Keywords: Clean Team, Portable toilet, Suldge characteristic, Storage effect, Anaerobic digestion

Sanitation is still a major issue in developing countries and is crucial to the health and wellbeing of populations. Several barriers to sanitation exist, such as the cost of facilities, high population density in urban areasand issues around ownership slow down the spread of adequate sanitation facilities.

In 2011, Unilever and WSUP started a sanitation business in Kumasi, 'Clean Team', testing an innovative model of portable toilets to address the lack of sanitation facilities available. The next step is the implementation of a treatment plant specific to the treatment of Clean Team waste. The scope of this thesis is to characterise Clean Team waste. A total of 41 samples were analysed, 36 from household cartridges and 5 from interim tanks. The characteristics of Clean Team waste are similar to mechanical chemical toilet sludge. The waste has a similar level of total solids in high strength sludge and similar total volatile solids in fresh faeces. There was no correlation between customer diet and faecal sludge properties. A more detailed survey on customers' diets might reveal correlations, however, this was not carried out in this study. Storage of waste in Clean Team tanks impacts pH level and the solids concentration distribution within the tank. The drop in pH may impact anaerobic treatment. However, storage of the waste over a short period of time does not appear to have any further effect on the physico-chemical characteristics of the waste.

Experiments undertaken in Kumasi indicated a low biodegradability of the waste and thus a low potential for bio-methane production, although despite this onsite observations demonstrated high gas production. Based on the COD concentrations in household cartridges, Clean Team might expect a maximum methane production of around 0.54 m 3 /week of CH4 per toilet or 205 m 3 /week for 381 toilets. Anaerobic digestion seems to be a viable option to treat Clean Team waste. Free ammonia and pH may inhibit the process although methanogenic bacteria might adapt themselves to these conditions. Therefore the process will need to be monitored carefully. Clean Team waste has the ii potential to be a good fertiliser after treatment provided that there is no significant levels of heavy metals present.

LIST OF FIGURES

Figure 1: Sanitation chain (adapted from [START_REF] Monvois | CMS Guide n°4 -How to select appropriate technical solutions for sanitation. s.l.:Concerted Municipal Strategies (CMS)[END_REF] (Lowry, 1999(Lowry, -2013, b) , b) [START_REF] Polprasert | Organic Waste Recycling: Technology and Management[END_REF] Sanitation is challenging, especially in urban areas where the context is complex. Cities are growing faster than ever before and piped sewerage networks are not a feasible option for many areas within cities. On-site sanitation is common in developing countries (DC) but several barriers restrain its implementation at the household level in an urban context. A major barrier is finance: the cost of private facilities is not affordable. There might be a willingness to pay for sanitation; people can pay for public toilets but they often not able to invest in private facilities. Another major barrier to the implementation of sanitation facilities is the issue over a lack of space. In a dense urban context, space may not be available to build a latrine. Moreover, insecure land ownership leads to a lack of investment in sanitation facilities [START_REF] Tearfund | Sanitation and hygiene in developping countries: identifying and responding to barriers -A case study from Madagascar[END_REF].

LIST OF TABLES

Sanitation -An integrated process

The chain of sanitation

Sanitation is the management of wastewater and excreta. This does not include only access to toilets; it is a whole process protecting human health against pathogens found in faeces [START_REF] Monvois | CMS Guide n°4 -How to select appropriate technical solutions for sanitation. s.l.:Concerted Municipal Strategies (CMS)[END_REF]. Figure 1 (below) presents an overview of the sanitation chain and its objectives:

The challenge of faecal sludge treatment

In development politics sanitation has been side-lined over the last few decades. Although the need for sanitation service is recognised in most agendas, human excreta is a major pollutant in DC that is hazardous to human health. Even in middle income countries, where people have access to a good level of sanitation services through piped sewerage networks, sewage still remains untreated. This lack of treatment causes major pollution and health issue, such as frequent cholera outbreaks [START_REF] Bartone | Water Pollution Control -A guide to the Use of Water Quality Management Principles[END_REF]. It is therefore critical to treat wastewater and excreta to ensure a complete sanitation and protect the health of populations.

Anaerobic digestion

Technologies and processes applied in wastewater treatment are numerous.

Whereas aerobic treatment methods are common in western countries, DC often focus more on anaerobic digestion (AD) processes because of their multiple advantages, in particular a low energy cost for treatment, the production of energy (in the form of biogas) as well as producing agricultural fertilisers in the process [START_REF] Barnett | Biogas technology in the Third World: A multidisciplinary Review[END_REF].

General overview

AD is the decomposition of organic and inorganic matter in absence of molecular oxygen, occurring by fermentation and oxidation. The process is multi-step oriented [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF]:

1. Hydrolysis (or liquefaction): complex and insoluble organic matters are converted to soluble compound as monomer [START_REF] Polprasert | Organic Waste Recycling: Technology and Management[END_REF].

2. Fermentation: Amino acids, sugars and fatty acids produced by hydrolysis are degraded further into acetate, hydrogen, carbon dioxide, propionate and butyrate [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF]. Some publications divide fermentation in Acidogenesis and Acetogenesis (El Mashad, 2003).

3. Methanogenesis: methanogenic organisms convert fermentation product into biogas, mostly methane (CH4) and carbon dioxide (CO2) [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF].

AD is a delicate balance between the rate of hydrolysis, fermentation and methanogenesis [START_REF] Chaggu | Sustainable Environmental Protection Using Modified Pit-Latrines[END_REF].

Digestion products

Waste treated by AD may be used as a fertiliser or soil conditioner as long as pathogens are removed. AD does not remove nutrients but instead changes their speciation and makes them increasingly available for crops. Organic content is reduced by 30-60%. Approximately 50% of nitrogen is dissolved ammonia which can be nitrified in nitrate when applied to crops. Phosphate availability is around 50% [START_REF] Polprasert | Organic Waste Recycling: Technology and Management[END_REF].

An advantage of AD is the energy recovery from biogas production. Gas composition varies depending on the initial waste:

 CH4 -55-65%  CO2 -35-55%  N2 -0.3%  H2 -0-1%  H2S -0-1%
 Water vapour and other gas

The range of heating values is 4,500-6,300 kcal/m 3 dependent on the content of other gases besides CH4 [START_REF] Polprasert | Organic Waste Recycling: Technology and Management[END_REF]. [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF] indicates a production of CH4 per unit of COD under anaerobic condition of 0.4 L CH4/g COD at 35°C and 1 atm.

Processes

Various AD processes have been developed; each has its own specificity and performance [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF]:

Faecal sludge characterisation and AD

The AD treatment process is dependent on the system feedstock. Each type of reactor requires specific conditions to operate at its optimum efficiency [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF]. The following section presents the necessary conditions for AD treatment.

Hydrolysis and methanogenesis are the rate-limiting reactions in AD process.

Various parameters need to be considered to ensure successful AD (El Mashad, 2003).

pH

Methanogenic bacteria are extremely sensitive to pH, which should be between 6.6 and 7.6, with an optimum range of 7 to 7.2. Below 6.6 methanogenesis is inhibited. A pH drop may be caused by the accumulation of volatile fatty acids (VFA) [START_REF] Polprasert | Organic Waste Recycling: Technology and Management[END_REF]. Thus the process is more stable when VFA concentration is low, this indicates a sufficient methanogenic population and sufficient time to minimise hydrogen and VFA concentration [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF].

Temperature

Temperatures favourable for methane production are mesophilic (25-40°C) or thermophilic (50-65°C), with reactions being faster in the thermophillic range [START_REF] Polprasert | Organic Waste Recycling: Technology and Management[END_REF].

Nutrients

Nitrogen is necessary for bacteria growth and enzyme production and is involved in total alkalinity, which helps to maintain a neutral pH. On the other hand, free ammonia can be toxic to methanogenic bacteria above concentrations of 500 mg/L NH3 [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF]. Free ammonia concentration increases with pH (El Mashad, 2003).

