On plot sanitation and sludge management

April 4, 2013

(This article was written circa April 2008 – a full 5 years ago)

With a vast majority of houses not connected to the main sewage lines in Bangalore the only recourse is to build septic tanks to receive waste water. Apartments on the outskirts too have septic tanks. Some house do away with this and build large soak pits, simple holes in the ground which receive the waste water and collect the solids but allow the liquids to leach away.

These septic tanks and soak pits are highly polluting, transferring the nitrates and pathogens into the groundwater aquifer and contaminating it severely. Most borewells in Bangalore report high nitrate even to the depth of 600 feet. All the nitrate contamination comes from domestic sewage primarily.


But there are many good alternatives emerging for the septic tank. One of them is called the DEWATS or the decentralised waste water treatment system. This in a broad sense is a major improvement on the septic tank with several up-flow chambers to promote anaerobic digestion. The treated waste water then comes to a reed bed chamber which makes use of sand filtration and reed bed treatment which takes up the nutrient load from the liquid effluent. Ultimately the remaining liquid is collected in a polishing pond and can be used for landscape use.

Eco-san or ecological sanitation systems is another alternative. Here the liquid and solid waste in a toilet are collected separately. The liquid which has a major component of nutrients and very little pathogens is often used as a soil nutrient or fertilizer. The solids which have a high degree of pathogens is collected separately and carefully composted to eliminate all the pathogens before being used as a soil fertilizer.

Waste water recycling plants are also coming into the market at an apartment scale and not yet at a domestic scale. These generally digest the organic load in the wastewater through a process of anaerobic digestion. After filtration and further treatment such as UV the remaining liquid is of sufficient quality to be used in landscapes or in gardens.

All these systems have the potential of reusing the nutrient value of what we term ‘waste.’ They also reuse the water for non-potable purpose and prevent pollution of soil and water.

Specially designed

But what if you already are using a septic tank or have a soak pit which is full? In Bangalore recently one sees a small spurt in specialised vehicles which make available the service of cleaning these filled septic tanks or soak pits. For a sum of Rs.1,300 or thereabouts, these vehicles, specially designed in Andhra Pradesh, will come to your doorstep and in a matter of 20 minutes empty your septic tank, sucking all the waste into the tanker through specially designed pumps. They will then transport the waste to the nearest treatment plant of the BWSSB for further processing or will ship it to the nearest agriculturist who will then use the manure rich in nitrates and phosphates.

Better process

Earlier, cleaning of the septic tank was a smelly, gut-wrenching process, dehumanising with respect to those who cleaned it and leaving a scar in the entire neighbourhood.

Nowadays, with entrepreneurship and modern technology, it has become easy to solve the problem. This is one sector where privatisation seems welcome.

Now, if a safe handling and disposal protocol is built, it will make the handling of waste in the city cleaner and more hygienic, stop pollution of the soil and the aquifers and make city living a more pleasant experience. More power then to these technologies and the people who make it happen.

Creating a business where opportunity exists and doing so to provide service to the community is but one small step in water wisdom. Managing wastewater is protecting fresh water and the water wise know that.


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