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Query: Low-cost technology for treating sullage in special soils, from Byrraju Foundation, Hyderabad (Advice).
Compiled by Pankaj Kumar, Resource Person; additional research provided by Ramya Gopalan, Research Associate
27 June 2006
Original Query: Vijaya Saradhi Atluri, Byrraju Foundation, Hyderabad
Posted: 20 April 2006
Byrraju Foundation is a non-profit organization dedicated to bringing about a tangible improvement in the quality of lives of the rural underprivileged. We are currently working in 150 villages across five districts of Andhra Pradesh, India and impact nearly 1 million rural lives. Our programmes include a water treatment plant, constructed by contribution from NRI and 50% by contribution from foundation. Plastic cans are used to deliver water and sold at 1.50 to 2 RS. Per liter and enough is recovered to pay for O and M cost of the plant.
Our sanitation program aims to usher in provision of a self-owned, manageable sanitation facility to every family in the below poverty line (BPL) Category. A total of 30,000 individual sanitary latrines are already constructed with 95% usage. Additionally 40,000 Individual Sanitary Latrines are being constructed to achieve 100% coverage in 150 villages with properly constructed sanitation facilities.
I would be grateful, if members of the community can share with me
· Known technological options available to treat sullage in rural areas, particularly where the soil is black cotton?
· What will be the per unit cost of treating this sullage
Responses received with thanks from:
1. Bhawna Vajpai, Water and Sanitation Consultant, New Delhi
2. Ajit Seshadri, The Vigyan Vijay Foundation, New Delhi
3. N.V.V. Raghava, World Bank, New Delhi
4. D.M. Mohan, Independent consultant, Secunderabad
*During the time period that this query was discussed, responses were moderated by Jyotsna Bapat, Former Resource Person
Further contributions are welcome!
Summary of Responses
Members’ responded to the query seeking technological options to treat sullage, by giving several choices for rural communities and specifically for black cotton soil. They highlighted contextual specifications when selecting an appropriate sullage treatment design and outlined suitable technology types.
Respondents noted that selecting an inappropriate technology, a faulty design and not considering the type of soil are some of the key reasons why toilets in rural areas are not used or are non-functional. The contextual situation requires consideration when deciding on the best form of treatment. For example, members suggested ‘Decentralized Wastewater Treatment Systems (DEWATS),’ which can treat various kinds of wastewater.
Selecting a Type of Toilet
Members mentioned several types of toilets that can treat sullage. The various on site and off site toilets options listed by members included- leach pit toilets, Ventilated Improved Pit (VIP) toilets and septic tanks. They also brought up alternative sanitation technologies like ecological sanitation and community treatment systems (i.e. wet composting). However, members cautioned that whatever technology is chosen, the selection criteria needs to take into account the level of the water table, construction costs (i.e. materials, availability of skilled labor during construction, etc.) and the long-term maintenance options and costs.
There are several factor, members explained, which influence the selection of toilet design pertaining to any specific area, they include:
In addition, when selecting the building material for a specific location it is important to keep in mind the following aspects:
The respondents suggested basic, low-cost Individual Household Latrines/Toilets (IHHL) are one type of toilet technology, which provide different options for the type of materials used to line the pit, sub-structure and super structure. There are two basic types of IHHLs, wet toilets and dry/VIP toilets. Wet toilets come in four forms- single, single offset, single pit with partition and twin pit. There are two types of dry/VIP toilet- single and double.
Members felt for rural areas the leaching pit type latrine with deep slope rural pan (32° slope) with a 20 mm water seal is one appropriate and economical type of toilet for rural areas. They recommended using two pits alternatively; the first pit at least 1 meter away from the second to avoid seepage of water from one pit into the other. The first pit is used and the other pit remains closed to allow for anaerobic decomposition of the night soil.
Toilet Options for Areas with Black Cotton Soil
Black cotton soil has a low water absorption capacity, thus members advised selecting toilets with more absorptive qualities; either by constructing a large pit or by providing a lining of sand and gravel all around the pit. Members suggested that a pit with a 1.2-meter diameter, 1.5 to 2 meters deep and a sand lining of 500 mm would work well.
On one-hand members opined, that a good low-cost option for treating sullage in villages is a soak pit. They felt soak pits work well in black cotton soils if there is a layer of sand about a foot wide on all sides. In Pune, this is the approach used, one member mentioned.
At the same time, members contended given that black cotton soil does not percolate sullage very easily, the soak pit option might not work. They suggested creating the conditions required to drain the water from sullage and felt a soak trench was a better option. A soak trench is similar to a soak pit, except that it is deep, long and covered. Members explained the exact depth and length of the trench is specific to the region and the depth of the black cotton soil. This option is a variable for individual households or a group of houses and the cost will vary accordingly. Members estimated the cost of one soak trench for an individual household would range from Rs. 3,000 to 5,000, with the unit cost decreasing with the number of households (group treatment).
