Managing Water Wastage from RO Purifiers
Wander into the kitchen at any home or office in urban India, and you’ll probably find a reverse osmosis (RO) water purification device ready to dispense drinking water. These devices have seen a significant uptake over the last few years, since they offer the promise of health and hygiene at little cost. Unfortunately, these advantages come at the cost of massive water wastage, which I believe can be avoided with a bit of imagination.
How it Works
If you aren’t familiar with RO systems, here’s how they work — pipe water is ingested through an inlet and pushed through a semi-permeable membrane which filters the water. Potable water gradually collects in a container, while refuse water is let out through a pipe. A tap is attached to the container and can be used to dispense drinking water. The filtration process kicks in periodically to refill the container to its maximum capacity.
The problem here is that these devices are quite inefficient. Typically, for every 1 unit of drinking water generated, 4 to 10 units of refuse water are discarded and go straight down the drain. This refuse water is usually just 10% more hard than the ingested water, i.e., it has a slightly higher mineral content, but it can still be used for pretty much anything from watering plants to cleaning utensils.
The logical solution here, aside from building more efficient filtration devices or having municipalities carry out purification at source, would be to have a second container that collects and stores refuse water. The general purpose tap in the kitchen could draw water from this container, and fall back to regular pipe water when the container is empty.
The catch here though is that since filtration efficiency is 20% at best, assuming equivalent use, this container would have to be 4 times larger than its drinking water counterpart, which is usually at least 1 gallon. 4 gallon containers are space consuming and are likely to make the product less appealing to consumers, which explains why RO purifier manufacturers haven’t looked to this solution.
Scale of the Problem
To give you a sense of the scale involved — at the Semantics3 office in Bangalore, we collectively consume ~20 litres of drinking water a day, which amounts to ~80 litres wasted per day or 1760 litres wasted per month. Multiply this number by the hundreds of thousands of homes and offices around the country and the number is staggering.
India struggles to provide clean water to its citizens. Supply of water at my home state of Tamil Nadu alone routinely falls short of demand by 20%. ~600,000 children die in India each year of diseases caused by a lack of clean water. In this backdrop, it seems criminal to let so much usable water go to waste.
There are many potential ways in which refuse water can be reused, including for washing dishes, refilling toilet flushing systems, hydrating plants, washing clothes and bathing. Most of these require some form of temporary storage, and a pipe system to route the water from one part of the house to another.
At my own house, my grandfather has setup a patchwork routing system to let the refuse water run off to the row of plants just outside. At times, we proactively catch the water in buckets and use it for bathing. Such solutions are highly customized, aren’t practical for everybody and require a lot of effort, which is why they aren’t very widespread.
In my opinion, this problem requires an elegant product-based solution, one that will work for a wide configuration of houses, and is painless for consumers to manage. Imagine an Ikea style DIY kit with simple instructions for anyone to setup. Or a smarter way to store and transport water. Maybe a set of fixed solutions for a standard set of house configurations. Or something from left-field — an attached mini desert cooler that utilizes the water just as fast as it comes in.
Personally, I’ve found it difficult to come up with workable ideas, since this challenge falls outside the standard framework of solutions (programming languages / mathematical constructs / marketing tools) that I’m familiar with. If you have any ideas or suggestions, do let me know via the comments section or @govind201. I’m all ears and quite interested, since here’s a chance to both think outside the box and do a lot of good.
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