The C/N ratio is an essential factor in AD. The ideal range is 20-30 for effective biological treatment, however in faeces there is a C/N ratio between 6 and 10.

An additional co-digestion feedstock rich in carbon is advised for faeces treatment [START_REF] Polprasert | Organic Waste Recycling: Technology and Management[END_REF].

Solid Retention Time (SRT) and Hydraulic Retention Time (HRT)

Retention time (solid or hydraulic) of the waste in the reactor needs to provide sufficient time for both bacteria growth and step successions. It varies considering the type of process [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF].

Toxic organisms

Toxic substances, such as sulfide produced by sulphate-reducing bacteria, are inhibiting methanogenic bacteria [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF].

Consequently, it appears crucial to characterize the FS which will be treated in order to choose the best treatment option. The next section presents data from the literature about FS.

Properties of faecal sludge

On-site sanitation facilities can be fed with a range of matter: faeces, urine, flushing water, toilet paper, etc. FS is collected from on-site sanitation facilities, such as pit latrines or public toilets [START_REF] Heinss | Solid separation and ponds systems for the treatment of faecal sludges in the tropics: Lessons learnt and recommendation for preliminary design[END_REF]. It is produced by storage of faeces that are partially digested [START_REF] Tilley | Compendium of Sanitation Systems and Technologies[END_REF]. FS composition is determined by the initial characteristics of faeces and the storage conditions. [START_REF] Feachem | Health Aspect of Excreta and Wastewater management[END_REF]. In absence of data, [START_REF] Feachem | Health Aspect of Excreta and Wastewater management[END_REF] suggests a working assumption of 250 g/p/d of faeces and 1.2 kg/p/d urine in urban area. A study conducted on Clean Team portable toilets finds lower figures for faeces production, with an average of 161 g/p/d for all the customers, including children, and 181 g/d for an adult [START_REF] Griesauer | Portable toilet sludge -Assessment of properties and treatment options[END_REF] (assuming that children below 10 have half the stool weight of adults [START_REF] Myo-Khin | A prospective study on defecation frequency, stool weight, and consistency[END_REF]).These low figures are in the range of figures from DC, but should be taken carefully considering the small range of the study (10 households).

The use of urine diverted toilets (UDT) influences the chemical composition of FS. Indeed urea is the source of 80% of nitrogen in human excreta [START_REF] Kujawa-Roeleveld | Anaerobic treatment in decentralised and source-separation-based sanitation concepts[END_REF]. Therefore, FS is not totally free of urine; in actual practice only 70-85% of urine is diverted in UDT, depending on the toilet design [START_REF] Tilley | Compendium of Sanitation Systems and Technologies[END_REF].

The following table presents some faeces and faecal sludge characteristics according to the literature. These figures show the variability of faeces and FS characteristics. They come from various studies, expressed in various units, calculated from analyses with different methodology. The populations investigated for these studies are also extremely varied by their geographical location thus climate and cultural habits including their diets and toilet uses.

Therefore these figures should be considered as an estimation of faecal sludge characteristics and it is expected that the figures produced by this study will differ from the other ones presented below.

Portable toilets

Portable toilets (also known as chemical toilets) are commonly used in camping, transportation and in the construction sector. A pilot project is currently testing their implementation in an urban context in DC through a sanitation business called Clean Team [START_REF] Cleanteam | Clean Team Ltd[END_REF].

Their design was initiated in the 60's and remains similar: a plastic toilet with a receptacle for waste mixed with chemical [START_REF] Corliss | Portable toilet. Unites States[END_REF]. They are designed to be compact, transportable and to not produce odours uncomfortable for users. Control of odours is critical, considering that these toilets are used in small confined spaces.

Odours are caused by gases produced during the decomposition of organic matter in the FS. This decomposition produces mostly hydrogen sulfide gas.

Even though odours are harmless to physical health of people, they matter in terms of physical stress and comfort. Odour control in waste collection system can be achieved by different approaches, which can be combined [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF]:

 Maintaining aerobic condition;
 Controlling anaerobic microbial growth by disinfection or pH control;

 Oxidizing or precipitating odorous compounds by chemical addition;

 Minimize the release of odours through design;

 Off-gas treatment: gas are collected and treated independently from waste.

Portable toilets combine the first four approaches described above. In perspective of treatment, additives used for the control of microbial growth and the oxidation can have a significant impact. Additives can be chemical or biological. In this study, only the main chemical additive for chemical toilets is reviewed. It contains glutaraldehyde, bronopol and surfactant.

Firstly used as a tanning agent, glutaraldehyde is a biocide used for several industrial purposes (NICNAS, 1994). Used as a chemical toilet additive, it slows down biological degradation of faeces, reducing odours. However, it loses its biological activity below about 10 mg/l (UNEP, 1998). Bronopol is an effective antibacterial preservative stable over a wide pH range and in alkaline media. It is especially active against Gram-negative organisms [START_REF] Bryce | The activity and safety of the antimicrobial agent Bronopol (2-bromo-2-nitropopan-1,3-diol)[END_REF].

Surfactant acts as a lubricant and cleaner, facilitating the emptying of cartridge [START_REF] Doege | Method for bacterially treating tank toilet systems and apparatus for using same[END_REF]. Although surfactant must be neutral to treatment process, Bronopol may disturb it by its antibacterial action.

Glutaraldehyde may impact treatment by its biocidal effect. Indeed metabolic activity of sewage bacteria can be inhibited by a concentration of glutaraldehyde above 16 mg/l [START_REF] Leung | Ecotoxicology of glutaraldehyde: Review of environmental fate and effets studies[END_REF]. The study conducted on Clean Team portable toilets suggest that glutaraldehyde may affect development of methanogenic bacteria and cause a drop of pH by the dominance of acid producing bacteria, both affecting anaerobic digestion, although results did not confirm an inhibition of microbial activity [START_REF] Griesauer | Portable toilet sludge -Assessment of properties and treatment options[END_REF]. The effect of glutaraldehyde may be temporary; the bacteria inhibition not being total. As a result, bacteria activity progressively overwhelms the chemical. Indeed glutaraldehyde degrades readily and its reaction with proteins removes a significant amount of it from waste (UNEP, 1998). This reaction depends on time, pH and temperature and is less efficient under alkaline conditions (NICNAS, 1994). Under anaerobic condition, glutaraldehyde is metabolized to 1,5-pentanediol and 3-formyl-6hydroxy-2-cyclohexen-1-propanal [START_REF] Leung | Ecotoxicology of glutaraldehyde: Review of environmental fate and effets studies[END_REF].

Effect of storage

Natural degradation of FS occurs during storage. As a result, degradable organic substances are partly mineralized and partly transformed into stable degradation products. The degree of degradation impacts sludge properties and therefore influences treatment possibilities [START_REF] Haug | The Practical Handbook of Compost Engineering[END_REF].

In the case of portable toilets, waste is stored firstly in the cartridge of toilets and then after collection in a tank before treatment. Storage in the toilet is generally short, only a few days, but sludge can be stored in an intermediate tank between their collection and their treatment, which can be assimilated to an accumulation system (AC). This is because an AC is an anaerobic reactor continuously fed with waste and only emptied when the reactor is full. In this type of system, solids settle at the bottom while scum layer is formed at the top during retention [START_REF] Chaggu | Sustainable Environmental Protection Using Modified Pit-Latrines[END_REF]. This intermediate step may modify the sludge properties.

Research Gap

This review of the literature shows how knowledge about FS is various, and limited for FS from portable toilets, before or after storage in a tank. However, this knowledge is essential in order to design a treatment plant. Considering the development of portable toilets as a concept to face urban sanitation challenges, data about FS from portable toilets are needed. Clean Team business offers the opportunity to fill the gap in data about FS from portable toilets in urban area context in DC.

