Water Purifiers: An Everyday Necessity

Bacteria and viruses are not visible to the naked eye but they are the major causes for water borne diseases. Bacteria cause gastro-enteritis, typhoid, cholera, paratyphoid, dysentery and diarrhoea. Virus causes polio, dysentery, gastro-enteritis, and diarrhoea. The type of impurities found in the drinking water coming to your home is mainly due to the source and distribution medium of water. Most common sources of drinking water are piped municipal corporation supply, hand operated water pumps, water tankers, lakes, rivers, bore wells, etc.

Why is Water Purifier Required?

Quality of water is getting deteriorated and contaminated day by day. There are many harmful contaminants that are present in water. These impurities are having an adverse effect on human health.  These include dissolved solids, arsenic, fluoride, antibiotics, micro plastics, rust, pesticides, disease-causing germs and bacteria and heavy metals such as arsenic, lead, iron, fluoride etc. These contaminants are responsible for causing serious health issues like cholera, hepatitis, jaundice, typhoid, and even cancer. These impurities affect the taste and smell of the water as well. Hence, it is important to remove these contaminants from the water, so that your family is provided with water that is free of any smell as well as safe and healthy for consumption.

Which type of water purifier is better for what kind of water?

There are different kinds of water purifiers available in India today. Water purifiers can be from just a simple water filter with filter cartridge element to the more advanced water purifiers using membranes for water filtration followed by sterilisation with UV filter.

• When water is hard and has high contamination, consider RO + UV purifier.
• When water is hard and has low contamination, consider RO purifier.
• When water is soft and has high or low contamination, consider UV purifier.
• If you don’t have installation feasibility for RO, UV water purifiers like running water, optimum water pressure, electricity, consider Gravity based filters
• Gravity based filter is the right purifier for municipality or corporation water, which is already chemically purified, and since this water comes from running water.

 How to find out which type of water purifier you require?

Water contains many dissolved salts, impurities which should be removed before drinking. TDS levels measure the amount of dissolved salts and heavy metals like lead, arsenic, mercury present in water.  The first thing to do is to get your home water tested for the type of pollution it may have. Accordingly you may decide which type of water purifier you need.

By measuring TDS Level in water, you will be able to make sure whether the water you are drinking is pure or impure. The maximum TDS level in water is 500mg/litre. You must make sure that it meets this mentioned level. If you see that the level is exceeding 1000mg/litre, we suggest that you do not drink that water.

 How to check the TDS Level in Water at Home?

The easiest method is digital TDS meter tester to check the TDS of water. You can easily buy a Digital TDS Meter for about Rs.150-200.

Water Purification Technologies & Uses

Reverse Osmosis (RO) Purifiers

Reverse Osmosis (RO) pushes the water molecules from the region of higher TDS level to the region of lower TDS level by applying external pressure with the help of a water pump to reverse the natural flow of water. Water with impurities or high TDS is pumped at high pressure into the RO chamber, this pushes the water molecules across the semi-permeable membrane to the other side while leaving the dissolved solids and other impurities behind. All the dissolved solids and impurities along with some input water, also known as RO waste water, are discharged through a separate outlet. RO purifiers are therefore always recommended for purifying water which has high TDS level.

Ultraviolet (UV) Purification

Ultraviolet or UV purification uses ultraviolet rays for the purification of water. A UV purifier works by throwing high intensity UV rays on the water which kills or inactivates the disease causing bacteria and viruses. However, UV purifiers cannot remove any dissolved or un-dissolved impurities or chemicals from water. Hence, most of the UV purifiers that are available in the market use some form of external sediment pre-filters to remove un-dissolved impurities and activated carbon filter to remove chlorine and some dissolved impurities. Therefore, UV water purifiers are only recommended for areas where the water source has low level of TDS. If the water has low TDS level but it is contaminated with bacteria and viruses and appears muddy, then you can use UF+UV water purifier.

Gravity based Water Purifiers

Water is allowed to flow from a top container to a lower container under the effect of gravity. Gravity-based water purifiers do not use electricity and therefore called non-electrical water purifiers. They typically use activated carbon or UF, which is made up of small carbon granules in order to absorb impurities from the water.

