Towards a water sensitive city

 

The imagination of water in a city should not be limited to its delivery and withdrawal in pipes alone. A good water management plan would mean and include the many roles of water such as the spiritual, the cultural, the ecological and the recreational in addition to the functional..

In the hierarchy of the development of water infrastructure in a city there is first the arrival of piped water supply. Drainage and sewerage follow after some time.  The city then starts to understand and manage its surface water like lakes, rivers and canals. Attention then usually shifts to groundwater management. If all this is done  and fountains dot the landscape , where rivers and lakes become clean and spots of recreation and where all waste-water streams are managed the city starts educating its citizens especially its young ones on water and spreading water literacy. This city can be said to have become water sensitive. Singapore comes to mind as one such city. Stockholm and Oslo also manage their waters accordingly and celebrate it. Seoul is getting there or nearly there. We in India are on the painful ladder and it will take time but the vision has to stay firm. Of course in a water sensitive city all citizens will have equal access to the resource and there will be no deprivation and appropriation of the commons.

In Coimbatore through a citizen government partnership the Big Tank the Ukkadam was de-silted and made ready to receive rainwater which it has collected in plenty. In Dindigul de-silting has begun of the old tank. In Karnataka State ,  Tiptur has refurbished and improved a large tank so have the towns of Sira and Tumkur.

In Bangalore the Bangalore Development Authority has invested over Rs 110 crores in improving over 14 tanks. Of these tanks Jakkur in the Northern part of the city seems to offer a potential comprehensive role of creating a water ecosystem which fits the role of what a water body can do in a city – as they say to function as its kidney.

The vast water spread of Jakkur Tank

The tank itself was a beautiful irrigation tank with a command area which grew paddy. As the city has caught up the role of the tank has now changed. There is a wetland on the upstream end which receives water from a waste-water treatment plant. The wetland further purifies the waste-water . The tank itself with a water spread of 53 Hectares is full and harbours lots of fish. Birds nest and a virtual array of them can be seen during the year.

Treated Waste-water comes in to a wetland

The tank has recharged groundwater in the surrounding areas and the some of the remaining water heritage of the city – the traditional wells- are full to the brim. Boys learn to swim in one of them. Another well is used for large scale irrigation of coconut and banana plants. The tank has a place for immersion of Ganesha idols in one place. Storm-water inlets to bring in rain when it occurs have well designed silt traps to allow only water to come in and not debris and solid waste.

Full wells – thanks to a recharged aquifer

The tank ecosystem fulfills many a function, from the ecological, to the cultural and spiritual, from the educational to that of recharge and many more.

This is truly a microcosm of what is called Integrated Urban water management in practice. Here we see the transformation of waste-water through a physical process of treatment followed by a biological process to drinking water.

Fish feeds the city with proteins and provides livelihood to fishermen

Water in a city is much beyond what flows in pipes. If designed and managed well it can enhance and provide for the needs of nature and man in myriad forms. The Jakkur Lake should be managed well so that it becomes a living lab for our citizens to see and learn how urban waters can be managed. This experiment can then be repeated in most other tanks of the city and also in other cities. Bangalore has been a pioneer in many ways to urban water management. Can it take a lead in this one too? In that would lie water wisdom.

A roof story – Bangalore

As the city expands and buildings fill it up to find open space becomes difficult. In Bangalore in the small sites it is impossible to have even a small garden. About 60 to 70 % of inner Bangalore will be roofs as a look at Google earth will show.

For an urban planner like me and for Chitra an Architect  this was a fascinating finding. What do roofs do and how are they designed?  Unfortunately we seem to poorly design our roofs apart from ensuring that they keep out the sun, rain and the elements. Most of the concrete and steel in the roof goes towards carrying its own self weight. Architect Laurie Baker had shown that we could make roofs lighter by using a filler slab.  Waste tiles were what he used as a filler material. This made roofs lighter, require less concrete and steel and also look beautiful from the inside. Scientists such as Prof Jagadish and Dr Yogananda had designed the flat tile arch panel roof, which was precast and which also was structurally lighter, more efficient and had a different aesthetic quality. We therefore used these roofs in our house.

A filler slab roof using Mangalore Tiles as a filler material

A calculation on what was happening  the outside of the roof was also interesting. Almost all the rain on the building site falls on the roof. In Bangalore it can rain 970 mm in an average year. This meant that our house roof with an area of 100 square metres had 97,000 litres of pure rainwater falling on it. With the idea why allow it to go waste, we started to harvest it? This harvesting was done at many levels.

