In the January 2015 issue of Water Technology, Jake Mastroianni outlines why reverse osmosis (RO) can be one of the best ways to treat water for residential and light commercial facilities. Challenges presented by hard water often arise. During the filtration process, hard water can cause scale, making it extremely difficult for RO’s membrane to work, and the result is lower quality of water.

Hard water is the result of having high mineral content, usually calcium and magnesium ions. The dissolved rock causes scale, which has been found to impede appliance performance and result in energy inefficiencies and increased utility costs.

Hardness can cause scaling of the membrane and will reduce the output of the membrane itself. It will reduce the quality of water that the membrane is putting out, and essentially, slowly kills the membrane.

The sticky calcium molecules are the ones that most affect an RO system. Calcium in the water is similar to cholesterol in a person’s blood stream, sticking to everything, hardening and thickening as more collects. On an RO membrane, the calcium molecules block the membrane, making backwashing necessary on a regular basis.

Test for minerals

Testing is the best way to deal with water hardness before installation. RO systems are designed to create a lot of pressure to a certain solution to separate out heavy minerals. Knowing what types of minerals are in the water can help when installing a system, and these tips can help reduce water hardness before RO:

  1. Following the manufacturer’s instructions for installation.
  2. Know the water. If the water has a specific issue such as iron, an iron filtration system should be installed in tandem with the RO.
  3. Continue to monitor the water to make sure scaling isn’t becoming a major problem in the RO system. If membranes of the RO system are changed frequently, it may be time to find another system and/or hardness solution.

Ion exchange is commonly used to soften water. During ion exchange, hard water is passed through a cylinder filled with resin beads that have been saturated with sodium. When this happens, hardness ions are attracted to the resin and sodium ions are released.

Lack of energy efficiency is one of the major downfalls of having hard water. The minerals that clog the RO and cause scaling make the RO unit work even harder, waste water and run up utility bills. Ways exist to prevent this from happening and help the environment.

The issue is serious enough that the water treatment industry is paying attention to the need to reduce discharge, save water and be more environmentally friendly.

There is little doubt that RO has been an effective filtration technology for several decades. While it has its waste and energy drawbacks, fewer more efficient and practical innovations are available for residential and light commercial use. As companies continue to go green with solutions for hard water and scale reduction, the focus will become more conscious of end users, the environment and the bottom line.