Sanitation project starts at UDSM

Dar es Salaam. The College of Engineering and Technology (CoET), in collaboration with Swiss Federal Institute of Aquatic Science and Technology, has introduced Faecal Sludge Dewatering Research (Eawag) Project that intends to produce biochar and improve sanitation.

Biochar is charcoal produced from organic matter, which is stored in the soil as a means of removing carbon dioxide from the atmosphere.

In Tanzania and other countries, a large amount of faecal sludge is discharged into water sources such as the Ocean, lakes, rivers and streams or valleys untreated.

Apart from understanding the process of faecal sludge dewaterability, development and optimisation of dewatering technologies, this research will provide cost estimates and design guidelines for full scale project implementation.

Therefore, research results are expected to contribute to the design of appropriate faecal sludge dewatering technologies in densely populated urban areas and decrease indiscriminate discharge of faecal sludge into water sources or valleys. According to CoET, faecal sludge is collected from households by vacuum trucks for discharge into Kurasini and Vingunguti wastewater stabilisation ponds.

Faecal sludge in urban areas

In order to receive faecal sludge for research purposes, a small number of vacuum trucks (on average one truck per day) will be redirected for discharge into the proposed pilot-scale dewatering facility at the University of Dar es Salaam (UDSM). Observation made by CoET has discovered that collection and transportation of faecal sludge in urban areas exists, but treatment is inadequate so the newly introduced project will address this problem.

The research is new to Tanzania, but in countries like Senegal and Uganda, Eawag has been implementing a similar research in collaboration with the University of Dakar and Makerere University. This research optimises faecal sludge dewatering in several ways.

What is done in other countries

In Dakar, covered drying beds maintained faecal sludge drying in the rainy season and turned faecal sludge on the surface of the filter layer reduced drying times by about 20 per cent and locally available conditioners were able to increase faecal sludge dewatering by 6 to -60 per cent depending on treatment goals.

In Kampala, geotextiles and turning of faecal sludge on full scale drying beds increased the treatment end product quality and drying rate respectively.

The principal researher, Dr Richard Kimwaga, from the department of Water Resources Engineering at CoET told The Citizen recently that both paper work of the research project and the construction of the facility started last year.

He said faecal sludge was typically 90 per cent water, which makes dewatering an important treatment goal as this reduces transport costs and increases the resource potential of treatment end products like soil conditioner, biochar or solid fuel.

Dr Kimwaga said the construction of the facility located at UDSM premises was funded by the Swiss Government at Sh31 million.

Start and end of the project

He said the three-year research project would start its operations next month and end in 2018, whereby the number of students from the department would get an opportunity to learn how it operates and its importance in addressing the sanitation problem at community level.

Further he said the research would develop design guidelines to treat faecal sludge that would later be disseminated to regional water authorities in the country.

Dr Kimwaga added: “In other countries like Uganda and Senegal there is faecal sludge, but in Tanzania this will be the first to be designed by CoET. With this project, we will produce biochar and help people stop using charcoal.”

For example, faecal sludge can be unstabilised, when collected from public toilets or partially stabilised, when collected from septic tanks.

How the machine operates

The facility will consist of a receiving tank, two settling-thickening tanks, a mixing tank and 12 drying beds. Faecal sludge will be discharged by vacuum trucks into the receiving tank from where it flows into settling-thickening tanks. After settling-thickening, the faecal sludge is transferred with a mobile submersible pump into the mixing tank. A permanently installed pump transfers the faecal sludge from the mixing tanks to drying beds.

The liquid faecal sludge fraction remaining in settling-thickening tanks and percolate from drying beds is discharged into waste stabilisation ponds. Besides this conventional faecal sludge dewatering, areas are reserved for research with conditioners and mechanical dewatering devices.

Electricity supply for the dewatering facility will be ensured by a diesel generator. A water tank will be constructed to provide water for cleaning of the facility.

Environmental impact and security

The proposed construction site of the pilot-scale dewatering facility is next to the wastewater stabilization ponds of UDSM. This will ensure that no untreated faecal sludge enters the environment.

This means that the discharge of faecal sludge into the waste stabilisation is small and is not expected to influence the functionality of the wastewater stabilisation ponds. For security reasons, the entire pilot-scale dewatering facility will be fenced.