Posts Tagged ‘sludge’


On the sludge management and reuse potential in Bangalore

May 12, 2014

One of the many critical factors affecting productivity in Indian soils is the absence of nutrients such as Nitrogen, Potassium and Phosphates. Even Carbon is in short supply as well as micro-nutrients such as Zinc and Boron.  AA substantial part of our artificial fertilizers is imported and we run up quite a huge bill. Fertilizer prices too are shooting up leading to an imbalance in their application. It has been reported for example that Urea which is relatively cheaper is over applied on soils causing more harm than good.

Cut to urban cities. Sewage treatment plants are coming up in large numbers. The Bangalore Water Supply and Sewerage Board –the utility responsible for sanitation and sewage, will eventually be setting up 25 sewage treatment plants treating nearly 1100 Million Litres Per day of sewage. These plants will mostly be secondary and tertiary treatment plants. Each million litre of sewage generates nearly a Tonne of sludge. Imagine 1100 Tonnes of sludge will be generated in the city of Bangalore alone. This is 120 truckloads of sludge.

There are smaller sewage treatment plants dotting the landscape in apartments and layouts too. These too generate smaller quantities of sludge. Overall this represents a management challenge of large proportions.

Research:  Currently at the GKVK-University of Agricultural Sciences – research work is going on to understand the nutrient value of this sludge. A Ph D student is pursuing her Doctorate and is experimenting on field trials using the sludge as manure. The initial test results show very good amounts of Potassium and Phosphates in the sludge.



Separately sludge is also being picked up from Ecosan toilets. These are source separating composting toilets which segregate urine and solids. The solids are covered with ash after every use and desiccated before application as a fertilizer on soils. Farmers of Kamasamudram and H.D.Kote have such toilets in their homes and are very happy with the fertilizer they get. In fact this compost is priced at Rs 10 a kg.


Sludge sells for upto Rs 10 a kg.

Similarly the landscape of rural India is dotted with pit toilets, more than 130 million of them at the last count. These too accumulate solid sludge and need to be emptied using mechanical systems. They are also found to be rich in Phosphates and Potassium.

All these various forms of sludge will be taken, tested applied on fields and crop productivity tested under expert supervision.

When research and application come together in a spirit of cooperation, it is possible to find solutions for India’s vast water, food and sanitation problems. At the base, this is a nutrient cycle at play. How we scientifically understand and manage it will show us the path to solutions. If every gram of sludge generated in our Sewage Treatment Plants become useful as manure it will partially solve India’s fertilizer needs and eliminate pollution. It will also increase productivity and richness of our soils as well as enhance the livelihood opportunities of farmers.

Recognizing and converting waste to a resource will help thousand of apartments and layouts, small and medium towns and even metropolis to manage their sewage efficiently for reuse and recycling. This would be water wisdom.


Building bye-laws and sanitation in urban india

September 16, 2013


1. Building bye-laws should recognize and insist on the provision of a rainwater harvesting recharge well within the site.

2. Building bye-laws should also recognize that non-sewered areas will have to make provision for two concrete ring lined pits for sanitation waste. One pit for black water and one pit for grey water. These can be mechanically emptied using vacuum trucks. The pits too should be located within the site of the building and not be allowed to discharge into storm water drains for public safety, health and hygiene.


Building bye-laws help regulate and maintain a certain discipline regarding the management of water and waste-water in urban areas apart from their role as a major urban planning tool.

Some of the good things they do are for example the insistence on identifying a toilet of a minimum dimension in any house construction before approval .In the Bangalore context rainwater harvesting is made mandatory and the building approval plan to be submitted has to show the recharge structure that is to be implemented.

It is surprising therefore that they miss out on some basics and do not refine the old. Take the rainwater harvesting detail that the Bruhat Bangalore Mahanagara Palike insists on. This is how the design looks like, a recharge pit filled with crushed stone and sand with a splash pad on top.



 In the days were sand dredging or mining has caused devastation to rivers and soil why insist on an archaic design that uses sand and gravel inside it? The design by the Bangalore Water Supply and Sewerage Board (BWSSB) is much better, a recharge well with no sand inside it. It works perfectly well and in fact, if the hydro-geology favours, a recharge well can easily become a withdrawal well. This building bye-law for a recharge well instead of a sand filled pit can easily be made mandatory for all the towns in Karnataka.


Sanitation: While building plans sent for approval have to show toilets, unfortunately there is no insistence on clearly indicating how the waste is to be disposed. While larger buildings and apartments have Sewage Treatment Plants made mandatory, the smaller ones do not have to show any system of appropriate waste disposal. Since septic tanks are costly precast concrete ring pits are used commonly as they cheap and easy to install. Unfortunately most buildings make only a single large pit located outside the house on the pavement or even sometimes the roads. This makes it very difficult for future road works or for water supply and sewage lines to be placed when infrastructure finally arrives in that area.

To remedy this situation the building bye-laws should insist that each building have two pits for sanitary waste disposal. One of the pits should be for the toilets and one for the grey water. The pits can have a small PVC pipe fit to the covering lid to enable emptying using the vacuum trucks called Honey-suckers. The pits should accessible and located appropriately to the front or to the side of the building.

 This one insistence in the bye-law can eliminate the scourge of manual scavenging, clean up the storm water drains and improve the hygiene of our small towns dramatically reducing the disease burden.

It is time for building bye-laws to recognize reality and become water wise.


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.


On embedding urban food production and linking it to productive sanitation for the city

March 2, 2013

Summary: Urban India is a repository of many crises. From housing shortage, congestion, water shortage, waste-water prevalence, transport problems, energy and food/ nutrition shortage. While in the long run better urbanization and land-use policies will have to be done in the short run there are some ameliorative steps that can be taken.

