9. Recycling of used water

If we get water at the turn of a tap, we tend to take availability of water for granted and do not bother about what happens to it once it goes into the outflow pipes: Which perhaps explains the phrase ‘Waste Water’. It is however more appropriate to call this as “Used Water”. Used water is of two types:- Grey water which is water after use for bathing , washing of clothes, vessels and floors. Black water is water that flows out from the closets. As stated earlier, black water accounts for 30% of the total usage and grey water accounts for 55- 60% of the total usage. Recycling of used water had been restricted till recently in most parts of the world to treating black water (i.e. sewage water) by a combination of mechanical, chemical and biological means and using the treated water for select uses in industry, such as in air-conditioning and in cooling towers. Some of the industries in the Manali belt have already started treating and recycling substantial quantities of water recovered from sewage. The CMWSSB supplies these industries with water obtained after tertiary treatment of sewage which is subjected to further refinement by these industries by the reverse osmosis process and used. Several hotels are also recovering and reusing water for similar purposes. Till the advent of apartments, only black water from individual houses went into the sewerage system. The grey water used to be led to the garden where it watered coconut palms, plantain clumps and other garden plants as well. This water percolated into the soil and was purified by natural processes in the soil. The purified water was then drawn for reuse from the wells along with rain water which would also have percolated into well through the soil. Today, because of the high cost of urban land, and the tendency to pave the limited area around the apartment complexes for parking of cars, very little of greenery exists around apartment complexes and so invariably grey water is drained along with black water into the sewerage system. This not only is detrimental to the recharging of the ground water table but also contributes to the loading of the sewage pumping stations. However, very little attention has been given to date to the treatment and reuse of grey water in urban environments. It is therefore worth exploring how grey water can be put to reuse in today’s urban context. Alacrity has been actively working over the last two years in evolving a suitable process by which this can be done. The process which has now been established is an environmentally friendly process, that involves low capital cost and very limited maintenance. This will be introduced shortly in Alacrity’s complexes, where the treated water will be used for flushing of toilets, washing of vehicles and the drive ways and for gardening needs and the rest will be put back into the soil. Such reuse will result in significant reduction in the quantum of water drawn from ground water sources, thus increasing the self-reliance of the complexes in their water needs. Earlier we had seen how efficient rain water harvesting will enable an 8 apartment complex to be self-reliant in its water needs for 133 days of the year. A conservative estimate indicates that if the grey water is treated by this process and put to reuse, self-reliance will rise from 133 days to 250 days. Since not every plot is covered by an apartment complex, rain water harvesting and grey water recovery in individual houses, office building, hotels, parks etc. will further enrich the ground water table and enable the complex to be self reliant in its water needs for the whole year.