Luminiţa Ghervase
email: ghervase@inoe.inoe.ro

Cristian Iojă
email: iojacristian@yahoo.com

Elfrida M Cârstea

Dan Savastru

GHERVASE et al

Keywords: Urban water, waste water, ecosystem, discharges, eutrophication

Bucharest is one of largest cities in Romania and disposes of natural and artificial lakes, which are utilized for different economical and leisure purposes. Water samples collected from lakes within the urbanized area were characterized by oxygen indicators (dissolved oxygen, chemical oxygen demand), nutrients related indicators (ammonia, nitrates) and spectroscopic response (fluorescence spectroscopy). The standard parameters were correlated with the fluorescence measurements and with pollution sources situated in the proximity of lakes. Degradation of water quality was noted for lakes which have individual residential areas in the proximity, in comparison with lakes surrounded by green spaces, collective residential or industrial areas, and even open fields.

INTRODUCTION

Water, as an environmental component, is essential for the life quality and the sustainable development of human settlements. Besides its value as a resource, urban water is a receiver of the environmental problems, specific to the urbanized areas: waste waters with different levels of biochemical charging, solid wastes, various organisms, and heat excess [START_REF] Iojă | Methods for environmental quality assessment in Bucharest Metropolitan Area[END_REF]. All these problems can reduce the economical utility of water resources and convert them into means of propagation and attraction of urban issues, like insalubrity, excessive growth of various animal and plant species, poverty, and loss of economical attractiveness of an area. Due to the continuous pressure human life puts on the natural water resources, several legal mechanisms have been developed in the European Union. Amongst these there is the Framework Directive 2000/60/EC, which has been transposed into the Romanian legislation by the Water Law and stipulates that all water ecosystems, must achieve good ecological status by 2015.

Bucharest is one the largest Romanian cities and the capital of the country. It has several lakes, used for different economical or leisure activities, which have a key role in maintaining the territorial balance of their locations. Conservation and preservation of these urban lentic ecosystems is important both from an economical and an environmental point of view and can be done by the rapid, accurate evaluation and monitoring of their state of health.

Lately, fluorescence spectroscopy has the method of choice for many water-related scientific studies [START_REF] Mcknight | Spectrofluorimetric characterization of dissolved organic matter for indication of precursor organic material and aromaticity[END_REF][START_REF] Jaffé R | Source characterization of dissolved organic matter in subtropical mangrove -dominated estuary by fluorescence analysis[END_REF][START_REF] Liu R | Fluorescence characterization of cross flow ultrafiltration derived freshwater colloidal and dissolved organic matter[END_REF][START_REF] Cârstea | Assessment of the anthropogenic impact on water systems by fluorescence spectroscopy[END_REF][START_REF] Ghervase | Fluorescence evaluation of anthropogenic influence on rivers crossing Sofia[END_REF], because it has several advantages over standard techniques: it represents a rapid pre-analysis method, it does not need high sample quantities or complicated pre-preparation steps and, moreover, it offers the possibility of in situ measurements. Water quality can be assessed through fluorescence spectroscopy, because of its dissolved organic matter (DOM) content. DOM is present in all natural waters in various proportions, and it comprises two chromophoric fractions: 40 -60 % is given by humic-like substances (humic acid -A, fulvic acid -C, recent humic substances -M) and the rest is represented by protein-like substances (amino acids, mainly tryptophan, T and tyrosine, B). Each of these components has specific excitation and emission wavelengths domains [START_REF] Coble | Characterization of marine and terrestrial DOM in seawater using excitation-emission matrix spectroscopy[END_REF][START_REF] Parlanti | Dissolved organic matter fluorescence spectroscopy as a tool to estimate biological activity in a coastal zone submitted to anthropogenic inputs[END_REF], which helps identify them in a fluorescence excitation -emission matrix (EEM).

The aim of the paper was to determine the ecological status of urban lentic systems, based on standard chemical analysis and optical techniques. For this purpose, several urban lakes were selected, with similar or different geo-morphological characteristics and impacted by various degradation sources. The characteristics of these lakes were correlated with the pollution sources by which each of them are affected.

MATERIAL & METHODS

A total of 16 urban lakes were included in the study: lakes situated along a river which runs near the city border (P1 -P8, "external lakes") and lakes situated inside the city (P9 -P16, which will be called from now on "internal lakes"), as illustrated in fig. 1. The water samples were collected in spring 2010. Based on the type of water supply, they can be divided into lakes with partial natural water supply and lakes with predominant artificial water supply (from medium and high depth groundwater sources and from the water supply network). These lakes are used for different economical and leisure purposes and are subjected to various degradation sources, as can be seen from Table 1. As can be seen, all of them are arranged for leisure activities and are used for fishing, even if the lake water is not very qualitative. Lakes P1 -P9 are affected by uncontrolled wastewater and dump discharges, as opposed to lakes P9 -P16 which are mostly affected by surface runoff. Prior to the spectroscopic measurements, the samples were analyzed for several standard chemical quality indicators: oxygen indicators (dissolved oxygen and chemical oxygen demand) and nutrients related indicators (ammonia and nitrates). The dissolved oxygen level was measured with HANNA HI 9145 oxygen meter, the nitrogen compounds with spectrophotometer with sulphanilamide and N-(1-naphtol)-ethylenediamine for nitrates, and for the chemical oxygen demand the US EPA 410.4 method was used.

Fluorescence was recorded in the form of emission spectra using spectrofluorimeter FLS-920 Edinburgh Instruments, equipped with 450 W Xenon flash lamp and double monochromators.

The emission was detected in the range of 250 -500 nm, with 1 nm step, for different excitation wavelengths, between 230 -400 nm. Both emission and excitation slits were set at 2 nm and the integration time was 0.2 s. The recorded data were processed using the Origin 7 software.

RESULTS AND DISCUSSION

The standard water quality parameters recorded for the lake water samples are presented in figure 2. The level of dissolved oxygen in natural waters is a balance between the oxygen depleting (respiration and decomposition) and the oxygen generating (photosynthesis) processes. Organic wastes may overload a natural water system, leading to depletion of the oxygen supply but for the investigated lakes, the organic loading did not seem to have a direct influence over the dissolved oxygen values for eutrophic lakes, due to the photosynthesis process. The values of dissolved oxygen varied unevenly from 4.17 (P12) to 10.2 (P1). The smallest value, detected for sample P12 can be related to the presence of more bacteria or animal populations using dissolved oxygen in excess.

As for the nitrogen compounds, high content of nitrates was found in samples P1, P2, P6, P7, P13 and P16, which are included in the fourth general quality class (Official Monitor of Romania, 2006), as opposed to samples P9 -P11 and P15 which had the lowest values. The ammonia content registered in the lakes varied from 0.03 (P9) to 5.89 (P7). Ammonia, as nitrogen source, is also nutrient for the aquatic vegetation and it can contribute to the overloading of natural waters. The high ammonia values found in lakes P1, P2, P7 and P8 could be related to the presence of larger fish communities.

