Out of the Frying Pan and Into Disinfection Byproducts: Simultaneous Compliance Issues Encountered During Arsenic Removal

摘要

Developing cost-effective strategies for arsenic removal is an ongoing challenge for many utilities, particularly small systems. From 2002 to 2011 the US EPA sponsored the Arsenic Removal Demonstration Program to provide field-scale data on practicable technologies including absorptive media, coagulation/filtration and ion exchange. Supplemental studies were conducted to determine how the addition of the arsenic removal technology might affect compliance with disinfection byproduct (DBP) requirements, particularly since some of the technologies required pre-oxidation to convert arsenic(Ⅲ) to arsenic(Ⅴ). Another challenge is that many small systems operate on-demand which can lead to wide variations in oxidant contact times. A case study of relationships between arsenic removal and DBP formation in one treatment system is presented in this paper. Results of bench-scale and in-plant testing are presented. Guidance is provided for screening of technologies to ensure that simultaneous compliance can be achieved in conjunction with treatment facility upgrades.