From the staircase rooftop which had an area of 10 square metres, we placed a Rain barrel and collected the water on the roof itself. A small platform was designed and the 500 litre Rain Barrel placed on it. On the staircase roof we placed a gutter to collect the rain. This came down into a vertical pipe with an end cap called the first rain separator. During the first rain and subsequently when we want to clean the roof or the rain gutter we open the cap and the dusty water flows out through the first rain separator. Then after a ‘Y trap’ rainwater flows in through a ‘dhoti filter’ into our rain barrel. We checked the rainwater quality using a H2S strip test and found the water potable. Sometimes when there is slight contamination we use a method called SODIS (Solar Disinfection) to treat the collected rainwater for drinking purpose. Here you fill a PET bottle with the rainwater and leave it in the sun for 5 hours. The water is now sterilized and can be brought into the house cooled and is ready for drinking. This is not a low cost solution for water treatment but a no-cost solution.  Our annual requirement of drinking cooking water comes from this rain barrel alone.

We also have an Ecosan toilet on the terrace. This pan in the toilet separates solids and liquids at source. We collect the urine in a barrel, dilute it and use it as a fertilizer for our terrace garden. The solids are covered with ash every time we use it. This is then transferred to some Blue drums we have kept on the terrace and again covered with earth or straw. We then plant trees in these drums. Trees such as Papaya, lemon, curry leaves, sapota are planted and they grow well. No waste from our toilet on the terrace leaves the roof.

The rainwater falling on the Ecosan toilet too is collected in a 200 litre rain barrel and used for ablution purpose.

We have a box type solar cooker to cook our lunch on the terrace. A solar water heater heats water for bath and for the kitchen. During cloudy days we use a ‘Gujarat boiler’ which uses bio-mass for the water heating. The Gujarat Boiler also generates ash for us to use in the Eco-san toilet. We have planted many trees in front of the house and the twigs and branches from the trees are used for the Gujarat Boiler.

Next we have placed a bathroom on the terrace itself. This also has a front loading washing machine which is one of the most water efficient ones in the market. We collect the water from the bath we have on the terrace bathroom as well as from the washing machine in a small ferro-cement tank placed just below the roof slab. We then pump it up to a planted reed filter to clean up the grey-water using a small pump. The reed filter is Cattails – reeds found in lakes- placed in 4 blue drums. In a fifth drum we have sand and gravel filter to clean up the grey-water further. This treated grey-water is then used for the terrace garden where we sometimes grow rice paddy.  Some extra grey-water is also used for flushing the toilet in the ground floor. No greywater is allowed to go waste.

The rice on the rooftop grows well on even a small area. We place 2 sheets of a pond lining material called Silpaulin with a brick edging. The sheet is then filled with a mix of compost, vermi-compost and red earth up-to a depth of 2 to 3 inches. Rice paddy is then planted in it. The water required for the paddy comes from grey-water alone. For the fertilizer the urine from the Eco-san toilet is used. Kitchen waste which is composted is also added to the soil. We have had productions of paddy to the tune of 1 kg per square meter. We have also found that we can grow 4 crops of rice in a year. Millets can also be grown instead of rice. Vegetables such as tomatoes, brinjals, lady-fingers, chilies all grow on the terrace though the monkeys who frequent this place can also be a nuisance at times.

A small wetland has also been created in a ferro-cement tank where different plants and fishes occupy and clean water.

Solar photo-voltaic panels on the roof provide enough power for us to store in batteries and use to light 11 bulbs in the house. The house incidentally has no fans let alone AC’s thanks to the cool terrace as well as thanks to the trees planted on the sides which enfold it in shade.

A well designed rooftop can provide all the water required for a house-hold, provide energy for cooking , lighting and water heating, provide food-grains and vegetables , enhance bio-diversity as well as absorb all the waste-stream from the house from the kitchen and bathroom / toilets and convert it to reuse .

A nutrient recycling system – looking at urban sanitation differently

City Ecosystem services and their management

A city needs a vast hinterland to support its population base as well as its economic engine. From here will come the food, water and other resources to keep it going. Of these water is a crucial limiting factor in the sense it has to be physically managed in large volumes to be delivered to every household daily.

Managing the catchment of the rivers which are the primary source for water will need to figure high on the list of priorities if a city wants to be sustainable and just.Catchment management will ensure that the forests and the groundwaters are protected so that the rivers continue to flow with high quality and quantity of water. These are upstream interventions for a river.

Catchment management can also mean taking care and protecting the water bodies within the city . Lakes and groundwater need to be kept away from pollution and encroachment as well as recharged with rainwaters.

Downstream needs : On the other hand the city also needs large areas of land downstream in a certain sense to manage the vast streams of waste that flow from it. Solid waste generated need land-fills as disposal areas. Liquid waste flowing through streams need large areas too for absorption of the nutrients.