Ultrafiltration (UF)

Ultrafiltration also uses a semi-permeable membrane with much larger pores (appx. 0.01 microns) as compared to RO with very small pores (appx. 0.0001 microns).The advantage of UF purifiers is it can work without electricity because the membrane has much larger pores and water can pass through it naturally using the force of gravity. Which means no external pressure or water pump is required. Since UF purifiers do not hold back any water, there is no wastage of water. But there are some limitations of using UF purifiers, because of the larger pore size, UF can only remove un-dissolved solids and larger impurities. It cannot remove the dissolved solids or reduce the TDS level. So, UF purifiers are not suitable for purification of high TDS water or hard water.

Activated Carbon Filter

These types of filters or purifiers are the simplest to use and provide the most basic water purification. These filters generally comprise of sediment or sediment + activated carbon filters which can remove large and un-dissolved impurities like mud and sand along with some chemicals and microorganisms.

Candle Filters

Ceramic candle filters have 2 stainless steel containers where the upper container is fitted with 1-3 ceramic candles. In the candles, silver powder is impregnated which acts as a strong repellent of the pathogenic bacteria. It is considered the safest conventional water filter as per Consumer VOICE repeated studies.

Comparison of Water Purification Technology at a Glance

Water Purifier Brands Available in Markets

Note: Prices may vary. For latest price, check on amazon.in or flipkart.com.

How and What to Choose

Having done the first round of research, you will have to first decide which water-purification method works best for your needs and also suits your preferences. Let’s do a quick recap.

Reverse osmosis (RO) purifiers

RO technology pushes the water molecules from a region of higher TDS level to one of lower TDS level by applying external pressure with the help of a water pump to reverse the natural flow of water. Water with impurities or high TDS is pumped at high pressure into the RO chamber, and this pushes the water molecules across the semi-permeable membrane to the other side while leaving the dissolved solids and other impurities behind. All the dissolved solids and impurities along with some input water, also known as RO wastewater, are discharged through a separate outlet.

The Bureau of Indian Standards (BIS) has specified the maximum TDS limit for safe drinking water as 500 ppm (500 milligrams per litre). There is absolutely no need to use an RO purifier if the TDS level is below 300 ppm. If your water source has low TDS, then the RO purifier will further reduce it to a very low TDS level. This means the purified water will then be devoid of essential minerals like calcium and magnesium which are required for our good health. Very low TDS may also not be acceptable to consumers due to its insipid taste.

RO purifiers are therefore recommended for purifying water that has high TDS level. However, there is also the fact that a significant part of the input water is discharged along with the dissolved impurities, which results in unnecessary wastage of water. On an average, RO purifiers produce 3 litres of wastewater for every 1 litre of purified water.

Ultraviolet (UV) purification

This technology uses ultraviolet rays for the purification of water. A UV purifier works by throwing high-intensity UV rays on the water which kills or inactivates the disease-causing bacteria and viruses. However, UV purifiers cannot remove any dissolved or undissolved impurities or chemicals from water. Because of this, most of the UV purifiers that are available in the market use some form of external sediment pre-filters to remove undissolved impurities and an activated carbon filter to remove chlorine and some dissolved impurities. 

UV water purifiers are only recommended for areas where the water source has low level of TDS. If the water has low TDS level but is contaminated with bacteria and viruses and appears muddy, then you can use a UF+UV water purifier.

Ultrafiltration (UF)

Ultrafiltration uses a semi-permeable membrane with much larger pores (approximately 0.01 microns) as compared to an RO (which has very small pores, of approximately 0.0001 microns).

The advantage of UF purifiers is it can work without electricity because the membrane has much larger pores and water can pass through it naturally using the force of gravity. This means no external pressure or water pump is required. Since UF purifiers do not hold back any water, there is no wastage of water. 

There are some limitations, though. Because of the larger pore size, UF can only remove undissolved solids and larger impurities. It cannot remove the dissolved solids or reduce the TDS level. So, UF purifiers are not suitable for purification of high TDS water or hard water.

Gravity-based purifiers (candle filters)

Gravity-based purifiers work on the gravitational force from higher compartment to lower compartment. These are simplest to use and provide the most basic water purification. These filters generally comprise of sediment or sediment + activated carbon filters that can remove large and undissolved impurities like mud and sand along with some chemicals and microorganisms.

There are ceramic candle-based filters with two stainless-steel containers where the upper container is fitted with ceramic candles. The candles are impregnated with a silver solution that acts as a strong repellant against pathogenic bacteria. It is considered to be the safest conventional water filter as per Consumer Voice’s repeated studies.

