Upflow filter – Constructed wetland – July 2019
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Location of the case study
Main treatment objectives
Description of the treatment process
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:
- Dumping chamber
- Filtration chambers
- Constructed wetland and
- Burial pits
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.
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’ 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.
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.
Description of the emergency context
The humanitarian crisis caused by escalating violence in Myanmar’s Rakhine State has been causing suffering on a catastrophic scale. According to UNHCR estimates, as of 31 December 2019, more than 910,619 (as of UNHCR_Population Factsheet – 20190515) forcibly-displaced Myanmar nationals are residing in Bangladesh. Different organizations have been providing humanitarian aid to these refugees including in the areas of water, sanitation and hygiene (WASH) in the makeshift camps as well as in host communities. Infrastructures and facilities – both those preceding the 2017 influx and those established in response to the influx – are already stretched due to population density. Rohingya community live in bamboo and tarpaulin made temporary shelters. In average, each family consists of 4-5 members and there is more than 50% women and children in the camp considered as vulnerable group. Out of the 1.2 million people in need of WASH services, thus far the sector has only been able to reach 768,000 people with access to safe sanitation. At the initial stages of the emergency, shallow latrines were constructed, many of which have now been decommissioned. New latrines have been established but some of the emergency latrines are still in use. While septic tanks have been introduced in the camps, space is limited. Combined with limited partner technical expertise in faecal sludge management, this has greatly inhibited the collection and treatment of waste. Daily volumes of faecal sludge removed are much lower than the accumulation rate. It has been stated in Rohingya Humanitarian Crisis Joint Review Plan 2018 (JRP) that due to congestion in the camps, the Sector has been struggling to identify land for final disposal and treatment of faecal sludge. To address faecal sludge management, multiple and phased technical solutions are underway. In response to the above scenario, Practical Action has intervened in Rohingya camps with a particular focus on faecal sludge management (FSM) which was initially overlooked by most agencies and which has now become a prime focus for Rohingya Response WASH Sector. Since November 2017 (immediately after the influx), Practical Action (PA) has established 18 FSM sites in five different camps (7, 8E, 8W, 9 and 15) which are adaptive to the camp environment. Through these FSM sites, Practical Action has desludged more than 3,500 latrines in these camps which resulted in more than 70,000 beneficiaries. With the existing PA FSM plant operation and coverage in above mentioned camps, PA has extended its service on 108,000 beneficiaries with 10 new FSM plants more along with hygiene promotion services at Ukhiya upazila in Cox’s Bazar district. Practical Action has also extended its technical support to other WaSH agencies i.e. World Vision, Gono Unnoyon Kendro, Christian Aid and Helvetas with 10 FSM plants in camp 8E, 13, 14 and 15. The FSM plant of three chambers adopting up-flow filtration technology has become a reliable method for the regular desludging of latrines as well as for engaging Rohingya community as FSM sanitation workers. With a proven filtration system, safe water quality (in comparison to other FSM practices in camps), operation friendly plant design and higher level of community engagement (deploying refugees from the Rohingya community as sanitation workers), Practical Action has stepped in camp 7, 8E, 8W, 9, 13, 14 and 15 of Kutupalong and Balukhali makeshift settlements in Ukhiya Upazila, Cox’s Bazar District. Practical Action FSM plant optimization has been affected by the absence of associated behaviour change communication (BCC) in terms of reaching its desired sanitation impact. As such, a BCC component has now been designed and integrated into the project extension period. According to a need assessment undertaken in Camps 7, 15 and 8W, there is a huge gap in terms of regular BCC interventions with a focus on open defecation. The Rohingya settlements are quite large to manage in single hand. Various consortiums are activated to response in Rohingya crisis for example camp management, WASH management etc. The consortiums are working in a collaborated way to mitigate the sufferings of the Rohingya people with their resources. WASH sector has a close collaboration with Camp Management to ensure safe water and sanitation accessibility for all Rohingya people. Below is mentioned some local and international actors with active role in the community:
|Site Management Agency:||WASH NGOs:||WaSH Governmental agency:|
|DRC, BRAC, CARE, Christian Aid||Practical Action, TDH, NGO-F, VERC, WVI, BRAC, Friendship, MSF-H, Mukti Cox’s Bazar||DPHE, Office of Civil Surgeon|
The challenges faced by Practical Action were the following:
- Place selection:
- The refugee community interrupts the work for FSM plant construction
- Availability of suitable place
- Authority or other WASH partners hinders activity as sometimes it collides with them
- It is difficult to construct in uphill areas
- Water crisis as water is needed for desludging.
- Carrying and handling of equipment in uphill areas
- Materials carrying in muddy road
- Slab of the burial pits are broken/ stolen.
- Security challenges for the protection of the plant area.