The chemical oxygen demand (COD) represents the capacity of a water system to consume oxygen for the decomposition of organic matter or for oxidation of inorganic substances and it is a measure of the degree of water pollution with organic matter. The highest levels of COD were registered for samples P1, P5 and P8, over 40, probably indicating highly eutrophic lakes.

Lakes P1 -P8 are more subjected to the antropic influence, because there are more individual residential areas in their proximity. Many of them are not connected to the city's sewage system and part of their wastewaters is released into the lakes, contributing to their degradation. On the other hand, lakes P9 -P16 are surrounded by parks and some collective residential locations, therefore mostly affected by surface runoff. Figure 3 illustrates the fluorescence intensities of the principal fluorophores encountered in the lake water samples. The humic acid A, showed maximum fluorescence signal between 380 -480 nm, when excited with 260 nm wavelength. The sample that had the highest A peak was P3, followed by P2 and P1. At the opposite end, samples collected from the lakes inside the city had the lowest humic-like substances concentrations, with a minimum recorded for P9, P13 and P15.

The maximum fluorescence emission of the fulvic acid (C) was detected in the wavelength domain of 420 -480 nm, for excitation with 340 nm. The samples with the highest concentrations of fulvic acid were P8 and P2 and the lowest intensities were detected for samples P9, P13 -P15. The high concentration of humic substances found in sample collected from the external lakes can be correlated with the input from surface runoff, bringing into the lakes the impurities from the shores and probably also, with excess vegetation.

The M component displayed the highest fluorescence signal in the emission range of 380 -420nm, when excited with 310 nm wavelength. This maximum is associated with the recent production of humic substances and often appears as a small "shoulder" of the fulvic-like component. This was evidenced here by the fact that C and M peaks showed the same tendency (an increase of the C maximum lead to an increase of M, also). The highest contribution of the M peak was found in samples P8, P2 and P1, possibly due the fresh production of organic matter deriving from the decay of aquatic vegetation. Once more, sample P9 had the lowest concentration, followed by P15 and P13.

The protein-like fraction, represented by the amino acids tryptophan, T and tyrosine, B was excited with 280 nm and exhibited the greatest fluorescence signal between 300 -350 nm. The amino acids are indicators of the microbial activity within a water sample, the high fluorescence intensity of this fraction generally signifying bad water quality. Lakes P2 and P1 had the most intense protein-like signal, which can be explained by the household and industrial discharges being released into the waters. Samples P14 and P16 also had higher concentrations of proteinlike substances, probably related to the presence of restaurants and larger aquatic birds communities. From the acquired fluorescence spectra, several indices were calculated, in order to describe the nature of DOM in the chosen lake water samples. The humification index, HIX [START_REF] Zsolnay | Dissolved organic matter: artefacts, definitions, and functions[END_REF] classifies DOM as a function of the relative proportions of humified and bacterial material. The biological index, BIX [START_REF] Huguet | Properties of fluorescent dissolved organic matter in the Gironde Estuary[END_REF] indicates the biological activity of aquatic DOM. The f 450 /f 500 index [START_REF] Mcknight | Spectrofluorimetric characterization of dissolved organic matter for indication of precursor organic material and aromaticity[END_REF], is an indicator of the organic matter source in water systems, differentiating between microbially and the terrestrially-derived DOM.

5.0x10

The graphical representation of the fluorescence indices is given in figure 4. HIX values ranged from 0.59 to 2.48, while BIX values varied between 0.76 and 1.31. These are very small variations and not enough to separate the samples into different classes. Both indices indicated the predominance of autochthonous DOM of microbial origin. Unlike HIX and BIX, the f 450 /f 500 values obtained (below 1.4) indicated terrestrially-derived DOM, probably due to a high input of organic matter coming from the slopes. This confirms previous statements that f 450 /f 500 might not be very suitable for all types of water samples [START_REF] Huguet | Properties of fluorescent dissolved organic matter in the Gironde Estuary[END_REF]. The reason behind this seems to be that this index was created to describe the fulvic-like substances, and could not describe very accurately water samples in which DOM derives from a variety of sources and samples which could contain important quantities of non-humic substances.

The fact that HIX and BIX indicated generally a low contribution of humified material and a stronger, predominantly bacterial origin of DOM in lakes is not surprising. Lakes are not very ventilated systems; most of them have a flow of only 1-2 m/s, which favours an increased activity of the protein-like components of DOM. Also, most of these lakes are influenced by surface runoff, aquatic vegetation and birds and illegal waste waters dumping, which increase the microbial degradation of the water bodies. Another indicator of the lake water quality is the chlorophyll-a production. This is related to the eutrophication level of a lentic system, which can be influenced by antropic inputs (mainly waste water discharge) and surface runoff. The fluorescence signal of chlorophyll-a can be detected at 680 nm emission, when using an excitation wavelength of 420 nm. Figure 5 illustrates the fluorescence intensity of chlorophyll-a, for all 16 lakes analyzed. According to this graph, the most eutrophic lakes are P1, P3, P2, P4, P8 and P14. This was also suggested earlier by the high concentrations of humic-like substances found for these samples. Degradation of the water quality was observed for lakes which are close to individual residential areas (P1 -P8) as compared with lakes surrounded by green spaces or collective residential areas (P9 -P16). Generally, it could be noted that the external lakes (P1 -P8) had higher concentrations of dissolved organic matter, as opposed to the internal lakes. Sample P9, with the lowest DOM concentration was characterized by the smallest values of ammonia, COD and nitrates and also had the least degree of eutrophication. The strongest fluorescence signal, of all major fluorophores, was detected for the eutrophic lakes which are closest to the entrance to the city, P1, P2 and P3. Correlated with the facts that these lakes were characterized by high values of the chemical parameters (COD, nitrates, ammonia, dissolved oxygen) and that they were ascribed to the third general water quality (Official Monitor of Romania, 2006), it could be concluded that high concentrations of dissolved organic matter generally indicate a bad ecological status of the water body.

CONCLUSIONS

From the analysis of chemical and fluorescence data of water samples from Bucharest lakes, it was found that external lakes have worst ecological status than the internal lakes. This could be explained by the fact that these lakes are subjected to the negative influence of the individual residential areas in their proximity, not connected to the sewerage system, opposing the internal lakes, which are surrounded by parks and collective residential areas and which are arranged only for leisure activities. The obtained results are important because of the ever growing need to protect and conserve the natural resources, including urban lentic ecosystems. This task can be facilitated by the rapid, accurate assessment of the water quality of these systems. The fluorescence response of the lake water samples analyzed here revealed similar features as the standard chemical analysis, leading to the idea that fluorescence could be used as pre-analysis method for the rapid assessment of the ecological state of urban lentic systems.

