Formation and Fate of Disinfection By-products in Water Treatment Processes
Date Issued
2010
Date
2010
Author(s)
Wang, Yun-Jie
Abstract
The treated wastewater effluent has known to be a source of disinfection by-products (DBPs) and DBP precursors. The discharge of effluent may also impact the quality of source water and raise the burden of drinking water treatment plant in the downstream area.
To gain a better understanding for the effects of the different treatment processes on the formation and fate of DBPs, this study investigated the degradation profiles of DBPs precursors and related water quality parameters within the wastewater and drinking water treatment plants. Furthermore, laboratory synthetic wastewater impaired natural water was prepared to assess the impacts from treated wastewater effluent and treatment efficiency after conventional drinking water treatment processes. The DBPs investigated in this study included: (1) traditional DBPs: trihalomathanes (THMs) and haloacetic acids (HAAs), and (2) emerging DBPs: N-nitrosodimethylamine (NDMA).
The results showed that in wastewater treatment plant, the concentrations of DBPs precursors were correlated with concentration of dissolved organic carbon, dissolved organic nitrogen, and UV absorbance due to the presence of the high concentrations of organic contents in wastewater. Moreover, the biological treatment could remove a great portion of organic precursors, where the precursor removal efficiencies (measured as DBP formation potential, DBPFP) of THMs, HAAs, and NDMA were 83.7%, 79.0%, and 97.5%, respectively. The concentration of NDMA in wastewater was around 13-23 ng/L in each treatment unit, but there was no obvious trend for concentrations of NDMA within the wastewater treatment processes.
In conventional drinking water treatment plant, the concentrations of DBPs precursors and organic carbon were found to be reduced after treatments. Indeed, the NDMAFP were decreased from 114.3-194.6 ng/L to 32.9-49.6 ng/L. Because of the great reduction of organic precursors, the NDMA concentration in finished water was very low (<10 ng/L). However, it was difficult to characterize the trend of dissolved organic nitrogen concentration in drinking water treatment units because of its relatively low concentration (0.6-1.1 mg/L as N) as compared with those observed in wastewater (17.2 mg/L as N).
The results of simulated drinking water treatment process showed that the concentrations of water quality parameters and DBPs precursors were significantly increased after spiking wastewater effluent into the natural water. The significant reductions of THMs and HAAs precursors after conventional treatment processes were similar to those obtained in full scale conventional drinking water treatments. However, different results of NDMA precursor removals were observed between simulated treatment tests and conventional drinking water treatment plant operation; and it was resulted from the different properties of raw waters used and the limitations between laboratory and full scale operations.
Subjects
Disinfection by-products (DBPs)
N-Nitrosodimethylamine (NDMA)
Water quality parameters
Dissolved organic nitrogen
Water treatment processes
Type
thesis
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