The objectives of this study funded by the Water Research Foundation were to i) investigate the change in the NDMA formation potential FPs at the DWTPs with different treatment configurations (conventional clarification, dissolved air filtration (DAF), membrane filtrations (MF and RO) that are currently optimized for USEPA's Stage 2 D/DBPR, ii) examine the impact of the seasonal and temporal changes on the removal of NDMA FP during the dynamic operation at full-scale DWTPs. Nine DWTPs using twelve different surface waters (rivers, lakes and reservoirs) in South Carolina, US have been monitored for 20 months. THM FP and selected water quality parameters also measured. The effects of weather conditions such as different seasons, dry/wet periods, and major rain events on the removal of NDMA FP as well as other water quality parameters on DWTPs were examined. The results showed that the average NDMA FP removals at DWTPs during different seasons and dry vs. wet periods were, in general, consistent, although a few exceptions were also observed. The average removal of NDMA FPs was 19% for alum coagulation alone and additional jar tests did not show a significant change in the NDMA FP removal with increasing alum dose. On the other hand, the average removal of NDMA FPs was 45% for alum coagulation with pre-oxidation with chlorine and/or chlorine dioxide, 43%, and 27% for post oxidation with only Cl2, and ClO2 prior to ammonia addition, respectively. The presence of DAF did not make a difference as compared to conventional sedimentation. NDMA FP removal increased with PAC dose (1 to 10 mg/L PAC), and good correlations (R2 >0.7) were obtained between the NDMA FP removal and PAC dose at two DWTPs. The removals of NDMAFP for RO and MF were an average of 81%, and 7%, respectively.

Temporal patterns of NDMA precursors' removal at drinking water treatment plants

248th National Meeting (2014)

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