Objectives

Considering the review of the literature above and the gaps identified, five objectives need to be considered:

1. Characterise the physical and chemical properties of faecal sludge collected in Clean Team portable toilets.

2. Analyse the impact of customers' diets on faecal sludge properties.

3. Study the effect of storage on waste characteristics.

4. Estimate the biodegradability of Clean Team waste.

5. Evaluate the treatment and reuse opportunities for Clean Team waste.

Material and Methods

Clean Team waste was characterised to address the objectives listed above.

The following methodology presents the Clean Team model, sampling and physic-chemical parameters analysed. The range of parameters analysed was determined by the combination of their interest for research question and their practical feasibility in the field. Tests were undertaken in triplicate.

Clean Team

As mentioned above, Unilever, WSUP (Water and Sanitation for the Urban Poor) and IDEO developed an innovative model to face the urban sanitation challenges: Clean Team. A pilot has been implemented in Kumasi, Ghana, since 2011 (Clean Team, 2012). Kumasi's population has low access to improved sanitation and it is current practice to pay for sanitation services through using public toilets or emptying bucket latrines [START_REF] Whittington | Household Sanitation in Kumasi, Ghana. A description of Current Practices, Attitudes and Perceptions[END_REF].

Clean Team is a sanitation business addressed to people who already pay for sanitation but cannot afford the cost of classic private facilities. As described in the figure below, each client receives a portable urine diverting toilet containing a removable cartridge filled with a chemical that reduces odours. So the waste is composed of chemical and faeces. The cartridge is replaced two or three times a week by a waste collector (Clean Team, 2012). Collected waste fills two interim tanks which are emptied on average twice a month (L. Hawkes, Personal communication, 2013). Storage time in Clean Team toilets is short, maximum four days between two collections for a client who registers for a twice weekly collection. Development of smell is observed after three days of storage independent of the type of additive or its concentration [START_REF] Griesauer | Portable toilet sludge -Assessment of properties and treatment options[END_REF]. Thus bacteria are still present and active.

Step 5 of the model is under development. Stopford, an engineering consultancy, orientated its design research to anaerobic digestion (AD)

processes. This type of treatment is coherent with the waste profile, appropriate for waste stabilisation, safe for human health and producing valuable products [START_REF] Stopford | FEED Study for a Micro-Scale Modular Anaerobic Digestion Plant -Options for waste treatment and possible AD configurations for Unilever[END_REF].

Sampling and data related

Two types of samples were analysed: household samples, directly from the cartridges; and tank samples, taken from the storage tanks.

Household samples

Sampling was done every morning when collected cartridges arrived on site for emptying and cleaning. Sampled cartridges were randomly selected from the consumer list. A number was attributed to each customer, written on a piece of paper and 36 papers were pulled out a hat. Considering time constraints, 36 cartridges were sampled during the field work period. At the beginning of the fieldwork, sampled households were surveyed about the number of adults and children using the toilets as well as their diets (See Appendix A).

Tank samples

Five tank samples were collected on one occasion, when the tank was full. The tank depth is 180 cm, so the samples were collected at a depth of 0, 40, 80, 120 and 160 cm. These samples were analysed for the same parameters as household samples and used for on-going analysis of Carbon Oxygen Demand (COD) in anaerobic digestion conditions and Bio-methane potential (BMP) tests in addition to other parameters. Depth of collection was recorded for each sample.

Analysis on site

The level of waste in the cartridges was determined with a ruler on site to estimate its approximate volume.

Temperature, pH and Oxidation Reduction Potential (ORP) were measured in each sample from cartridges and tanks with a probe.

Analysis in KNUST laboratory

Samples collected (41) were brought back to a local laboratory every day to be analysed immediately. However, due to delay in chemical delivery, the 7 first samples were stored for two weeks in a freezer. Prior to any analysis, samples were homogenised with a mechanical blender. The table below summarises the analyses realised.

Physical parameters

Total and volatile solids were analysed for each sample following standard methods APHA 2540 B & E. Samples were dried at 105°C until sample weight stayed stable for total solids (TS), and then ignited at 550°C in a furnace for total volatile solids (TVS) until sample weight stayed stable [START_REF] Apha | Standard methods for the examination of water & wastewater[END_REF].

Chemical parameters

Total nitrogen and ammonium were analysed from the fresh homogeneous sample. COD, phosphate, nitrate and potassium parameters were measured from the soluble solid free fraction, prepared by centrifugation and filtration.

Nitrate and total potassium were carried out on randomly selected samples due to time constraints.

 Total nitrogen

The total nitrogen is the measurement of ammonium, nitrite, nitrate and organic nitrogen. The measurements were done by spectrophotometry after digestion at 120°C for one hour of the sample in presence of alkaline peroxodisulfate solution according to the Koroleff method (analogous to EN ISO 11905-1).

 Ammonium 5 or 10 g of the samples were diluted in 200 ml of water. The insoluble part settled and ammonium were analysed from the supernatant in a cell test by spectrophotometer (DIN 38406 E5).

 Soluble COD Samples were centrifuged and filtered through a 0.45 µm filter. After dilution at 1/50, 2.0 ml of the liquid phase was mixed in a cell test heated at 150°C for 120 min. COD was measured by photometry.

 Total phosphate

Total phosphate was analysed following the protocol APHA 4500-P E. [START_REF] Apha | Standard methods for the examination of water & wastewater[END_REF].

 Nitrate and total potassium

Samples were centrifuged and filtered through a 0.45 µm filter. Liquid phase was then analysed carrying out the cell test methodology.

On-going analysis

Five samples from the tank were set up in anaerobic conditions for on-going analysis of BMP and biodegradability.

BMP test

There is no standard protocol to measure BMP; various methods have been developed in several research projects for different purposes [START_REF] Wagland | Test methods to aid in the evaluation of the diversion of biodegradable municipal waste (BMW) from landfill[END_REF]. Volumetric method is one of the most common in the literature [START_REF] Esposito | Bio-Methane Potential Tests To Measure The Biogas Production From The Digestion and Co-Digestion of Complex Organic Substrates[END_REF]. The following BMP protocol is adapted from protocols proposed by the Environment Agency [START_REF] Turrel | Guidance on monitoring of MBT and other treatment processes for the landfill allowances schemes (LATS and LAS) for England and Wales[END_REF] and from [START_REF] Esposito | Bio-Methane Potential Tests To Measure The Biogas Production From The Digestion and Co-Digestion of Complex Organic Substrates[END_REF].

 Principle

The amount of gas produced by a substrate under anaerobic condition is the direct measurement of the mineralised organic carbon and the biodegradability.

Most of the protocols described in literature recommend to ignite the substrate and to seed it with digested sludge to add methanogenic bacteria. The seeded substrate is then placed in an aqueous mineral medium and literature recommends incubation at 35°C. The volume of gas produced is monitored.

 Substrate preparation

As mentioned in the chapter 1.5, sludge collected in the tank is already in anaerobic condition. Therefore, as an inoculum, 10 g of sludge from the tank and 1 ml of sludge from the bottom of the tank was used in order to ensure the presence of methanogenic bacteria. The substrate was mixed in a vessel with 70 ml of tap water. The substrate was regularly agitated to avoid settlement.

 Gas collection

The gas was supposed to be measured through water displacement in water saturated with table salt, preventing any dissolution of the gas into the water.

However, the BMP tests run in Kumasi failed due to technical issues. Leaks in the apparatus did not allow any gas measurement.

The total volatile solids were measured at the end of the test in order to assess the bacteriological activity during the test.

