Towards sustainable sanitation and toilet design

Seetha Gopalakrishnan
Monday, February 23, 2015 - 14:02

Author: Madhu Thakar

Open defecation cannot be eliminated just by providing a hole in the ground with an oversized umbrella over it and christening it a ‘toilet’. There appears to be an unseemly hurry in building toilets all over the country without understanding the theory behind them.

Constructing toilets is a significant part of the overall Water, Sanitation and Hygiene (WASH) initiatives of the Government as well as corporate entities assisting it. Sustainability should be the guiding principle here.

Factors to be considered before constructing toilets

Each geography has unique characteristics - unique soil conditions, depth of water table, flooding , temperature variation, availability of sunlight, distribution of households, means of extraction or supply of water,  the existence or absence of a sewage system. These factors guide the understanding of the requirements of the area and help determine suitable toilet designs.

 Disease causing bacteria can travel 10 m down vertically and 50 m horizontally. These must be prevented from contaminating ground water resources such as wells, ponds and underground water streams.

 Social norms dictate defecation habits. These must be taken into account while locating public toilets. Sulabh International led by the legendry Dr. Bindeshwar Pathak has years of experience and tons of knowledge about the history and practicality of toilet building. It must be tapped into intelligently.

At the same time, new knowledge must not be disregard. Many new toilet designs are being created around the world based on varied experiences, availability of new materials, opportunities in excreta management and considering ‘waste’ as a resource , thus making toilets a viable option to open defecation.

Thorough understanding of need and environment

Toilets must be made to adapt to the public and not the other way around. Going in for the cheapest standard specifications to meet quantity and time targets will defeat the purpose in the long run.

A detailed need and socio economic analysis is essential for understanding the various design options available. Only after such a detailed study and cost analysis, the designs most suitable for ease of use and maintenance, durability and environmental impact should be selected.

Going in for the most basic design will be akin to offering cars with hand cranked engines of yesteryears when  remote operated auto ignition models are available in the market.

Women and child health

It is now indisputable that sanitation is an essential component in child health. Defecating in unhygienic environments due to lack of toilets has found to cause physical stunting in children in addition to inhibiting mental growth. Hand washing after defecation and before eating is a very important part of hygiene and must therefore be an essential part of toilet facilities.

In women the lack of toilets is a major factor in many diseases including urinary tract infections, kidney failure etc. It also leads to security issues and the chances of being prone to rape are much higher. Low self esteem further impacts the family adversely.

Menstrual hygiene management

Menstrual hygiene should be given importance while designing toilets. Disposal of sanitary napkins or cloth napkins should be a considered while designing the facility. Both dumping napkins in landfills and incineration cause pollution.

Reusable silicone menstrual cups which can be inserted into the vagina and used for 10-15 years have been suggested as an alternative option. Although these cups reduce pollution, concerns of medical safety remain. The quality of silicone rubber, method of manufacture and also user carelessness can result in undesirable effects. Evangelizing the use of menstrual cups would be a challenge. The organization building toilets must examine whether they can take on this additional responsibility.

Making toilets affordable – Exploring up and coming technology options

When these factors are incorporated or even considered for incorporation into the design, the initial capital cost naturally to go up. Now, affordability of toilets appears to be a deterrent. A new approach thus becomes necessary and the toilet needs to be redesigned to make the ‘waste’ as an economic resource.

Urine has many uses. It can be separated and put to many uses some of which include its use as a fertilizer in agriculture and horticulture, in beauty treatment products and even in the production of electricity. Likewise, fecal waste can be turned into bio char, a fertilizer. In some laboratories the fecal waste is being converted into fresh water fit for drinking as recently demonstrated by Bill Gates.

(Please take a look at for more on this)

Bill and Melinda Gates Foundation, has in the past few years, funded research in ‘Reinventing the Toilet’ around the world. In India, it partnered with BIRAC, a Govt. of India undertaking under the Ministry of Science and Technology. The idea is to make toilets affordable.

The Defence Research & Development Establishment (DRDE) has done considerable work on this front. They have developed bacteria that work as effective inoculums to degrade fecal matter over a large range of temperatures, making it suitable for use from the cold expanses of Himalayas at Siachen to the hot deserts of Rajasthan.

Bio Digester Toilets are a major step forward in eliminating manual scavenging. Now there is no need to remove sludge from the septic tank for years on end. The sludge is the feed for the bacteria which converts it into water and traces of methane. In community toilets where the production of methane is considerable, it can also be used as fuel for cooking and lighting.

