Process Description

  Typical Contactor

  Design Criteria

  Photos, Plans & Specs

  Treatment Performance

  Operational Skills

  Automation Potential


  Limitations & Concerns

  Pilot Plant Objectives



  Contacts & Facilities



A limestone contactor is a layer or bed of limestone which water flows through. It stabilizes water to reduce the uptake of lead and copper from pipe and plumbing fixtures. Lead and copper can pose health impact if present higher than the concentration allowed in the Lead and Copper Rule. This rule states that if more than 10% of the lead and copper monitoring results are higher than the lead action level of 0.015 mg/L and/or the copper action level of 1.3 mg/L, corrosion control treatment is required.

Limestone contactors may offer advantages over other corrosion control methods including conventional chemical addition such as: (1) pH and alkalinity adjustment using lime; (2) calcium adjustment; and (3) silica or phosphate-based corrosion inhibition. Compared to conventional chemical addition, a limestone contactor is easier and safer to operate, reduces operating cost, self adjusts the water pH without risk of alkali overdose, requires minimal maintenance and operator skills, and does not require continuous feed of chemicals (Benjamin et al., 1992; Letterman, 1995; Spencer, 1998; and De Souza et al., 2000). Therefore, they are more suitable to be installed in small public water systems.

Due to its suitability for small public water systems, limestone contactors have been used to stabilize corrosive water since early 19th century. The earliest documented full-scale limestone contactors used for corrosion control was in Germany. In Germany, limestone contactors had successfully treated from 8 to 11 million gallons of water per day since 1908 (Cox, 1933).

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