FINANCIAL CHRONICLE, THURSDAY, SEPTEMBER 19, 2013 - PAGES 4
Water management is key in any green building project. Harvesting rainwater helps, of course, but there are many other ways to increase water efficiency in housing complexes
CHANDRASHEKAR HARIHARAN
W
HEN we talk about green buildings, it is not just about energy efficiency, it is also about water efficiency. How we make the best use of the water available to us, and how we can conserve it to the largest extent possible. How does that happen? What is actually done in a building in order to make it water-efficient? Let us try and understand how this works. Before purchasing a house or an office space, these are some questions you must ask before you decide. What is the builder’s plan for water availability beyond the water supply board connection that he has provided as infrastructure? What is the total water demand of the apartment block or the campus? What is the builder’s assurance to you of long-term water security? How many houses or flats has the builder created over how many acres of land? If it is 80 apartments to an acre, you can be sure that the water demand over the long term will be far higher in that community than in another community that has, let us say, only 40 flats per acre. You have to also understand what he has done as water efficiency without compromising comfort and convenience for you. You will also need to ask: Is the builder treating water 100 per cent and recycling? This will ensure that your freshwater demand has dropped dramatically by 30 per cent. Also ask if he has implemented any rainwater harvest plans? This will ensure that about 10 per cent of water demand for the year is made available from this ‘localised’ source. Let’s offer you an example. For any amount of general discourse on going green will not help half as effectively Let’s start with the density of a settlement. If I have reduced in an apartment the number of families or apartment homes to let us say 40 homes an acre, then I have brought a dramatic drop of about 40 per cent from the norm of about 70-90 flats an acre of housing development that you have across the building industry. What this means effectively is that with the simple expedient of reducing the density of the settlement -- of the number of people who will live in an apartment or layout or enclave — you will have brought down
THE WATER TABLE A housing complex is considered water efficient if it meets the following criteria Effective groundwater recharging is followed in the entire site. Percolation pits have been designed at plot, cluster and site-level to recharge the groundwater table and wells in the site. The overflow from the percolation pits is diverted to a nearby lake through a natural trail. 100 per cent rainwater harvesting by rooftop collection and storm water runoff diversion from each villa or apartment building. Use of low-flow fixtures that curtail the net water demand by as much as 35,000 litres a year per house and saves around 1,05,000 litres of water per house. Aerators are fixed to taps to reduce and control the quantity of water flowing through the fixtures, yet maintaining the required optimal pressure. 100 per cent treatment of domestic sewage generated from individual houses by sewage treatment plant by a network of sewers. The sewage treatment plant treats the entire wastewater and the treated water is used for landscaping through drip irrigation. With this, not a single drop of water in the site goes waste and is not exported. the pressure on water supply needed. But then that is not always the solution, because the dictates and demands of the market will suggest that they have greater density and smaller houses because markets and prices are not something that we can govern at levels of sensitive urban planning. If apartment builders have raised a campus with something like 70 flats to an acre and with a total gross freshwater demand of about 50,000 litres, you will have to figure out how you will address three aspects of supply-side management. One, to see that you have designed to install faucets and showers that drop the flow of water to as little as 5 litres per minute (lpm) from the norm of about 12 lpm that continues to be sadly the norm. The newgeneration Zed-engineered (or zero energy developed) faucets and sanitary fittings are enabling a sharp drop with installations called aerators or flow restrictors. They don’t cost too much either, the price difference is marginal considering their efficiency. With such aerators, the flow of
water, to you as a layperson, is much the same as it is with regular faucets. But from the context of demand-side management, you will see that there is a drop of very nearly 70 pc in the demand for fresh water. The other solution is that you need to see the water that flows off your kitchens, showers and washbasins are all directly plugged out of the building; this is called grey water. Typically in the building industry, this grey water is combined with black water that comes off water closets. We have been advocating and practicing the separation of grey water and black water from a building and treating them in a way that the black water is used for gardens and the grey water is recycled on a loop for your flush tanks. There are systems that treat the waters together and provide treated, clean drinking water. The other aspect of such demand-side management is harvesting rainwater. For every 100 square metres or 1,000 sq ft of a terrace you can harvest nearly 250,000 litres in a year. So you can imagine what you can
do in an apartment block if you used all the water that falls on your terraces as well as on all the hard surfaces that flank the buildings. This means essentially that for about three acres you will have about 2.5 million litres or 25 lakh litres of rainfall that can be captured and utilised with some basic treatment for purposes of freshwater itself in your apartment campus! Now, between the three strategies, the demand for freshwater reduced is dramatic. As much as 70 per cent. So you have a story where 35,000 litres of regular demand in an apartment, drops down by 70 per cent to 12,000 litres, essentially because you have done effective, strong demand-side management of these three practices of rainwater harvesting, of flow restrictors and aerators at every faucet and shower, and of treating all your grey and black water and reusing it in a mode that is not so much about recycling as much as it is about upcycling. There is, however, one more aspect when it comes to demand side planning. That has to do with efficient landscaping architec-
ture. As a matter of fact, whether it’s the Green Business Council or other professional bodies, they understand how indigenous plants don’t claim as much water as exotic species. What does this mean? At the time, you plan your planting and vegetation in the apartment or the residential or commercial project, you look for hardy, water-efficient species. Please ensure that you have a qualified professional who knows how to pick endemic, water-efficient species, as well as water-efficient irrigation systems. That’s a subject that needs some delving in greater detail. How you manage the supply of this efficiently designed system as far as water needs go and how you introduce them in, is another story. There are about 70 different approaches, each distinct and solution-oriented, to making a building green or energy-efficient. That is the difference we need to bring to our urban homes. ❚❚ (The writer is an authority on sustainable living solutions and the chairman and co-founder of BCIL)