terms of findings for water management issues.

Urban wastewater reuse for irrigated agriculture in Jordan: Soil sustainability, perceptions and management -Gemma CARR

METHODS

To reflect the interdisciplinary nature of the work, several different research methodologies have been utilised. These included soil sampling and laboratory analysis, mathematical modelling to further understand the processes affecting the soil and semi-structured interviews with stakeholders involved with water reuse.

Soil and water sampling and analysis

In this work it was hypothesised that soil irrigated with treated wastewater would have a greater quantity of ions such as sodium (Na + ), chloride (Cl -) and boron (B + ) which are plant toxic in high quantities. These solutes enter the water through the use of domestic cleaning products in which NaCl and B are often present [START_REF] Patterson | Wastewater quality relationships with reuse options[END_REF]Reuben, 2004;Reuben, 1965). The limited availability of domestic water in Jordan leads to high concentrations of solutes which are not removed by standard treatment methods, and so when applied to the soil with the irrigation water over time, they can accumulate. Accumulation leading to soil salinisation is of particular concern in arid and semi-arid regions because the high rates of evapo-transpiration require large quantities of water to be applied to meet the crop water demand. The water is used by the plants or evaporated from the soil surface resulting in large quantities of salts becoming deposited in the soil. The accumulating ions can only be removed through the application of excessive quantities of water and the subsequent dissolution and transportation of the salts down through the soil profile. The accumulation of salts in the plant root zone jeopardises plant health and productivity and it may reduce the quality of the soil structure and lead to reduced soil fertility. The careful management of saline waters is required to prevent high levels of salts accumulating which threaten the sustainability of the soil system.

Soil sampling was conducted at several localities in Jordan to compare sites with higher and lower precipitation rates, with different qualities and quantities of irrigation water and with the application of management methods such as leaching. Soils were sampled from a number of depths in the soil profile down to 50 cm. Water samples were also collected at the same localities as the soil sampling in order to compile corresponding data on water quality.

Analyses were conducted to determine the salinity and pH of the soil through saturating a known quantity of soil with ultra-pure water and then removing this water by suction following the method suggested by [START_REF] Rowell | Soil Science. Methods and Applications[END_REF]. The removed liquid (the soil saturation paste extract) could then be analysed to determine the overall salinity (electrical conductivity) of the extract (ECe), the pH, the quantity of major cations (e.g. sodium, potassium, calcium, magnesium and boron) using ICP-AES, and the quantity of anions (e.g. chloride, bicarbonate, phosphate, sulphate) using ion chromatography. The EC and pH of the water samples were measured in the field using hand held instruments and sub-samples were also collected for analysis using ICP-AES and ion chromatography.

Mathematical modelling

Modelling soil salinity changes through the use of treated wastewater offers a way to determine the sustainability of agriculture. The Hydrus model (Šimůnek et al, 2005) is currently being applied to identify long-term salinity changes, leaching water requirements and therefore determine the overall water requirement for maintaining soil productivity.

Semi-structured interviews

Extensive semi-structured interviews were conducted with 56 farmers and 29 organisations who work with treated wastewater. The aims of the farmer interviews were to gauge the perceptions of the water, to identify perceived and real problems and benefits and to document local knowledge of how the water is managed to minimise adverse effects on crops and soil. To investigate the differences in perception and management between farmers reusing the water close to the treatment plants and those using it indirectly in the Jordan Valley time was spent interviewing farmers in three different locations. These were the Jordan Valley, around Khirbet As Samra wastewater treatment plant and around Ramtha wastewater treatment plant (in the northern highlands). At each locality a variety of farmers were selected with an even distribution of those managing large farms with access to secure export markets through to those cultivating small holdings producing crops for the local market. The interviews were conducted in the field via a translator with advanced knowledge of Jordanian agricultural systems. Notes were taken during the interviews and often a tour of the farm was given to clarify and explain management methods and issues. The interview notes were typed up and expanded according to memory immediately after the interviews. Each data bit (piece of information) within the interview transcript was then coded and grouped according to its code. This method meant that similarities and discrepancies between the farmers' views became clear and factors that were frequently mentioned or ignored became highlighted [START_REF] Kitchin | Analysing and interpreting qualitative data[END_REF].

The organisation interviews were held with individuals working actively in the field of water reuse in the private sector, governmental, non-governmental and research institutions in Jordan. These interviews focussed on the perception of wastewater, but also covered wider management and implementation challenges, priorities for future research and management directions. These interviews were conducted in English and were either recorded or notes were taken during the interview. They were transcribed immediately after the interview with additional observations and comments. For analysis they were coded according to various themes and the coded data were analysed to identify similarities and differences between the individuals and the organisational groups. Quotes were identified for each theme and compiled together in order that narratives could be developed on water reuse from the perspective of the organisations.

