AWWA ACE68623

The objectives of this work were to investigate the formation of Halonitromethanes (HNMs) atwastewater treatment plant effluents under different disinfection conditions, to study the effect ofultraviolet light (UV) disinfection in wastewater treatment facilities on HNM formation potentials, and toquantify the actual occurrence of HNMs at the effluents of selected wastewater treatment plants. Theresults showed that among the five disinfection scenarios tested, HNM yields per DOC were in the orderof ozonation-chlorination >>> ozonation-chloramination > chlorination > chloramination > ozonation.Pre-ozonation prior to chlorination and chloramination significantly increased HNM formation, whileozonation alone did not produce any HNMs. Therefore, HNM formation is expected to be problematicmainly in treatment plants using ozonation followed by chlorination. The use of chloramines afterozonation significantly decreased HNM formation compared to using chlorine after ozonation.Chloramination produced the least amount of HNMs of all the disinfection scenarios tested. Despite someof its disadvantages (e.g. weak disinfectant, nitrification problems in distribution systems), it appears thatchloramination produces significantly lower amounts of HNMs as well as regulated trihalomethanes andhaloacetic acids than chlorination. The typical UV disinfection conditions in full-scale municipalwastewater treatment plants (WWTPs) using low pressure lamps did not change the HNM formationpotential (compared to the same water prior to UV disinfection) in wastewater effluents. Also, actualHNM concentrations at the effluents of full-scale WWTPs using chlorine disinfection were below 2 µg/L,while no HNM formation was observed at the effluents of WWTPs using UV disinfection. It appears thatat the typical disinfectant doses and detention times of wastewater disinfection processes, trace amountsof HNMs will form. However, WWTPs still release HNMs (and other DBP) precursors, as observed withthe formation potential tests, to downstream users. Includes 10 references, table, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2008

Number of Pages:

9

File Size:

1 file , 1.2 MB