Figure 1 :

 1 Figure 1: Map with sampling locations

Figure 2 :

 2 Figure 2: Standard chemical parameters of the lake water samples

Figure 3 :

 3 Figure 3: Standard chemical parameters of the lake water samples

  Variation of the fluorescence indices: a) the humification, b) the biological and c) the f 450 /f 500 index

Figure 5 :

 5 Figure 5: Chlorophyll -a levels in the urban lentic systems

TABLE 1 : Description of lakes' use and degradation sources

 1

	Lake	Use	Degradation sources
	P1	Fishing, recreation	Household discharges, industrial wastewaters, nutrients loading, pluvial waters, vegetation
	P2	Fishing, irrigation, flooding mitigation, recreation	Household discharges, industrial wastewaters, nutrients loading, petroleum products, pluvial waters, vegetation
	P3	Fishing, irrigation, flooding mitigation, recreation	Household discharges, industrial wastewaters, nutrients loading, petroleum products, pluvial waters, vegetation
	P4	Fishing, flooding, mitigation, recreation	Household discharges, nutrients loading, solid wastes, pluvial waters
	P5	Fishing, irrigation, flooding mitigation, recreation	Household discharges, industrial waste waters, solid wastes, nutrients loading, pluvial waters
	P6	Fishing, irrigation, flooding mitigation, recreation	Household discharges, industrial wastewaters, nutrients loading, pluvial waters
	P7	Fishing, irrigation, flooding mitigation, recreation	Household discharges, industrial wastewaters, nutrients loading, pluvial waters
	P8	Fishing, irrigation, flooding mitigation, recreation and industrial water supply source	Household discharges, industrial wastewaters, nutrients loading, pluvial waters
	P9	Fishing, recreation	Pluvial waters
	P10	Fishing, recreation	Household discharges, solid wastes and waste waters
	P11	Fishing, recreation	Pluvial waters, vegetation, sediments from lake bottom, aquatic birds
	P12	Fishing, recreation	Pluvial waters, vegetation
	P13	Recreation	Pluvial waters, vegetation
	P14	Fishing, recreation	Pluvial waters, vegetation, sediments from lake bottom, restaurants, aquatic birds
	P15	Fishing, recreation	Vegetation, aquatic birds, pluvial waters
	P16	Fishing, recreation	Sediments from lake bottom, vegetation, birds, restaurants, pluvial waters


Mathieu Cladière
email: mathieu.cladiere@leesu.enpc.fr

Johnny Gasperi

Catherine Lorgeoux

Bruno Tassin

Discharges of endocrine disrupting chemicals by combined sewer overflows into receiving water: case-study of the Paris conurbation

Keywords: Bisphenol A, nonylphenol, octylphenol, combined sewer, overflows

Alkylphenol ethoxylate (APEOs) and bisphenol A (BPA) are well known as endocrine disrupting compounds. Among sources of these compounds within receiving waters, wastewater treatment plant effluents have been widely studied. However, Although APEOs and BPA are regularly quantified within wastewater and to a lesser extent in runoff, few studies deal with their discharges by combined sewer overflows. In this context, this study was launched to investigate the concentrations and the mass loads discharged per year by CSO in the Seine River. Therefore, discharges occurring at the one of the most important CSOs of Paris conurbation from June to November 2010 were sampled. During this period, eight events were collected by automatic samplers and even mean sample were analyzed in laboratory using liquid chromatography coupled to a tandem mass spectrometry. The first results highlight an important contamination of CSOs by BPA and levels of APEOs close to those reported in wastewaters. At the annually scale and according to our mass load calculation, CSOs do not appear as a relevant source of BPA and APEOs within the Seine River.

INTRODUCTION

During the last two decades, alkylphenol ethoxylates (APEOs), mainly composed of nonylphenol ethoxylates (NPEOs, 80%) and octylphenol ethoxylates (OPEOs, 20%), were regularly pointed out by the literature. APEOs are of concern because their biodegradation products, 4nonylphenol (4-NP) and 4-tert-octylphenol (4-t-OP) have endocrine disrupting properties and can also affect aquatic wildlife (Brian et al. 2007). APEOs are used in a large amount of industrial, domestic and commercial applications such as detergents, lubricating agents or oil additives. Similarly, bisphenol A (BPA), recognized as endocrine disrupter (Wetherill et al. 2007), is mainly used as a monomer in the manufacture of polycarbonate plastics or epoxy resins. Owing to these different uses, the annual consumption of APEOs were evaluated about 500,000 tons per year in 2002 (Ying et al. 2002), and about 450,000 tons per year for BPA according to Vandenberg et al. (2007). Due to their endocrine disrupting properties, occurrence and behaviour of these pollutants within wastewater treatment plants (WWTP) and surface water are well documented (Ahel et al. 1994;Cailleaud et al. 2007;Giger et al. 2009).

Many old capital cities as Paris (London, New York city, Washington) are drained by combined sewer systems. During wet weather, wastewater and city runoff are combined and transferred to WWTP. However, during huge storm events, combined sewer flows could be higher than treatment flow capacity of WWTP and lead to combined sewer overflows (CSOs). As a result, combined wastewater and runoff are directly discharged, generally without any treatment, into surface waters. To the best of our knowledge CSOs are known as an important source of pollutants into surface waters (Gasperi et al. 2010) and more especially for pollutants highly removed by WWTP such as APEOs and BPA (Weyrauch et al. 2010). Unfortunately, even if pollutants are regularly detected in wastewater and runoff water (Jackson and Sutton 2008;Björklund et al. 2009), few studies deal with concentrations and loads of these pollutants within CSOs and impact of these events on surface water quality (Gasperi et al. 2008;Musolff et al. 2010). To fulfill this lack, the present study, supported by the OPUR research program, focuses on concentrations and mass loads discharged by CSOs in the Seine River at one of the most important combined sewer outfall of Paris conurbation sited in Clichy. On a second step, the total mass loads discharged during small, medium or high CSO events were compared to the total daily loads of the major WWTP of Paris conurbation (account for 80% of treated water released into the river) and the daily loads exported by the river. Finally, annual loads of APEOs and BPA discharged during CSOs were estimated and then compared to annual loads of these pollutants exported by the Seine River to the downstream part of its basin.

MATERIAL & METHODS

Site characterization and sampling procedure

In order to study concentrations of pollutants within CSOs, 8 events were collected at Clichy outfall, sited downstream of Paris city (Figure 1) from June to November 2010. The volume discharged profile for these eight events are shown in Figure 1, and the main characteristics such as total volume discharged (m 3 ), conductivity (µS.cm -1 ) and the wastewater proportion based on the conductivity measurement are reported in Table 1. Samples were collected by an automatic sampler linked to the trigger mechanism of the outfall pump, at fixed time step (five minutes) during a total sampling period of three hours. The automatic sampler was outfitted with twelve 1L glass bottles (fifteen minutes to fill one bottle). A manual mixing of the bottles proportionally to the flow volume was then performed to constitute a flow-weighted mean sample representative of the whole rain event. The total volume discharged, at Clichy outfall, during the eight CSO events sampled ranged from 34,596 m 3 on the 6 th June to more than 1,000,000 m 3 on the 14 th July 2010 (Table 1). The distribution of volumes discharged during these eight sampled events is in accordance with the distribution of volume discharged at Clichy outfall from the five last years. Indeed, during the five past years, 68% of CSO events were smaller than 150,000 m 3 discharged, 26% were between 150,000 and 500,000 m 3 and only 5% of events were higher than 500,000 m 3 of combined water released into receiving water.

