Assessment of the impacts of local conditions and sampling methods on the characteristics of faecal sludge

Since 1990, almost 1.9 billion people have gained access to an improved sanitation facility, while 2.6 billion people still live without access to improved sanitation. In urban areas of low- and middle-income countries, the majority of household rely on onsite sanitation systems, producing huge amounts of faecal sludge (FS) that end in the environment every day. FS has to be managed in a proper way, integrating onsite system, storage, transport, treatment, disposal and reuse. In the past years, several FS treatment technologies have been developed and implemented, however partly due to the lack of knowledge on the FS characteristics, many of them have encountered failures. Reliable assessment of FS characteristics is essential in order to design adequate FS treatment facilities. However, FS is a highly variable waste and no methodology has been established to better understand this variability and the characteristics so far. This Master project, which takes place in the framework of the PURR project (Partnership for Urban Resource Recovery) that is a collaboration between the Sandec (Department of Water and Sanitation in Developing Countries, Switzerland), EPFL (Swiss Institute of Technology of Lausanne, Switzerland) and IESE (Institute of Environmental Sciences and Engineering of Hanoi, Vietnam), aims to answer this important gap of knowledge. To assess the influence of the local conditions on the characteristics of FS, fifty nine samples of household septic tank have been collected in Hanoi, the capital city of Vietnam. Fourteen factors reflecting local conditions and twenty eight parameters have been measured. QA/QC procedure together with the analysis of the organic compounds helped to determine the reliability of the data. Therefore, only reliable data was discussed, including seven factors (number of inhabitant, septic tank age, FS age, bio-additive, water addition in the septic tank, septic tank volume and number of trucks to empty the septic tank) and twenty parameters (temperature, pH, TS, TSS, VS, VSS, COD, carbohydrate, lipid, protein, VFA, TN, NH4+, TP, PO43-, total fibres, Ni, Pb, Fe and Zn). A degradation of the solids (TS, TSS), organic fraction (VS, VSS, COD, carbohydrate, protein, VFA) and nitrogen compounds (TN, NH4+) is mainly observed during the ten first years of storage. Addition of bio-additive potentially contributes to this process. The size of the septic tank seems to influence also the emptying frequency and then the degradation of the matter. Six sampling methods (S, HG, HT, B, M and D methods) have been tested over six samplings of household septic tank in Hanoi. First method with direct sampling inside the septic tank (S). Two methods collecting sludge from the manhole with different heights of collection (HG=15.4cm, HT=4cm). Three methods from the discharge valve of the truck (B=at beginning; M=at middle; D=at beginning, middle and end of the discharge with a volume ratio of 1:2:1 respectively). Sampling methods seems to not have influence on pH and temperature and soluble compounds concentrations. However, solids, organic content and nutrients concentrations are influenced. HG tends to under-estimate the concentrations when B and D could over-estimate it. HT and M seems to be the more accurate and reliable sampling methods of FS tested. Such knowledge on the FS variability could allow reducing the number of samples needed to obtain representativeness of FS. Indeed, collecting information related to the factors previously mentioned at the household level could work as predictor together with the characterization study to evaluate FS characteristics of a specific area. This allows savings in terms of time and budget. Moreover, the influence of the three factors (FS age, bio-additive addition, septic tank volume) on the FS characteristics, could constitute a basis for the development of policies and regulation. In order to reduce pollutant concentration in FS, appropriate emptying frequency and adequate storage tank design could be determined. The sampling methods HT and M would constitute low cost sampling methods, which would be simple to handle, fast, efficient and reliable to collect FS, and easily reproducible in different context. This is a real step forward for the improvement of knowledge about FS characteristics.

Selecting appropriate treatment technologies for faecal sludge (FS) from onsite sanitation systems

Magalie Diane Bassan, Christof Holliger, Viet Anh Nguyen, Linda Strande

Context Worldwide: FS production much larger than treated volumes In Vietnam: • Urban households required to own septic tanks • Combined onsite and centralized sanitation • FS emptying frequency up to 10 years or more Negligible FS volumes treated before discharge PURR: Partnership for Urban Resource Recovery • Developing knowledge for adequate FS treatment in urban Vietnam • Testing feasibility of anaerobic digestion for FS treatment Study goal To understand the local context and factors influencing the selection of appropriate FS treatment technologies in case study cities in Vietnam Methods Field visits in 5 cities Review of literature and legal documents Interviews with local authorities and stakeholders in charge of wastes and FS Household surveys in sewered / non-sewered, poor and rich areas (100 houses per city) Results • 73% septic tanks have less than 5 years and need to be emptied within 5 to 15 years (emptying frequency in 5 case study cities >10 years) ->FS will continue to be produced in urban Vietnam and strategies are required in short term • A variety of stakeholders and management systems exist between cities with a lack of willingness to manage FS ->Need for a coherent sanitation strategy at the national level, with geographical separation of areas with onsite/centralized systems • Different waste management infrastructures exist in each city ->Different technologies are required, even in the same country Conclusions and perspectives • Current engineering approaches and sectorial strategies are not adequate • Comprehensive context assessment is required • Possibilities for co-treatment of organic wastes with FS to optimize financial flows, public and environmental protection will be assessed

