RO-Reverse Osmosis Water Filters – What Consumers Need to Know

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RO-Reverse Osmosis Water Filters - What Consumers Need to Know


The National Green Tribunal in India ordered to Ban use of RO, Reverse Osmosis Water Filters in Delhi areas with Total Dissolved Solids (TDS) less than 500 per liter. So, presenting you here the information you need to know about RO Water Filters.

Facts Analysis:

The National Green Tribunal (NGT) in India ordered prohibition of RO Filters in Delhi areas with Total Dissolved Solids (TDS) less than 500 per liter. They cited consumers’ health and also environmental concerns. They pointed the current system of Reverse Osmosis discards about 80% of processed water leading to huge wastage. The Tribunal also directed the Ministry of Environment to frame rules for manufacturing and sale of RO filters in India. So, let us examine in detail the concerns about the RO water filter systems.

What is Reverse Osmosis?

Reverse osmosis (RO) is a water purification process using partially permeable membrane to remove ions, unwanted molecules and larger particles from drinking water. The purification involves application of pressure to overcome Osmotic pressure and force molecules through the semi-permeable membrane.

In the beginning, demineralized water, distilled water, deionized or reverse osmosis-treated water use included only for – industrial, technical and laboratory purposes. Their use in drinking water treatment began from 1960’s because of increasing water demands due to various reasons like population growth, high living standards and industrialization. Notably, demineralization of water was in fact needed where the primary or the only abundant water source available was highly mineralized brackish water or sea water. Unfortunately, their use in treating drinking water increased widely both from Governments and also consumers’ side at domestic-front.

Pros & Cons of Using Reverse Osmosis Water Filters

Many countries around world use Reverse osmosis water filters purification to improve water for the sake of drinking and cooking. On the other hand, there are also concerns of its use. RO filters do not just kill the bacteria; they also remove all salts and essential nutrients like Calcium and Magnesium. World Health Organization (WHO) suggests the minimum/optimum concentration of calcium and magnesium in drinking water signifies “energy content”.

WHO Report – Health Risks from Drinking Demineralized Water

A 1980 WHO report mentioned completely demineralized water (distillate) has unsatisfactory organoleptic properties and a definite adverse influence on the animal/human consumer. For example, many studies show higher water Magnesium is related to decreased risks for Cardiovascular disease (CVD) and especially for sudden death from CVD. On the other hand, consuming water low in Magnesium and Calcium are related to neural and bone issues among others. The WHO report concluded making international and national authorities responsible for drinking water quality. WHO said they should set guidelines/standards for specifying the minimum content of the relevant elements like Calcium, Magnesium and TDS.

Rejected Water Wastage

Many urban homes are using RO filters/devices to purify water. Apart from offering clean drinking water, they also cause a huge amount of water wastage in return. On an average, for every one liter of water purified, RO filters reject about three to four liters. The waste water carries with it the rejected contaminants. If there’s high content of total dissolved solids (TDS), the water rejected is not even suitable for gardening, bathing or cleaning vessels. It’s only use is in flushing toilets. Moreover, there are also concerns if metals and chemicals trapped in the brine can cause an environmental impact.

Such water wastage has been a disastrous consequence for mega cities like Delhi where large-scale use of household RO devices has increased the total water demand. In its order, NGT also directed wherever RO is permitted, manufacturers should ensure recovery of more than 60 % water.

Expert Opinions

M V Shashirekha, former chemist at the Department of Mines and Geology in Bangalore explained the matter. She said RO plants are good for highly contaminated groundwater with nitrate, fluoride, etc. “From other sources though, RO filtered water can be harmful as it removes all essential nutrients“, she adds. Unfortunately, the current RO plants do not have a calibration to consider the water source.

S Vishwanath, a water expert with the Biome Environmental Trust in Bengaluru says RO is an overkill most times.

RO is an overkill most times. In Bengaluru, 95% of the tap water is good to drink. We assume that it is not potable and invest in devices like these without a thought“.

If there are only physical impurities in the water, a simple candle filter is good enough. For biological impurities like bacteria or viruses in the water, then an ultra violet (UV) filter can be used. If only chemical properties are bad — like the presence of TDS — then an RO is necessary,” he adds.

On the other hand, an expert committee set up by The National Green Tribunal suggested RO technology “is generally not required for the places having piped water supplies (primarily supplied by Municipal Corporations/Municipalities) from surface water sources like rivers, lakes and ponds. These sources have TDS levels for low as compared to groundwater sources.” NGT directed Ministry of Environment and Forests to create awareness that TDS of at least 150 – which includes dissolved calcium and minerals in drinking water – is necessary for healthy water.


Delhi water quality row: RO manufacturers move SC against ban on RO filters by NGT

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Prashanth Damarla