To RO or Not to RO Has Become a Difficult Question

RO Delhi

Almost all of us are well acquainted with the reverse osmosis machine that adorns every middle-class household. It is used for purifying water and removing dissolved chemicals, including salts from the water. Once considered essential in most homes, the RO machines have recently come under acute scrutiny as we try to assess how they are needlessly wasting large quantities of water .

Water from the tap is generally believed to be full of impurities, which make it unfit for all forms of consumption. By passing this water through a filter or purifier, we can get rid of these contaminants. This filter is chosen on the basis of the type and quantity of the impurities. Reverse Osmosis filtration is a membrane-based filtration system. Here, the membrane filters act as a barrier to separate contaminants from water, or they remove the particles contaminating the water.

However, all particles in water are not harmful to life. Minerals like calcium and magnesium are needed by the body, while other minerals like arsenic, heavy metals and fluorides are toxic and need to be removed. All these substances are present in the water and together constitute the TDS (Total Dissolved Solids).

What is TDS?

TDS are solids, larger than 2 microns in size, left in the water after the normal filtration process. The presence of moderate-high TDS changes the taste of water, renders it impure and has ill effects on the health of the consumer. Mineral RO technology works to maintain the levels of TDS within the range as prescribed by WHO and other authorized bodies within the country. UV filtration is also capable of removing microbial contamination.

The tap water in Delhi, supplied by the DJB, usually has a TDS count of as less as 85 mg/L, which is good even by global standards. According to the Bureau of Indian Standards, the upper limit of TDS in water is 500 gm/L. According to the WHO, a 300 mg/L TDS level is more than acceptable. Excessively low TDS levels (<50 mg/L) are harmful as they completely lack the essential minerals that makeup water.

According to a recent study published in the Times of India, both affluent colonies and disorganized slum dwellings show reasonable TDS count in their supply water. For example, RK Puram Sector-3, a government colony, gets water within the range of 80-90 mg/L TDS, but the neighbouring JJ colony has almost identical water quality of 95-95 mg/L. This study also found how sometimes the quantity of TDS generated by deploying RO systems can lower the TDS count beyond 50 and strip the water of essential minerals. A lot of water is also wasted while doing so.

Why are we talking about this?

In a city with already dwindling groundwater sources and extremely contaminated surface water sources, this waste of drinkable water is very reckless. A study by MIT has stated that RO systems discard as much as 75% of the raw water fed to them, which is thrown away instead of using it for gardening or other household practices. In fact, most of this water is safe to drink.

The NGT has stepped in to solve this and has instructed the Government to ban the use of ROs in households where TDS levels are below 500 mg/l. The Tribunal had also ordered RO manufacturers to ensure that more than 60% of water is recovered. This is in stark contrast to the current scenario, where RO systems discard about 80% of water which is processed, leading to huge wastage.

But is it really time to do away with RO systems that currently occupy a space in almost all Indian homes?

TDS is not the sole criterion for judging water purity. When the water supply by the Delhi Jal Board to various districts was tested, 65-70 parameters were employed. The only places where RO is not needed is in localities with low TDS tap water. Bacterial count and the presence of trace metals can also be detrimental and requires specialized filters.

Unfortunately, various sectors in Delhi still do not receive tapped water. According to one estimate, 19% of the NCT does not have access to tapped water. The groundwater obtained from bore-well sources, which is used to supply most of South Delhi’s water, has shown high levels of TDS compared to the rest of the city. These places still require RO purification systems to regulate the water quality.

There are various added social constructs that hinder a complete switch to tap water. Illegal water theft from direct pipelines leads to contamination, and the uneven supply of water has made a large section of the public question raw water sources.

Another reason why purification of tap water supplied by the DJB is needed is because of the taste and odour deficiencies. Though this water is well within permissible TDS limits, in many places it contains contaminants and gets a foul colour from the corroded pipes that it travels through. Seasonal flooding also leads to the spread of contaminants in the water systems. A regular checking of the pipelines is recommended to the DJB.

So what is the solution?

The first step towards a solution is to make consumers aware of the needless RO purification systems that are doing more harm than good. This can be done by informing them about the quality of water supply reaching their residences.

A menacing problem is the low-quality water purification systems being manufactured and sold in lower-income households. Currently, people do not have access to any cheap purification systems, so they move towards shoddy but most accessible options. The most sensible option is switching to UV or other purification systems, which retains the TDS count while eliminating odour and taste deficiencies from tap water.

New systems are also being designed and implemented. Recently, a group of students in Gurugram made up a DIY water purification system design that can save  up to 1,00,000 litres of water in 15 days. This system has already been reported to set up in some restaurants as well as commercial offices around the city. Such projects need to be recognized and funded by the government as well as scientific organizations.

Following the NGTs order, the Government has now drafted a notification for a future RO system ban in places with acceptable limit of drinking water. After this ban is implemented, region-wise detailed consultation will be needed before implementation of any water purification system. It is hoped that this will also reduce the extra water discharged and wasted in the process.

Anoushka Raj

Anoushka Raj is an Environmental Engineer and her areas of interest include water conservation, biodiversity, and polymer sciences.

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