Although water-purifier makers try to differentiate their products from competitors, most of them actually use a mix of three major purification approaches – reverse osmosis (RO), ultraviolet (UV) and UF (ultrafiltration).

Get the Right Thing

1. a) RO systems are useful where the TDS levels are above 500 ppm and water hardness is on the higher side. If the municipal water supply is quite satisfactory and has permissible TDS levels (below 500 ppm), RO purifiers are not required – UV purifiers should be used instead.
2. b) You may get your water tested. It will help you make a decision based on facts and figures. If the water has a very high amount of magnesium, fluoride, nitrates or calcium salts, RO purifier will be the best for you.
3. c) If the water supplied at your location is highly contaminated (with microbes, bacteria and virus) and is dirty as well, RO/UF + UV purifiers are the best solution. The UV rays destroy the microbes and the RO/UF filters out their dead bodies and other contaminants.

 The presence of bacteria and pathogenic (disease-causing) organisms is a concern when considering the safety of drinking water. Pathogenic organisms can cause intestinal infections, dysentery, hepatitis, typhoid fever, cholera and other illnesses. Water may also be contaminated with pesticides and arsenic.

What a Waste Otherwise!

A high percentage of water wastage is a major cause for worry. If you are using a RO water purifier at your home or office, you can consider the following options to reuse the wastewater.

1. a) Test the TDS in the wastewater stream. If the TDS is below 1,000 ppm, you can use the water in your plants.
2. b) Alternately, mix some of that water with tap water to mop the house. Make sure you dilute it with tap water because if the TDS is high and you use just the RO waste to mop the floor, you may see some salt deposition after the water dries.
3. c) You can use the wastewater to clean the sewage pipe at home or kitchen because of its saline nature.
4. d) You can use it to flush toilets.

Comparison at a Glance: Of Popular Brands/Models of Water Purifiers

Note: Price may vary from retailer to retailer. Before buying please check detailed specification on the company’s website and compare the models.

After-Sales Service and AMC

All water-purifier brands offer after-sales service. However, it depends on various factors such as availability of service centres in your city, accessibility to spare parts, and so on. Most brands also offer regular AMC (annual maintenance contract) services. The rates depend on various factors. Usually, it is in the range of around Rs 4,000 per annum.

Try to get hold of customer reviews and ratings of the water purifier before purchasing it. This will give you a better idea about the product and the quality of the after-sales service because the customer has already used that product.

Some of us boil water before drinking it; some of us are resigned to buying packaged water regularly; and some of us invest in water filters and water purifiers. The last mentioned is a relatively expensive proposition but consumers are opting for it because it is considered to be the best bet against unsafe or contaminated water. The market for water purifiers – ranging from simple filters and gravity-based purifiers to those with latest technologies such as Reverse Osmosis (RO), Ultrafiltration (UF) and Ultraviolet (UV) and their combinations – is growing tremendously and various brands are available in each category.

Predictably, this vast range has also increased the complexity of buying the right purifier, whether for your home or office. Be that as it may, how many of us realize that the water purifier we buy should be as per the quality of water supplied in our homes/offices? Do we know what impurities are removed by which type of water purifier? Do we even know what these impurities are? The first thing you need to choose is the water-purification method, and knowing the quality of water in your area will help here. Also, know that some technologies involve wasting a lot of water to recover pure water, while those that involve less or no wastage may not be the best suited for the water in your area. The following guide will help you sort out the various parameters that you may want to assess before making a purchase.

Having done the first round of research, you will have to first decide which water-purification method works best for your needs and also suits your preferences. Let’s do a quick recap.

RO PURIFIERS OR REVERSE OSMOSIS PURIFIERS

RO technology pushes the water molecules from a region of higher TDS level to one of lower TDS level by applying external pressure with the help of a water pump to reverse the natural flow of water. Water with impurities or high TDS is pumped at high pressure into the RO chamber, and this pushes the water molecules across the semi-permeable membrane to the other side while leaving the dissolved solids and other impurities behind. All the dissolved solids and impurities along with some input water, also known as RO wastewater, are discharged through a separate outlet.