Members also suggested another sullage treatment option in areas with black cotton soil, which is taking sullage outside the village/community. After straining away the solids (using coir material placed in a pot, located in a chamber), the sullage could be channeled through PVC pipes, and held in holding ponds to be used for irrigation. In addition, members noted that if sullage is free from septic tank effluents and composed purely of bath and kitchen waste, the BOD will be low and thus the sullage can be disposed on land through either irrigation or land utilization. For example, rural communities in Punjab are using constructed wetlands and duckweed ponds as sullage water treatment plants. Members also mentioned root-zone beds are another possible land utilization sullage disposal method.
Rural communities, members felt, need assistance in building awareness on ecological sanitation and appropriate technology for their region. This would help rural communities better utilize and maintain available toilets, preventing a return to status quo.
It is a long pit- 6 m long, 0.5 m wide and 1 m to 1.5 m deep. For black cotton soil, if the pit bottom reaches the murram layer, then the conditions for soakage are very favorable. The pit should have a soakage conduit pipe and be perforated along its bottom with slits or holes. This is supposed to create a leakage surface from the lower side of the pipe and use the upper pipes to hold the soil away and prevent collapse, which would choke the conduit passage. For details
Leach pit toilets are a low cost toilet, starting from Rs. 500. For example, constructing a pit lined with brick will cost between Rs. 2,500 to Rs. 4,700. The substructure (twin pit, pit cover, brick and sand lining, connecting pipe) cost Rs. 1500, the foundation (junction chamber, sitting platform, rural pan, trap and foot rest) cost Rs.700 and the costs for the superstructure range from Rs. 300 to Rs. 2500
DEWATS is a set of treatment systems, which does not transport waste over long-distances. It mostly uses anaerobic treatment, multiple baffle septic tanks for sewage, polishing ponds and aquatic plants with root-zone aeration systems, and sand bed or gravel filters. Read more
A duckweed based stabilization pond functions as an anaerobic pond except at the top layer where aerobic condition prevails. The pond is able to control effectively any odor problems. Duckweed is capable of up taking nutrients from wastewater, making it a biological purifier. This low costing technique facilitates resource recovery and environmental protection. It is being promoted by the Punjab State Council for Science and Technology. Read more
Reed Bed System for Waste Water, Sullage and Sewage Treatment (from Ramya Gopalan, Research Associate)
The INDION reed bed system is an engineered simulation of a natural wetland ecosystem for treating and recycling of sullage, sewage and industrial effluent. It combines physicochemical and biological processes into a single operation to form a complete treatment unit, using minimal energy. Read more
Punjab State Council for Science and Technology (from D.M. Mohan, Independent Consultant, Secunderabad)
MGSIPA Complex, Adjacent Sacred Heart School, Sector 26, Chandigarh Punjab; Tel: 0172- 2792325/2793300/2793600; Fax: 0172-2793143; email@example.com; http://www.pscst.com/en/index.htm
Contains information on their sullage treatment technologies promoted in rural communities
BORDA-Bremen Overseas Research and Development Association (from Ajit Seshadri, The Vigyan Vijay Foundation, New Delhi)
FEDINA-BORDA, DEWATS Coordination, #220, 4th ‘A’ Cross, 3rd Block, HRBR Layout, Kalyan Nagar, Bangalore 560043 Karnataka; Tel: 91-8025431772; Fax: 91-8025431773
Recommended for details DEWATS-Process-Decentralized Waste Water treatment systems for definitive concepts for various types of waste water
National Environmental Engineering Research Institute (NEERI) (from Ramya Gopalan, Research Associate)
Nehru Marg, Nagpur 440020 Maharashtra; Tel: 91-07122249886/88; Fax: 072224900
Researched problems from sewage farming, crop and soil responses to wastewater treatments, formed guidelines for sewage farming systems, and related health effects
From Ajit Seshadri, The Vigyan Vijay Foundation, New Delhi
Decentralized Wastewater Treatment Systems (DEWATS)
Details DEWATS’s technical approach, and provides data drawn from some sullage treatment projects Vigyan Vijay Foundation conducted, which yielded satisfactory results
Explains with illustrations the functioning of soak trench technology and the context in which its application is suitable
Punjab State Council for Science and Technology; 2005
Provides details on constructed wetland technology as an alternative to conventional systems like Activated Sludge Plants and Trickling filters in the rural areas of Punjab
From Ramya Gopalan, Research Associate
Duckweed Based Wastewater Treatment System and Assessment of Nutritive Value and Economic Return
Parvesh- Newsletter from Central Pollution Control Board
Studies efficacy and assesses the economic returns from pisciculture (fed on duckweed) and evaluates its nutritive value when applied to treat sullage ponds
Treatment Wetland Applications in India’s Villages for Sullage Quality Improvement
By John Pries, Kapil Chaudhery, and Dr. Rajesh Grover; Department Biologie, Universiteit Utrecht; Utrecht, The Netherlands; July 1, 2004
Abstract on existing natural (duckweed and subsurface flow wetland) wetlands as a relatively low cost and effective sullage treatment system in India
Update No. 2, March 2004
ION Exchange (India) Ltd.; Mumbai
This issue spotlights some of the drinking water and sewage treatment projects undertaken for communities and townships.