Biodegradability

A second test was carried out to evaluate the biodegradability of the FS through soluble COD measurement. 10 g of each sample was mixed in 350 ml of tap water and seeded with 1 ml of sludge from the bottom of the tank, producing five "micro-digester". A sample of each "micro-digester" was collected every week to analyse soluble COD according to the protocol described above.

Analysis in Cranfield laboratory

The following parameters will be analysed for twenty household samples and Samples have been brought back to UK frozen on ice blocks. These analyses are out of the scope of the present thesis.

Statistical analyses

As samples and analyses are independent, it is reasonable to assume that data have a normal distribution and are therefore parametric.

Student's T-test

In this study, student t-tests were used to determine if two set of data were or were not significantly different from each other. This test is one of the simplest but most powerful statistic test (Lowry, 1999(Lowry, -2013, b), b).

Two values are considered: df and t-value. Each df is associated to a critical tvalue for a specific interval of confidence. The actual t-value is compared to the critical t-value to determine the significance of the interaction (Lowry, 1999(Lowry, -2013, b), b). The meaning of the student test is expressed by the t-value, that is used to reject or not the "null hypothesis" comparing the t-value with a certain significance level. The null hypothesis is the logical antithesis of the hypothesis that the investigator is examining. If the actual t-value is above a critical t-level, the "null hypothesis" is rejected. If the actual t-value is below a critical t-level, the "null hypothesis" is rejected accepted. The significance level is the level of confidence in the accuracy of the results. (Lowry, 1999(Lowry, -2013, b), b).

In this study, the significance level used is 0.05, meaning that the result are true with a confidence of 95%.

Matrix correlation

Correlation refers to the relationship that exists between two variables so a correlation is a way to determine quantitative functional relationship between parameters. The more you have of one variable, the more or the less you have of the other. If a linear regression, producing an equation linking parameters, with a specific interval of confidence can be establish between two parameters, these are correlated (Lowry, 1999(Lowry, -2013, a), a).

Results

External factors influencing analysis

In this study 36 household samples were analysed. Due to logistical issues, household samples were not collected within the exact same conditions. The three different situations are described in the table below. Before doing any further analysis, it is necessary to know how the storage and the change of initial chemical volume affect results. -Two weeks storage in a freezer affects the characteristic of samples;

-Reducing the initial volume of chemical in the cartridge from 7l to 5l affects the characteristics of samples.

Prior to the T-test, parameters were converted from g/l to g/p/d by dividing the number of users and the number of days between collections. The purpose is to eliminate interference from two parameters: household size variation and number of collection per week.

Storage factor

Storage has a statistically significant effect on the parameters of total nitrogen and COD. The results of Student's T-test are presented in the table below for each parameter. This seems coherent with an un-stopped biological activity during storage. Due to power shortage, stored samples experienced an unknown number of defrostfreezing cycles leading to an alteration of initial nitrogen and COD parameters by bacteriologic activity. Therefore these results suggest recommending an analysis of nitrogen and COD as soon as possible without any storage, particularly in DC where power shortages are more likely to occur. In case of sampling in DC and analysis in Europe, researchers must be cautious to not defrost their samples.

Initial volume of chemical factor

It appears that the variation of initial chemical volume does not affect statistically significantly the result for any parameter. The results of Student's Ttest are presented in the table below for each parameter. Volume and concentration have been adjusted by Clean Team according to the feedback given by customers about odours. From the chemical perspective, it seems that the quantity of glutaraldehyde contained in 7l has no more effect than the quantity contained in 5l. However, complaints from customers about odours increased following the reduction of volume. [START_REF] Griesauer | Portable toilet sludge -Assessment of properties and treatment options[END_REF] observed the development of smell after 3 days with every additive tested. Further experiment seems still necessary to adjust volume and concentration to an optimum. Clean Team aims to be consistent in providing safety and comfort to the customers and limiting the consumption of chemical by the business. In any case, the concentration of glutaraldehyde should be below the limit of 16 mg/l to limit its impact on the treatment process (see chapter 1.4).

Household samples

Survey results

36 Clean Team customers were interviewed to determine the number of regular users of their toilets and their diets. The user number is 4.6 on average within the sampled customers. By the end of July 2013, Clean Team had a number of 381 customers. According to the customer database, the average household size is 3.9 people. The slightly higher household size obtained can be explained by a simple effect of statistics; but also by the fact that customers tend to reduce the size of their families in their answers to Clean Team in order to have less collection, leading to decrease their fees. Considering that the surveyor was presented as a student from Cranfield University, customers might have been more truthful with their answer during interviews due to the absence of any financial consequences.

In regards to customers' diets, all of them eat starch at every meal. It is generally rice, yam or maize. The figure below presents the habit of Clean Team customers about diet with the frequency of meat/fish and vegetable during a week. The absence of interaction could be explained by the similarity of diet observed.

A questionnaire that is more detailed about diet might give different results.

Tank samples

Overall tank data

Tank samples were stored for two weeks in a freezer, so the value of total nitrogen and soluble COD are not reliable (see chapter 3.1.1). However, they are presented in the table below in order to show the correlation with the depth of sampling. 948.8 (412.9) 484.3 (120.9)

From the cartridges to the tanks: evolution of parameters

The pH is slightly lower in the tanks than in the cartridges. [START_REF] Griesauer | Portable toilet sludge -Assessment of properties and treatment options[END_REF] observed that pH reduced during storage. As explained in chapter 4.1, the pH drops come from the absence of urea hydrolysis and the accumulation of VFA.

Average TS is higher in tank samples due to an accumulation of solid matters at the top. Below 80 cm, TS are similar in the tank and in the cartridge.

Every other parameter does not show significant variation between household and tank samples.

Correlation between depth and characteristics

Two parameters have statistically significant interaction with the depth:

temperature and soluble COD. The t-values are presented in the table below.

The decrease of soluble COD and temperature with depth is shown in the figure There is no direct interaction between depth and total solids but there is a thicker layer at the top of the tank, due to the buoyancy of the faeces.

On-going analysis

In order to measure biodegradability two apparatus set-ups were used, one for the BMP test, one for the biodegradability test. The samples were under anaerobic conditions in both.

As a leak in the dispositive did not allow any gas measurement in the BMP test, total volatile solids were measured at the end (3 weeks later) in the substrate as a replacement but the result didn't show any bacteriological activity.

Soluble COD were analysed every week in triplicate in the biodegradability test as a second evaluation of the bacteriological activity occurring in the samples. 18.9 13.9 -6.5 (32%) T5

19.4

16.9

17.2 15.7 -3.7 (19%) Mean 25.5 (6.7) 10.7 (4.7) 22.4 (5.4) 20.2 (5.7) -5.3 (21%) (3.0)

The results obtained the first week are inconsistent with the other measurements. It could be due to a lack of homogenisation at the start of the experiment. Although these results are included in the Figure 9, they are excluded from the discussion. During the first week, production of gas was observed by distortion of the plastic bottle used for the experiment. However, a volume measurement was not possible due to the apparatus used. Whereas the volatile solids show a stable quantity of organic matter, the COD test showed a significant reduction and an emission of gas.

Discussion

Faecal sludge characteristics

Household data can be compared with the existing literature (see chapter 1.3).

Clean Team customers produce on average 89 l/cap/year of waste (chemical + faeces), nearly twice the volume cited by [START_REF] Tilley | Compendium of Sanitation Systems and Technologies[END_REF] although they use urine diverted toilet. This comes from the initial volume of chemical in the cartridge; therefore it might evolve if Clean Team keeps adapting the chemical's volume. In addition to the chemical, Clean Team customers produce a mean value of 244 ml of waste per person per day. Consequently, it will be possible to estimate the total volume of waste from the number of customers, the number of collections, and the initial volume of chemical. As a design parameter, the value of 244 ml/cap/day needs to be considered as an approximate estimation instead of a reliable value. In addition to this methods of volume measurement

were not precise to the millilitre.

