AWWA WQTC69447

This paper reports on a study which quantitatively measured the effectiveness of commercially available phosphate-based sequestrants in reducing or delaying manganese precipitation over a 96-hour period. Five rounds of tests were performed to test 6 available sequestrants on multiple sources under various conditions and blend ratios. Results indicate that 2 of the 6 sequestrants performed the best in controlling manganese in the targeted groundwater when tested at 5 times the manufacturers' recommended dose. Both products demonstrated effectiveness up to 48 hours. These results demonstrate that these sequestrants can reduce the manganese precipitation problem, but their use will not eliminate the concern. Further, results of this study provide a strategy for the City of Issaquah to use existing groundwater sources to meet peak summer demands immediately and to meet reliably increasing demands in the future. Includes tables, figures.