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On-site Septage treatment & developing a viable slum based pit emptying business

Developing onsite septage treatment system using membrane technologies to separate solid and liquid part of pit contents

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 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 (  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.  

How would you describe the stage of development of your idea?

  • Ready for piloting

How big or scalable is the potential of your idea?

It has been estimated that 1.77 billion people use pit latrines globally (Graham & Polizzotto 2013). Furthermore, approximately are 1.2 billion urban residents are in need of faecal sludge management services (BCG 2012) which all could potentially be direct beneficiaries. Conservatively, we estimate that 30% of latrine owners in urban area suffer from rapid pit fill up rates and have pit water management problems, which equates to 360m people. The urban dwelling portion of the pollution in India is 35m, Uganda 3.9m and Malawi 2m (WHO data). Private sector commercialization is our chosen avenue to scale and will be first achieved with a sole Asian or Africa plastic manufacture supported by the specialist design and manufacturing skill of American Standard. Once awareness and demand for the product has grown supply will be switched to a more local manufacturer.

Explain the sustainability aspect of your idea

Water For People has a dedicated team of Fund raisers who are trying their level best to establish linkage with the government , high net-worth individuals, donor agencies etc . We are showing them the impact that their money and our work is having and the return on their investment. Here we are trying to develop a cutting edge technology which has the potential to transform the FSM space in India and around the globe. As the prototype is showing positive results we are now extremely confident that we will change the game of pit emptying business not only in India but around the globe . During the conceptual ,testing and pilot phase we are dependent on the donor money for moving forward. But if it works , it can easily be marketed to Municipal bodies and tanker operators across India. This product is the single most important fit to make the whole Fecal Sludge Management value chain sustainable.

What types of financing would be required for your idea to be successful?

At this stage we are looking at multiple sources for financing the idea. 1. Grant component- For Water For People & WASH Institute to develop the technology and physical product. Grant is also required to pilot the technology and services in any of the non sewered slum area of West bengal or Bihar. 2. After the pilot stage financing would be required to develop the supply chain of the product. 3. Investment would be required once we go to scale with slum based viable pit emptying business model pan India .

If you are proposing to partner with other organizations, please explain their role and reason for partnership.

1. Water for People. Supporting the testing, product development, market testing, managing relationship with city authorities and monitoring. 2. WASH Institute -Technical aspects of the membrane and product development, cost benefit analysis, performance testing, documentation 3. BASIX- A social enterprise having their own micro-finance wing and experienced in taking similar product and services to the market

In-country experience

  • Yes, for two or more years

If you have been operating in India, what has been your focus?

Water For People began working in India in 1996, with a small pilot project in West Bengal to help eliminate naturally occurring arsenic in water supplies. In 2005, Water For People established a full-fledged country program with an office in Kolkata, and by the end of 2010, had programming in several districts in West Bengal. In 2012, Water For People expanded work to Sheohar and Muzaffarpur , Bihar. For us, it isn't just about building wells, installing toilets, and setting up pumps, we're looking to create long-lasting water and sanitation infrastructure by talking to local community members, governments, and business owners, to find out how they live and what they need to feel healthy, safe, empowered, and successful. We're designing solutions based off of long-term needs and long lives. We don't want to be around forever, but we want these systems and services to last for generations to come.

Is your organization currently legally registered in India?

  • Yes

What states or districts will you target/are you targeting within India?

We would be targeting non-sewered slum areas around Kolkata , West Bengal and Muzaffarpur , Bihar for piloting our services.

Tell us a bit about yourself.

According to the most recent Joint Monitoring Program (JMP) Report by UNICEF and WHO, 96% of people in urban areas and 89% in rural areas have access to safe water. Access to sanitation is much lower, with 60% of urban and 24% of rural dwellers using improved sanitation facilities. These numbers, however, do not provide an accurate and complete picture of water and sanitation access in India. Across the country, there is wide disparity among districts, and access is significantly lower in the rural areas where Water For People-India works. We are trying to develop sanitation services that last and deliver affordable, beautiful toilets and/or quick hygienic emptying services . The team will be led by Steven Sugden of Water for People( previously of London School of Hygiene and Tropical Medicine)with 25 years sanitation experience in developing countries . Few other key members will be Mr. M Sahana , MD , BASIX (BDS and MFI), The WASH Institute , Samrat Gupta and others.

