Residential Point-of-Entry Point-of-Use Strong Acid Cation Resin* Weak Acid Cation Resin Reverse Osmosis Distillation
Insoluble ionic form, cadmium may be removed from water using standard, strong acid cation (SAC) resin regenerated with salt (NaCl or KCl). SAC resins have a higher selectivity for cadmium than hardness, so a whole house softener should perform well to remove cadmium as long as it is still removing hardness. Care should be taken to avoid operating past the hardness exhaustion by downgrading the operating capacity by 25%. For cartridge applications, weak acid cation resins (WAC) in sodium (Na) form will exhibit higher capacity and selectivity than will SAC resins. WAC resins are effective well beyond the hardness capacity. WQA Technical Fact Sheet: Cadmium Cadmium can also be removed by coagulation, precipitation, and filtration treatment when pH is raised. It can also be removed as a part of a lime softening process. Reverse osmosis systems can effectively reduce all ionic species of cadmium by 92-98 percent of the influent concentration for influent water concentrations up to at least ten times greater than the MCL when operated at pressures greater than 50 psig and at temperatures between 40° and 85° F. There are several types of membrane materials in use. Acceptable operating conditions for each type are different. Care must be taken to ensure that operating conditions for the specific membrane material are adhered to, especially feedwater pH, particulates, and oxidants, to maintain effectiveness. Periodic testing for percent rejection should be performed. Another effective means of reducing cadmium is distillation. Precipitated and insoluble species of cadmium that may exist in some waters can be reduced with filtration that effectively removes particles of 0.5 microns in size. Water sampling and analysis, using recognized analytical procedures to verify performance, are recommended to assure that the MCL of 0.005 mg/L can be met by the water treatment system at all operating conditions. The treatment methods listed herein are generally recognized as techniques that can effectively reduce the listed contaminants sufficiently to meet or exceed the relevant MCL. However, this list does not reflect the fact that point-of-use/point-of-entry (POU/POE) devices and systems currently on the market may differ widely in their effectiveness in treating specific contaminants, and performance may vary from application to application. Therefore, the selection of a particular device or system for health contaminant reduction should be made only after careful investigation of its performance capabilities based on results from competent equipment validation testing for the specific contaminant to be reduced. As part of point-of-entry treatment system installation procedures, system performance characteristics should be verified by tests conducted under established test procedures and water analysis. Thereafter, the resulting water should be monitored periodically to verify continued performance. The application of the water treatment equipment must be controlled diligently to ensure that acceptable feed water conditions and equipment capabilities are not exceeded. REGULATIONS The US EPA has established a Maximum Contaminant Level (MCL) of 0.005 milligrams per liter (mg/L) for cadmium in drinking water. The Agency has found cadmium to potentially cause a variety of effects from acute exposures, including nausea, vomiting, diarrhea, muscle cramps, salivation, sensory disturbances, liver injury, convulsions, shock, and renal failure. Drinking water levels that are considered "safe" for short-term exposures are 0.04 mg/L for a 10-kg (22 lb.) child consuming 1 liter of water per day for one- to ten-day exposures, and 0.005 mg/L for a longer-term (up to 7 years) exposure. WHO established a guideline of 0.003 mg/L for lifetime consumption. No Canadian guidelines exist.
Cadmium is an element found naturally in the earth’s crust and soil. It is used in batteries, paints, pigments, coatings, and some types of inexpensive jewelry. Cadmium in the water formula is Cd2+. Cadmium occurs naturally in zinc, copper, lead, and ores, in coal and other fossil fuels, and in shales. These deposits can serve as sources to ground and surface waters, especially when in contact with low total dissolved solids (TDS) and acidic waters. Major industrial releases of cadmium are due to waste streams and leaching of landfills, and from a variety of operations that involve cadmium and/or zinc. These may include many different types of industrial operations. More commonly Cadmium is found in drinking water supplies as a result of deterioration of galvanized plumbing, along with industrial waste contamination, or surface water contamination by certain fertilizers... Although it is possible for trace cadmium to be chelated or sequestered as with any metal, it will generally be found in the dissolved ionic form. Food is the major source of cadmium in Humans. Leafy vegetables contain approximately 0.05 – 0.12 mg cadmium/kg. The EPA has established a Maximum Contaminant Level (MCL) of 0.005 milligrams per liter (mg/L) for cadmium in drinking water. Heavy metals can leach into drinking water from household plumbing and service lines, mining operations, petroleum refineries, electronics manufacturers, municipal waste disposal, cement plants, and natural mineral deposits. Heavy metals include arsenic, antimony, cadmium, chromium, copper, lead, selenium, and many more. Heavy metals can contaminate private wells through groundwater movement and surface water seepage and run-off. People that consume high levels of heavy metals risk acute and chronic toxicity, liver, kidney, and intestinal damage, anemia, and cancer. The Agency has found cadmium to potentially cause a variety of effects from acute exposures, including nausea, vomiting, diarrhea, muscle cramps, salivation, sensory disturbances, liver injury, convulsions, shock, and renal failure.
A low level of cadmium is found naturally in surface and groundwater throughout the United States. Higher levels of cadmium in water can result from the use and disposal of items containing cadmium. For example, water draining from a landfill could have higher levels of cadmium. Drinking water levels that are considered "safe" for short-term exposures are 0.04 mg/L for a 10-kg (22 lb.) child consuming 1 liter of water per day for one- to ten-day exposures, and 0.005 mg/L for a longer-term (up to 7 years) exposure.
Cadmium has the chronic potential to cause kidney, liver, bone, and blood damage from long-term exposure at levels above the MCL. There is inadequate evidence to state whether or not cadmium has the potential to cause cancer from lifetime exposures to drinking water.