Practical Action has designed Fecal Sludge Treatment unit adopting proven technology of ‘up-flow filtration technique’. A series of filtration chambers has been designed for solid- liquid separation. The raw fecal sludge thickens after separation. The thickened sludge is collected after a certain interval and buried with lime in the designated burial pits having a sand envelop for ensuring safe management. After a certain time, the buried sludge will be converted into compost and if needed, the compost can be excavated to reuse the pits. The liquid portion of the sludge will pass through another two chambers for further filtration and the final treatment of the effluent will take place through a constructed wetland where the pollutants will be absorbed naturally by Canna Indica plants.

This process of up-flow filtration is more environment friendly as all the sludge is kept in the filtration chamber. The main advantage of these plants are that the solid and liquid portion of the sludge are separated. Also another major advantage is that the liquid portion of the sludge is treated with the 3 filtration chambers. There is almost no smell and the desludging process doesn’t follow any manual labor as all the activity is done with proper equipment. One FSM plant on average can cover 220 latrines around its 500 – 800 feet coverage area.

The faecal sludge management unit has four components:

1. Dumping chamber
2. Filtration chambers
3. Constructed wetland and
4. Burial pits

Dumping Chamber:
The sludge from toilets are mostly emptied using motorized collection equipment like super sucker or any other centrifugal pump and then dumped into the dumping chamber. The capacity of the dumping chamber is 300 liters. The unwanted materials, if any like cloths, sanitary napkins etc. are screened from the disposed sludge in dumping chamber. From the dumping chamber, sludge enters into the first filtration chamber of the faecal sludge management plant through gravity flow. The valve at the bottom of the dumping chamber regulates the flow of sludge into the filtration unit.

Filtration Chamber:
Each filtration chamber is made of steel structure with waterproof tarpaulin fitted inside the structure with a capacity is 5 m³ per day. Graded filter materials are placed inside the chambers. Each filtration chamber contains valves at its exit to control the outflow of sludge and effluent respectively at different elevations. Each chamber of the filtration unit is interconnected in a baffled system. The sludge flows through the filtration units following ‘up-flow system’. The solid portion of the sludge gets trapped at the bottom part while the liquid portion rises up through the filter media and flows to the next chamber.

Constructed Wetland:
‘Constructed wetland’ is a kind of shallow trench having Canna Indica plants over stone bed to absorb pollutants naturally. The bottom and sidewalls of the trench are lined with waterproof tarpaulin to avoid contamination by any seepage. The capacity of this chamber is at least 6 cum. While the effluent passes through the constructed wetland, the microbial contents inside the effluent form gelatin and the roots of the plants reduce the pathogenic organisms. From the entry into the filtration chamber to the final discharge point, the retention time of the effluent will be maximum 5 days. Finally, the effluent is collected and tested in laboratory to confirm parameters for safe discharge in surface water bodies.

Burial Pit:
The burial pit has been constructed using locally available RCC rings of having maximum depth of 7ft depending on the groundwater level of the site. Each pit contains a sand envelop of 4 inches that acts as a filter media at outer periphery and the bottom of the pit. Once the thickened sludge in the first chamber gets emptied every week and buried into the adjacent pit having sand envelop with lime. The same process takes place in the rest filtration units but rate of deposition is very slow and therefore burial of thicken sludge will be infrequent.

An expert team of Practical Action Consulting, a sister concern of Practical Action in Faridpur Upazila of north Bangladesh arranges or outsources all the necessary materials. According to the deed between Practical Action and Practical Action Consulting, they are also responsible to fabricate the FSM structures in camps. For the filter media Practical Action calls for tenders and collects estimated quotation from vendors. Through a comparative statement Practical Action selects a vendor to supply the required filter materials. Vendor selection is the most vital part of installation to ensure quality services for the Rohingya people.

Three tiers of monitoring are maintained during construction and installation of FSM plants. Technical experts ensure the installation process following proper guidelines and confirms the good quality of filter materials. The Field Coordinator and his team of Field Officers provide HR support to ensure proper arrangement of the whole construction and installation progress. The Monitoring, Documentation and Reporting Officer checks all the progress and gives alert for due activities. Despite of these technical and operations team, the Finance and Admin Officer does his designated duties in terms of payment and procurement procedures.

It takes over a month generally 30-45 working days for site selection and site approval from CiC of respective camps. To intervene in a camp, Field Coordinator collects need analysis of FSM plants from respective Camp Wash Focal and then moves to RRRC office for taking approval of FSM intervene in the camps through submitting the need analysis report. In the meantime, the frontline staffs do transect walk and search for suitable places. There are some land specifications like at least 800 square feet site above ground water level of 10 feet and having no land slide risk. Moreover, field officers often avoid top hilly area as it is quite difficult to collect the faecal sludge from the latrine pits against gravitation. Field Officers select random sites with the collaboration of Camp Wash Focal and Site Management. Field Coordinator and Project Engineer then visit the identified sites and finalise the places that meet most of the land specifications. When Govt. authorizes the requested intervention in specific camps, field officers then secure the selected sites for FSM plant.

Project Engineer prepares the layout design for FSM plants considering land context. It usually takes 2-3 days for site preparation and site fencing depending on weather. A mason works with 3/4 assistants to construct RCC basement of the plant in 4-5 days. A sanitation worker takes care and waters the basement for 3 consequent days. An expert team of Practical Action Consulting fabricates the FSM structure within 3-4 days. A water leak test is run for 5-7 days to assess any leakage of fabrication before placing the filter medias in the chambers. Parallel construction of burial pits, soak well and wetland goes on within this period of fabrication and water leak test. After a successful water leak test, filter materials are placed in the chambers within 3-4 days and roofing is essential to protect the chambers from rain water infiltration. Water for filtration chamber leak test is a resource temporally needed for construction and installation.

The land is at least 800 square feet site above minimum ground water level of 10 feet and having no land slide risk. Moreover, it is essential to avoid top hilly area for site selection as it is quite difficult to collect the faecal sludge from the latrine pits in the lower part of the hill against gravitation. Field Officers select random sites with the collaboration of Camp Wash Focal and Site Management. Field Coordinator and Project Engineer then visit the identified sites and finalise the places which meet most of the land specifications. When Govt. authorizes the requested intervention in specific camps, field officers then secure the selected sites for FSM plant.

Sanitation workers are provided caps, goggles, gloves, gum boots and apron for their personal safety to avoid direct contact with the human excreta. They wear the PPEs for their regular services. The materials are provided regularly to ensure health and protection safety of the sanitation workers which itself is a challenge for check and balance between estimated budget and safety. The frequency of desludging activity decelerates during the monsoon season due to heavy rainfall and risk of land sliding. It becomes difficult to walk in the slippery pathways carrying heavy weighted machines.