Is this a new or recent idea for your organization? How does it differ from what you are already doing?

The application of the technology is a first of its kind in India and possibly around the globe .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 test the new membrane technology and the business model in real market conditions by establishing 10 small toilet entrepreneurs in slums 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.

What are the two or three biggest risks for your idea and how will you manage the risks?

As this is a completely new an innovate approach, the economics of both businesses and the performance of the membrane technology are based on spreadsheet modelling and making a series of assumptions, such as each latrine having 100 customers a day all willing pay Rs 1 per use, and the latrine requiring emptying every 10 days. The accuracy of these assumptions is impossible to explore without undertaking the market testing, as proposed in this application. The slum areas are politicized and any form of business could be attacked by people with a political, as opposed to health based, agenda as been exploitative of the poor. This risk is reduced through only working with toilet entrepreneurs from within in the same slum area and not ones considered to be from ‘outside’. This makes both the businesses more difficult to accuse of been exploitative. In addition the prices charged will be in line with other, usually nonviable, attempts to provide community latrines.

How would you propose to track or record the households or customers reached?

As this is as the market testing phase, which in itself is form of research, all aspect of the toilet companies’ financials, usage and performance will be monitored including the use of flush counter to accurately gain usage information, testing the quality of the discharge water, fill up rates, loan repayment rates, sludge density, customer satisfaction, who is using customer?, who is not? and community acceptance. The aim is to finalize the technology and develop the business model.

If you had two years and $250,000 USD in funding, how many households or customers would you reach?

The amount would be invested for the following 1. Product development 2. Piloting the business model At the pilot phase , the key activities would involve in fabrication of 100 modular toilets and tanks. It is expected that it would be catering to 10000 to 15000 customers every day. Apart from this the 10 entrepreneurs would be generating dignified employment for over 100 individuals for emptying and cleaning services.

How would you propose to invest $250,000 USD if you received philanthropic/grant funding support from

The amount would be used for the following purpose. 1. Product development - consulting Cranfield university/IITs , modification of the prototypes already developed, labratory testing , certification by external agencies , market testing. 2. Developing/piloting the business model - We would be targeting the following in the next two years 1. fabrication of 100 modular toilets and tanks , 2. 3 onsite septage treatment units , 3. Selection of 10 sanitation entrepreneurs and sites, 4. Business development support for the entrepreneurs 5. Reaching 15000 customers

What type of support beyond grant funding are you most interested in?

The project and partner team (MFIs and Business development service provider)has a good depth of skill and knowledge about many aspect of business develop and are experienced in financing, innovation development, marketing, and technical aspects. But would benefit from a more structured and rigorous approach, particular over deciding the relative importance and attribute of the various latrine components.

Does your organization have Foreign Contribution Regulation Act (FCRA) approval?


Attachments (1)

Proposal for On-site Septage treatment.pdf

Description of the proposed work in detail


Join the conversation:

Photo of Christopher

Very interesting idea!

Photo of Leah

This seems like a really interesting idea. One of the things I am wondering is what sets this idea apart from the other toilets in India that required to be pumped out? Does this system depend completely on natural processes to be sustainable? I'm interested in learning more!

Photo of Samrat

Hi Leah, thanks for your interest. I have elaborated about the principle and USP of our product in the proposal itself. Kindly have a look at it. thanks

Photo of Leah

Is there any anticipated ecological harm from the implementation of these membrane technology systems?

Photo of Samrat

Thanks Leah for you query . The prototype we have developed is giving results beyond expectation. BOD, COD and coliform counts are all within permissible limit. Moreover the effluent is safeguarded by 3 stage filtering process.  

Photo of Shane Zhao

Hi Team, we notice your post is currently unpublished. Was this your intention? We'd love to have it included on the challenge. If you decide you'd like it included, you can publish it by hitting the Publish Entry up there at the top of your post. 

Photo of OpenIDEO

Hi Samrat, we've added new Refinement questions to your original idea submission form. To answer the new questions, hit the Edit Contribution button at the top of your post. Scroll down to the entry fields of the new Refinement questions. Hit Save when you are done editing.

Photo of Shane Zhao

Hi Samrat, we have 4 days before the conclusion of the Refinement phase. It'd be fantastic if you might answer the new questions we added to your idea submission form. To update your post, please follow the tips in the previous comment from OpenIDEO. Looking forward to learning more!