Arsenic can be found in groundwater from areas that are in contact with arsenic rich rocks or other industrial pollution. In the US, this naturally occurring contamination is generally focused in areas of the Southwest, Northeast and Midwest, however, many small areas of contamination exist outside these regions and are linked to industrial activities, pesticides and wood preservatives.
The most significant needs for treatment of arsenic in groundwater sources relates to protection of human health. Industrial and manufacturing processes utilizing groundwaters containing arsenic need to address treatment as it relates to the influent, recycle and reuse requirements.
Groundwater used for non-potable applications, such as feed to an industrial and/or manufacturing process, also requires attention and possible removal of arsenic. In addition to the concerns already stated for human health and the environment, arsenic removal occurs in industrial applications in order to meet influent water quality requirement needed by the manufacturing process and equipment.
With reference to human consumption, the Environmental Protection Agency (EPA) drinking water standards require arsenic levels to be less than 10 ppb. Exposure to arsenic above this maximum contaminant level (MCL) has been linked to skin damage or problems with circulatory systems and may cause an increased risk of cancers of the bladder, lungs, skin, kidney, nasal passages, liver and prostate.
The US Environmental Protection Agency has designated the following treatment methods as Best Available Technology (BAT) for removing arsenic from groundwater.
Precipitation technology uses chemicals to transform dissolved contaminants into an insoluble solid The solid is then removed from the liquid phase by clarification or filtration. Precipitation/coprecipitation is more often used to remove contaminants other than arsenic from the water, such as hardness or suspended solids. However, the precipitation/coprecipitation processes applied to groundwaters usually also removes arsenic.
Ion exchange is also frequently used as a treatment technology for arsenic removal. As contaminated water is passed through the resin, contaminant ions are exchanged for other ions in the resin. Ion exchange is often preceded by treatments such as filtration to remove organics, suspended solids, and other contaminants that can foul the resins and reduce their effectiveness. Ion exchange resins must be periodically regenerated to remove the adsorbed contaminants and replenish the exchanged ions. Regeneration water and spent resin containing high levels of arsenic would require additional treatment prior to disposal or reuse. Alternatively, single-use, non-regenerable ion exchange resins may be used.
Evoqua Water Technologies offers a service-based treatment option for handling arsenic contamination. For non-potable applications, our Wastewater Ion Exchange (WWIX) approach integrates equipment and service option combinations, thereby minimizing a plant’s capital investment and reduces overall space requirements. The system vessels are selected based upon available manpower, space limitations, access limitation and the specific water quality required. Based on the particulars of the contaminant to be removed and inlet quality requirements, we have access to a variety of ion exchange resins and other removal medias, such as activated carbon. Wastewater Ion Exchange provides the ultimate flexibility to add or remove treatment capacity as your business grows or compliance limits change. If needs change, we can simply change the media types and/or tank size, thereby saving our customers significant capital expense.
Once exhausted, the exchange vessels are removed and replaced with fresh, DOT-compliant vessels and returned to service. For non-potable applications, exhausted vessels are transferred to our central treatment and processing facility where the hazardous/non-hazardous contaminants are removed from the media/resin for reuse.
For waters destined for potable use and drinking water applications, Evoqua offers Potable Ion Exchange (PIX) Service. PIX utilizes potable ion exchange resin canisters for the removal of organic and inorganic contaminants in surface and groundwater sources to meet drinking water standards. Each application is examined to determine the system configuration that best meets current and future needs. Once the treatment media is spent, or reaches the end of it's useful life, the potable canisters are removed from the site and delivered to a local regeneration facility for destruction and/or landfill.
Both WWIX and PIX minimize the need for handling and on-site storage of chemicals and wastes for improved safety and compliance at your site. This option also saves valuable manufacturing space while minimizing your maintenance and installation requirements.
Membrane filtration treats arsenic by passing it through a semi-permeable barrier or membrane. The membrane allows some constituents to pass, while blocking others. Membrane filtration is used less frequently because it tends to have higher costs and produces a larger volume of residuals than other arsenic treatment technologies.
Arsenic Removal Technologies:
Membrane Filtration and Separation
Separation and Clarification
Siemens Delivers Temporary Arsenic Treatment System While Permanent Solution is Engineered for Bucks County Water Authority
In April 2006, Siemens Water Technologies was contacted by the Bucks County Water Authority in Solebury, PA to provide assistance in treating arsenic contaminated drinking water. New federal drinking water standards required a reduction of the arsenic level to 5 ppb. With less than 4 months to comply, the water authority needed a temporary solution to meet the new regulation and avoid formal notification of the violation to their current customers.
Read Full Case Study