MIEX® treatment of an effluent‐impacted stream

Abstract

A case study was conducted to examine the magnetic ion exchange (MIEX®) process for treating water impacted by wastewater treatment plant effluent and removing disinfection by‐product precursors. The plant effluent increased dissolved organic carbon, ultraviolet absorbance at 254 nm (UV254), anions, and disinfection by‐product precursors at the discharge and downstream locations. The MIEX1 process reduced dissolved organic carbon by 42–47%, UV254 absorbance by 61–68%, and trihalomethane and haloacetic acid formation potential (FP) by 50–70% at different downstream locations. On the other hand, halonitromethane FP was reduced by only 10–15% and N‐nitrosodimethylamine (NDMA) FP increased as a result of chloramination after MIEX treatment. Uniform formation condition experiments showed that NDMA concentrations remained below 10 ng/L when chlorine alone or 40 min of chlorine contact time before ammonia addition were used for postdisinfection. However, use of preformed chloramine resulted in 36 ng/L of NDMA formation. Because MIEX substantially removes trihalomethane and haloacetic acid precursors, it may allow the use of more chlorine for longer contact time, which can lead to less NDMA formation.

Removal of Selected C‐ and N‐DBP Precursors in Biologically Active Filters

“…On the other hand, the feed water at WTP 2 showed 1,146 ng/L in the NDMA FP test. Once again, the elevated levels of the NDMA precursors in this source water were attributed to the wastewater influence in the source water (Gan et al 2013a, 2013b). NDMA formation was decreased by 38–50% after the treatment by biofilters.…”

“…Water quality parameters (e.g., DOC, dissolved nitrogen [DN], ultraviolet absorbance at 254 nm [UV 254 ]) were determined in accordance with USEPA methods or Standard Methods (Eaton et al 2005). The detailed information about the analytical methods for water quality parameters and DBP analyses can be found elsewhere (Gan et al 2013a, 2013b; Kanan 2010). A summary of methods and their respective minimum reporting levels (MRLs) is provided in Table 2.…”

“…Oxidants used during drinking water treatment can react with organic matter and bromide/iodide to form disinfection by‐products (DBPs) (Knappe 2014, Gan et al 2013a, Plewa et al 2004). DBPs in drinking water are a concern to public health because of their various potential health effects (Plewa et al 2008).…”

“…To meet the stringent Stage 2 Disinfectants and Disinfection Byproducts Rule (D/DBPR), some water utilities in the United States have been switching from chlorine to alternative disinfectants to lower the concentrations of regulated C‐DBPs. Although alternative disinfectants such as chloramine and ozone reduce the formation of regulated C‐DBPs, formation of some nitrogenous DBPs (N‐DBPs) such as nitrosamines and halonitromethanes (HNMs) have been reported at higher levels than found with disinfection using chlorine (Selbes et al 2016, Gan et al 2013a). Furthermore, research has shown that unregulated N‐DBPs (e.g., HNMs) exhibit orders of magnitude higher cytotoxicity and genotoxicity than any of the regulated C‐DBPs (Plewa et al 2008, 2004).…”

Carbonaceous and Nitrogenous Disinfecion By-Product Formation Potentials of Amino Acids

“…Either standard methods (SM) or USEPA methods were used in the DBP analyses with minor modifications. The detailed information about these methods can be found elsewhere (31). For DOC, DN and DBP analyses, samples were analyzed in duplicates.…”