Depending on the source, raw water can have co-occurring contaminants that need to be treated before it can be used as potable drinking water. Some common contaminants found in groundwater include arsenic, iron, nitrate, radium, manganese and microbes, among others. Many water utilities across the country will need to invest in treatment systems that address one or a few of these contaminants; however, some of these systems may not treat all of the co-occurring contaminants to maximum contaminant level (MCL) recommendations. According to the U.S. Environmental Protection Agency (EPA), “choosing a treatment technology that can remove several co-occurring contaminants may be more efficient and cost effective” than selecting a technology specializing in treating or removing only one particular contaminant.
There are treatment solutions available to address co-occurring contaminants in water, including mixed bed ion exchange, anion exchange, oxidation/filtration, lime softening and reverse osmosis. And while some of these treatment methods do treat one or more contaminants—mainly arsenic, radium and uranium—they have not been noted to address all of them. Operating parameters may have to vary for each contaminant.
A suggested treatment method for water utilities wanting to effectively and efficiently address multi-contaminant removal is reverse osmosis (RO). RO systems use membrane technology to remove ions, molecules and particles from raw water. According to the EPA, RO treatment is the best available technology for the filtration of arsenic, radium, fluoride, microbes, nitrate, uranium, TOC, most metals, sulfate, calcium, magnesium, potassium and phosphorous.
While reverse osmosis successfully addresses multi-contaminant removal from drinking water, it is not without its challenges. There are several operational issues that a water utility will need to be aware of in order to determine if an RO system is best for its treatment needs. Pre-treatment is key for long-term membrane operation and performance. Before raw water passes through RO membranes, it will need to be filtered through sediment filters and/or activated carbon filters to trap organic chemicals and chlorine, which can be harmful to RO membranes. In addition, RO systems can have more upfront costs and require advanced operator skill than other available treatment methods.
Even with these challenges, it is the most effective treatment option for multi-contaminant removal. Despite the higher upfront investment, it can also help to save water utilities more money in the long run. If your water utility is looking for a solution to address treatment for multi-contaminant removal, research the different options available and find out which treatment approach is best for your needs.