TS characteristics are similar with data from the literature about mechanical chemical toilet and high/low strength sludge (TS = 1-20%, see Table 2, ATV (1997), [START_REF] Feachem | Health Aspect of Excreta and Wastewater management[END_REF], [START_REF] Griesauer | Portable toilet sludge -Assessment of properties and treatment options[END_REF][START_REF] Lopez Zavala | Characteristing of feces for discribing the aerobic biodegradation of feces[END_REF] and [START_REF] Yadav | Vermicomposting of sourceseparated human faeces for nutrient recycling[END_REF]). Clean Team waste has lower TS than fresh faeces (TS = 18-20%, see Table 3, [START_REF] Doku | The potential for the use of upflow anaerobic sludge blanket (UASB) reactor for the treatment of faecal sludges in Ghana, s.l[END_REF]), this can be explained by the addition of chemical, the liquid phase decreasing the percentage of solids.

In contrast, TVS are similar to fresh faeces (TVS = 82%, see Table 2, [START_REF] Griesauer | Portable toilet sludge -Assessment of properties and treatment options[END_REF][START_REF] Lopez Zavala | Characteristing of feces for discribing the aerobic biodegradation of feces[END_REF] and [START_REF] Yadav | Vermicomposting of sourceseparated human faeces for nutrient recycling[END_REF]), due to short storage, and lower than TVS of high strength sludge (HSS) (TVS = 60%, see Table 3, [START_REF] Doku | The potential for the use of upflow anaerobic sludge blanket (UASB) reactor for the treatment of faecal sludges in Ghana, s.l[END_REF] and [START_REF] Klingel | Faecal Sludge Management in Developing Countries -A planning manual[END_REF]). HSS are more stabilised due to longer storage, therefore organic matter decreased. This storage did not occur in Clean Team cartridges as they are collected and cleaned at least twice a week. So organic matter is not stabilised and TVS are similar to fresh faeces that contain a high level of organic substances. TVS are 78.9% of TS, so TVS are 3.6% of total waste. TS and TVS both impact waste treatability which will be discussed in chapter 4.4.

The pH values are consistent with Griesauer (2011) study. Clean Team waste has a lower pH than chemical toilet (pH=7-11) sludge or stabilized sludge from public toilet (pH=8), and a higher pH than fresh sludge (pH=5.3). In faecal sludge, the hydrolysis of urea ensures a high alkalinity by the formation of ammonia bicarbonate, preventing a drop in pH [START_REF] Strauss | Treating Faecal Sludges in Ponds, Duebendorf[END_REF]. This phenomenon cannot occur in Clean Team toilets as they are urine diverted.

That is why the pH is below 8. However, urine diversion is never complete [START_REF] Tilley | Compendium of Sanitation Systems and Technologies[END_REF], and faeces are mixed with a liquid phase, which can explain that pH is higher than 5.3. The pH has a significant impact on anaerobic digestion, which will be discussed further in chapter 4.4.

Soluble COD presented in the table is lower than COD values described in the literature. In a study about pit latrines, [START_REF] Nwaneri | Biological degradation processes within a pit latrine[END_REF] found that soluble COD was a third of total COD. Assuming a similar proportion, the total COD of Clean Team waste is estimated at 75 g/l or 42 g/cap/d. This value is in the range of mechanical chemical toilets and faeces, but above high strength sludge. As waste is stabilizing, the COD is decreasing. This 75 g/l are also similar to the value found by [START_REF] Chaggu | Sustainable Environmental Protection Using Modified Pit-Latrines[END_REF] in ecological toilets after 4 months.

Compared to the values obtained by Griesauer in 2011, total nitrogen is at the top of its range of values. However, total nitrogen is slightly lower than values shown in the literature, possibly due to a low bacteriological activity in the cartridges, reduced by the chemical additive.

Storage effect in tanks: the evolution of characteristics with depth

Currently waste is stored for two weeks under anaerobic conditions in two separate tanks. The storage affects the waste characteristics.

Tanks receive waste every other day and are emptied by a vacuum truck every fortnight. Therefore depth can be linked with storage time, assuming that mixing is negligible. As waste collectors observe gas emissions, it seems reasonable to assume that the tank is favourable to bacteria growth and that bacteria concentration increases with depth. Indeed they have a longer time frame to develop in the bottom than in the top. Moreover, tanks are never completely emptied; a bottom layer is remaining, preserving the long term growth of bacteria. This hypothesis is confirmed by the negative correlation between depth and soluble COD. As bacteria activity increases, concentrations in oxygen decrease. From this hypothesis, a decrease of total volatile solids would have been expected, but the BMP test failed to show any variation linked with depth of sampling; therefore the hypothesis about bacteria distribution has to be considered cautiously. The biodegradability and bacteria activity are discussed in the next chapter.

Biodegradability of Clean Team waste

The on-going tests to assess biodegradability were contradictory: the bacteriological activity seems absent in the BMP tests but present in the biodegradability tests according to the TVS measurement. Anaerobic digestion can be limited or even inhibited by several factors: a high concentration in VFA, a lack of methanogenic bacteria, a lack of nutrients, low temperatures, a pH below 6 and a toxic level of ammonia (see chapter 1.2.4). Substrates were diluted in 350 ml for the COD tests and in 70 ml for the BMP test, every other parameter remaining identical. This suggests an inhibition by the VFA or ammonia in the BMP test, these inhibitors being diluted in the COD test. VFA level will be measured at a later date in Cranfield , but the ammonium NH4-N (NH4 + + NH3) was above the toxic level of 500 mg/l [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF] in both tank samples and household samples (948.8 and 519 mg/l). This means that if the pH goes above the ammonium pKa of 9.25, the ammonia form is predominant, being toxic. As the initial pH is low and more likely to drop than to go up, ammonia toxicity is not the best explanation. In absence of analysis, VFA toxicity remains plausible.

However, this does not totally exclude a lack of methanogenic bacteria, a low temperature or pH. Gas emissions from Clean Team tanks were observed by the waste collectors, meaning that conditions are favourable to methanogenesis in the tanks. As tests were run on a short time with small substrate quantities, a lack of methanogenic bacteria seems to be another valid hypothesis.

Temperature was certainly more variable and lower in the laboratory than in Clean Team tanks, which are black and exposed to the sun daily, so low temperature could have emphasised the inhibition by other factors. Finally, pH was initially close to 6, so any pH drop might have inhibited the methanogenesis. A last factor might be the duration of the test: usually, BMP tests last at least 60 days, where here the tests lasted 21 days.

On the other hand, [START_REF] Griesauer | Portable toilet sludge -Assessment of properties and treatment options[END_REF] observed the development of smell after 3 days with all additives tested, the decrease of pH and a stable ammonia concentration. His conclusion is that chemical additives tested in his study did not affect sludge degradation.

Assuming that the inhibitory factors mentioned above do not affect the methanogenic bacteria, it is possible to estimate a potential methane production from the COD. According to [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF], a production of 0.4 L of CH4/g of COD can be expected at 35°C and under 1 atmosphere, meaning that Clean Team may assume a production of 30 l of CH4/l of waste. On average, Clean

Team collects 9 litres of waste per household and currently has 381 customers.

Assuming a minimum collection twice a week, the methane potential production can be calculated as following:

Equation 5: Clean Team potential methane production

This rough estimation gives a potential production of 0.54 m 3 /week of CH4 per toilet or 205 m 3 of CH4 per week with the current number of customers.

However, the actual production may be much lower than this potential value considering the limiting factors of anaerobic digestion. This point will be developed in chapter 4.4.1.

Future use of Clean Team waste

Currently, tanks collecting Clean Team waste are emptied by vacuum trucks and waste is treated by Kumasi waste treatment plant. Yet Clean Team aims to implement their own treatment plant to valorise their waste through the treatment and reuse. The last scope of this study is to evaluate the possible process based on waste characteristics.