RESULTS

Water quality

Table 1 shows the composition of water samples collected in 2006 and 2007 from the Khirbet As Samra research station. The electrical conductivity (EC) is used as a measure of salinity and the treated effluent in Jordan typically has an EC of 2 dS m -1 , which guidelines suggest gives the water a slight to moderate restriction to use [START_REF] Ayers | Water Quality for Agriculture[END_REF]. Of greater concern is the concentration of chloride in the water, which can reach 400 mg l -1 and which exceeds a recommended maximum concentration of 350mg l -1 [START_REF] Ayers | Water Quality for Agriculture[END_REF].

Urban wastewater reuse for irrigated agriculture in Jordan: Soil sustainability, perceptions and management -Gemma CARR

Soil sustainability

Results from sites irrigated with reclaimed water for known lengths of time reveal that salts do accumulate from water reuse. Figure 2 shows salinity data from an experimental site irrigated with known quantities and qualities of water for two consecutive years. The data show that after one year of irrigation the salinity of the soil increased dramatically relative to an un-irrigated control. However, at the end of the second season the salinity dropped. This is probably a result of the greater number of higher magnitude rainfall events in the second year which contributed more freshwater over a shorter time, leading to increased solute leaching. From the experimental data, especially those collected after just one year of irrigation, it could be hypothesised that soil salinity rises with wastewater irrigation and that rainfall is essential in maintaining suitably low soil salinities in the plant root zone. Yet figure 3 shows data collected from a farm irrigated with reclaimed water for almost 3 decades. These data have been collected from a locality that has had no freshwater input for 28 years, yet the soil salinity has been maintained at a level very suitable for crop production. These data emphasise that with good management, soil solute accumulation can be avoided. For comparison, soil salinity data from an olive plantation irrigated for 18 years is shown. This shows higher soil salinity in the top 50 cm than in the site irrigated for 28 years, which demonstrates that the soil salinity will rise if leaching is not practised. The deeper rooting depth of the olive trees mean that such high salinity in the soil surface is not detrimental for plant productivity.

Interviews

Interviews with farmers. The results of the soil analysis emphasise the importance of management methods in maintaining soil productivity and the farmers interviewed were all asked about the management strategies they employed. It was clear during the interviews that there is a distinct difference in the perception of the water and the use and management of the land between the direct water re-users and the indirect re-users.

A typical comment from a direct re-user was, "I like the wastewater because before the treatment plant there was no water for supplementary irrigation. I make more money now." Directly around the treatment plants the water is being used for the continuous production of fodder crops such as barley, clover and maize. The yield is sold to diary farms in Jordan and can earn the farmers a substantial income. All farmers around the treatment plants were aware of the beneficial plant nutrients within the water and said how they usually did not add additional chemical fertilisers to the soil which gave them considerable financial savings. It also became clear during the interviews that the farmers felt able to speak with the staff of the wastewater treatment plant if they required any information about the water or if they had any concerns. One example was frequently given of how large amounts of chlorine were previously being added to the wastewater before it was released from the treatment plant. The chlorine was damaging the crops and so the farmers spoke with the plant manager to ask him to reduce the quantity of chlorine. Action was taken to reduce the chlorine additions and irrigation was able to continue successfully without detrimental effects on the crops. No farmers reported any soil salinity issue and most associated the management of this potential risk to the use of flood irrigation around the treatment plants. This results in large quantities of water being applied to the soil regularly giving plenty of leaching of solutes down through the soil profile.

By comparison, the indirect water re-users had a more negative opinion of the water. Typical comments were, "The water has bad things in it for the plants, there are no good things." "The Urban wastewater reuse for irrigated agriculture in Jordan: Soil sustainability, perceptions and management -Gemma CARR water quality is bad. There is a high pH and there are many soil born pathogens that come with the water and attack the plants." These negative opinions may occur for several reasons. Firstly, the Jordan Valley has historically been irrigated with freshwater from the Yarmouk River. As more and more of this water is redirected to Amman for domestic purposes the freshwater has been replaced by the treated wastewater coming from Khirbet As Samra. Older farmers therefore remember the past when good quality freshwater was available. Secondly, the land of the Jordan Valley is mainly used for the cultivation of high value vegetable and fruit crops. Soil pathogens are both common and very costly to farmers through lost productivity. Any potential for increased risk to the crop, however unscientifically proven, is understandably viewed negatively.

