Geotube – Filtration – October 2018
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Location of the case study
Main treatment objectives
Capex per design input flow
Opex per real input flow
Description of the treatment process
This approach uses a combination of Hydrated Lime Treatment, Geotextile Tubes known as ‘Geotubes’ and Filtration. In the first step, the faecal sludge is pumped out of the pit latrines using mechanical sludge pumps. The sludge is emptied into barrels with a lime (calcium hydroxide: Ca(OH) mix. The stabilised sludge is then poured into a Geotube from barrels through a mesh screen to remove any solid waste. A Geotube consists of a permeable membrane which allows for dewatering of the sludge. The liquid portion of the sludge drains out of the Geotube into a primary filtration unit consisting of three layers of filtration media. This effluent then flows into a secondary filtration unit after which it can be discharged into the environment. The solid fraction of the sludge is retained inside the Geotube and then can be transported to a disposal site or incinerated.
The dried sludge and effluent are not fully stabilized and may require further treatment or storage, depending on the desired end-use.
Description of the emergency context
The project site – Unichiprang is a hilly area and is currently hosting an estimated 21,300 Rohingya refugees (ISCG Full Situation Report, 11 March 2018). Refugees are continuing to cross the border into Bangladesh, with a total of 3,236 new arrivals reportedly entering the country in February 2018 alone, bringing the number to over 5,000 newly arrived refugees so far in 2018. The population is predominantly Muslim.
It is essential that the community is informed about the risks related to faecal sludge before the desludging process is initiated. The community needs to be aware of the need to keep a safe distance during the operations, for them and their children and can be part of the planned hygiene promotion activities. Additional awareness raising measures are required to avoid pit latrines being used for solid waste. PPE should be worn and training for involved staff is needed to ensure safety and the proper functioning of the technology. This technology is appropriate for the stabilisation of faecal sludge in the acute phase of an emergency and can be implemented quickly, where the appropriate geotextile and good quality lime (CaOH2) is available. The infrastructure is not permanent. Once there is land available, the capacity of the system can easily be scaled up by increasing the number of barrels, geotextile tubes and infiltration beds. It is effective in decreasing the sludge volume (through dewatering) which is especially important when sludge needs to be transported elsewhere for end-use or disposal.