Treatability of Clean Team waste

Clean Team would like to implement an AD process in order to valorise waste by producing methane and fertilisers (L. Hawkes, Personal Communication, May 2013). Considering the gas emissions observed on site by the waste collectors, this technology seems a sensible choice. Clean Team waste characteristics are higher than the optimum described by [START_REF] Polprasert | Organic Waste Recycling: Technology and Management[END_REF]. This does not exclude anaerobic as a possible treatment but suggests an attached-growth digester with a long retention time.

The main concern for an AD is the inhibitors: temperature, pH, free ammonia and VFA.

Low temperatures do not seem to be an issue. The study took place in July, the second coldest month in Ghana and the waste temperature were always above 25°C. The issue will be to stay below the 35°C and avoid the unfavourable temperature between 40 and 50°C (see chapter 1.2.4.2).

The pH is more likely to be an issue as the pH was low in cartridges and dropped in the tanks. A drop below 6 will stop methanogenic bacteria activity.

On the other hand, an increase of pH will also be an issue because it will also increase the concentration of free ammonia leading to an increase of VFA concentration, the two other main inhibitors (El Mashad, 2003). The NH 4 -N concentration has the potential to be above the toxicity level of 500 mg/l ammonia cited by [START_REF] Tchobanoglous | Wastewater engineering: treatment and reuse[END_REF] so the NH 4 -N must be kept in acid form. The current pH could be a reasonable explanation for the current gas production from Clean Team waste although the potential presence of inhibitors; and it opens good scope for future treatment. Moreover El Mashad (2003) listed several toxic levels from literature, the lowest being 1,500 mg/l. So the actual NH 4 -N concentration may not be an issue even in case of increase of pH during the digestion. [START_REF] Koster | Characteristics of the pH-influenced adaptation of methanogenic sludge to ammonia toxicity[END_REF] and [START_REF] Zeeman | The influence of the total ammonia concentration on the thermophilic digestion of cow manure[END_REF] demonstrated the adaptation of existent methanogenic bacteria population to toxic levels of free ammonia.

The C/N ratio is another limiting factor. The total carbon will be analysed later, but the C/N ratio of faecal waste is usually from 6 to 10, lower than the optimum of 25 to 30 [START_REF] Polprasert | Organic Waste Recycling: Technology and Management[END_REF]. The ratio can be raised by the addition of organic matter rich in carbon to the waste, as food or vegetal waste. Food waste collection could be a development of Clean Team business and a positive income for treatment.

Reuse of Clean Team waste

The final product of AD can be used to produce fertiliser. Clean Team waste is rich in nutrients (nitrogen, phosphorus and potassium), and a composting or drying process is a way to increase nutrient recovery [START_REF] Yadav | Vermicomposting of sourceseparated human faeces for nutrient recycling[END_REF]. NH 4 -N is also an issue for reuse because it may volatilize during composting or drying; decreasing the total nitrogen content of the fertiliser, yet this phenomenon can be controlled by appropriate techniques.

However, Clean Team waste might still be polluted after treatment [START_REF] Polprasert | Organic Waste Recycling: Technology and Management[END_REF] that is why the analysis of heavy metals is necessary in order to validate the reuse of Clean Team waste. It may also still be harmful to human health due to pathogens in the effluent, therefore this will also need monitoring.

Conclusion

Several aspects of Clean Team portable toilets waste have been investigated in order to reach the research objectives. The findings are summarized below.

1. Characterise the physical and chemical properties of faecal sludge collected in Clean Team portable toilets.

Clean Team waste characteristics are similar to mechanical chemical toilet sludge. This study confirms the results obtained by [START_REF] Griesauer | Portable toilet sludge -Assessment of properties and treatment options[END_REF]. Waste has similar levels of total solids to high strength sludge and similar total volatile solids to fresh faeces. This is coherent with the waste storage time in Clean Team toilets.

Analyse the impact of customer diet on faecal sludge properties.

A correlation between customer diet and faecal sludge properties was not found. A more detailed survey of customers' diet might reveal some correlations, but they do not appear in this study.

Study the effect of storage on waste characteristics.

Storage of waste in Clean Team tanks impacts the pH and the distribution of solid matter throughout the vertical profile of the tank. The drop of pH may impact anaerobic treatment. However, the storage time seems short enough to not significantly alter the waste further.

Estimate the biodegradability of Clean Team waste;

Experiments undertaken in Kumasi indicated a low biodegradability thus a low potential for biomethane production, although on-site observations demonstrate a high gas production. Considering the initial levels of TVS and COD, and the limitation of the experimental process, BMP and COD tests do not seem to match the actual biodegradability.

Based on the COD concentration in household cartridges, Clean Team might expect a maximum methane production of around 0.54 m 3 /week of CH4 per toilet or 205 m 3 /week for 381 toilets.

5. Evaluate the treatment and reuse opportunities for Clean Team waste.

Anaerobic digestion seems to be a viable option to treat Clean Team waste.

Free ammonia and pH may inhibit the AD process although methanogenic bacteria might adapt themselves to these conditions. The process will need to be monitored carefully.

Clean Team waste should be a good fertiliser after treatment as long as it is heavy metal and free of pathogens.

Appendix B -Correlation of parameters from household samples -Scatterplots

Scatterplot of COD (g/l) against Total solids COD (g/l) = 16.0431+184.7328*x; 0.95 Conf.Int.

  3.3.1 Overall tank data .............................................................................. 3.3.2 From the cartridges to the tanks: evolution of parameters ............... 3.3.3 Correlation between depth and characteristics................................. 3.4 On-going analysis ................................................................................... 3.4.1 BMP test ................................................... Erreur ! Signet non défini. 3.4.2 Biodegradability test ................................. Erreur ! Signet non défini. 4 Discussion ..................................................................................................... 4.1 Faecal sludge characteristics .................................................................. 4.2 Storage effect in tanks: the evolution of characteristics with depth ......... 4.3 Biodegradability of Clean Team waste .................................................... 4.4 Future use of Clean Team waste ............................................................ 4.4.1 Treatability of Clean Team waste ..................................................... 4.4.2 Reuse of Clean Team waste ............................................................ 5 Conclusion ..................................................................................................... References ....................................................................................................... APPENDICES .................................................................................................. v

Figure 2 :Figure 3 :Figure 4 :Figure 5 :Figure 6 :Figure 7 :Figure 8 :Figure 11 :Figure 12 :Figure 13 :Figure 14 :Figure 15 :Figure 16 :

 2345678111213141516 Figure1: Sanitation chain (adapted from[START_REF] Monvois | CMS Guide n°4 -How to select appropriate technical solutions for sanitation. s.l.:Concerted Municipal Strategies (CMS)[END_REF] ..................... 10 Figure 2: Scheme of anaerobic digestion (adapted from El Mashad (2003); Polprasert (2007) and Tchobanoglous (2003)) .......................................... 12 Figure 3: Clean Team model ............................................................................ 24 Figure 4: BMP test apparatus ........................................................................... 28 Figure 5: On-going COD micro-digester ........................................................... 29 Figure 6: Diet patterns of surveyed Clean Team customers ............................. 35 Figure 7: Correlation between depth and temperature in the tank .................... 39 Figure 8: Correlation between depth and soluble COD in the tank ................... 40 Figure 9: On-going soluble COD (g/l) ............................................................... 41 Figure 10: Correlation between TS and soluble COD in household sample ..... 58 Figure 11: Correlation between TS and phosphorus in household sample ...... 58 Figure 12: Correlation between TS and ammonium in household sample ....... 59 Figure 13: Correlation between TS and total nitrogen in household sample .... 59 Figure 14: Correlation between TS and TVS in household sample .................. 60 Figure 15: Correlation between phosphorus and ammonium in household sample ....................................................................................................... 60 Figure 16: Correlation between phosphorus and total nitrogen in household sample ....................................................................................................... 61 Figure 17: Correlation between ammonium and total nitrogen in household sample ....................................................................................................... 61

