The objectives of this work were to investigate the formation of Halonitromethanes (HNMs) at
wastewater treatment plant effluents under different disinfection conditions, to study the effect of
ultraviolet light (UV) disinfection in wastewater treatment facilities on HNM formation potentials, and to
quantify the actual occurrence of HNMs at the effluents of selected wastewater treatment plants. The
results showed that among the five disinfection scenarios tested, HNM yields per DOC were in the order
of ozonation-chlorination >>> ozonation-chloramination > chlorination > chloramination > ozonation.
Pre-ozonation prior to chlorination and chloramination significantly increased HNM formation, while
ozonation alone did not produce any HNMs. Therefore, HNM formation is expected to be problematic
mainly in treatment plants using ozonation followed by chlorination. The use of chloramines after
ozonation significantly decreased HNM formation compared to using chlorine after ozonation.
Chloramination produced the least amount of HNMs of all the disinfection scenarios tested. Despite some
of its disadvantages (e.g. weak disinfectant, nitrification problems in distribution systems), it appears that
chloramination produces significantly lower amounts of HNMs as well as regulated trihalomethanes and
haloacetic acids than chlorination. The typical UV disinfection conditions in full-scale municipal
wastewater treatment plants (WWTPs) using low pressure lamps did not change the HNM formation
potential (compared to the same water prior to UV disinfection) in wastewater effluents. Also, actual
HNM 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 that
at the typical disinfectant doses and detention times of wastewater disinfection processes, trace amounts
of HNMs will form. However, WWTPs still release HNMs (and other DBP) precursors, as observed with
the formation potential tests, to downstream users. Includes 10 references, table, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.2 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 9 |
| Published : | 11/01/2008 |
