Integrated faecal sludge management scheme for the cities of Burkina Faso

The National Utility for Water and Sanitation in Burkina Faso (ONEA) has recognized the dif ﬁ culty in providing sewered sanitation to the entire urban population and has opted for a strategy involving onsite sanitation. Most of the country ’ s population is served by onsite systems that generate large amounts of faecal sludge, and are responsible for a high prevalence of water-borne diseases. ONEA and the Department of Water and Sanitation in Developing Countries (Sandec) at the Swiss Federal Institute of Aquatic Science and Technology (Eawag) have a collaborative project that aims to establish an enabling environment for the development of the faecal sludge sector at the institutional and technical level. The project ’ s participatory process has allowed the design of a treatment plant adapted to local conditions, and the elaboration of the ﬁ rst institutional framework for faecal sludge management including several new of ﬁ cial documents. Several technical studies ﬁ lled knowledge gaps of faecal sludge characterization, and the feasibility of implementing planted drying beds. Lessons learned are transferable nationally and internationally.


INTRODUCTION
Centralized, sewer-based wastewater systems have not been adequate in meeting sanitation needs in urban areas of developing countries; and 2.5 billion people worldwide still lack access to 'improved' sanitation (UNICEF & WHO ). In West Africa, the majority of the urban population with access to sanitation are served by onsite facilities (e.g. pit latrines, septic tanks) that produce large amounts of faecal sludge, and require a management plan (Mbéguéré et al. ). Faecal sludge is defined here as the 'raw or partially digested slurry or solid that results from the storage of blackwater or excreta' in onsite sanitation systems (Tilley et al. ). Urban sanitation systems based on faecal sludge management have been shown to be adequate and much more affordable than sewer-based systems (Dodane et al. ). At this time, there is no management or treatment of the faecal sludge from onsite systems in Burkina Faso, and the legal framework only weakly addresses these aspects. A lack of regulation is well known to be a major stumbling block in achieving adequate sanitation (Strauss and  To address the sanitation and public health challenge, the National Utility for Water and Sanitation of Burkina Faso (ONEA) has adopted Strategic Plans for the two biggest cities (Ouagadougou and Bobo-Dioulasso) that include wastewater and faecal sludge management (Vezina ). After the completion of a sewer based system, ONEA launched a parallel program for faecal sludge management in these cities.
ONEA signed an agreement with the French Development Agency to build two faecal sludge treatment plants (FSTPs) in Ouagadougou that were designed by a consultant. Following this agreement, a 3-year collaborative project between ONEA and the Department of Water and Sanitation in Developing Countries (Sandec) at the Swiss framework for faecal sludge management, which can also be implemented in other cities in Burkina Faso. This paper presents the activities carried out to meet these objectives during the period of January 2010 to June 2012.

Context
Ouagadougou, the capital city of Burkina Faso, has an estimated population of 1,475,233 (INSD ). It is located in the sahelo-soudanese region of Africa that is characterized by a dry season from October to May, and an intense rainy season from June to September, with a mean annual rainfall of 773 mm (Sou ). The faecal sludge production of Ouagadougou is greater than 500 m 3 /day (Koanda ), and 88% of its population is served by onsite sanitation (Somda ).

Technical advice on the FSTP technologies
The decision to use unplanted drying beds was made by the consultant based on the following important criteria: financial sustainability (e.g. salaries, cost of consumables, amortization), land characteristics (e.g. availability, cost of land), local context (e.g. legal framework, existing stakeholders, hydrogeology, geography), and operational and reuse potential of liquid and solid end products (Strauss & Montangero ). A literature review on appropriate technologies for faecal sludge treatment was presented in a report to strengthen the capacity of local stakeholders (Bassan et al. ). Information workshops on the selected technical options were organized with all the important stakeholders, whose activities are crucial for the sector (e.g. municipality, technical professionals and police, and collection and transport companies) (DFID ). Influential stakeholders that have decision powers (e.g. the Ministries of Environment and Health) were also included, as were local non governmental organizations (NGOs) and universities active in faecal sludge management. The completion of the FSTPs is scheduled for mid-2013. At this time a technical assessment of the design and performance will be conducted.

Research studies conducted in Ouagadougou
In order to meet the project objectives, two research studies were conducted. does not require specialized equipment and consumables, and there is a potential for using treated faecal sludge in agriculture in the outskirts of Ouagadougou. The O&M is less demanding than settling/thickening tanks or stabilization ponds, which require intensive dredging, and the logistics are simpler than co-composting, which requires transport of solid wastes to the treatment plant.
The FSTPs were designed to treat 125 m 3 /day with a TS load of 21,000 mg l À1 , and will have 48 drying beds with a surface area of 128 m 2 . Faecal sludge will be discharged to a channel with one 1 cm grid bar screen prior to the drying beds. Once the beds are fully loaded (nominative load 150 kg TS m À2 /year), they will be left to dry for up to 3 weeks (Pöyry ). The liquid fraction that percolates through the beds will be further treated in nearby waste stabilization ponds designed with anaerobic, facultative and maturation basins. The dried solids will be stored in a

Research studies conducted in Ouagadougou
It is planned to assess the possibility to adapt the unplanted drying beds into planted drying beds to ensure adequate treatment during the rainy season. This could enhance treatment performance and lower maintenance fees (Koottatep et al. ). Important parameters to assess for this adaption include plant acclimatization and demand for end products. The market demand study revealed a strong acceptance of fodder from faecal sludge drying beds among sellers and buyers of fodder. They showed acceptance of 90 and 86%, respectively (Somé Dagba Gbessin ). Benefits include that 'fresh' plants can be available even during the dry season when other vegetation is desiccated. Two local fodder species were selected that have a good agronomic potential and reproduce readily by cuttings in wet environments: Sporobolus pyramidalis and Echinochloa pyramidalis. These species will be tested in experimental planted drying beds to assess the feasibility of full scale operation.

Faecal sludge characterization studies conducted in
Ouagadougou during the dry and rainy seasons revealed that the BOD 5 and TS design values for the FSTPs are overestimated by a factor of 2 (Mahamane ; Zöllig ).
These characteristics were estimated based on literature values prior to the start of the ONEA-Sandec project. Estimating faecal sludge characteristics in different contexts is very difficult due to the high spatial variability, which depends on the type and usage of onsite systems, the collection and transport technologies, the climate and the hydrogeology. This study illustrates the importance of conducting local characterization studies prior to design. The FSTPs' capacities are overdesigned, but fortunately the operation can be adapted, and the load increased. In the end, this will allow for an increased volume of 250 m 3 /day, a treatment capacity that was planned for 2020.  This will help ensure a future enabling environment for this sector. The collection and transport companies were successfully included in the collaborative development of faecal sludge management, and could review institutional documents prior to implementation. This will help guarantee that the businesses will be successful, faecal sludge will be delivered to the FSTPs, and that the FSTPs will function as designed. The developed project approach and solutions can be readily expanded for the implementation of faecal sludge management in other countries. Lessons learned from this project include:

Development of institutional framework and
• Detailed technical and institutional studies at the local level are necessary to accurately design FSTPs; • Faecal sludge management involves multiple private and public stakeholders whose activities need to be coordinated for the system to work effectively, and can be more complicated than sewer-based systems. To ensure success, multiple stakeholder assessment and participative workshops must be conducted; • The enforcement of a new institutional framework for faecal sludge management involves capacity strengthening for the stakeholders in the field of technical, financial, and human resource management together with public outreach campaigns for proper maintenance of onsite systems, and ongoing support of collection and transport companies.