In a strange conundrum the valley of the Vrishbhavati river is one of the greenest areas around Bangalore while the surrounding areas suffer from drought and a shortage of water. The city generates waste-water in the millions and about 500 million litres per day should flow out in the Vrishabhavati valley. The Byramangala reservoir , spread over 420 acres of land , receives all this water. It is a surprisingly scenic spot and deceptively beautiful .  Built in 1940 this reservoir continues to provide irrigation water through canals to many a farm field. The reservoir itself used to be a breeding ground for fish but all that has gone with the introduction of the African catfish into it.

The deceptively beautiful Byramangala lake receives about 50 % of the citys waste-water

Downstream the waste-waters undergo a remarkable transformation. The soil , the vegetation and farmers transform this nutrient rich water into a green bounty. Slowly and surely as the river progresses one sees an improvement in the quality of the waters and by the time it joins the Arkavathy it can hardly be recognized as a foul smelling black stream which leaves the city. The Ecosystem services provided by nature is truly remarkable.

Slowly but surely nature transforms black-water into better quality

This is not to say that there are no problems. Industrial effluents should not enter the stream at all . Domestic sewage too should be treated to a certain minimum standards before release to the river. Groundwater in around 50 % of the bore-wells was reported as contaminated especially with nitrates and bacteria according to a study. Farmers and field workers too have been reported to suffer from skin disease and other ailments.

How green is my nutrient laden valley ?

While source control and elimination of the problem there is the best way it is still true that these waters are now essential for the livelihoods of hundreds.

Can waste-water irrigation be integrated with the ecosystems approach of managing it?

Can the city think of identifying the entire area of the Byramangala reservoir and its command area as a zone which produces ecological benefits and for which the city should support the land and its cultivators ? Can this land be bought by the city and managed with the farmers and a palate of crops developed which will not enter the food chain of the residents of Bangalore? Can the villagers downstream be supported to access safe water and also be rid of the disease impact of using the waste-water? Can we think other than conventional waste-water treatment plants but say vast bio-diverse managed wetlands to clean the sewage that emanates from our city and for which each and every citizen is personally responsible? Can the institutions in our city rise up to the challenge and can the  city become ecological and water wise ? If any city can be the first this city has a fair shot at it.

On the reuse of nutrients and water

The city is faced with a massive challenge when it comes to treating wastewater. Of the 1000 million litres per day of wastewater generated only about 430 million litres gets treated every day. Stormwater drains are thus full of sewage and this ends up in our rivers, lakes and groundwater.

Under a new set of projects additional waste-water treatment plants are being put up yet they may prove to be inadequate. On the other hand when one looks at smaller wastewater systems the city has more than 2000 of them according to Dr Anant Kodavasan, a member of an expert committee looking into the issue. Many of them are however are either dysfunctional or are performing below par. The installed capacity of these systems are close to 200 million litres per day, a significant volume.

The best bet is for all the apartments and institutions that have these plants to get them evaluated and brought into efficient performance levels. The cost of the treated waste-water ready for use as non-potable water could vary between Rs 18 to Rs 30 a kilo-litre , significantly less than the water being purchased from private water tankers.

The State Pollution Control Board insists on every apartment or layout which has more than 80 flats to have its own waste-water treatment plant. If these plants are located well , not hidden in basements, they consume less energy , treat water well and produce quality good enough to be used for flushing toilets and for the landscape. A systematic re-evaluation of these plants is therefore necessary to fit them into the overall strategy of managing waste-water in the city.

The other advantage with these systems such as the one in the Jayadeva Institute of Cardiology, a hospital in the southern part of the city , is that they produce not only treated wastewater for reuse but also other byproducts such as biogas for cooking and bio-sludge manure for gardening. As Dr Ravishankar the designer of the system explains ‘ these plants not only look well, there is no odour and there is no waste. All byproducts are reused and the system pays back for itself in 4 to 4 and a half years.”

With some treatment plants there is an excess of waste-water available on site. A system of sharing between apartments has to evolve and a market for its distribution created. ITC –Windsor Manor for example is able to give its treated wastewater to the golf club opposite since it has more than its requirement. These markets need to evolve further and should be facilitated by the BWSSB and the Karnataka State Pollution Control Board.

Apartment owners, layout residents and institutions are doing the right ecological and economic thing by installing these WWTP’s for not only do they save money they ensure that the environment is not polluted. Investing in R and D , developing better models for operations and maintenance and better consumer education will go a long way in ensuring better water management for the city.

The commodity that is water

Water as a commodity

The open well close to Jakkur is a beautiful structure. It is at least 50 years old and was built in the old style of dry stone pitching. Unlike many other such wells which dotted the landscape it did not have the beautiful flight of steps sweeping in to the water level. The water was used for all domestic purpose including drinking by the farmer.