Paris 10 km

Combined sewer outlfalls

Seine

Marne

N

Seine

Clichy Paris

km

Combined sewer outlfalls

Seine

Marne

N

Seine

Clichy Paris

km

Combined sewer outlfalls

Assuming that the conductivity of wastewater is close to 1,000 µS.cm -1 and runoff conductivity between 100 -200 µS.cm -1 , High and low hypotheses on wastewater proportion were determined according to the conductivity of each flow-weighted water sample. Thus, the proportion of wastewater to CSOs ranged from 6-11% on the 14 th July to 35-39% on the 8 th November 2010 (Table 1). For the eight sampled CSOs the proportion of wastewater is fairly well negatively correlated to total volume discharged (R² = 0.72). The higher the total volume discharged, the smaller the proportion of wastewater into combined sewer water.

Dissolved phase extraction

Flow-weighted mean samples were filtered through a 0.45 µm porosity glass filter, in order to separate dissolved and particulate phases. After filtration, 100 ml of dissolved phase was spiked with 50 µl of an internal standards mixture (BPA-d6; n-OP-d17 and NP 1 EO-d2) for extraction follow-up and stored overnight at 4 °C to reach an equilibrium state. The extraction was performed on an Autotrace SPE Workstation (Caliper LifeScience) using an Oasis HLB (200 mg, 6 ml) cartridges. Firstly, the cartridges were conditioned with 10 ml of methanol and 10 ml of ultrapure water, and then samples were extracted at 5ml.min -1 and neutral pH. After drying the cartridges under nitrogen stream during 35 minutes, elutions were performed with 12 ml of a mixture methanol/dichloromethane/ethylacetate (40:40:20, v/v). As method development of particulate extraction is not yet completed, results of this work will only focus on dissolved phase Pollutant analysis

LC-MS-MS conditions

Additionally to BPA, nonylphenol mono and diethoxylate (NP 1&2 EO), octylphenol mono and diethoxylates (OP 1&2 EO), 4-NP, 4-t-OP and the nonylphenoxy acetic acid (NP 1 EC), resulting from aerobic biodegradation of APEOs, were analyzed (Table 2). Before analysis, extracts are spiked with internal standard for quantification (BPA-d16, n-NP, n-NP 1 EO and n-NP 2 EC). The analysis is performed by liquid chromatography coupled to a tandem mass spectrometry, LC-MS-MS (AQUITY UPLC / TQD, Waters). APEOs and BPA are separated on an AQUITY UPLC / BEH C 18 column, heated at 40 °C, with ultrapure water containing 4.5 mM NH 4 OH (A) and methanol containing 4.5 mM NH 4 OH (B) as mobile phase. Equilibration takes place with 50 % B at 0.4 ml.min -1 and 10 µl are injected. The mass spectrometer is outfitted with an electrospray interface used in positive ionization mode (ESI+) for NP 1-2 EO and OP 1-2 EO and negative ionization mode (ESI-) for all other compounds. All compounds were detected in multiple reactions monitoring mode (MRM) with two mass transitions, for quantification and qualification. Cone voltage and collision energy were optimized for all compounds (Table 1).

Quantification and quality control

The quantification was performed using internal calibration based on areas relative to the internal standards. Internal standard n-NP was used for the quantification of NP, OP and n-OP-d17. Similarly, BPA-d16 was used for BPA and BPA-d6, n-NP 1 EO for OP 1 EO, OP 2 EO, NP 1 EO, NP 2 EO and n-NP 1 EO-d2 and n-NP 2 EC for NP 1 EC. For each compound, calibration curves were drawn and satisfactory determination coefficients were obtained (R² > 0.99). Experimental blanks for SPE extractions, as well as mobile phase blanks were processed. No quantifiable contamination was observed. Finally, during a sequence, two calibration controls (lower and higher concentrations) were injected every 10 samples. A deviation between the control and the calibration curve lower than 20 % validates the quantification.

RESULTS AND DISCUSSION

Combined sewer overflow quality

Flow-weighted mean concentrations of APEOs and BPA are reported in Table 3. CSOs are featured by the predominance of BPA with concentrations ranging from 878 to 1,849 ng.l -1 (median being 1,272 ng.l -1 ). The high concentrations of BPA in CSOs can be partially explained by high levels reported in wastewater (Hohne and Puttmann 2008). However, since no clear relation can be drawn between BPA concentrations and the wastewater proportion, contributions of other sources have also to be considered (sewer deposit erosion and runoff) (Gasperi et al. 2010). Considering that BPA is the main component of polycarbonate plastics widely used in building materials because of its properties and its high resistance (Kang et al. 2006), high level of BPA could be expected in runoff linked to the leaching of building materials. This hypothesis has to be confirmed since, currently, no study deals with occurrence of BPA in runoff.

For APEOs, total concentrations vary between 886 and 3,843 ng.l -1 , median being 1,305 ng.l -1 (Table 3). NPEOs are predominant (from 765 to 3,686 ng.l -1 ) and are approximately ten times more concentrated than OPEOs (from 73 to 176 ng.l -1 ). As for BPA, NPEOs and OPEOs concentrations are not correlated to proportion of wastewater meaning that other sources of contamination have to be considered. Among these sources, runoff can be probably considered as an important source since Bressy et al. ( 2011) reported high levels of 4-NP and 4-t-OP in runoff (470 and 38 ng.l -1 respectively). According to the authors, these high levels may results from building and road leaching.

Comparison of the CSO discharges to the daily WWTP and Seine River loads

This section aims to compare the CSO discharges at the scale of the rain events to the daily WWTP pollutant loads (Figure 2A), as well as, to the daily pollutants loads of the Seine River during dry weather periods (Figure 2B). The pollutant loads discharged by CSOs were calculated based on CSO quality at Clichy outfall and total volume discharged during each event. Events can be classified as three categories, less than 300,000 m 3 , between 300,000 and 1,000,000 m 3 and more than 1,000,000 m 3 of combined water discharged per event. x < 300,000 300,000 < x < 1,000,000 1,000,000 < x

CSO loads/ Exported loads

x : total volume discharged (m 3 ) per event BPA loads discharged during small events, which are the most frequent in Paris conurbation, account for 184% of WWTP loads. Medium and high events could represent from 4 to more than 14 fold the total WWTP daily loads. These results highlight the importance of these kinds of event on total loads released into surface water, especially for highly removed pollutants (Weyrauch et al. 2010). During wet weather, BPA loads released by CSOs during small and medium events account respectively for 18 and 38% of dry weather exported loads by the Seine River, while high events represent more than 100% of these same exported loads. Thereby, small and medium events could have a moderate impact on surface water loads, and high events may have a major impact on BPA loads exported by the Seine River during wet weather period.