  .......................... vii LIST OF EQUATIONS Equation 1: df ................................................................................................... Equation 2: t-value ........................................................................................... Equation 3: estimate σ M-M ................................................................................. Equation 4: variance of the source population .................................................. Equation 5: Clean Team potential methane production ..................................Adequate sanitation is crucial for human health; that is why "reducing by half the proportion of the population without sustainable access to safe drinking water and basic sanitation" is one of the objectives of the Millennium Development Goals (MDG) for 2015. Yet, two years from the deadline, the target is clearly out of reach (UN, 2010). Access to sanitation can be divided in four categories according to the Joint Monitoring Programme (JMP) for Water Supply and Sanitation-the mechanism for monitoring progress towards reaching the MDGs:  Improved facilities;  Shared facilities, such as public toilets;  Unimproved facilities;  Open defecation, which is no access at all to sanitation. In 2010, the proportion of urban population who have access to improved facilities was the same as in 1990 (43%) and access to shared facilities only increased 3% in 20 years. While the MDG target has been reached for drinking water, projections estimate global access to improved sanitation of 67% in 2015, far from the MDG target of 75% (UNICEF & WHO, 2012).

Figure 1 :

 1 Figure 1: The sanitation chain (adapted from (Monvois, et al., 2010)).

Figure 2 :

 2 Figure 2: Schematic of anaerobic digestion (adapted from El Mashad (2003); Polprasert (2007) and Tchobanoglous (2003))

Figure 3 :

 3 Figure 3: Clean Team model

Figure 4 :

 4 Figure 4: BMP test apparatus

Figure 5 :

 5 Figure 5: On-going COD micro-digester



  the five tank samples in Cranfield by laboratory technicians to confirm results from the field work:  Methane potential;  Total Carbon -Nitrogen -Hydrogen; Heavy metal;  Volatile Fatty Acids (VFA); Total phosphate.

Figure 6 :

 6 Figure 6: Diet patterns of surveyed Clean Team customers

Figure 7 :Figure 8 :

 78 Figure 7: Correlation between depth and temperature in the tank

Figure 9 :

 9 Figure 9: On-going soluble COD (g/l)

Figure 10 :Figure 11 :Figure 12 :Figure 13 :Figure 15 :Figure 17 :

 101112131517 Figure 10: Correlation between TS and soluble COD in household sample

Table 1 :

 1 Anaerobic digestion processes ...........................................................

Table 2 :

 2 Faeces and waste from chemical toilet characteristics .......................

Table 3 :

 3 Faeces and sludge characteristics .....................................................

Table 4 :

 4 Number and type of samples analysed for each parameter ...............

Table 5 :

 5 Equation for t-test

Table 6 :

 6 ........................................... Actual sampling and analysis conditions ............................................

Table 7 :

 7 Student's T-test value for storage factor .............................................

Table 8 :

 8 Student's T-test value for chemical factor ...........................................

Table 9 :

 9 T-value of diet parameters ..................................................................

Table 10 :

 10 The mean (std err) concentrations of physique & chemical characteristics of sludge collected from Clean Team toilets ......................

Table 11: The mean (std err) production of physique & chemical characteristics of sludge collected from Clean Team toilets .............................................. Table 13: Tank samples characteristic ............................................................. Table 14: Household and Tank parameters means .......................................... Table 15: T-value of student test with depth in the tank ................................... Table 16: Total volatile solids removal in the failed BMP testErreur ! Signet non défini.

Table 17 :

 17 On-going soluble COD (g/l) in the biodegradability test ....................

Table 18 :

 18 Optimum for anaerobic digester

Table 1 : Anaerobic digestion processes Category of processes Type of reactor

 1

		Complete Mix-process
	Anaerobic suspended growth processes	Anaerobic contact process
		Anaerobic sequencing batch reactor
		Upflow anaerobic sludge blanket (UASB) reactor
	Anaerobic sludge blanket processes	Anaerobic baffled reactor (ABR)
		Anaerobic migrating blanket reactor (AMBR®)
		Upflow packed-bed attached growth reactor
	Attached growth anaerobic	Upflow attached growth anaerobic expanded-bed reactor
	processes	Attached growth anaerobic fluidized-bed reactor
		Downflow attached growth processes
		Covered anaerobic lagoon process
	Other processes
		Membrane separation anaerobic treatment process

Table 2 : Faeces and waste from chemical toilet characteristics Source Clean Team waste Chemical toilet sludge

 2

				Faeces
				estimation. in			Faeces
				urban DC
		Griesauer (2011)	ATV (1997) cited in Griesauer (2011)	Feachem, et al. (1983)	Heinss, et al. (1998)	Lopez Zavala, et al. (2002)	Kujawa-Roeleveld & Zeeman (2006)	Tilley, et al. (2008)	Yadav, et al. (2010)
	Total mass	161 g/p/d 181 g/adults/d		250 g/p/d	250 g/p/d		0.07-0.17 g/p/d	50 l/p/y
	TS	3.5% (1.7-5.3%)	1-20%	20%		18.2%			20%
	TVS	86.3% of TS (82.3-89.6%)				84.4% of TS			82% of TS
	COD		4-90 g/l			1.45 mg/g of dw 45.7-54.5 g/p/d
	BOD 5	1	2-44 g/l	19.3 g/p/d			14-33.5 g/p/d
	N	229-2240 mg/l	2-7 g/l	5-7% of dw 2	4-7% of dw	6.0% of dw	1.5-2 g/p/d	10%	4.1% of dw
	P		0.2-3.3 g/l	3-5.4% of dw	4% of dw	0.5% of dw	0.3-0.7 g/p/d	30%	1.1% of dw
	C			44-55% of dw	48% of dw				42.5% of dw
	K			1-2.5% of dw	1.6% of dw		0.8-1.0 g/p/d	12%	2.2% of dw
	Organic matter		88-97% of dw	92% of dw
	pH	5.8-6.8	7-11						5.3

Table 3 : Faeces and sludge characteristics Source Faeces - Rural area High strength sludge (HSS) -Public toilet or bucket Low strength -Septage

 3

		Gotaas (1956)	Strauss, et al. (1997)	Heinss, et al. (1999)	Doku (2003)	Klingel, et al. (2002)	Strauss & Heinss (1995)	Strauss, et al. (1997)
	Total mass 135-270 g/p/d
	TS	35-70 g/p/d	> 3.5%	52.5 g/l	2-19%	< 3.5%	14 g/l	< 3%
	TVS				62% of TS > 60% of TS
	COD		20-50 g/l	49 g/l	47.6 g/l	20-50 g/l	8.5 g/l	< 10 g/l
	BOD 5			7.6 g/l	8.8 g/l	> 0.5 g/L	630 mg/l
	N	5-7%
	P	3-5.4%
	C	44-55%
	K	1-2.5%
	Organic matter	66-80%
	pH			7.9

Table 4 : Number and type of samples analysed for each parameter

 4

	Measurement	Household sample Tank Sample
	Volume	32	-
	pH	12	5
	Temperature	36	5
	ORP	36	5
	Total solid	34	5
	Total volatile solids	34	5
	Soluble COD	36	5
	Total Nitrogen	36	5
	Ammonium (NH4 + )	36	5
	Phosphate (PO4 3-)	36	5
	Nitrate (NO3 -)	7	-
	Total Potassium	6	-

Table 5 :

 5

Equation for t-test (Lowry, 1999-2013, b) Equation 1: df Na and Nb being the respective size of sample A and B considered.