Sourcebook of Alternative Technologies for Freshwater Augmentation in some Countries in Asia
and Technical Publications, United Nations Environment Programme
Provides details the experiences of different countries using alternative technology to treat wastewater, including technology descriptions, systems and processes
Related Past Consolidated Replies
Low cost and ecologically sound sanitation practices, from Dinesh Kumar, IWMI, Anand (Comparative Experience). Issued 3 October 2005
Identifies low-cost, ecologically sound sanitation practices for urban and rural areas, and experiences in adopting these methods
Treatment of Wastewater for Reuse, from K.A.S Mani, APFAMGS, Hyderabad, (Experiences). Issued 14 March 2006
Explores range of approaches in wastewater treatment covering small household level treatment devices, middle range technologies and large intensive solutions
Responses in Full
Bhawna Vajpai, Water and Sanitation Consultant, New Delhi
I am an
Independent Water and Sanitation Consultant, selection of inappropriate
technology option is also a big factor for non-use/ non-functional toilet in
rural areas. I have seen in many villages due to faulty design and
non-consideration of soil type lead to malfunctioning/ non-operational toilets.
Even if community is willing to use toilet, but in rural setting if once their
toilet is blocked/ non-functional they usually start going back to
Various on site and Off site toilets options are leach pit toilet, VIP toilet, Septic tank, alternative sanitation technologies like ecological sanitation, various community treatment system like Wet composting etc shall be selected by taken in mind the water table, construction cost, maintenance, ease of skilled labour etc.
Leaching pit type latrine with deep slope rural pan (32° slope) having 20 mm water seal is found most appropriate and economical for rural areas. Two pits are used alternatively. One pit is connected at a time while the other is closed for anaerobic decomposition of night soil. A distance of 1 m is recommended between 2 leaching pits to avoid seepage of water from one to the other.
I would also suggest mobilizing the community about the ecological sanitation toilets especially in water scarce areas, since they require minimum water and are ecologically sustainable.
UNICEF, Bhopal has recently published a Guidebook/module on various toilet technologies based on soil type authored by Dr. Sam Godfrey, project Officer and myself. Guidebook is in Hindi and you may contact Dr. Godfrey to know more about guidebook.
Basic Low cost IHHL Technology:
1. Wet Toilet (Leach pit)- Four Type (Single pit/ single offset pit/ twin pit/ single pit with partition).
2. Dry/VIP Toilet- Two type (Single pit or double pit)
Above basic toilet type may further create various option by using different type of pit lining, sub structure and super structure material.
Selection of design shall depend upon following factor
1. Type of soil (Normal soil, Black cotton, Sandy, Rocky, high water table areas)
2. Availability of local material, especially for pit lining and superstructure
Water availability in the area (VIP toilet, Wet toilet, eco san
4. Up gradation possibility.
Selection of Material:
§ Type of Pit lining; Brick, Cement concrete, Stone, Clay ring, bamboo sheet, drum, RCC ring etc.
§ Squatting platform; RCC, Ferro cement etc
§ Junction Chamber; PVC pipe, stone lining drain, Masonry junction chamber etc
§ Superstructure; Mud, Jute cloth, Tin sheet, Brick, stone, bamboo etc.
Toilet in Black Cotton soil:
Black cotton soil has low water absorption capacity; toilet should be designed for more absorption either by constructing large pit or by providing the lining of sand and gravel all around the pit.
Pit of 1.2-meter diameter and 1.5 to 2 meter depth with Sand lining of 500 mm is appropriate. For all rural toilet use of deep slope rural pan should be made.
Approximate cost of twin pit toilet in black cotton soil: Cost shall vary depending upon the material use, I am putting example of brick lining leach pit toilet other. Other low cost option by using low cost/ local material can be made that may range from 500 onward.
1. Substructure (twin pit, pit cover, brick and sand lining, connecting pipe): Rs. 1500/-
2. Foundation (Junction chamber, sitting platform, rural pan, trap and foot rest): Rs.700/-
3. Superstructure: Rs. 300 to Rs. 2500/-
I shall be happy to provide any other input on rural toilet technology.