For APEOs, the loads discharged by CSOs do not exceed 45% of WWTP loads even for high events, meaning that CSOs are not the main sources of APEOs during wet weather (Figure 2B). Moreover, along very high event, as 14 th July 2010 which is the most important CSO event of the five past years, APEO loads represent less than 30% of exported loads by the Seine River. Smaller events are even less important. Medium and small events only account respectively for 14% and less than 5% of exported loads. These results clearly reveal that CSOs are not important point sources of APEOs, these events may have only low impact on receiving surface water quality

Annual loads discharged into receiving water

Assuming that results found for Clichy outfall is representative of all CSOs of Paris conurbation, the median annual load discharged into receiving water by all CSO outfalls, at the scale of Paris conurbation, was determined (Table 4). Therefore, data about volume discharged from 2005 to 2010 were provided by the Interdepartmental Association for sewage Disposal in the Paris conurbation (SIAAP) and the Paris municipality. Table 4 reported the CSO annual loads of BPA and APEOs (kg.y -1 ) and compared them to the Seine River loads. For the Seine River pollutant loads, data were calculated according to twelve sampling campaigns performed during dry weather period on 2010.

Annually and according to our calculation, about 22.8 kg.y -1 of APEOS and 17 kg.y -1 BPA are discharged in the Seine River by CSOs (Table 4). Despite the high contamination of CSOs by BPA and APEOs, the contributions of these events to exported loads are rather low. Indeed, BPA discharged annually by CSOs only account for 3.7% of exported loads, while APEOs contributions do not exceed 1.3% for 4-NP. These low contributions of CSO to BPA and APEOs exported loads are probably a consequence of the small annual volume discharged by CSOs compared to annual water flow of the Seine River (only 0.2%). -: no annual loads for the Seine River because of concentrations were regularly below quantification limit.

Finally, the annual loads released by WWTP into the Seine River were also estimated (Table 4).

As reported in Table 4, the contributions of WWTP to exported loads by the Seine River are higher than contributions of CSOs. As APEOs studied are biodegradation products of alkylphenol polyethoxylates, processes occurring along WWTPs are sources of these compounds, especially for NP 1 EC (González et al. 2007). Indeed, while CSOs loads of OP 2 EO, NP 1 EC and NP 1 EO account respectively for 0.8%, 0.4% and 1.0% of exported loads, the annual loads released by WWTPs could explained the entire exported loads by the Seine River. Contrary, as BPA is highly biodegradable, annual loads of WWTP effluents are not much higher than CSO loads, 7.1% for WWTP effluents against 3.7% for CSOs. At last, the sum of CSOs and WWTP effluents loads for BPA, 4-t-OP and 4-NP respectively account for 11%, 29% and 34% of exported loads, highlighting the existence of non urban sources. To the best of our knowledge, no clear comprehension of all pathways of introduction for these pollutants does exist. However, agricultural drain water and groundwater are pointed out by the literature as potential non-urban sources for APEOs and BPA (Zgola-Grzeskowiak et al. 2009;Musolff et al. 2010).

CONCLUSIONS

As a conclusion, at the scale of a year, CSOs are not relevant sources of BPA and APEOs because of the low and discontinuous volumes discharged (0.2% of Seine River volume). Results have to be confirmed by integrating result on particulate fraction and by evaluating total mass loads. As distributions of APEOs and BPA between dissolved and particulate phases are link to the type of water, the influence of the particulate phase should not be the same for combined water and Seine river water.

However, CSO events could be considered as point sources of pollutants, during wet weather, more especially for pollutants highly removed by WWTP such as BPA. In order to improve our understanding of impacts of CSOs on surface water quality, sampling campaigns should be performed on the Seine River from the upstream of CSO outfalls to the outlet of Paris conurbation. These campaigns should enable us to follow the CSO pollution plumes into surface water, on the one hand, and evaluate the proportion of CSO loads on exported loads by the Seine River under wet weather conditions, on the other hand.

ACKNOWLEDGMENT

The authors would thank the Interdepartmental Association for sewage Disposal in the Paris conurbation (SIAAP) for the accessibility of their CSO outfall sited in Clichy. The authors also thank the Paris Municipality and the SIAAP who provided data on the volumes discharged during each events.

• Ahel, M., W. Giger and M. Koch (1994) Jonkers, A. Marcomini and J. P. Sumpter (2007). Evidence of estrogenic mixture effects on the reproductive performance of fish. Environmental Science & Technology, 41, pp. 337-344.

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Seasonal variation of hydrophobic organic contaminant concentrations in the water-column of the Seine Estuary and their transfer to a planktonic species Eurytemora affinis (Calanoïd, copepod). Part 2: Alkylphenol-polyethoxylates. Chemosphere, 70, pp. 281-287.

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• Gasperi, J., M. C. Gromaire, M. Kafi, R. Moilleron and G. Chebbo (2010) • González, S., M. Petrovic and D. Barceló (2007). Removal of a broad range of surfactants from municipal wastewater -Comparison between membrane bioreactor and conventional activated sludge treatment. Chemosphere, 67, pp. 335-343. • Hohne, C. and W. Puttmann (2008) Determination of nonylphenol and short-chained nonylphenol ethoxylates in drain water from an agricultural area. Chemosphere, 75, pp. 513-518. 12-WWW-YES-2011-Cladiere-Paper-2011_04_04_19.doc

FIGURE 2 :

 2 FIGURE 2: Comparison between loads (g.d -1 ) discharged during CSO event and A: WWTP daily loads; B: daily exported loads by the Seine River

  . Behaviour of alkylphenol polyethoxylate surfactants in the aquatic environment--I. Occurrence and transformation in sewage treatment. Water Research, 28, pp. 1131-1142. • Björklund, K., A. P. Cousins, A.-M. Strömvall and P.-A. Malmqvist (2009). Phthalates and nonylphenols in urban runoff: Occurrence, distribution and area emission factors. Science of The Total Environment, 407, pp. 4665-4672. • Bressy, A., M. C. Gromaire, C. Lorgeoux and G. Chebbo (2011). Alkylphenol in atmospheric depositions and urban runoff Water Science and Technology, 63, pp. 671-679. • Brian, J. V., C. A. Harris, M. Scholze, A. Kortenkamp, P. Booy, M. Lamoree, G. Pojana, N.

