Full Description

The proposed Disinfectants/Disinfection Byproducts (D/DBP) Rule requires 20 to 50% removal of total organic carbon (TOC) by enhanced coagulation, depending on source water TOC and alkalinity. In addition, the proposed maximum contaminant levels (MCLs) of 80 and 60 ug/L for TTHM and HAA5, respectively, must be met in Stage 1 of the rule. In Stage 2 of the D/DBP Rule, the proposed MCLs for TTHM and HAA5 are 40 and 30 ug/L, respectively. For many utilities, enhanced coagulation alone may not achieve these proposed MCLs. To obtain information on the treatability of a wide range of waters by granular activated carbon (GAC) and membranes, the Information Collection Requirement (ICR) Rule will require many utilities to perform bench or pilot-scale treatment studies with GAC or membranes. Utilities required to perform both enhanced coagulation and GAC treatment studies may be interested in examining GAC performance following enhanced coagulation. Pretreatment by enhanced coagulation may significantly improve the performance of the GAC for the removal of natural organic matter (NOM) and DBP precursors due to lower TOC loading on the adsorber, since the adsorption capacity of an NOM mixture increases with decreasing TOC. Thus, more water can be treated before GAC adsorption capacity is exhausted. Furthermore, since NOM is less soluble at lower pH values and therefore better adsorbed, GAC performance may be improved if the lower pH levels required for enhanced coagulation are maintained through the adsorber. The cost savings due to increased bed life of the GAC between activation cycles may offset the increased chemical costs and material costs due to operation at high coagulant doses and at lower pH. The results of a cost analysis have been presented.

Product Details

Published: 01/01/1995 ISBN(s): 0898678331 Number of Pages: 17 File Size: 1 file , 570 KB