2014

Epuration des eaux usées par lagunage à microphytes et à macrophytes en Afrique de l'Ouest et du Centre

Doulaye Koné

Stabilization ponds and water lettuce-based systems in West and Central Africa - State of the art, removal performances and design criteria Despite several projects undertaken so far, sanitation remains a huge challenge in West and Central Africa. Big cities are growing without sustainable solution for sanitation planning. Sewage systems and wastewater treatment plants are underdeveloped or absent. Stabilization ponds have been introduced 30 years ago, but this low-cost technology remains marginal in wastewater treatment systems. The climate context is favourable to develop a set of low-cost wastewater treatment plants, particularly macrophyte-based systems. Pilot scale studies show the enormous potentialities of such sustainable technologies for water pollution control and treatment. None of the full scale applications works and this is due to the low economic level and the lack of political support. Another important reason is the lack of training and research. This situation requires the development of a collaborative network in which African researchers can share knowledge and promote sustainable wastewater treatment plants, as sanitation demand is growing exponentially in conjunction with the population growth in the cities. Stabilization ponds account for only 7% of the whole wastewater treatment technologies built in West and Central Africa, against 75% of activated sludge processes that in most cases failed. In spite of their bad quality, the effluents are widely reused in urban agriculture. Experimental data showed a maximum removal rate of 30% and 60% for COD and BOD5, respectively, and a maximum loading rate of 500 kg BOD/ha/d. Macrophytes-based systems are even more scarce (3%). The link of this technology with potential risks of malaria has slowed down its development. Nevertheless, data from studies in Niamey and Yaounde, and from rice culture irrigation zones showed that this correlation is not significant. Little research is done on wastewater treatment technologies for local application. This is one more reason why this study was based at EIER in Ouagadougou (Burkina Faso). The aim of this work was to determine the parameters for optimal removal performance and to elucidate design criteria of water lettuce-based wastewater treatment systems, possibly in combination with stabilization ponds to promote restrictive irrigation in market gardening. In secondary treatment, the maximum admissible loading rate was found to be 500 kg BOD5/ha/d (400 mg O2/l). Above this value, sludge accumulation at the pond surface caused by intensive methanogenic degradation of the sediments lead to plants die-off. COD and BOD5 removal rate was not correlated to redox state or dissolved oxygen concentrations. This indicated that the removal was mainly due to settlement and trapping of suspended solids in roots and sediments. Aerobic degradation remains low because the extent of oxygen release by plants cannot explain the yield obtained. COD and BOD5 removal performance reaches an optimum rate of 75% and 85% in two weeks hydraulic retention time, respectively. Regression equations between applied (λappl) and removed (λrem) loads is expressed by λrem (COD) = 0.75λappl (COD) – 10.4, (r2 = 0.99). The first order kinetic constant for BOD5 removal, kT = 0.14 d-1 (or kT = 0.11 d-1 for the DCO) can be used for designing of treatment ponds with the equation from the International Water Association (IWA). From the total nitrogen entering the treatment ponds, depending on the nitrogen load, between 44% and 60% were removed in the configuration with three ponds and a HRT of 18 days. Nitrogen can be removed by plant uptake with the harvest, by settlement or trapping with the suspended solid or by elementary nitrogen formation which occurs by the combination of nitrification, denitrification, and anaerobic ammonium oxidation. Nitrogen removal by plants was estimated to account for 10% to 39% in total nitrogen removed from ponds with a HRT of 18 days based on the steady growing and nitrogen uptake rate found. With a weekly harvesting rate of 50% of total plant biomass in the ponds, the water lettuce growing rate and the nitrogen uptake were 50 ± 1 g dry weight/m2 (182.5 t dry weight/ha/year) and 0.36 g N/m2/d (1314 kg N/ha/year), respectively. Trapping and settling of organic nitrogen present mainly in the suspended solids fraction removed about 25-48% of total nitrogen. It was found that water lettuce-based treatment systems conserved quite large amounts of ammonium in the effluents, a fact that is favourable for irrigation water reuse. Nevertheless, nitrogen loss by nitrification-denitrification occurred in water lettuce ponds, and perhaps even anaerobic ammonium oxidation. Nitrification became visible when COD dropped below 140 mg O2/l. With nitrogen loading varying from 31 to 97 kg N-NH4+/ha/d, the ammonium removal rate varied from 15-40% with a HRT of 18 days and from 20-60% with a HRT of 21 days. Hence, 40-80% of the ammonium was conserved in the water lettuce-based systems. In addition to conserve ammonium, water lettuce ponds also perform better than facultative ponds in organic pollutant removal, 75% against 50% in DCO reduction, respectively. When discharging the facultative pond effluent in a water lettuce pond, removal performance of the combined (upgraded) system is equal to that of a water lettuce pond. Faecal coliform removal in the two systems is very close, three weeks were necessary to ensure a reduction of three logarithmic units in faecal coliform concentration. To reach the objective of irrigation reuse, water lettuce-based treatment plants should not significantly affect the availability of the treated water. It was shown that the additional water loss due to the presence of Pistia stratiotes is lower than 10% of the average evaporation rate of microphytes ponds. Based on the results obtained during this study the following recommendations can be made. If the surface occupied by a plant is a limiting parameter, the footprint of the ponds can be decreased by designing a water lettuce based system with ponds depth bigger than the recommended 70 cm. This depth has been proposed to promote oxygen release in ponds, which was supposed to support aerobic oxidation. According to our results, organic matter removal is not correlated to oxygen availability. In addition, increasing the pond depth could also increase the ammonium conserved in the effluent. For restrictive irrigation, in market gardening, a hybrid system combining facultative ponds with water lettuce ponds is suitable, not only to secure the effluent quality, but also to reduce constrains related to plant management. During this thesis, the beginning of a network for collaboration has been created between members of different research teams including the Abdou-Moumouni University in Niamey, the Cheick Anta Diop University of Dakar, the University of Yaounde and the Ecole Inter-Etats d'Ingénieurs de l'Equipement Rural (Ouagadougou) in Burkina Faso. Several topics investigated during this study should be studied in more detail, and this best within the framework of this network of collaboration in West and Central Africa.