  Occurrence and temporal variations of the xenoestrogens bisphenol A, 4-tert-octylphenol, and tech. 4-nonylphenol in two German wastewater treatment plants. Environmental Science and Pollution Research, 15, pp. 405-416. • Jackson, J. and R. Sutton (2008). Sources of endocrine-disrupting chemicals in urban wastewater, Oakland, CA. Science of The Total Environment, 405, pp. 153-160. • Kang, J.-H., F. Kondo and Y. Katayama (2006). Human exposure to bisphenol A. Toxicology, 226, pp. 79-89. • Musolff, A., S. Leschik, F. Reinstorf, G. Strauch and M. Schirmer (2010). Micropollutant Loads in the Urban Water Cycle. Environmental Science & Technology, 44, pp. 4877-4883. • Vandenberg, L. N., R. Hauser, M. Marcus, N. Olea and W. V. Welshons (2007). Human exposure to bisphenol A (BPA). Reproductive Toxicology, 24, pp. 139-177. • Wetherill, Y. B., B. T. Akingbemi, J. Kanno, J. A. McLachlan, A. Nadal, C. Sonnenschein, C. S. Watson, R. T. Zoeller and S. M. Belcher (2007). In vitro molecular mechanisms of bisphenol A action. Reproductive Toxicology, 24, pp. 178-198. • Weyrauch, P., A. Matzinger, E. Pawlowsky-Reusing, S. Plume, D. von Seggern, B. Heinzmann, K. Schroeder and P. Rouault (2010). Contribution of combined sewer overflows to trace contaminant loads in urban streams. Water Research, 44, pp. 4451-4462. • Ying, G.-G., B. Williams and R. Kookana (2002). Environmental fate of alkylphenols and alkylphenol ethoxylates--a review. Environment International, 28, pp. 215-226. • Zgola-Grzeskowiak, A., T. Grzeskowiak, R. Rydlichowski and Z. Lukaszewski (2009).

Seine Marne N Seine Clichy

	30 000
	25 000
	20 000
	15 000
	10 000
	5 000
	0
	00:00	01:12	02:24	03:36	04:48	06:00	07:12
			duration

of CSO (hh:mm) Volume discharged (m 3 /5min)

	06/06/2010
	12/07/2010
	14/07/2010
	08/09/2010
	24/09/2010
	26/09/2010
	08/11/2010
	09/11/2010
	FIGURE 1:

Sampling site and profile of CSO events sampled

Table 1 : Main characteristics for the eight CSO events sampled

 1

	Dates	06/06	12/07	14/07	08/09	24/09	26/09	08/11	09/11
	Volume (m 3 )	34,600	426,400	1,001,300	38,000	279,300	144,000	42,000	285,900
	Conductivity (µS.cm -1 )	449	284	201	380	260	346	451	374
	% wastewater	35 -39	16 -21	6 -11	27 -31	13 -18	23 -27	35 -39	26 -30

TABLE 2 : compounds analyzed and optimized parameters for LC-MS-MS analysis

 2

	Compound	M (g.mol -1 )	ESI Mode	Retention time	(min)	Quantification Transition (m/z) Collision	energy	(eV)	Qualification Transition (m/z) Collision	energy	(eV)	Cone voltage	(V)
	BPA	228	ESI-	1.82	226.9 → 133.0	25		226.9 → 212.2	25		30
	4-t-OP	206	ESI-	3.25	205.5 → 134.2	17		205.2 → 133.2	30		45
	OP 1 EO	250	ESI+	3.34	268.2 → 113.4	10		268.2 → 139.2	12		20
	OP 2 EO	294	ESI+	3.38	312.3 → 183.3	10		312.3 → 121.2	18		20
	4-NP	220	ESI-	3.52	219.2 → 147.2	26		219.2 → 133.2	26		40
	NP 1 EC	278	ESI-	2,47	277.2 → 219.2	18		277,2 → 133	38		35
	NP 1 EO	264	ESI+	3.58	282.4 → 127.3	8		282.4 → 85.4	15		20
	NP 2 EO	308	ESI+	3.61	326.4 → 183.3	10		326.4 → 71.2	20		40

TABLE 3 : Concentrations (ng.l -1 ) of BPA and APEOs for the eight CSO events sampled

 3

	Dates	06/06	12/07	14/07	08/09	24/09	26/09	08/11	09/11	Median
	BPA	1,644	1,705	938	1,849	1,497	1,041	878	1,047	1,272
	4-t-OP	61	88	64	117	71	38	45	63	63
	OP 1 EO	66	56	44	138	68	21	117	8	61
	OP 2 EO	13	14	14	24	17	14	14	13	14
	4-NP	272	346	281	703	3,083	398	330	478	372
	NP 1 EC	344	335	221	572	207	245	214	232	238
	NP 1 EO	434	252	102	694	238	331	503	240	282
	NP 2 EO	91	81	160	232	158	304	230	89	159
	Sum APEOs	1,280	1,172	886	2,482	3,843	1,331	1,452	1,123	1,305

TABLE 4 : annual loads discharged into receiving surface water (kg.y -1 )

 4

		Σ Paris outfalls	Σ WWTP effluents	Seine River	% Σ Paris outfalls	% Σ WWTP effluents
	Volume (m 3 .y -1 )	14,443,482	772,705,000	9,486,374,400	0.2	8.1
	BPA	17.3	33	468	3.7	7.1
	4-t-OP	0.9	28	101	0.9	27.6
	OP 1 EO	0.9	-	-	-	-
	OP 2 EO	0.2	33	29	0.8	115.4
	4-NP	9.8	251	777	1.3	32.3
	NP 1 EC	4.0	923	1,007	0.4	91.7
	NP 1 EO	4.4	344	469	1.0	76.6
	NP 2 EO	2.9	501	449	0.5	106.8
	Sum APEOs	22.8	2,080	2,831	0.8	73.5

  . Contributions of wastewater, runoff and sewer deposit erosion to wet weather pollutant loads in combined sewer systems. Water Research, 44, pp. 5875-5886. • Giger, W., F. d. r. L. P. Gabriel, N. Jonkers, F. E. Wettstein and H.-P. E. Kohler (2009). Environmental fate of phenolic endocrine disruptors: field and laboratory studies. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 367, pp. 3941-3963.


Elizabeth Oluseyi

Abimbola Ewemoje

Oluseyi E Ewemoje

Abimbola Y Sangodoyin

Developing a Pilot Scale Horizontal Sub Surface Flow Constructed Wetlands for Phytoremediation of Primary Lagoon Effluents

Keywords: Constructed wetlands, Wastewater effluents, Treatment, Developing countries

HAL is

INTRODUCTION

Exploitation of natural resources to ensure comfort and well being under an illusion that the demand for the natural resources could never exceed supply has led to depletion of natural resources with little regard for conservation and its sustainability. The generation of liquids and solids wastes as a result of human settlement and industrial activities pollute most of the watercourses (Abdel-Halim et al., 2008). It is noted that the quantity of wastewater will increase along with population growth. The increasing scarcity of water in the world along with rapid urbanization calls for concern and the need for appropriate water management practices.

