Rain water harvesting is defined as the process of collecting and storing rain for later productive use. Given our quest for water, it is but logical to look at the rains as primary source of water, as one of the major resource for a city like Delhi. Laws and notifications, directives and executive diktats are often being issued, that require us to capture water to the extent possible and harvest it for either replenishing the dwindling ground water level or to use it during the months when its availability is less.
Modifications in the building by-laws have been made by the Ministry of Urban Development and Poverty Alleviation, Government of India, vide S.O. 730, date 28.07.2001 by which rain water harvesting in all new buildings on plots of 100 sqm or above is now mandatory.
Today, there is a great deal of interest in society to take responsibility for water consumption and its conservation. There are innovations in capturing and using rainwater. The government too, is following the trend and has brought in legislative measures to persuade citizens to harvest rainwater.
Rooftop water harvesting offers an affordable means of accessing good quality water at the point of consumption, where the control of the water supply lies at the user level. Rooftop Rainwater can be stored for long periods in tanks without deterioration of quality as it is purest form of water.
Rainwater harvesting (RWH) involves the collection, storage and use of rainwater and run-off for domestic or agricultural purposes. Essentially, RWH systems use the principle of conserving rainwater ‘where it falls’, in the process recharging groundwater.
DMRC has installed rain water harvesting structures at elevated stations, viaducts and depots. This installation shall continue in ongoing phase-III. As an illustration, a schematic diagram of capturing rain water harvesting from viaducts, till the collection chamber is shown in Figure A. Figure B depicts the recharge of ground water through filter media to the recharge well.
DMRC has provided 22 new rain water harvesting structures with 93 pits having a total capacity of 1752.78 cum in the last year. The increased capacity of rain water harvesting in the year is 25% against the target of 10%. Currently DMRC has 84 rain water harvesting structures with 464 pits which have a total capacity of 8607.08 cum. In the coming FY 2016-17, DMRC has planned to install 24 new RWH systems with 107 pits with a total capacity of 1350 cum. DMRC is exploring more possibility of minimizing fresh water consumption by treating and reusing the waste water.
Provision of ETPs, STPs and bio-digesters in DMRC
In order to meet the criteria set under “General Standards for discharge of Environmental pollutants” – Schedule VI of The Environment (Protection) Rules, 1986, Sewage Treatment Plants and Effluent Treatment Plants have been provided in depots and colonies.
Waste water treatment is an important initiative to be taken for the betterment of the society and for future generations. Treating waste water and reusing the treated water is an important part of water conservation effort. Waste water treatment is a process, wherein the contaminants are removed from waste water to produce effluent suitable for reuse or discharge in waste water drain.
An Effluent Treatment Plant treats the waste water to remove any toxic and non toxic materials or chemicals from the waste water. A Sewage Treatment Plant (domestic waste water treatment) removes contaminants from waste water and household sewage. The treated water from ETP/STP if it meets the standards, can be reused or else to be discharged into drains.
Given the nature of activities associated with the organization, DMRC understood its impact upon water resources right from beginning and to conserve this precious resource ETPs and STPs were installed at depots, colonies and also at a few metro stations.
The treated water is being used for horticulture and toilet flushing to the maximum extent possible. Currently the excess treated water from ETP/STP, after meeting the potential for reuse, is being sent into drains. Since the treated water is much cleaner, it helps to bring down the pollution load of drains by dilution.
Total capacity of ETPs and STPs installed in DMRC is 761 cum and 1,744 cum from which 678 kilolitre treated water is being reused per day. DMRC has taken a new step towards recycling of waste water by installing bio-digester tank. In bio-digester tank, a consortium of anaerobic bacteria has been formulated and adopted to work at temperature as low as 5 º C. This is the component which acts as inoculum (seed material) to the bio-digester and converts the organic waste into methane and carbon dioxide. The anaerobic process inactivates the pathogens responsible for water borne diseases. Bio-digester serves as reaction vessel for bio-methanation and provides the anaerobic conditions and required temperature for the bacteria. The optimum temp is maintained by microbial heat, insulation of the reactor and solar heating at places wherever required.
Work Process of Bio-digester tank