Remineralization Methods Used in Reverse Osmosis Treated Water

Ninad
February 20, 2020

Dubai has one of the highest water consumptions in the world, with an average of approximately 550 liters per day per person as compared to 170-330 liters per day per person, internationally. The exponential economic development, rapid urbanization, coupled with extreme high temperatures are some of the factors contributing to the excessive water consumption. Primary source for drinking water is desalinated seawater from the Arabian Gulf as most of the groundwater reserves are depleted. Approximately 42 percent of the total water demand is met through 70 desalination plants. The water quality characteristics of desalinated water without any post-treatment can vary significantly based on the type of desalination technology implemented such as Reverse Osmosis (RO), thermal desalination and on the design and operation of the desalination plant. However, in any case, the treated water has low pH or acidic, contain low buffering capacity, and has low alkalinity and hardness (i.e. the concentration of calcium and magnesium is very low). This low pH and low alkalinity and hardness water may have undesirable consequences to the distribution system plumbing /pipe materials, downstream wastewater systems, and may not be favorable for drinking or irrigation purposes. Several studies suggest prolonged usage of RO treated water (without any post treatment for remineralization) can result in calcium and magnesium deficiencies.

Therefore, it is imperative that desalinated water should undergo remineralization as a post treatment. The type of remineralization varies depending upon the type of application such as drinking and cooking, irrigation, etc. The treatment methods also vary for public water systems, homeowners, and business owners. This article provides a comparison or evaluation of the different methods to remineralize RO-treated water.

REMINERALIZATION METHODS FOR REVERSE OSMOSIS TREATED WATER

There are several methods to remineralize water. Remineralization can be added as a post-treatment process at the desalination plants. However, this process requires large capital investment. Desalination plants are already known to be energy and cost-intensive and this added step might increase cost of treated water. A cheaper alternative is to install some sort of remineralization system in individual house depending upon the intended use. Following are some of the different methods for remineralization.

1. Limestone Dissolution with Carbon Dioxide

Desalinated water that is carbon-dioxide acidified is passed through limestone contactors which are basically a bed of domestic limestone. This is a typical example of a post-treatment process to be conducted at a desalination plant. Dissolution with limestone provides two essential ingredients to the water – bicarbonate alkalinity and calcium residual. One of the advantages of this process is that limestone is readily available, but the design of limestone dissolution beds is a complicated and expensive process due to lack of data on the kinetics of dissolution of limestone by carbon dioxide acidified water.

2. pH Neutralization System

The CO2 neutralization system provides automated pH neutralization of acidic CO2 added to water for remineralization of drinking water or industrial process water that has been treated by reverse osmosis. This type of system injects a precisely calibrated dose of soda ash solution into the water, helping to ensure that the pH level of the water is slightly alkaline or neutral as opposed to acidic.

3. Remineralizing Filter Cartridges

Calcite and Carbon Filter Cartridges – these are inline cartridges that are comprised of a mix of activated carbon (such as coconut-based Granular Activated Carbon (GAC)) and calcite filters. This type of cartridge would be specifically useful for RO treated water where taste and remineralization both need to be achieved.
Calcite Cartridges – these are special cartridges consisting of calcite alone to raise pH of water to non-corrosive equilibrium.

Remineralization is an important process post reverse osmosis or desalination treatment of water. The above discussion gave a comprehensive overview of remineralization technology. Saniwater helps you understand what type of remineralization technology is suitable for your home. Our filter consultants have a broad range of solutions available. $\"water$ will help you choose what type of remineralization filters your house needs, be it calcite filters, calcite and carbon filters, etc. depending upon your budget and needs. Our technicians can also help with the installation of the recommended filter products. Saniwater is dedicated to offering the best solutions to meet the drinking water requirements of our customers.