Untreated or partially treated wastewater release is harmful to the environment; hence, restrictions should be imposed on wastewater discharge to protect the environment (Katayon et al., 2008). Very little investment has been made in the past on sewage treatment facilities. Water supply and treatment often received more attention and priority than wastewater collection and treatment (Abdel-Halim et al., 2008). However, due to trends in urban development wastewater deserves greater emphasis. Currently, there is a growing awareness of the impact of sewage contamination on rivers and lakes. The United Nations Environmental Programme (UNEP), World Health Organization (WHO) and Global Environmental Monitoring Systems found organic material from Agro-industrial effluent municipal waste and domestic sewage to be the most common water pollutant (Adelegan, 2007). It was observed that about two-thirds of the populations in developing countries have no hygienic means of disposing excreta and even greater number lack adequate means of disposing total wastewater. Inadequate sanitation is one of the prime causes of disease. Also, the provision of sanitation is not keeping up with population growth (Abdel-Halim et al., 2008).

Constructed wetlands are artificial wastewater treatment systems consisting of shallow (usually less than 1m deep) ponds or channels which have been planted with aquatic plants. The systems rely upon aerobic bacteria, biological, physical and chemical processes to treat wastewater (Akratos and Tsihrintzis, 2007). These constructed wetlands have impervious clay or synthetic liners, and engineered structures to control flow direction, liquid detention time and water level. Depending on the type of system, they may or may not contain an inert porous media such as rock, gravel, or sand. The subsurface flow (SSF) consists of a basin or channel with a barrier to prevent seepage, but the bed contains a suitable depth of porous media. Rock and gravel are the most commonly used media. The media also support the root structure of the emergent vegetation (Vymazal, 2010).

The uses of constructed wetlands are alternative to conventional activated sludge wastewater treatment methods which are often used to improve facultative lagoon effluents. The benefits include, low cost associated with maintenance, operation and energy requirements and overall decrease of risk posed to the environment and public health by discharge of contaminated wastewater (Katsenovich et al., 2009). Constructed wetlands treatment facilities confers significant benefits to agricultural efforts, in particular to the growth of non-food crops, because many essential nutrients and minerals found in wastewater considerably reduce the need for expensive chemical fertilizers. The performance of constructed wetland facilities under tropical conditions has not been extensively researched in previous studies (Katsenovich et al., 2009). In spite of the assumption that the performance of constructed wetland processes are more efficient in equatorial regions than those in temperate regions, plant growth and microbiological activity throughout the year round are encouraged by warmer weather with positive effect on treatment parameters (Bojcevska and Tonderski, 2007).

Constructed wetlands are complex systems with large number of active physical, chemical, and biological processes that mutually influence each other. Therefore constructed wetlands have been often considered as "black boxes" and only little effort has been made to understand the main processes leading to wastewater purification (Brix and Johansen, 1999). The design of constructed wetlands has been carried out with different models, among which are; rules of thumb and regression equation, the well known first-order K-C* model, monod-type equations and a complex dynamic compartmental model. The constraints and parameter uncertainty of each model was reported by Rousseau et al., (2004). However, many parameters are difficult to measure and therefore many assumptions must be made. Hence it is important, to realize that more complex models do not necessarily bring more precise design parameters. However, no matter which design model is used for municipal sewage, the area of horizontal flow constructed wetlands is usually about 5m 2 PE -1 (Vymazal and Kropfelova, 2008). To achieve the outflow BOD 5 and TSS concentration of 30mg/l, the U.S. EPA recommends the respective in flow loads of 6g/m 2 d and 20g/m 2 d (Vymazal, 2010).

Horizontal subsurface flow constructed wetlands have been designed using either simple "rule of thumb" set at 5m 2 PE -1 or plug-flow first order models (Kadlec et al., 2008). Recently, more complex dynamic, compartmental models (Langergraber et al; 2009) have been developed. Sizing of horizontal subsurface flow constructed wetlands is usually based either on volume or area. Volume-based methods use a hydraulic retention time to assess the pollutant removal while area-based method wetlands assess pollutant reduction using the overall or total wetlands area necessary to remove BOD 5 , TSS, Phosphorus, Nitrogen, Organic nutrients and pathogens (Katsenovich et al., 2009).

Problem Statement: Conventional high-technology wastewater treatment system are in many situations not a suitable solution in developing countries because it is not sustainable to install wastewater treatment facilities which require guaranteed power supply, replaceable spare parts and a skilled labour for operation and maintenance (Konnerup et al., 2009). Another issue is treatment requirement. In developed countries, the goal is elimination of all pollutants like pathogens, nutrients, organic and inorganic chemicals. Whereas, the primary treatments aim in developing countries is protection of the public health through control of pathogens to prevent transmission of water borne diseases (Kivaisi, 2001). For this purpose constructed wastewater systems are suitable since they can be efficient in removal of BOD 5 , pathogens and nutrients (Konnerup et al., 2009). Despite the recognition of constructed wetlands technology as an excellent alternative for conventional wastewater treatment systems, not much work has been done to determine its applicability in humid tropical environment.

Hence, this study aims at developing a pilot scale horizontal subsurface flow constructed wetlands system for treatment of primary lagoon effluent (sewage) located opposite Obafemi Awolowo Hall, University of Ibadan (Figure 1). The project also evaluates the effectiveness of three aquatic tropical plants (Canna Indica, R. Phragmites australis and Sacciolepis africana), varied hydraulic retention time and hydraulic loading rate on the strength of the final effluent. The specific objectives were to design, construct and conduct operational testing of horizontal subsurface flow treatment wetlands over a period of two years with the use of three different aquatic tropical plants in treatment of primary lagoon effluents. Also, the study sets to investigate the effects of varying hydraulic retention time (HRT) and varying Hydraulic loading rate (HLR) in mass removal rate of BOD 5, COD, TSS, TN, NH 4 -N, TP, and FC in gravel based subsurface flow treatment wetlands. Furthermore, seasonal effects on the treatment efficiencies of the constructed subsurface flow treatment wetlands will be analyzed. Experimental site will be located within the University of Ibadan, Nigeria. Ibadan is in the south western part of Nigeria with a tropical climate of variable rainy and dry seasons. The city is situated in the forest zone close to the boundary between the forest and the savannah. Ibadan lies roughly between latitude 07 0 29' 16N and longitude 03 0 54' 44E, at an altitude of about 213.4m above mean sea level (Eze, 1997). It has a humid equatorial climate with warm temperatures, high humidity and rainfall with peak dry and wet seasons around February to April and June to August respectively. Annual rainfall for Ibadan is between 1000-1600mm, with the mean around 1270mm (Lal, 1993). Approximately, 50% of the average annual rainfall occurs between April and July while 40% occur between August and October. November to March is usually the driest months and temperature tends to be higher.

METHODOLOGY

Experimental set up would consist of three vegetated cells and one non-vegetated cell to serve as a control experiment. The cells would be replicated; each bed will be X meters long, Y meters wide and Z meters deep. The exact size of matrix of the subsurface wetlands to be constructed depends on the influent Biological oxygen demand (BOD 5 ), Total suspended solids (TSS) and Nitrate (N0 3 -) concentrations of the wastewater according to Metcalf andEddy (2004), Katayon et al., (2008). The treatment area would be packed with 5-10mm diameter pea gravel while bigger and larger gravel of 20-50mm diameter will be used at the inlet and outlet areas in order to prevent clogging of the filter media. The cells will be coated with anti-rust paint and lined with water resistant material such as a low-density polyethylene sheet. The constructed wetlands cells would have bottom slope of 0.5-1.0% to facilitate hydraulic head measurement.