Sanitation systems

There are many systems of sanitation which must be studied for their relevance to a given population. These systems encompass technologies that involve collection, containment, transport, transformation and utilization.

Eawag, Switzerland has compiled the commonly known sanitation systems and  a synopsis of these are given below.

1. Single pit system

 This system can be used with or without flushing. A single pit is used to collect and store urine, feces, anal-wash water, flushwater and dry cleansing water. This system fills up rapidly and needs to be closed and new pits need to be dug for which enough space is needed. It would be useful in sparsely populated settlements where the soil can absorb the leachate.

The water resources should be deeper than 10 m and should be located more than 50 m from the toilet so that these do not get contaminated by disease causing bacteria. It is not recommended in areas of heavy rains or floods causing overflows. Sludge management is an issue and requires considerable human, technology and monetary resources. Though least expensive initially, the cost of maintenance may make the overall life time quite inflated.

2. Waterless pit system without sludge production

This is a system in which anal cleansing water is kept separate from fecal droppings and the urine may also be separated to reduce water in the feces chamber. Urine can be put to use while the fecal matter is allowed to dry up. Alternating pits may be used for defecating so that while one is being used, the content in the other has enough time to degrade and be converted into usable compost. Flushing water into these pits is not encouraged.

Since the system is permanent it can be used where space is limited. The humus needs to be removed manually and is especially appropriate for water scarce areas and where there is an opportunity to use the humus as fertilizer for the soil.

3. Pour flush pit system without sludge production

This twin pit system allows flushing into one pit at a time. Urine, feces, anal water, flush water and dry cleansing material are collected and stored in one pit and allowed to accumulate. Upon filling, the second adjacent pit is used.

Since the pits are lined with porous material water leaches through while the solid degrade into wet humus. This may take up to 2 years. The pit size has to be appropriately sized for the number of persons using the toilet.

As there is considerable amount of flushing, water availability is a concern. Since leachates can contaminate groundwater resources, pit depth and proximity to water source must be borne in mind before installing the system. It is not suitable in flood prone areas. Removal, transportation and use of the humus must be done carefully.

4. Waterless system with urine diversion

This is similar to the waterless pit without sludge production. However, in the feces chamber there is a constant supply of ash, lime, soil or sawdust to cover the feces. This helps absorb humidity, minimizes odor and provides a barrier between feces and potential disease causing vectors such as insects and flies. If ash or lime is used, the pH increase will help to kill the pathogenic organisms.

This system is particularly useful in rocky areas where digging is difficult and also in places with high groundwater table as well as in water scarce areas.

5. Bio-gas system

A bio-gas reactor is used to collect, store and treat the excreta. The reactor produces bio-gas which can be used to fuel for domestic cooking and lighting. The amount of gas produced can be increased by adding kitchen waste and animal waste. A biogas unit can work with or without urine.

This system is best suited to rural and semi-urban areas where there is appropriate space, a regular source of organic substance for the reactor and a use for the digestate and bio gas.

The reactors can be varied in size and connected to separate cabins to suit different numbers of users. This can be an important consideration in densely populated slums where the hours of use are mainly between 5am to 9am and space is a constraint. The bio gas tanks can even be built underground. Grey water should not be added to the bio reactor as it reduces the hydraulic retention time. The discharge water which is rich in pathogens must be treated chemically if let into the earth.

6. Blackwater treatment system with infiltration

 This is a flush type toilet which receives a large quantity of flush water, feces, urine, anal water as well as dry cleansing materials. The user interface is connected to a septic tank or an anaerobic bioreactor or an anaerobic filter. The anaerobic process reduces the organic and pathogenic load but the effluent is still not suitable for direct use. Further chemical treatment is necessary.

There should be an appropriate method of sludge disposal and there must be sufficient space and soil capacity to absorb the sludge. This system is suitable where de-sludging services are available and affordable. This system can be adopted for cold climates even when there is ground frost. However, this system requires a constant source of water.

7. Black water treatment with effluent transport

This system is  similar to the Blackwater treatment system with infiltration except that collection and storage or treatment units serve as ‘interceptor tanks’ and allows the use of smaller sewers as the effluent is free from solids that settle. The effluent may be discharged into the storm water drainage network or the or for groundwater recharge  system. This system is particularly useful at the household level.