EPFL2002

Vers un assainissement urbain durable en Afrique subsaharienne

Halidou Koanda

Justification In Sub-Saharan Africa, excreta and wastewater disposal is characterised primarily by on-site sanitation systems. This sanitation option is more likely to increase as governments, municipalities, communities, private operators and donor agencies strive to reach the Millennium Development Goals aimed at reducing by half the proportion of people without access to basic sanitation facilities. Due to increased urban population growth in Sub-Saharan Africa, the faecal sludge volumes will increase to alarming quantities in the coming decades. An evaluation of faecal sludge management practices reveals that the main shortcomings relate to the widespread lack of involvement and foresight by the municipalities, the paucity of effective legal provisions and organization, and the absence of stakeholder coordination. Stakeholder involvement for planning and implementing faecal sludge management is virtually inexistent or excluded from urban sanitation planning processes. In the majority of situations, faecal sludge management is financially not viable. This is a major cause of the indiscriminate dumping of faecal sludge in urban areas or its untreated use in urban agriculture. These practices not only pose permanent and serious health risks but also contaminate both scarce ground and surface water. Objective and general approach On the basis of these facts, which present a real challenge to sector specialists, the overall objective of our research is to develop an innovative strategic planning approach for sustainable faecal sludge management in urban areas which allows minimising public health and environmental risks. Focus is placed on developing a reproducible methodology for stakeholder involvement, on enhancing population awareness for improved faecal sludge disposal and attributing a leading role to the dynamic private faecal sludge emptying and transport operators. These aspects form the three pillars of our search for a comprehensive methodological approach. The municipality of Ouahigouya in Burkina Faso with a population of about 65'000 inhabitants was used as pilot site to launch, implement and scientifically validate the approach. Analysis and stakeholder involvement The stakeholder-based planning approach developed in Ouahigouya relies on a combination of stakeholder identification and analysis, and participatory planning techniques (focus groups, workshops, informal meetings, all-stakeholder workshops). A quantitative survey among households allowed collecting stakeholders' proposals and evaluating suggestions for improvement of faecal sludge management and neighbourhood hygiene proposed by the population. The main steps in the stakeholder involvement approach include: Jointly clarifying the objectives of the planning process together with the stakeholders; Identifying stakeholders and their interests; Classifying stakeholders according to their importance and influence based on defined criteria and confirmed by the stakeholders themselves; Identifying the interactions between the stakeholders; Verifying the results of the stakeholder analysis by the stakeholders themselves; Choosing stakeholder involvement techniques; Implementing the chosen method of stakeholder involvement: development of faecal sludge management scenarios, acceptance of the scenarios by the stakeholders in focus groups, choice and acceptance of a basic scenario for development of the future strategy in an all-stakeholder workshop; Evaluating the chosen involvement process by the stakeholders. The experience gained with the planning methods developed and implemented in Ouahigouya reveals that the "Stakeholder analysis" method is efficient and provides answers to questions such as: Who are the important and influential stakeholders? Who should participate in the planning process and in which manner? This experience also revealed the need for capacity building of certain stakeholder categories (emptying operators, women's associations, etc.) to increase their degree of involvement in the planning process. Improvement in stakeholder involvement was achieved thanks to a combination of workshops, focus groups and other informal meetings allowing less influential stakeholders (associations of local women, horticulturists, emptiers) to share information and to freely express their opinions and concern and to defend their interests. Thus, providing an excellent example of local democracy appreciated by all stakeholders of Ouahigouya. The approach developed provides tools for policy-makers and planners to