Removal of effluent dissolved organic matter of different molecular sizes by advanced treatments and soil infiltration.

Removal of municipal effluent-derived dissolved organic matter (DOM) of various apparent molecular weights (AMWs) was compared among ozonation, nanofiltration, ultrafiltration, and magnetic ion exchange (MIEX) resin coagulation. These advanced technologies were applied as pretreatments for soil aquifer treatment (SAT). Soil aquifer treatment alone removed 20 to 30% of dissolved organic carbon (DOC) and UV254. Soil aquifer treatment effectively removed 100% and 76% of DOM with AMWs of 21.3 to 31.6 kDa and 0.4 to 1.0 kDa, respectively. With pretreatments of ozonation, MIEX resin coagulation and nanofiltration, substantially higher removals (40 to 75%) were achieved for DOC and UV254. The removal efficiency of the entire system decreased as nanofiltration-SAT > ozonation-SAT > MIEX-SAT > ultrafiltration-SAT, which is positively related to the removal efficiency for medium AMW (1.8 to 7.7 kDa, mainly humic substances) DOM during pretreatments. Different pretreatments should, therefore, be chosen in accordance with the water quality of feed water and water products and SAT removal efficiency.