AWWA QTC97065

The 1994 proposed rule for Disinfectants/Disinfection Byproducts (D/DBPs) included enhanced coagulation/enhanced softening requirements in addition to maximum contaminant levels for trihalomethanes and haloacetic acids. The removal of total organic carbon (TOC) would be used as a performance indicator for DBP precursor control. The rule would also have required 20 to 50% removal of TOC, depending on influent water quality. Evidence indicated that the TOC removal levels suggested were achievable by 90% of the systems implementing enhanced coagulation. If a system could not meet the prescribed TOC removal criteria, it was proposed that jar or pilot tests be performed to determine how much TOC removal could be reasonably achieved. In the preamble to the proposed rule, a number of outstanding issues on enhanced coagulation were identified including: whether the TOC removal levels actually represented what 90% of systems could achieve; whether a slope of 0.3 mg/L of TOC removal per 10 mg/L of alum should be considered representative of the point of diminishing return for coagulant addition; and, what was the best method of reporting jar or pilot testing data to primary agencies so that the data reflects changing water quality yet minimizes costs. This paper discusses the rationale for revising portions of the enhanced coagulation requirements in the D/DBP Rule, which addressed these outstanding issues.

Product Details

Published:

01/01/1997

ISBN(s):

0898679583

Number of Pages:

17

File Size:

1 file , 89 KB