Table 6 : Actual sampling and analysis conditions

 6

	Category	Number of samples	Initial volume of chemical in the cartridge	Analysis conditions
	1	7	7l	Stored 2 weeks in the freezer
	2	14	7l	Analysed the day of sampling
	3	15	5l	Analysed the day of sampling
	Two hypotheses were tested by Student's T-test with an interval of confidence
	at 95% for each parameter:

Table 7 : Student's T-test value for storage factor

 7

	Parameter	t-value	df	p
	Soluble COD	2.252	19	0.0364
	Total Nitrogen	4.819	19	0.0001
	Total solids	-0.0002	17	0.9999
	Total volatile solids	-0.838	17	0.4139
	Ammonium	-0.006	19	0.9949
	Phosphate	1.328	19	0.1999

Table 8 : Student's T-test value for chemical factor

 8

	Parameter	t-value	df	p
	Soluble COD	-0.819	27	0.420
	Total Nitrogen	0.975	27	0.338
	Total solids	-1.280	25	0.212
	Total volatile solids	-1.362	25	0.185
	Ammonium	-0.819	27	0.420
	Phosphate	0.727	27	0.473
	Considering the way waste collectors are filling clean cartridges with chemical,
	there is a volume variation within all cartridge. Initial volumes are not strictly 7 or
	5 liters and values were measured out approximately

Table 9 : T-value of diet parameters

 9

	Number of time a	Number of time a
	customer eats	customer eats
	meat/fish per week	vegetable per week
	t-value df	p	t-value df	p

Table 10 : The mean (std err) concentrations of physical & chemical characteristics of sludge collected from Clean Team toilets

 10

	Cat. Users	Days between collection	Volume (l)	pH	Temperature (°C)	ORP	Total solids	Total volatile solids 3	Soluble COD (g/l)	Total nitrogen (g/l)	Ammonia (g/l)	Total Phosphate (mg/l)	Potassium (g/l)	Nitrate (mg/l)
	1	7.71 (7.40)	2.9 (1.0)	11.8 (3.2)	6.29 (0.73)	26.7 (6.2)	-287.5 (91.8)	4.05% (1.46%)	80.21% (4.96%)	13.3 (7.4)	0.41 (0.34)	0.41 (0.40)	249.4 (22.0)	-	-
	2	3.86 (2.38)	3.6 (0.6)	9.7 (0.3)	6.61 (0.17)	27.0 (2.5)	-173.6 (165.0)	4.05% (2.28%)	75.73% (12.84%)	20.5 (6.6)	1.94 (0.59)	0.43 (0.29)	396.8 (154.3)	12.6 (6.6)	90.6 (14.7)
	3	2.80 (0.98)	4.2 (0.7)	7.9 (0.5)	-	26.6 (1.9)	-224.5 (136.7)	5.20% (2.18%)	80.76% (4.47%)	27.4 (10.2)	3.19 (1.29)	0.66 (0.45)	464.0 (127.2)	45.6 (15.1)	52.5 (20.6)
	All	4.17 (4.06)	3.7 (0.69)	9.0 (2.06)	6.43 (0.27)	26.8 (1.5)	-216.9 (147.5)	4.56% (2.17%)	78.87% (8.80%)	24.09 4 (9.33)	2.59 4 (1.19)	0.52 (0.40)	396.2 (149.0)	29.1 (0.0)	68.8 (26.3)

Table 11 : The mean (std err) production of physical & chemical characteristics of sludge collected from Clean Team toilets Cat. Volume of waste produced by customer 5 (ml/cap/d)

 11

	Soluble COD	Total nitrogen	Ammonia	Total Phosphate	Potassium	Nitrate
	(g/cap/d)	(g/cap/d)	(g/cap/d)	(mg/cap/d)	(g/cap/d)	(mg/cap/d)

Table 12 : Tank samples characteristic

 12

	Sample Depth	pH	T	ORP	Total	Total	Soluble	Total	Ammonia	Phosphorus
		(cm)		(°C)		solids	volatile solids 6	(g/l) COD	(mg/l) Nitrogen	(mg/l)	(mg/l)
	T1	0	5.82 27.5 -243.7 20.05% 83.85%	38.2	173.3	1,726.7	705.0
	T2	40	6.03 27.4 -291.0 11.61% 86.95%	25.1	315.6	812.0	503.3
	T3	80	6.28 27.2 -302.7 4.92%	85.51%	24.3	193.3	858.7	451.7
	T4	120	6.13 27.1 -289.0 5.85%	85.77%	20.4	177.8	488.0	408.3
	T5	160	6.22 26.9 -287.3 5.09%	85.18%	19.4	180.0	858.7	353.3
	Mean	-	6.09 (0.16)	27.3 (0.2)	-282.7 (20.3)	9.50% (5.82%)	85.45% (1.00%)	25.5 (6.73)	208.0 (54.2)

Table 13 : Household and Tank parameters means

 13

	Parameters	pH	T° (°C)	ORP	Total solids	Total volatile solids	Soluble COD (g/l)	Total nitrogen (g/l)	Ammonia (g/l)	Total Phosphate (mg/l)
	Household	6.43	26.8	-216.9	4.56%	78.87%	24.09	2.59	0.52	396.2
	means	(0.27)	(1.5)	(147.5)	(2.17%)	(8.80%)	(9.33)	(1.19)	(0.40)	(149.0)
	Tank	6.09	27.3	-282.7	9.50%	85.45%	33.6	2.3	948.8	484.3
	means	(0.16)	(0.2)	(20.3)	(5.82%)	(1.00%)	(10.8)	(1.0)	(412.9)	(120.9)

Table 14 : T-value of student test with depth in the tank

 14

	Parameters	t-value	df	p
	T (°C)	1,866	8	0,099
	Soluble COD (g/l)	1,914	8	0,091
	pH	2,613	8	0,031
	ORP	12,074	8	0,000
	Total nitrogen (mg/l)	-3,267	8	0,011
	Ammonium (mg/l)	-4,169	8	0,003
	Phosphorus (mg/l)	-6,059	8	0,000
	Total solids	2,825	8	0,022
	Total volatile solids	2,798	8	0,023

Table 15 : On-going soluble COD (g/l) in the biodegradability test Sample Day 0

 15

			Week 1	Week 2	Week 3	Total loss
	T1	38.2	7.3	31.0	29.0	-9.2 (24%)
	T2	25.1	<6	26.5	24.8	-0.3 (1%)
	T3	24.3	<6	18.5	17.7	-6.6 (27%)
	T4	20.4	15.8

Table 16 : Optimum for anaerobic digester (Polprasert, 2007)

 16

		Digester type	Volatile solids	COD	HRT
	Dispersed-growth digester	1-4 kg VS/m 3 /d	1-6 kg COD/ m 3 /d	10-60 days
	Attached-	Anaerobic filter	1-15 kg VS/m 3 /d 5-30 kg COD/ m 3 /d	1-10 days
	growth digester	Up-flow sludge blanket			0.5-6 days
	Clean Team waste	36 kg/m 3	75 kg/m 3

BDO 5 = Biological Demand in Oxygen for 5 days

dw = dry weight

Expressed in percentage of total solids

Data from samples of category 1 are excluded of the mean.

The initial volume of chemical is not include in this volume

Expressed in percentage of total solids

partial fulfilment of the requirements for the degree of MSc (NB. work, as well as Zakiyah Abubakari for her help with customers' interviews. The support of Lisa Hawkes from Unilever is gratefully acknowledged.

Household sampling

The following tables present the overall means and standard errors (in brackets) for each parameter for each category and all the samples. Waste is characterised by its concentration (Table 9), but data are also significant when converted to production per capita per day. This calculation has been done when relevant for Clean Team waste and is presented in Table 10.

APPENDICES