Article by Rajul Parikh in SWI on Water Quality Basics & Treatment Options for Home Water Purification

Lets understand our basics. India is a diverse nation, both from a cultural and a geographical perspective. There is a saying: “vaani aur paani har 100 km mein badalta hai” which when literally translated means that in India, there is a difference in language and quality of water every 100 kms. India also has the distinction of having 16% of the world’s population and only 4% of the planet’s freshwater resources. In terms of quality of water supplied to its citizens, India ranked 120^th among 122 countries(2010). End result? 38 million Indians suffer from water borne diseases annually  – resulting in 780,000 deaths, that too mostly infants and children.

The Scenario today

Essentially, water used for consumption comes from two sources: groundwater and surface water. Groundwater is water extracted from the earth using bore wells &  tubewells. Groundwater is the result of seepage of water from the earth’s surface into the ground. Groundwater is essentially rich in mineral content, mixed with hues of mineral & chemical deposits found in that particular region. Groundwater emanating from natural springs in the Himalayan region is rich in natural minerals (nutrients) which are beneficial for the human body and devoid of impurities. Calcium, magnesium & iron,  in well balanced quantities constitute ideal mineral water. However, such pristine sources of groundwater are relatively elusive in areas with high population, agricultural and industrial activity. It is estimated that about 70% of India’s groundwater is contaminated. Dumping of untreated sewage into water bodies which ultimately seep into surrounding areas, discharge of industrial effluents directly into the ground, and overuse of pesticides in agriculture, have been responsible for groundwater contamination. Over exploitation of ground water to meet the demands of agriculture, industry and consumption outside city limits have lowered the water tables to critically low levels. With falling water tables, contaminants and salts dissolved in water (TDS) reach high levels. Punjab, Haryana, Andhra Pradesh, and Gujarat have low groundwater tables and face severe pollution of ground water. Contaminants in groundwater include but is not restricted to Chemical contaminants which include naturally occurring organic chemicals, salts, metals, pesticides etc. Excessive fluoride and arsenic levels in groundwater can spell disaster on the human body with long term usage.

Surface waters are found in reservoirs, lakes, ponds and rivers and is essentially rain water. Surface waters are naturally soft and contain very few dissolved impurities. Here again, the problem begins with source contamination, which is the start of the problem. Discharge of sewage and industrial effluents into water bodies cause serious contamination. (It is estimated that 90% of wastewater in developing countries is discharged into rivers and water bodies without treatment.) Surface waters become the feed for treatment plants operated by civic authorities (municipalities). This water is pumped to the treatment plant. Post treatment, water is distributed via pipelines to residents within defined urban areas. Water is supplied intermittently in most cities. Ageing pipelines run parallel to sewage lines, This intermittent supply creates a vacuum in unpressurized water pipes, allowing for contaminants from the sewage lines to be sucked into the drinking water lines, many of them riddled with leaks.  These impurities are pathogenic in nature, mostly bacteria and viruses which cause serious water borne diseases like typhoid, cholera, gastroenteritis and diarrohea especially during periods of heavy contamination (eg. Floods) leading to outbreaks of epidemics.

What does this mean?

What this means is that both groundwater and surface water are often contaminated beyond permissible  limits. Groundwater may contain more than the permissible TDS and municipal supplies may get re-contaminated during  distribution and storage. The level of microorganisms may again exceed permissible levels. Most educated citizens will be able to identify their primary source of water, and this is the beginning. The treatment options available today are based on this fundamental recognition. (it is important to note that most water supplied by commercial tankers is groundwater and may contain higher levels of TDS)

Technologies available to treat drinking water

Filtration, ion exchange, separation and disinfection are 4 broad categories of technologies available to purify water. Within these, there are further sub technologies, eg microfiltration ,ultrafiltration, reverse osmosis, and disinfection Depending on the water quality, separation(membrane) and disinfection technologies are used to create safe drinking water free from excessive TDS an/or microorganisms to adhere to WHO standards of drinking water. Reverse Osmosis (RO) is an effective way to treat water with higher than permissible levels of TDS, which may also contain substances such as fluorides and arsenic.  A high TDS level is normally associated with hardness and an undesirable taste. In many cases, the main driver of RO usage is the noticeable change in taste post treatment by RO. RO treated water has a pleasant taste, akin to bottled water. It is important to remember that most RO membranes reduce TDS by 90% . So if the TDS is 600 mg/ml to begin with, the treated water will have a TDS of 60. Ideal TDS levels should be in the range of xx mg/ml. Ground water often contains microorganisms as well, so disinfection post RO is often good protection. (The primary job of an RO membrane is to separate the dissolved impurities, not disinfect.)

When the source of water is surface, filtration and disinfection technologies normally suffice to make the water safe.. A chemical based gravity purifier or a chemical free UV purifier does a good job of disinfection. Adding an RO to treat surface water which has low TDS to start with, is normally unnecessary and akin to antibiotic treatment being administered for a common cold.

Making the right choice

Begin by Checking the TDS content of your water. A water test checking for chemical contamination can be done, especially in areas known for arsenic or fluoride contamination. Else, a simple TDS meter carried by most sales / service staff of reputed purifier companies will determine the TDS levels in your water. If the TDS level is greater than 500 ppm, as may be the case in water supplied by tankers and from bore wells, and the taste undesirable, then a Reverse Osmosis (RO) based water purifier would reduce TDS levels by about 90% and make your water better tasting. If the TDS is low  (below 500) as is the case of water supplied by the municipality,  an RO water purifier would serve no purpose.  Disinfection treatment devices eg. chemical based gravity filters or a well designed UV water purifier will do the job. Household budgets often play a role in this choice. In case there is a reason to suspect microbiological contamination, a micro test in a lab or a home check kit available in the market will reveal if the water is microbiologically unsafe.

Next see what companies are offering. With jargon being thrown at you, check the meaning and implications of systems which have RO + UV, RO + UV + UF, TDS meter etc. Some of these are unnecessary and increase the cost of the equipment and maintenance , without adding any real value. A TDS meter /controller is nothing but a simple flow meter meant for controlling the mix between RO water (devoid of minerals)and regular tap water which contains minerals. This is done so that you are not drinking water with very low TDS. So the question is: did you need to use an RO purifier in the first place?

Know the pros and cons of each technology. For example, in an RO water purifier as much as 80% of the water is rejected and only 20-30% is used for drinking.  In many non electric gravity based storage type water purifiers, chlorine may be the chemical used for purification. In a UV purifier, know that hard water will not become soft and that the cartridges and UV lamp need replacement at regular intervals,  besides regular cleaning. Understand the costs in maintaining each system and cost of consumables.

Understanding whether you have sufficient water pressure while using an online water purifier is important. Online water purifiers normally need a pressure of between 5-40 PSI (pounds per square inch) for them to work effectively.  An easy way to calculate the pressure in your tap is to see how many floors you are from the terrace from where water is distributed by gravity. So if you are in a 10 story building and you live on the 8^th floor, then your water pressure is likely to be   10PSI, because every 10 feet from the top is equivalent to 5 PSI. If you live on the 1^st floor, then the pressure in your tap will be around 45 PSI. In that case, a pressure reducing valve will be required along with the online water purifier.

For homes with very low pressure, a booster pump will help or alternately a UV purifier which works on loft tank pressure can be opted for.

Finally, check the after sales service track record of the company. Water purifiers irrespective of technology need frequent cleaning and regular maintenance and replacement of consumables.  Visit the website, check reviews on social media. See what customers are really saying.

I hope this article has been useful in understanding basic water quality, technologies and treatment options, and practical considerations before investing in a water purifier for your family. Cheers to your good health!