All the best wishes for your endeavour.
Ajit Seshadri, The Vigyan Vijay Foundation, New Delhi
There are simple methods of process and treatment of sullage water i.e waste water other than sewage. For sewage the time tested septic tank-soak-pit combination is ideal other than locations with sub-soil water being at lesser depths.
There is a forum called BORDA-Bremen Overseas Research and Development Association with their India office at Bangalore address FEDINA-BORDA,Dewats Coordination, #220, 4th ‘A’ Cross, 3rd Block, HRBR Layout, Kalyan Nagar, Bangalore 560043, India. Tel nos 91 80 25431772, Fax- 91 80 25431773 Email: firstname.lastname@example.org and email@example.com Concerned person Mr. Pedro Kraemer - Co-ordinator.
The members may be already aware that this forum has been propagating DEWATS-Process-Decentralized Waste Water treatment systems for developing countries and have definitive concepts for various types of waste water etc.
We have done training under them and have also been implementing projects on these lines and in 6 sites with satisfactory results. And also have some researching data from IIT-Delhi.
The solution being explained has the data drawn from some projects and of-course some site specific moderations would have to be done. But in generality some feasibility and costs can be worked out on this process.
N.V.V. Raghava, World Bank, New Delhi
possible lower cost option for treating sullage in villages is Soak Pits. To
make them function in black cotton soils, there could be a sand layer of about a
foot wide both on the sides and bottom. In Maharashtra, this option is being followed in
The other option for black cotton soils could be to take sullage to a point outside the village, after straining away the solids (using coir material placed in a pot, located in a chamber), through PVC pipes, and hold the sullage in holding ponds and use it for irrigation. But this might have mosquito nuisance, and may require minimal treatment.
D.M. Mohan, Independent consultant, Secunderabad
from a rural community is amenable for treatment as long as the sullage is free
from septic tank effluents and is purely from bath and kitchen waste since
BOD values will not be high the sullage can be disposed on land by
Such methods for disposal include root zone bed, constructed wetland, duckweed pond etc. Recently I had an opportunity to visit a few plants for treatment of sullage water (including septic tank effluents) in rural communities of Punjab. These sullage plants are Constructed wetland and Duckweed pond.
In both sites the sullage was effectively treated. I am not sure whether these will be successful in black cotton soil. Howvever in Punjab, the Punjab State Council for Science and Technology have been prmoting the technology for providing sullage treatment facilities in rural communities. More details can be obtained from them. Their web site is www.psct.com and telephone nos are 0172- 2792325, 2793300, 2793600.
Raj Kumar Daw, UNICEF, New Delhi (response 1)
The substance of the query is that black cotton soil does not percolate the sullage very easily. So you need to ceate the conditions so that the water from sullage is drained out. A soak pit option here does not work. Creating a long infiltration trench is the objective of the technical solution.
A deep trench of 1.5 meters deep by 0.5 meters broad and 5 to 6 meters long should be constructed. Ideally at that depth if you reach 'Murum' a hard porous type of soil half the battle is won. Alternately dig a bit deeper till you hit 'Murum'. The you lay a PCV pipe of 6 inches diameter. This pipe should be porous at the bottom and covered from top. In the market you get porous pipes that are porous all round. So you need to cover the top part of the pipe with tarpaulin to ensure only lower half is porous. Then there should be a vertical PVC non porous pipe at the end of the porous pipe at the end of the trench. Ideally fill the trench with a layer of gravel or broken construction material and then lay the pipe and then cover it with gravel again. Then put a layer of sand over it so it fills up to 0.5 meters. Fill up the remaining trench with the material dug from the trench.
This trench needs to be connected with a two chambered collection pit built from bricks needs to be created below ground level to collect the sullage. This can be a trench of 2 by 3 feet collection chamber that is two feet deep. The two chambers are separated by a partition wall that is 4 to 5 inches below the top. The first chamber also called the pre-sedimentation chamber, will allow for the sullage to settle and the overflow will enter the trench.
The main cost of the solution is in the perforated PVC pipes that are needed to be fitted inside the trench and the vertical pipe to this horizontal perforated pipe buried underground. The rest of it is labor cost for digging trench and filling it up. At a household level it would cost between Rs. 3000 to 5000 and the cost will comedown in group treatment due to economies of scale.
The technical solution will be specific to the region and the depth of the black cotton soil. This solution can be used for individual households or for a group of houses. The cost will vary accordingly.
Raj Kumar Daw, UNICEF, New Delhi (response 2)
Following my earlier response please see the document explaining further the details of soak trench as a method to dispose waste water (sullage)
Many thanks to all who contributed to this query!
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