Drinking Water Hardness and Doc – Major Factors Driving Reclaimed Water Quality

Abstract

The scope of this study was to investigate how dissolved organic carbon concentration and ion composition of drinking water affect the concentration of organic compounds in wastewater treatment effluents. Full-scale wastewater treatment facilities in the Southwestern U.S., which differ in drinking water quality used in their service areas, were investigated. In addition, bench-scale and pilot scale studies were performed to study the impact of cations on the character and amount of soluble microbial products (SMP) generated during wastewater treatment. Based on the results of these studies, increasing divalent cation concentrations seemed to lead to improved sludge characteristics resulting in lower dissolved organic carbon (DOC) concentrations in treated wastewater. The complementary batch experiments showed that the presence of divalent cations led to lower release of organics as compared to monovalent cations. Findings from the controlled studies were consistent with observations made at full-scale facilities. These results indicate an important role of drinking water composition in water reuse systems which seems to influence directly (via drinking water DOC) and indirectly (via cation composition) the residual DOC concentration of reclaimed water.