This overcomes the need for sludge removal over a long time. The system is especially suitable for urban settlements where the soil is not suitable for infiltration of effluent. Since the sewer network is shallow and ideally water tight, it is also applicable for areas with high ground water tables.

Things to keep in mind before initiating construction

It might be pertinent to offer some suggestions which may be suitably altered and adopted at an individual decision making level.

1. Create a geographical unit for consideration: For example create a ‘Sudoku’ template of nine sub districts over a district map.

2. Socio, economic and geographic matrix for each sub district: This will show up the number of households, schools, communities, market places, religious establishments, public places that should have toilet facilities, the number of persons that need to be served, the hours of use etc. Find the number of existing facilities under each category. This will give an idea of number of facilities required.

3. Community toilets – estimating the number of seats: For community use, consider that a majority of the population will use it in a two hour window say 6am to 8 am. Considering a 5 minute use per person time frame and a  gap of about 2 minutes between users, one would come up with an average use of 8 persons per hour for two hours and another 8 persons for the rest of the day i.e. 25 per toilet seat per day. This would provide a rough number of toilet seats required for the given population.

Keeping this in mind, the size of the pit, septic tank or bio digester tank can be determined. This would also help calculate the amount of water required and the amount of sewage waste generated. Similar calculations would be applicable to schools and other establishments.

4. Collection of geographic and demographic data: Geographical mapping would help collect data on population density, street width and accessibility for trucks, carts etc. temperature variation, climate conditions, soil conditions, flood prone, water table depth and availability. This would be useful in choosing the most appropriate sanitation system for the area.

5. Disease prevention: For high density usage in crowded areas transmission of disease from users of a toilet cabin becomes an issue. The cough, spit and handling of fixtures fro disease carrying persons infects other users. Such cabins can be coated with nano particles that reduce the ability of viruses to survive in the cabins.

6. Profiling the users: The user profile would determine the accessory selection within and outside the toilet. For a women-only police barrack or a secondary girls’ school one would need menstrual hygiene management accessories like sanitary pads dispenser, used sanitary pad holding bag dispenser, waste bins, hand and self wash faucet, incinerator.

7. Area specific concerns: In a community where it’s difficult to make ends meet, it would be worthwhile to consider using methane for providing lighting in an otherwise dark alleys slum. Fertilizer production from fecal waste and urine may provide sufficient money for an individual to take on the responsibility of maintaining a toilet.

8. Menstrual hygiene management: It may be worthwhile to distribute silicone menstrual cups free of cost on a trial basis. This would overcome the high recurrent cost of sanitary pads for women and also obviate the need to provide disposal facilities like incinerators or landfills near the toilets. Landfills are invariably poorly supervised and very soon dogs, cats and pigs scavenge there and scraps are strewn all over.

9. Determining costs: Costs do play an important role in the decision making. However different communities can afford different prices and this must be borne in mind as specifications get written. Some communities can contribute a part of the cost, in some because of the large corporate house activities large sums of CSR funds are available for a small population. These considerations should form a part of tender specification writing.

In order to give an idea of costs a single family to serve 5 persons pit latrine would cost between Rs.15-25,000. A bio digester latrine to serve a family of 5 would be in the region of Rs.20-30000. These costs can change depending on the accessories chosen and the choice between brick and mortar or pre fabricated metals and plastic. However it is important to note that the life time costs for a 10 year period are not very different as the former require higher maintenance out flows and additional infrastructure costs. The latter are relatively lower operational and maintenance costs as no sludge removal is involved.

In brick and mortar toilets, the quality of materials and workmanship needs to be monitored closely making quick and widespread adoption difficult. Pre fabricated toilets can be made in large numbers in factories to comparable costs to high quality standards, can be deployed very quickly, are sturdy but are subject to transportation costs and taxation. Government would do well to eliminate VAT/GST/Excise on pre fabricated toilets for the next 10 years.

Wanted: suitable and sustainable toilet construction

Each administration would do well to micro map the user profile and geography and not rush into standard but incomplete specifications at a standard price point.  It is unfair to the public if a standard blueprint of a pit or bio digester received from a Ministry at the Center is distributed to schools, PWD offices or companies for their CSR spend regardless of the requirement and the environment.

No amount of ‘tablet’ vigilance will result in effectiveness unless the toilet construction is suitable and sustainable within the WASH system.