It is possible to link water, productive sanitation, waste management and agriculture in a cyclical consumption pattern where the output becomes an input for the other sector. It is possible to find solutions at the household level and also at the city level with intermediate steps also part of the scale of solution.  One such example is presented in the paper below.

Introduction: Urbanization is a phenomenon which India like many other developing nations is experiencing. Though progressing at a slow pace the country is slowly but surely urbanizing with the percentage of population in urban areas as a ratio to rural population on the increase.

The Census of India 2011 identifies the presence of more than 7000 census towns, areas showing urban characters either in terms of density of population, employment in non-agricultural sectors or in terms of definition as urban areas.

Urban India as it expands converts its peripheral land from agricultural and ecological uses to urban uses. Often fertile lands are converted to industrial or housing use. The urban value of land being of higher economic value agriculture is a big loser.

On the other hand the fast growing cities need more and more food grains and vegetables to feed the ever increasing population. Vast streams of water are now to be transported over great distance to slake the thirst of the city. Groundwater from the city is pumped up from great depths to supplement piped water. Both the surface and groundwater so consumed now is let out as waste-water. This waste-water full of nutrients and pollutants flows in our sewage lines – if they exist – or in storm water drains and null

The Census of India 2011 revealed some startling data on the sanitation situation in India. Of the total households numbering 246,692,667 a staggering   53.10 % had no toilets. While a large percentage was rural, urban areas too reported open defecation.

Urban sanitation:  In urban areas underground water borne sewerage systems are slowly making progress but if all the towns in India  are to be fully  covered it will take large investments and a long time not to mention large volumes of water needed for flushing. In the meantime people are building septic tanks and pit toilets for themselves which will need to be emptied and the septage managed in a hygienic way and if necessary the nutrients recovered to aid the soil in the peri-urban areas in becoming productive.

Enter the ‘Honey-sucker’, a truck or tractor based pump, store and transport system developed in the formal but mainly in the informal sector. These pit emptying trucks are rapidly expanding and providing service especially in the Southern and Western states. In the city of Bangalore for example there may be 200 to 300 such trucks providing assistance to over 150,000 households for pit emptying.


Honey-suckers – Pit and septic tank emptying trucks equipped with de-sludging pumps

When pit toilets or septic tanks are full, at the call of a mobile number these honey-suckers will arrive and do a pit emptying job in 15 to 20 minutes without any human contact with the waste. They charge a small fee of Rs 1200 to Rs 1500.  They then take the sludge to farms in some cases where farmers after composting the sludge in turn sell it for Rs 2000 a tractor load. The whole enterprise is financially sustainable and has no subsidy component anywhere.

Rural Sanitation: While eco-sanitation systems (which is usually Urine diverting toilets collecting urine and faeces separately to be managed) are slowly increasing in numbers they form a minuscule portion of the total toilets being constructed.

The overwhelming numbers of toilets in the 10’s of millions are single pit or double pit toilets. These pit toilets, connected to our flush latrines, are filling up fast and will need to be emptied. With the Manual Scavenging Act being rigorously enforced the only way to do it legally will be through a process of mechanization which means a smaller version of the Honeysucker.

Smaller Honeysuckers for rural areas are a possibility

Honeysuckers emptying into and Sludge composting beds set up by a farmer


Composted sludge used as a fertiliser to grow bananas – replaces costly artificial fertiliser


The Bangalore method of composting faecal sludge: This method of composting was developed at Bangalore in India by Acharya (1939). The method is basically recommended when night soil and refuse are used for preparing the compost. The method overcomes many of the disadvantages of the Indore method such as problem of heap protection from adverse weather, nutrient losses due to high winds / strong sun rays, frequent turning requirements, fly nuisance etc. but the time involved in production of finished compost is much longer. The method is suitable for areas with scanty rainfall.

Preparation of the pit Trenches or pits about one metre deep are dug; the breadth and length of the trenches can be made depending on the availability of land and the type of material to be composted. The selection of site for the pits is made as in the Indore method. The trenches should preferably have sloping walls and a floor of 90-cm slope to prevent water logging.

Filling the pit: Organic residues and night soil are put in alternate layers and, after filling, the pit is covered with a 15-20 cm thick layer of refuse. The materials are allowed to remain in the pit without turning and watering for three months. During this period, the material settles down due to reduction in volume of the biomass and additional night soil and refuse are placed on top in alternate layers and plastered or covered with mud or earth to prevent loss of moisture and breeding of flies. After the initial aerobic composting which is for about eight to ten days, the material undergoes anaerobic decomposition at a very slow rate and it takes about six to eight months to obtain the finished product.


Vijayapura:  It is a small town about 60 kilometers from Bangalore surrounded by rich agricultural land. As water shortages increase and as groundwater tables fall all around our cities and towns interesting behavior patterns emerge and consolidate around waste-water. Imagine a farmer cultivating his 5 acres of land. His bore-well which has gone 1000 feet deep now runs dry because there is no rain and therefore no recharge of groundwater. He sees the city’s sewage water flowing nearby. What should he do? Overcoming his own apprehension he starts to use it on his field. He realizes that the water has nutrients too but they need careful handling since they may burn his crop or destroy his soil. He learns quickly and develops a palate of plants that can tolerate the waste-water and still be productive. He has also to manage the waste-water that the farm labourers do not run away.  He carefully now husbands this resource and makes productive use of it. He grows fodder, he grows maize and he finds a market demand for it. Is he doing the right job?

Conclusion: Embedding food production as part of the vast waste-water movement cycle of cities is happening at an informal level. These systems need to be better understood and tweaked to remove negative externalities and public health issues if any.