Nitrates have no detectable color, taste or smell at the concentrations involved in drinking water supplies, and can occur both naturally and from man-made sources. Because they do not evaporate, nitrates/nitrites are likely to remain in water until consumed by plants or other organisms. Nitrate contamination originates mainly from agricultural operations including farm runoff and fertilizer usage, septic system failure and improper discharge of industrial and food processing waste and wastewater. Since they are very soluble and do not bind to soils, nitrates have a high potential to migrate to ground water. The primary inorganic nitrates which may contaminate drinking water are potassium nitrate and ammonium nitrate both of which are widely used as fertilizers.
Nitrates can occur in water sources at a level that does not generally cause health problems. The concentration level and length of exposure, however, can cause illness and death. In infants, serious illness is due to the conversion of nitrates by bacteria in the stomach to toxic nitrites. This can interfere with the oxygen-carrying capacity of the child's blood and can cause an acute condition in which health deteriorates rapidly over a period of days. Symptoms include shortness of breath and methemoglobinemia, a condition known as "blue baby" syndrome.
The US Environmental Protection Agency (EPA) has set a Maximum Contaminant Level Goal (MGL) for nitrates at 10 parts per million (ppm), and for nitrites at 1 ppm, because EPA believes this level of protection would not cause any of the potential health problems described above.
The EPA- approved treatment methods for removing nitrates/nitrites in waters destined for drinking purposes includes ion exchange and reverse osmosis.
Ion exchange is the most frequently used treatment technology for nitrate removal. This technology removes nitrate ions from the aqueous phase by replacing them with the anion present in the ion exchange resin. As contaminated water is passed through the resin, contaminant ions are exchanged for other ions, most often chlorides in the resin. Alternatively, nitrate-selective resins may also be used. The advantages of ion exchange are simple operation; the process is independent of temperature, can be automated, and is essentially unaffected by varying nitrate concentrations.
Evoqua Water Technologies offers a service-based treatment option for handling nitrate 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.
Nitrate removal by reverse osmosis uses a semi-permeable membrane to selectively remove various inorganics within the water. Pressure is applied to the water to force it through the membrane. As the water passes through the membrane and effectively leaves the impurities behind. Membranes do not exhibit high selectivity for any given contaminant, and therefore, the RO process results in the removal of many contaminants, including nitrates. Estimates predict that from 85 to 95 percent of the nitrate can be removed with reverse osmosis. Actual removal rates may vary, depending on the initial quality of the water, the system pressure, and water temperature.
Nitrate Removal in Groundwater Treatment Technologies
California Water Services Company Commences 10 Year Contract for Treatment of Nitrate and Perchlorate in Community Water System
California Water Service Company had recently acquired another water company who was responsible for this community drinking water system. The community has approximately 100 connections and is located in a remote agricultural section of the Central Valley. Annual well testing had shown levels of Nitrate at or near the Maximum Contamination Level (MCL) of 45 ppm NO3, also perchlorate was found in the groundwater at levels above the PublicHealth Goal (PHG) at 10 ppb.
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