ensure an effective stakeholder involvement in the process of developing a common vision and implementation of improved urban sanitation measures. The conditions for replicating the approach developed and tested in Ouahigouya are due to participatory democracy, great commitment of the local authorities and the high motivation of the stakeholders involved. Levers for the willingness-to-improve faecal sludge management and neighbourhood hygiene The evaluation method of the willingness to improve faecal sludge management by the population was based on a combination of the planned behavior model of Ajzen and the contingent valuation method, financial analysis of the pit emptying and faecal sludge enterprise, and on focus groups of stakeholders. By focusing on local practices, perceptions and individual behavior, this method revealed that financial viability – often reduced to willingness-to-pay – is not the only factor to consider when planning improvement of sanitation practices. Willingness-to-improve is highly dependant on psycho-sociological factors such as attitude towards and beliefs in an improved neighbourhood environment, social pressure on the households by the neighbourhood as well as the subjective costs and benefits expected from improved faecal sludge management. These factors therefore present levers allowing planners and decision-makers to encourage, increase and develop the demand for improved latrine emptying services, e.g. though social marketing. Promoting private entrepreneurs According to market analysis of emptying services and stakeholders involved, small private and mainly informal enterprises play a leading role in faecal sludge management in most cities of Sub-Saharan Africa. These operators, dynamic but fragile, require an appropriate institutional, jurisdictional and economic environment based on a balanced partnership between the municipality (public) and the private sector. Our study reveals that for a company truck to be profitable, about 1'000 trips per year (at 6'000 FCFA per trip) are required or the equivalent of a city of 56'000 inhabitants. In the case of Ouahigouya, profitability is increased if the emptying operators apply the latest management and professional tools and techniques, and manage to provide emptying services in neighbouring towns. Decision support tools The research led to developing decision support tools for professionals and policy-makers. These tools facilitate the development of a tariff-oriented policy to avoid uncontrolled faecal sludge discharge into the environment, to render investments by private operators profitable, and still make emptying services accessible to low-income households. This involves: Analysis of the cost structure of 3 pit emptying companies has revealed that fuel, maintenance/repair and personnel costs make up 45%, 20% and 30%, respectively, of an enterprise's operating expenses. An Excel programme was developed to allow municipalities and private operators to determine the operating costs of emptying services. This allowed to establish a sustainable money flux between the different stakeholders involved and to define the tariffs. To prevent faecal sludge discharges in the immediate residential environment or on unauthorised sites, it might under specific circumstances prove necessary and feasible to reimburse rather than charge entrepreneurs for delivering faecal sludge to the treatment sites, hence, create a strong incentive for good emptying and haulage practice. Evaluation methods of the sludge quantities to be disposed of have been developed to allow faecal sludge planning by the municipal authorities, assessment of the potential market and return on investment by the private operators. Advantages of the approach for the population of Ouahigouya Based on the results of our study, it was possible to formulate practical recommendations for the organisation of the urban sanitation sector for the municipality of Ouahigouya – now in possession of a sustainable faecal sludge management strategy. Our study has also contributed to promoting local consultation and raising the awareness of the role and contribution of each stakeholder group, in particular the previously neglected manual emptiers in their daily efforts to improve the living conditions of the urban inhabitants. The "Strategic Excreta and Wastewater Sanitation Plan", that was developed and supported by the "Office National de l'Eau et de l'Assainissement - National Water and Sanitation Agency", provides an excellent framework for the implementation of the elaborated faecal sludge management model (as part of the this strategic plan).