Part 1- Developing the trans-formative onsite septage treatment technology .( Our confidence in the membrane liquid separation has grown since the original proposal was submitted and we now would be able to move the proposed work forward 6 months and start to develop the urban slum business model and latrine technology, the real reason for developing the dewatering membranes)
Develop Solid-Liquid separation and Treatment (TYPE I)
As long as faecal sludge and water mixed, management of the same is cumbersome. It will be easier if sludge and liquid is separated. Solid separation shall be done by a combination of coagulation, sedimentation and filtration ( membrane process). Chemical disinfection or membrane treatment shall be done for pathogenic organisms removal. Necessary back wash arrangement shall also be incorporated and coupled. All the units shall be mounted on truck with compressor and will be as mobile unit. The following Two models shall be field tested ( Model I with Centrifuge and Model II with reciprocating pump and membrane).
Model I ( With Centrifuge )
In model I, the faecal sludge from the septic tank/leach pit shall be pumped and after coagulation it will be passed through a centrifuge wherein the sludge is separated and collected in a container for further composting and reuse. Usually the solid content will be much less comparing the liquid part in faecal sludge. The liquid part received from the centrifuge is passed through micro-filtration and ultra-filtration successively to remove any fine solid particles and micro-organisms removal respectively. BOD and COD besides other parameters shall be analysed before and after to assess the efficiency of the model.
Model II ( With Reciprocating Pump)
In the Model -II design, it is proposed to construct an air tight cylindrical tank with an inlet and out arrangements. A piston is placed in such a way that it moves up and down in the cylindrical tank. At the down end of the cylinder a membrane filter will be placed and a liquid storage cum disinfection unit is attached to the filter bed to collect liquid which pass through the membrane. The inlet is connected to a long hose with a mixing blade arrangements – this would help to mix the sludge with supernatant water to lift to the cylindrical tank. The cylindrical tank is operated similar to 2 stroke engine that inlet open, the sludge pumped into the chamber. Once sludge reaches to the maximum permissible level, the inlet valve closes, the piston start its move from top to bottom end and it compress the sludge, which forces the liquid in the sludge to separate from the sludge and pass through the membrane. The solid sludge accumulate at the end of the chamber will be removed through the outlet. COD and BOD level of the liquid which passes through the membrane will be tested before disposal. The main purpose of the whole cylindrical is getting rid of liquid from the sludge, which would reduce the transport cost of the sludge to the STPs.
Liquid separation from leach pit (TYPE II)
In order to increase the longevity of the leach pit and to have longer emptying interval, it is proposed to erect a filter unit inside the leach pit to get the liquid filtered for pumping out. Disinfection system is also provided for killing the pathogenic micro organisms.
The filter may be of following three forms:
- Micro filtration membrane: Micro-filtration membrane shall be wound cylindrically in diameter lesser the diameter of the leach pit so as to erect the same inside the pit as shown in figure below. So fabricated filtration unit shall be lowered inside the leach pit. As the micro-filtration membrane permits only liquid to pass through, liquid gets collected. Thus collected liquid part will be pumped out either by hand pump or electrically operated pump to a collection chamber for chlorination by either chlorination or electro-chlorination. Disinfected effluent is suggested for irrigation.
- Porous concrete : In order to filter the liquid part and increase the longevity of the leach pit, a permeable cylinder is cast using porous concrete ( Cement and 20 mm hard broken stone ). The Porous concrete shall be kept inside the leach pit. The liquid which gets collected shall be pumped out either by hand pump or electrically operated pump. The liquid ( effluent ) shall be reused after disinfection by any one of the methods described above.
Sand filter: As the sand is the universally available natural material for filtration, a filter unit with sand as media shall be made and erected into the leach pit for liquid separation. The liquid portion shall be pumped by above method. Disinfection will be done as above and sent for reuse.
The analysis of chemical and bacteriological quality of the treated ( disinfected ) shall be done as per the standard testing procedure stipulated by the American Public Health Association. .
Treatment of liquid effluent from septic tank (TYPE III)
In the case of septic tank, the liquid effluent shall have pathogenic organisms. Improper disposal leads to environmental pollution. In order to kill the pathogenic organisms, the Overflow from the septic tank shall be collected in a tank having one day holding capacity in a chamber and disinfected before discharge either by chlorination or electro-chlorination as shown in the process flow diagram(refer the attachment). Treated effluent shall be reused for cultivating vegetables etc. Both type of disinfection shall be tried for evaluation. Total coliform and faecal coliform counts will be analysed.
Part 2- Developing and piloting the slum based pit emptying business model
The proposed business model is based on the one operated by Sanergy in Kenya (http://bit.ly/1xvve2V). It is designed for non-sewered areas and involves slum based entrepreneurs running small pay-as-you-go toilet blocks for the local residents. They make a small income and ensure the cleanliness and maintenance of their toilet in order to ensure a good flow of customers. The toilets are bought from the service provider business who also provide them with access to a loan facility to buy the toilet. The toilets are modular so as to enable quick erection to a good consistent standard. The service company operates an emptying and treatment service from which earns its income from supporting a large number of toilet entrepreneur situated throughout the slum area. The two forms of companies are dependent on each other and cannot operate independently.
This has long been a business model which has intrigued Water for People wanted to replicate in India, but there are three factors which would make replication commercially unviable. The first is that the Sanergy model is based on a ‘dry’ system where feaces and urine are separated and sawdust used instead of flushing with water. The dry approach is not considered desirable in India would not enable the slum based entrepreneurs to charge a sufficiently high user fee to make their venture viable. Potential customers would only consider paying for toilet use if it used the pour flush approach and enabled the anal cleansing with water. Secondly the Sanergy is based on a drum and hand-cart based primary collection process, which would not be allowed by the authorities in India as it would considered to be the outlawed, but still ubiquitous, manual scavenging process. Thirdly the Sanergy model uses daily excreta collection processes and like most emptying business, the high transport cost this entail represent a major drain on company profits. Our simple spreadsheet based calculations show that if emptying frequency can be increased to once every 10 days, or longer, the viability of the collection and disposal service significantly improves.
The technology's innovative aspect of the approach is the use of a membrane based dewatering device to remove the water from the sludge collection chamber situated beneath the toilet. This takes the vast majority of contents out of the chambers and enables it to be harmlessly discharged, pathogen free, into a nearby drain. With the water removed the sludge density will increase, make more efficient use chamber limited volume and allow a longer period before the need to empty.
This is a new form of business approach for Water for People and is of particular importance as it aimed as unregistered slums, which contains some of the worse, most intransigent and most difficult problems to tackle throughout India, possibly the world. Water for People wants to tests the new membrane technology and the business model in under real market conditions by establishing 10 small toilet entrepreneurs in a slum in the target areas . This will allow the numerous assumptions to be tested and to no doubt discover other unexpected constraints and opportunities. Although there are many potential hazards to the success of the approach, the risks are worth it as the potential high rewards are high.