The city then crept in and farming was given up as an occupation. The land was rented out and the renters of the small rooms built on the land, drew water from the well using buckets and a pulley.  Times changed and now there is a water scarcity in the city. Construction works need water and are not provided for by the piped network. Apartments have sprung up and they need enormous quantities of water. The price of water is Rs 600 for a tanker load of 6000 litres.

The well has now been ‘auctioned’ for Rs 15,000 a month to a water tanker operator. The more trips he makes the more money he makes. He now extracts water using a pump and has sunk a small tube-well within the open well too. Water is now a commodity and its value is Rs 100 a kilo-litre. The original users of the water now have to struggle to bring it from far off places.

The water in the well is being treated as a private resource whereas in truth it should be treated as a community property resource. In actuality a waste-water treatment plant funded by the state treats and releases waste-water into the Jakkur lake, which too has been redone with public monies. These public investments recharge the aquifer all around and keep the wells with water. The extraction of the water is however private and land-owners and tanker operators are making the money from this public investment.

The key challenge for the institutions is to regulate this withdrawal of water in a sustainable fashion and to draw enough through cess and tax to keep the ecosystem running in a condition that the lake is always full and the waste-water treated.

The true cost of water is captured when it is returned to nature at no negative impact and when the ecosystem is maintained to ensure continuous supply. Policies should be framed and laws put into place so that this outcome is realized on the ground. Public monies invested should generate public goods and not private benefits.

Recognizing and seizing such opportunities , the city should set up waste-water treatment plants in or close to all lakes, build constructed wetlands around these lakes to further improve water qualities , fill up the lakes to enhance bio-diversity and then to make full use of the recharged groundwater so that the entire city benefits.

This form of commodification of water and wastewater which benefits all people in the city as well as the ecosystem is the way forward. That would be one step in water wisdom.

Reusing wastewater – treatment systems

WATER WISE

This waste could be a resource

A look at some emerging technologies for wastewater treatment by S. Vishwanath

Try them out: (Top) Soil biotechnology system in Mumbai; (below) let waste-water have its uses

Managing waste-water as a resource has become the new paradigm, what with water resources being seriously competed for and the general difficulty of accessing water. Added to this scarcity value of water are the tougher laws on the environment and for pollution control.

Some of the interesting new technologies include DEWATS or decentralised wastewater treatment systems and SBT or Soil Bio-technology.

The DEWATS system looks at treating wastewater from a small 1000 litres to 1000 cubic metres per day. This system can handle wastewater from homes, apartments, institutions and even small and medium industries.

It is a four-step process which involves sedimentation, up-flow anaerobic digestion, aerobic treatment in horizontal planted gravel filters and, finally, aerobic treatment in a polishing pond.

The website says that more than 350 DEWATS systems have been implemented all across South Asia. The one at the Arvind Eye Hospital in Pondicherry has been an outstanding model.

Ideal combination

The SBT treatment or the Soil Bio-Technology system has been developed by Professor Shankar from IIT-Mumbai. The system also uses what is called a combination of organic and inorganic matter in a soil layer with bacteria and earthworms as a mode of treatment.

A three million litres per day treatment plant is running in Mumbai for some time and the results have been extremely positive. In Bangalore, two experimental plants of smaller scale have been running and have shown excellent preliminary results.

Both DEWATS and SBT use nature as their source of treatment. Bacteria and soil-based creatures do their job sometimes in an anaerobic condition as with part of the DEWATS and sometimes in aerobic conditions as in SBT.

Both require low energy, if at all, and there are no moving parts, thus reducing maintenance issues and cost. Both can be integrated into landscapes and the treated wastewater used for productive irrigation applications as well as for non-potable uses such as toilet flushing.

Zero discharge

The systems help in ensuring ‘zero discharge’ for the building where they are used.

More information on DEWATS is available on the website http://cddindia.org/ which is the Centre for Dewats Dissemination Society in India.

It organises regular training programmes too.

Information on for SBT from Prof H.S.Shankar should be available on the e-mail hss@iitb.ac.in.

China has seen a boom in wastewater treatment systems over the last five years. Similarly India too will see a boom in the business. Solutions for wastewater treatment will necessarily have to adapt to Indian conditions and work on reducing maintenance cost and manpower requirement.

The nutrients recovered from the waste-water treatment need to be used productively for soil enhancement rather than to pollute water bodies.

One of the biggest threats to the environment resulting in contamination of both surface water and ground water has been domestic sewage. Treating this will protect the environment and fresh water supplies, thus enhancing sustainable water availability. This is the path to water wisdom.

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