Surge tank of 1000 litres capacity will receive wastewater while two settling tanks of 500 litres capacities each would be connected to surge tank. A 2Hp pump will be connected to the settling tank which would pump wastewater to an over head storage tank of 1000 litres capacity. The arrangement of the inlet and outlet pipes and distribution of wastewater within the cell would be similar to previous studies (Ghosh and Gopal, 2010;Konnerup et al, 2009). The young sprouts of the three plants to be used would be planted equidistantly at 20cm interval in all the treatment cells. The plants shall be allowed to grow and multiply until dense stand are formed in the cells over four month period. There will be a periodic application of wastewater to serve as a source of nutrients for the plants, before selected inflow rates of wastewaters is introduced.

Operational procedure: The primary lagoon effluents would be piped into the cells and flows through. The elimination processes takes place during this passage. They are based on various complex physical, chemical and biological processes within the association of substrate, macrophytes and microorganisms: settling of suspended particulate matter, filtration and chemical precipitation through contact of the water with the substrate, chemical transformation, adsorption and ion exchange on the surface of plants, substrate, sediment and litter breakdown, transformation and uptake of pollutants and nutrients by microorganisms and plants, and natural die -off of pathogens. To evaluate the effect of HRTs on treatment efficiency, each of the cells will be operated with different HRT. The flow pumped to each treatment cell would be calculated by taking into account the stated theoretical HRT, porosity and area.

Sampling: Sampling shall be done twice a month for duration of 2-years. Samples shall be transported immediately from point of collection to laboratory for analysis. Samples shall be measured for pH, Temperature, total Suspended Solids (TSS), Biological oxygen demand (BOD 5 ), Chemical Oxygen Demand (COD), Total Phosphorus (TP), Total Amnonia Nitrogen (NH 4 + ), Nitrate (NO 3 -) and Total coliforms; following the procedure of APHA (1999).

Data Analysis: SPSS software shall be used for the analysis, using one way Analysis of Variance (ANOVA) and post hoc test after ANOVA.

Preliminary Results

The Design: Constructed treatment wetlands modeling consists of first-order equations which in case of constant conditions (e.g. influent, flow and concentrations) and an ideal plug-flow behavior predict an exponential profile between inlet and outlet (Rousseau, et al., 2004). Because of complex web of interactions in a constructed treatment wetland leading to parameter uncertainty and some unexplainable assumptions in design, this study applied the "rule of thumb". Though it is a conservative design model, easily applicable and can guarantee good quality effluents, it tends to increase the investment costs.

The preliminary study on the primary lagoon effluents by Ewemoje and Sangodoyin (2009), showed the following physico-chemical and microbiological parameters (Table 1) of treated sewage wastewater. The preliminary results which will serve as the influent into the constructed wetland are used in the horizontal subsurface flow wetland systems design. Where; A h is surface flow of bed (m 2 ); Q d is average flow (m 3 d -1 ); C in is influent BOD 5 (mg l -1 ); C out is effluent BOD 5 (mg L -1 ); and K BOD is the rate constant (md -1 ).

The K BOD value is usually lower, ranges between (0.07-0.1m d -1 ) but according to Vymazal (2008) many countries used values around 0.08m d -1 .

Size Calculations: To determine the Population Equivalent(P.E.) for each cell based on typical unit organic loading 45g /P.E./day and this varies from 0.13 -0.44 P.E. depending on Hydraulic Retention Time (HRT). From equation (i);

Figure 1 :

 1 Figure 1: Anaerobic Lagoon for Sewage Treatment.

  h = 5.08m 2 PE -1 11th WWW YES, Arcueil 6 -10 June 2011 Urban waters: resource or risks?

Table1: Characteristics of the Primary Lagoon Effluents

  All parameters in mg/l except where stated Having considered all the different models for design of constructed wetlands, this study base its design on the following equation first proposed by Kickuth, and is widely used for sizing of horizontal subsurface flow wetlands systems for domestic sewage treatment.(Vymazal, 2008)

	Parameter										Effluent Ranges	FEPA Limit
	COD												420 -450	80
	BOD 5												245 -287	30
	Total Solid										3050 -3165	-
	Total Dissolve Solid						1050 -1160	2000
	Suspended Solid							1997 -2005	20
	Turbidity ((NTU)							95 -193	-
	Total Coliform Count (cfu/100ml)		2.2 -3.3	500
	Ammonia										200 -215	-
	Nitrate												103.5 -110	20
	h A	=	d Q	(	InC	in	-	InC	out	)	/	K	BOD	…	(i)

11th WWW YES, Arcueil 6 -10 June 2011 Urban waters: resource or risks?

However this sizing is suitable for BOD 5 and suspended solids removal but not appropriate for removal of nitrogen and phosphorus. The aspect ratio (Length: width) also changed over the years, while the early system used to have long and narrow trenches with aspect ratio (length: width) > 1. Based on this, a length to width ratio of 3:1 will be used in the design. Therefore the surface area of each cell given by Fowler ( 2003) is:

Substituting values gave 5.08 = 3W 2 Therefore W = (5.08/3) 0.5 = 1.30m Hence, L = 3 x 1.30 = 3.9m However, the width currently being used according to Vymazal (2008), is less than 1. Hence a W value of 0.75m is chosen, for ease of construction, considering that each cell will have a surface area of 2.25m 2 for effective BOD 5 removal (Katsenovich, et al., 2009). Therefore to have a length to width ratio of 3:1, the actual length of constructed wetland will be 3.0m to minimize cost of construction and maintenance of the wetlands without undermining its treatment efficiency.

Thus actual area of wetland designed is 2.25m 2 (i.e. 0.75 x 3.0m 2 )

CONCLUSIONS

This is an ongoing first year PhD research work and design considerations with wetlands treatment bed size matrix which is one of the set out objectives has been achieved. However, at the end of this research work it is expected that the designed and constructed treatment wetland would be used in treating primary lagoon effluent with three different aquatic tropical plants. Also, the effects of varying hydraulic retention time (HRT) and varying Hydraulic Loading Rate (HLR) would be investigated. Furthermore, mass removal rates of BOD 5 , COD, TSS, TN, NH 4, NO 3 , TP and FC in gravel based subsurface flow treatment wetlands effluents would have been studied while seasonal effects on treatment efficiencies of the constructed subsurface flow treatment wetlands effluents in tropical environment over a period of two years would be determined.

• ABDEL-HALIM W., Weichgrebe D., Rosenwinkel K. H. and Verink J. (2008) 13-WWW- YES-2011-Ewemoje-Paper-2011-06-26.doc