Reverse Osmosis (RO) water purifiers have made a big impact in Indian households. Some RO water purification systems are very popular amongst Indian families mainly because they are assumed to be good at getting rid of water hardness, turbidity, and harmful microorganisms. Due to these assumptions many people around the country rushed to buy RO water purifiers without even bothering to check if the Total Dissolved Solid (TDS) level in water sources at their home was much lower than the recommended level of 500 mg/litre. Due to this many people ended up consuming water from RO water that was too low in TDS (dissolved minerals, acidic in nature and sometimes even tasteless. Apart from the taste, it is also harmful to drink demineralised water which is acidic as it may result in digestion problems, weaker bone density and other mineral deficiencies. To overcome this problem, RO water purifier companies provided two techniques, one technique was to use a TDS controller and the second technique was to use an Alkaline mineral cartridge to try and retain essential back to the RO purified water. But did these two techniques work? We will now find out…
Alkaline Mineral Cartridges
A few RO water purifier systems in the market use an alkaline mineral cartridge to add minerals back in the purified water. But sometimes this doesn’t make sense to do as the composition of water is being tampered with. An Alkaline mineral cartridge usually consists of several different layers of materials such as pelletized activated carbon, mineral balls, PH booster balls, anti-bacterial balls, ceramic balls, tourmaline balls, etc.
How does an Alkaline Mineral Cartridge work?
By using these cartridges in water purifiers, the water becomes artificially flavoured and it also sometimes increases the pH level of water. This usually happens after the water has passed through the RO membrane. During the process, it extracts essential minerals from the mineral balls which are present in the cartridge. Other Alkaline cartridges come with pH booster balls as well so the pH of the water also increases making the water alkaline. The quality of the Alkaline mineral cartridge is something that is very important to look out for as it dictates the variety of minerals which get added to the purified water. Some Alkaline mineral cartridges also claim that they provide additional benefits by energising water but these are just marketing gimmicks.
Disadvantages of Alkaline Mineral Cartridges
One of the biggest disadvantages of installing an Alkaline mineral cartridge is that you have no control over the TDS of output water and this directly demineralised the water. This is mainly because the output water TDS level would highly depend on the TDS of source water and the quality of mineral cartridge being used. If the mineral cartridge being used is of poor quality, then the TDS of output water in this case would be just 30 or 40mg/litre which is highly unacceptable and you will not be able to adjust the TDS as per your preference leaving you with water which is stripped of its essential minerals. Another disadvantage of installing an Alkaline mineral cartridge is that it becomes a recurring cost. Mineral cartridges have a short shelf life as they need to be replaced approximately every 6 to 9 months depending on the number of times it’s being used. This adds up to the annual cost of maintaining a RO water purifier system.
TDS Controller
A TDS Controller is a device which is screw-based that controls the level of salts in the output of purified water. It works as a bypass valve which takes an adjustable percentage of source water bypassing RO membrane to the output water which is filtered through a UF or carbon filter and/or UV chamber. Usually when a TDS controller is used, raw water is mixed with purified water to maintain the TDS level. This technique is considered as an outdated technique of purifying water. As the water is not being naturally retained the essential minerals are also being removed which leads to the water being demineralised.
How does a TDS Controller work?
While using a TDS controller, the water which goes into the Reverse Osmosis filter is divided into 2 parts. One part of it goes into the RO membrane and undergoes RO water purification. The second part of water does not go through the RO membrane as it goes through a UF membrane or a UV Chamber depending on the RO specifications. Although while using a UF membrane sometimes the membrane usage is not enough and while using a UV light, minerals are removed as it only disinfects pollutants and does not remove hardness or organic compounds so it defeats the purpose of using it. The output water is usually a mixture of the water purified from part one added to a small portion of part two. This mixture is then controlled using a valve which is added to the assembly of part 2, thus controlling the TDS.
Disadvantages of a TDS Controller
One of the major disadvantages of a TDS Controller is that the output water from a RO water purifier with TDS controller is not 100% purified. This is mainly because the TDS controller mixes a part of water that did not go through RO membrane to the output water, it will have all the minerals and chemicals present in it that were originally present in the input water, though in very minimal amounts. So essential minerals which are beneficial for human consumption are usually removed in this process. Sometimes when the source water is heavily polluted with heavy metals, like lead, nitrate, cadmium, and arsenic then this becomes a problem. The water will only be safe to consume if these heavy metals are removed from the output water.
Alkaline Mineral Cartridge vs TDS Controller
| Alkaline Mineral Cartridge | TDS Controller |
| Suitable for source water with TDS up to 2000mg/litre | Suitable for source water with TDS up to 1200 mg/litre |
| No control over TDS of output water | Full control over TDS of output water |
| Increases the annual maintenance cost | Economical & Environmentally Friendly |
| No leverage to change the TDS of water | Flexible to adjust the TDS levels |
| Doesn’t have the risk of heavy metals in the output water. | Heavy metal concentration in water not removed |
What’s the best alternative to RO Water purifiers?
If the TDS levels of the water being supplied to your home are less than 500mg/litre and you are searching for an automated water purification system, then you should choose one that uses Nanotechnology. Some of the best water purifiers for home use Nanotechnology which revolves around the use of an intelligent semi permeable membrane with pore size in the nano scale of less than 10 nanometres surround by a charge field, which enables the membrane to distinguish between impurities and essential mineral to provide you with the purest mineralised water. Depending on your water issue, both Reverse Osmosis and Nanotechnology can be used to purify water. But overall Nanotechnology is considered as the best water purification system for water purifiers as it retains all essential minerals which are fit for human consumption when an RO filter gets rid of these minerals.