The Bureau of Indian Standards (BIS) has specified the maximum TDS limit for safe drinking water as 500 ppm (500 milligrams per litre). There is absolutely no need to use an RO purifier if the TDS level is below 300 ppm. If your water source has low TDS, then the RO purifier will further reduce it to a very low TDS level. This means the purified water will then be devoid of essential minerals like calcium and magnesium which are required for our good health. Very low TDS may also not be acceptable to consumers due to its insipid taste.

RO purifiers are therefore recommended for purifying water that has high TDS level. However, there is also the fact that a significant part of the input water is discharged along with the dissolved impurities, which results in unnecessary wastage of water. On an average, RO purifiers produce 3 litres of wastewater for every 1 litre of purified water.

UV WATER PURIFIERS OR ULTRAVIOLET PURIFICATION

This technology uses ultraviolet rays for the purification of water. A UV purifier works by throwing high-intensity UV rays on the water which kills or inactivates the disease-causing bacteria and viruses. However, UV purifiers cannot remove any dissolved or undissolved impurities or chemicals from water. Because of this, most of the UV purifiers that are available in the market use some form of external sediment pre-filters to remove undissolved impurities and an activated carbon filter to remove chlorine and some dissolved impurities.

UV water purifiers are only recommended for areas where the water source has low level of TDS. If the water has low TDS level but is contaminated with bacteria and viruses and appears muddy, then you can use a UF+UV water purifier.

UF WATER FILTERS OR ULTRAFILTRATION (UF)

Ultrafiltration uses a semi-permeable membrane with much larger pores (approximately 0.01 microns) as compared to an RO (which has very small pores, of approximately 0.0001 microns).

The advantage of UF purifiers is it can work without electricity because the membrane has much larger pores and water can pass through it naturally using the force of gravity. This means no external pressure or water pump is required. Since UF purifiers do not hold back any water, there is no wastage of water.

There are some limitations, though. Because of the larger pore size, UF can only remove undissolved solids and larger impurities. It cannot remove the dissolved solids or reduce the TDS level. So, UF purifiers are not suitable for purification of high TDS water or hard water.

CANDLE WATER FILTERS OR GRAVITY BASED PURIFIERS (CANDLE FILTERS)

Gravity based purifiers work on the gravitational force from higher compartment to lower compartment. These are simplest to use and provide the most basic water purification. These filters generally comprise of sediment or sediment + activated carbon filters that can remove large and undissolved impurities like mud and sand along with some chemicals and microorganisms.

There are ceramic candle-based filters with two stainless-steel containers where the upper container is fitted with ceramic candles. The candles are impregnated with a silver solution that acts as a strong repellant against pathogenic bacteria. It is considered to be the safest conventional water filter as per Consumer VOICE’s repeated studies.

Although water-purifier makers try to differentiate their products from competitors, most of them actually use a mix of three major purification approaches – Reverse Osmosis (RO), Ultraviolet (UV) and UF (ultrafiltration).

 WHICH TYPE OF WATER PURIFIER TO BUY?

1. RO systems are useful where the TDS levels are above 500 ppm and water hardness is on the higher side. If the municipal water supply is quite satisfactory and has permissible TDS levels (below 500 ppm), RO purifiers are not required – UV purifiers should be used instead.
2. You may get your water tested. It will help you make a decision based on facts and figures. If the water has a very high amount of magnesium, fluoride, nitrates or calcium salts, RO purifier will be the best for you.
3. If the water supplied at your location is highly contaminated (with microbes, bacteria and virus) and is dirty as well, RO/UF + UV purifiers are the best solution. The UV rays destroy the microbes and the RO/UF filters out their dead bodies and other contaminants.

The presence of bacteria and pathogenic (disease-causing) organisms is a concern when considering the safety of drinking water. Pathogenic organisms can cause intestinal infections, dysentery, hepatitis, typhoid fever, cholera and other illnesses. Water may also be contaminated with pesticides and arsenic.

HOW TO USE RO DISCARDED WATER?

A high percentage of water wastage is a major cause for worry. If you are using a RO water purifier at your home or office, you can consider the following options to reuse the wastewater.

1. Test the TDS in the wastewater stream. If the TDS is below 1,000 ppm, you can use the water in your plants.
2. Alternately, mix some of that water with tap water to mop the house. Make sure you dilute it with tap water because if the TDS is high and you use just the RO waste to mop the floor, you may see some salt deposition after the water dries.
3. You can use the wastewater to clean the sewage pipe at home or kitchen because of its saline nature.
4. You can use it to flush toilets.