AWWA WQTC69320

In 1991, the U.S. Environmental Protection Agency (USEPA) promulgated the Lead and Copper Rule, which established a copper actionlevel of 1.3 mg/L in a 1-liter, first-draw sample collected from the consumer's tap (FederalRegister, 1991a, 1991b, 1992). The rule was established due to potential health concerns causedby elevated copper levels in drinking water. Excessive corrosion of copper can lead to elevatedcopper levels at the consumer's tap, and in some cases, copper corrosion can also lead to pinholeleaks and pipe failure. Water chemistry has a large impact on the type of copper corrosionsolubility that takes place. Phosphate-based chemicals (ortho-, poly-, and blended-phosphates)have been used to control lead solubility and iron precipitation in many drinking water systems.The usefulness of orthophosphate to reduce copper release has also been recognized. Therelationships between the type of orthophosphate, chemical dosage, water quality and coppersolubility are not well defined, nor are the mechanism(s) by which the phosphates work. Somework has shown that polyphosphates can increase metal levels such as lead in water (Holm &Schock, 1991). Polyphosphates are commonly used to stabilize iron particles, and may similarlyimpact the mobility of copper particles in drinking water in distribution systems. There is alsopreliminary work being conducted which suggests that polyphosphates may be beneficial inpreventing pitting corrosion of copper. The objective of this work was to better understand theeffect of phosphates on copper corrosion and release in water.A recirculating copper pipe loop system was used to meet the study objective. Thebench-scale treatment system consists of plastic reservoirs, pumps, copper pipes, tubing and achiller. Experiments were initiated by adding 10L of building deionized water to eachof the plastic reservoirs. An appropriate amount of sodium bicarbonate (DIC), sodium sulfate(SO₄), sodium chloride (Cl^-), free chlorine (Cl₂ Free), hydrochloric acid, sodiumhexametaphosphate (SHMP), and sodium phosphate (Na₃PO₄) were added to the designatedreservoir to meet desired experimental conditions. Includes 7 references, table, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2008

Number of Pages:

6

File Size:

1 file , 1.5 MB