RO water purification systems

Context (DTE): Experts warn that Reverse Osmosis (RO) water with dangerously low levels of mineral content can have an adverse impact on health.
Reasons to prefer RO water: Concerns about tap water quality, contaminated groundwater, and irregular water supplies.
The water purifier market in India is expected to double from $3,080.7 million in 2023 to $6,880.3 million by 2032.
Despite its dominance, the effects of RO water on health and industry regulations remain unclear.

Need for RO water purification systems

Water contains helpful microscopic organisms and essential minerals like calcium and magnesium, which aid in muscle and heart function.
- Sodium, potassium, copper, iron, and zinc are also present in small amounts.
Polluted water can carry disease-causing microbes, fertilisers, and heavy metals like chromium and lead.
Groundwater may contain elements like fluorides and heavy metals such as chromium, arsenic, and lead, which can cause health issues if consumed in large amounts.
The presence of minerals and heavy metals in water is known as total dissolved solids (TDS), responsible for its taste and hardness.
High levels of total dissolved solids (TDS) in water can cause unpalatable taste and hardness.
Reverse osmosis (RO) systems are becoming popular for purifying water as they can remove impurities and lower TDS levels.
An RO system consists of a semi-permeable membrane with tiny pores (0.0001 to 0.001 microns in size) that separate dissolved salts and impurities from water under pressure.
As untreated water passes through the membrane under applied external pressure, dissolved salts, impurities, and germs are separated, providing clean and sweet water.

RO systems claim to remove 90-100% of TDS. However, essential minerals like calcium and magnesium are also lost in the process.
- This loss could be a public health concern as many people in the country suffer from micronutrient deficiency.
- In most houses surveyed by SPECS, RO water has TDS levels of 18 to 25 mg/l, which is considered unsuitable for drinking. ( PECS, an NGO in Dehradun
- According to SPECS, drip candle filters can be used for purification in many areas. However, due to a lack of awareness, people opt for RO systems unnecessarily.
In August 2023, a study by researchers from Medical College Baroda found that RO systems remove 90-92% of beneficial calcium and magnesium.
- The study, published in the Journal of the Indian Medical Association, linked RO water usage to joint pain among urban citizens of Vadodara.
Another study in Vadodara, published in January 2022, found that RO water causes micronutrient deficiency.
- It analysed patients at SSG Hospital in 2017-18 and found a significant association between RO water usage and vitamin B12 deficiency.
- Factors like a vegetarian diet, dark complexion, and socio-economic status were also linked to vitamin B12 deficiency.

In a 2005 paper, the World Health Organization (WHO) documented cases from the Czech and Slovak populations.
- They began using RO systems in home taps around 2000-02.Shortly after, complaints of cardiovascular disorders, tiredness, weakness, and muscular cramps emerged.
- The WHO paper suggests acute magnesium (and possibly calcium) deficiency as the cause.
BIS cautioned in its 2015 standards that RO systems aren’t suitable for areas where arsenic levels exceed 0.1 mg/l and fluoride levels surpass 8.0 mg/l, but this was removed from the updated 2023 standards.

National Green Tribunal (NGT) in May 2019, the Union Environment Ministry directed the issuance of a notification to prohibit the use of RO purifiers where TDS in water is less than 500 mg/l. Wherever RO is allowed, a requirement was set for more than 60% water recovery.
- The report stated that RO systems are not useful if TDS is less than 500 mg/l.
- It also highlighted the removal of important minerals and wastage of water by RO in such cases.
- In March 2022, the Supreme Court stayed the NGT order following a challenge by the Water Quality India Association, a non-profit in Mumbai.
The Union environment ministry issued the Water Purification System (Regulation of Use) Rules, 2023, In November.
- These rules provide guidelines for managing reject water and discarded elements from purification systems. RO companies have one year to comply with these rules.
WHO’s 2017 drinking water standards recommend TDS levels between 600 and 1,000 mg/l. However, there’s limited data on whether high or low TDS affects health.
Bureau of Indian Standards (BIS) has set the maximum TDS limit at 500 mg/l since 1991. Europe, the US, and Canada set TDS standards at 500 to 600 mg/l

Experts suggest that the necessity of RO depends on the region and water condition, recommending it only for areas with hard surface or groundwater.
In places where surface water is used for drinking, a combination of candles, activated carbon, and UV filters is usually sufficient to purify the water.
Experts urge that the water supplied through pipes to every household should meet BIS standards, eliminating the need for RO in such areas.

Yellowness in water indicates excess iron or bacterial infection, which can be eliminated by boiling (According to the National Institute of Hydrology).
Water with low TDS is termed hungry water. Drinking such water gradually absorbs enzymes and minerals from the body, potentially leading to issues like diarrhoea.

Flow Direction: Less concentrated solution High concentrated solution.
- For example, if you had a container full of water with a low salt concentration and another container full of water with a high salt concentration, and a semi-permeable membrane separated them, then the water with the lower salt concentration would begin to migrate towards the container with the higher salt concentration.
Osmosis is a naturally occurring phenomenon. Examples of osmosis are when plant roots absorb water from the soil and our kidneys absorb water from our blood.
No energy required.

Reverse Osmosis - PMF IAS

Flow Direction reversed: High concentrated solution Less concentrated solution (under pressure)
Reverse Osmosis works by using a high-pressure pump to increase the pressure on the salt side of the RO and force the water across the semi-permeable RO membrane, leaving almost all (around 95% to 99%) of dissolved salts.