In 1991, the U.S. Environmental Protection Agency (USEPA) promulgated the Lead and Copper Rule, which established a copper action
level of 1.3 mg/L in a 1-liter, first-draw sample collected from the consumer's tap (Federal
Register, 1991a, 1991b, 1992). The rule was established due to potential health concerns caused
by elevated copper levels in drinking water. Excessive corrosion of copper can lead to elevated
copper levels at the consumer's tap, and in some cases, copper corrosion can also lead to pinhole
leaks and pipe failure. Water chemistry has a large impact on the type of copper corrosion
solubility 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. The
relationships between the type of orthophosphate, chemical dosage, water quality and copper
solubility are not well defined, nor are the mechanism(s) by which the phosphates work. Some
work 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 similarly
impact the mobility of copper particles in drinking water in distribution systems. There is also
preliminary work being conducted which suggests that polyphosphates may be beneficial in
preventing pitting corrosion of copper. The objective of this work was to better understand the
effect of phosphates on copper corrosion and release in water.
A recirculating copper pipe loop system was used to meet the study objective. The
bench-scale treatment system consists of plastic reservoirs, pumps, copper pipes, tubing and a
chiller. Experiments were initiated by adding 10L of building deionized water to each
of the plastic reservoirs. An appropriate amount of sodium bicarbonate (DIC), sodium sulfate
(SO<sub>4</sub>), sodium chloride (Cl<sup>-</sup>), free chlorine (Cl<sub>2</sub> Free), hydrochloric acid, sodium
hexametaphosphate (SHMP), and sodium phosphate (Na<sub>3</sub>PO<sub>4</sub>) were added to the designated
reservoir to meet desired experimental conditions. Includes 7 references, table, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.5 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 6 |
| Published : | 11/01/2008 |