The management methods in the Jordan Valley primarily involve leaching and soil solarisation (a method of sterilising the soil using the sun's radiation during the summer). Most farmers spoke of the importance of leaching to maintain soil productivity and they said how they aimed to leach annually prior to planting at the start of the season. However, they also said that they rarely have enough water to leach adequately and so are forced to leach either only a small section of their land or to abandon leaching altogether. The low availability of water when it is needed was attributed to both the very limited water resources of Jordan and the weak management of the available resources by the responsible government agency. Farmers were asked if they are able to save money on chemical fertilisers because of those contained within the water. Few farmers recognised any benefits in the form of nutrients coming from the water. Even those who had been trained about the nutrient value of the water admitted to adding chemical fertilisers so as to ensure a good harvest. The cultivation of nutrient demanding vegetable crops in the Jordan Valley and the intensity of cropping also leads most farmers to the decision to add chemical fertilisers, sometimes in excessive quantities.

Interviews with organisations. The interviews revealed that 50 per cent of organisations recognised that damage to soil was a risk from water reuse yet none of the organisations considered that water management to reduce this risk was a priority for sustainable development of agriculture using wastewater. The organisations instead spoke frequently of the importance of monitoring to check for adverse effects from irrigation with wastewater. They spoke of a need to train farmers how to manage this water and of the need for more research to provide information to decision makers. All the organisations considered water reuse to be important because of the limited availability of water and its corresponding importance for Jordan's water strategy. Only 7.5 per cent of organisations spoke of the positives from water reuse such as the nutrient benefits.

An issue of considerable importance in Jordan is the allocation of water to different agricultural types and geographical localities and particularly the potential conflict between the direct and indirect water re-users. This was identified by several of the organisations working to develop agriculture in the international and NGO sector:

"But then there's another challenge coming up. Because the (waste) water quality is better the farmers upstream are more interested in it so it could happen that the water doesn't even reach the Jordan Valley (JV), although the farmers (in the JV) have their water rights. This is a bad thing for the livelihoods of the farmers, and also you have to ask why invest in uphill farming when there's no farming there at the moment. It would seem that the topic of water allocation between the indirect and direct agriculture is worthy of serious discussion by planners and decision makers.

CONCLUSIONS

The interdisciplinary work allows us to draw several conclusions with regards to the sustainability of water reuse. The soil analysis has shown that water reuse for irrigation does alter the soil salinity but it is very important to notice that the salinity changes are highly dependent on several factors such as the quantity of water applied, the rainwater inputs and especially the management methods used on the farm. For this reason it is very important that laboratory results and field experiments are not extrapolated directly to the farm. It is essential that the farmer's knowledge, his perception of the water and the management methods that he chooses to apply are considered when assessing the effects of water reuse on soil. The decisions made by stakeholders away from the farm are also very important in the sustainable management of water reuse and it seems that many organisations do not realise their role in maintaining soil productivity through water management off the farm. It is expected that water reuse for irrigation will increase in the future as greater volumes of urban wastewater are produced, collected and treated. The allocation of this water between direct reuse around treatment plants and indirect reuse at a distance from the plants is worthy of considerable discussion, as there are disadvantages and benefits of each system.

Figure 1

 1 Figure 1 Schematic diagram and corresponding map of the water pathways in north-west Jordan

Figure 2 :

 2 Figure 2: Soil salinity (ECe) at Khirbet As Samra research station

Figure 3

 3 Figure 3 The salinity of soil from farms irrigated with wastewater for extensive periods of time

TABLE 1 : Selected parameters of the water samples from Khirbet As Samra and the Jordan Valley

 1

		Month
	Location	and year of sampling	water (mg l -1 ) Solutes detected in the	Additional Parameters
									Total
								Sodium	Organic
						Electrical		Adsorption	Carbon
			Chloride (Cl)	Sodium (Na)	Boron (B)	Conductivity (EC) dS m -1	pH	Ration (SAR)	(TOC) ppm
	Khirbet As Samra	Nov 2006	440.05	253.30	1.03	2.04	8.12	4.87	n/a
	Khirbet As Samra	May 2007	174.25	265.31	0.84	1.68	7.83	5.83	10.97
	Jordan Valley -
	Deir Alla	May 2007	299.54	173.21	0.55	2.09	7.50	3.45	9.45

  World Wide Workshop for Young Environmental Scientists WWW-YES-2008: Urban waters: resource or risks? 13-16 May 2008"The water that comes from the Khirbet As Samra means that agriculture can continue in the Middle Jordan Valley. And if this stops the situation will be very bad, I cannot imagine, because there is no (other) water for agriculture. And from a social and economic point of view the (waste) water is the only guarantee for the sustainability of agriculture."

This threatens groundwater resources and damages the good market advantage that the Jordan Valley has during the winter. Because the uphill farming is summer farming. They don't get as much money as the farmers in the Valley as there's a market gap there. It's always an economic decision what or where the water is used. And if they come up with these ideas of growing industrial crops it would be a disaster." 8th

8th World Wide Workshop for Young Environmental Scientists WWW-YES-2008: Urban waters: resource or risks? 13-16 May 2008