A municipal water tanker trundles into a neighbourhood that has not received water in its taps for days. Amid much jostling, a swarm of hassled residents promptly converge on it, carrying bottles, buckets, vessels, drums and basically anything that can store water. This is a familiar scene during the scorching summer months in many Indian cities.
Every year during summer, India appears to be on the verge of a water crisis once again despite witnessing bountiful rains the previous year. Recently, Bengaluru’s worsening water woes made it to the headlines, with scary statistics warning that India’s IT capital would go the Cape Town way if preventive action is not taken immediately.
As JA Carney wrote in her 1845 poem, little drops of water and tiny grains of sand make up the mighty ocean. And its past time that we Indians started saving those precious drops. One of the most effective ways of doing this in everyday life is greywater recycling, a method of recycling wastewater from kitchen sinks, showers and laundry fixtures.
Here is all you need to know about this simple, safe and sustainable water-saving system.
Why is greywater recycling so awesome?
Greywater recycling helps reduce household water usage by about 50% — potentially halving your water bills as well as your water footprint.
It is also a smarter use of resources. When you use greywater to irrigate your plants, you’re getting twice as much good out of that water. First the bath; now the garden.
Furthermore, when you clean it on-site, you are reducing the effort and infrastructure invested in moving this water to a treatment facility far away. By not sending polluted water, you are also preventing lakes from frothing and catching fire.
Moreover, unlike a rainwater harvesting system (which relies on rainfall), greywater is in plentiful supply on a daily basis — the more clean water that you use to wash yourself, your food and your dishes, the more greywater you will have to recycle.
How can you do greywater recycling at home?
Step 1: Find the source and connect to collection tank
The first step is to map the plumbing to find the sources of greywater. The shower (or bathtub), washing machine and kitchen sink will provide the most water, so choose these locations for the greatest return on investment. However, remember to collect only as much grey water as your garden can use, otherwise you’ll be left with bucketfuls of gradually putrefying water.
In most houses, there will be a pipe that runs from the bath and kitchen sinks down to the sewer. Install a valve and diverter pipe to ensure that all the greywater runs to a small tank (equipped with a submersible pump made from stainless steel).
This pump will send the greywater into an overhead tank, which in turn is connected to all the flush toilets in the building. To clear the water of any soap sediments, dirts and bad smell, add small amounts of alum and bleach.
[TBI Tip: Try to use eco-friendly detergents, shampoos and soaps (based on soap berries and soap nuts) for washing clothes, bathing and for the dishes. Here’s how you can make your own all-natural soap. Also, reuse the wastewater generated by RO purifiers for household chores, flushing toilets and more. Know more here.]
Step 2: If you have the space, prepare a simple plant-based treatment system.
Unused patches of land in and around apartment buildings can be used to build reed/soil beds and divert greywater towards them. This is also a great way to bring the community together in an eco-friendly initiative.
On a level bed of garden soil, plant water-loving saplings giving at least 2.5 sq. ft. per plant and leaving one foot gap between plants. You can use Canna indica (Indian shot), Hedychium coronarium (white ginger lily), the cyperus plant (umbrella plant), Colocaesia, or even banana.
Ensure that the plants are exposed to at least moderate sunlight and water them for two or three weeks till they take root and stabilise. Then start diverting excess greywater into the bed in gradually increased volumes over a week. Thereafter, the process is practically self-sustaining.
The plant-soil bacteria combination helps in decomposition of the suspended solids while the soil layer beneath filters the water. The filtered water can be collected in an underground collection pit through percolation and pumped to an over head tank. Or it can be allowed to naturally augment the shallow water table and be drawn for reuse through a dug well.
Step 3: Maintenance, final filtration and utilisation of treated water.
As the water is absorbed quickly by the plant-based treatment bed, there is no mosquito breeding or stench. However, it does need periodical maintenance — the plants must be removed once it flowers to allow fresh plants to grow. Also, forming of mounds around the plants must be prevented since these impede the smooth flow of water across the entire bed.
To clean the stored water further, you can use a simple filter unit made of layers of gravel, pebbles and charcoal. The treated greywater is now ready to use for watering your plants, washing your car or for cleaning the front of your house. Trust us, your kitchen garden will love the treated greywater and give you excellent vegetables!
In fact, Chennai resident A.Sanjeevi told The Hindu,
“We have adopted the method to both recharge groundwater and re-use part of the treated waste water for flushing and gardening purposes. We recover about 500 litres of water from the process daily.”
What are the benefits of greywater recycling for India?
According to a 2011 study by the Centre for Science and Environment (CSE), more than 70% of the 920 litres of water supplied per household per day is consumed in kitchen use, showers and laundry. This greywater (different from blackwater that is dispensed to sewage from toilets) is seldom trapped by building systems for non-potable use such as toilet flushing, gardening, washing cars and fire fighting.
Instead, they drain it out along with blackwater (sewage from toilets), burdening the STPs (sewage treatment plants) and increasing their running costs. More importantly, the precious water is lost.
In contrast, countries such as Japan use greywater recycling extensively to successfully tide over their water deficit. In fact, through a multi-pronged strategy involving small treatment plants and closed-loop water supply at building level, Japan reuses more than 53 million litres of water every day.
As for the effectiveness of this technique in Indian cities, environmental engineers from Bengaluru have demonstrated that greywater recycling reduces nearly 70% of the total domestic water requirement in a residential complex with 500 inhabitants. The experiment also helped the complex save Rs 10.3 lakh per annum and reduce groundwater exploitation at the site.
As can be deduced, greywater recycling is an eco-friendly, economical and effective way of providing considerable water security to every household in India. At a time when freshwater supplies are diminishing fast, implementing solutions like this aren’t just a good idea, they’re absolutely vital for the well-being of the nation and its future.