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LIST
OF CONTENTS
Introduction
Process Description
Typical
Contactor
Design
Criteria
Photos, Plans & Specs
Treatment
Performance
Operational
Skills
Automation
Potential
Advantages
Limitations
& Concerns
Pilot
Plant Objectives
Costs
References
Contacts & Facilities
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INTRODUCTION
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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