Halogenated aliphatic and phenolic disinfection byproducts in chlorinated and chloraminated dairy wastewater: Occurrence and ecological risk evaluation

The increasing demand for dairy products has led to the production of a large amount of wastewater in dairy plants, and disinfection is an essential treatment process before wastewater discharge. Disinfection byproducts (DBPs) in disinfected dairy wastewater may negatively influence the aquatic organisms in receiving water. During chlorine and chloramine disinfection of dairy wastewater, the concentrations of aliphatic DBPs increased from below the detection limits to 485.1 mu g/L and 26.6 mu g/L, respectively. Brominated and iodinated phenolic DBPs produced during chlor(am)ination could further react with chlorine/chloramine to be transformed. High level of bromide in dairy wastewater (12.9 mg/L) could be oxidized to active bromine species by chlorine/ chloramine, promoting the formation of highly toxic brominated DBPs (Br-DBPs), and they accounted for 80.3% and 71.1% of the total content of DBPs in chlorinated and chloraminated dairy wastewater, respectively. Moreover, Br-DBPs contributed 49.9-75.9% and 34.2-96.4% to the cumulative risk quotient of DBPs in chlorinated and chloraminated wastewater, respectively. The cumulative risk quotient of DBPs on green algae, daphnid, and fish in chlorinated wastewater was 2.8-11.4 times higher than that in chloraminated wastewater. Shortening disinfection time or adopting chloramine disinfection can reduce the ecological risks of DBPs.

Automated summary

The increasing demand for dairy products leads to a large amount of wastewater in dairy plants, and disinfection is necessary before wastewater discharge. Disinfection byproducts in disinfected dairy wastewater could negatively affect aquatic organisms. Chlorine and chloramine disinfection of dairy wastewater led to an increase in aliphatic disinfection byproduct concentration. Brominated and iodinated phenolic disinfection byproducts could further react with chlorine/chloramine. High levels of bromide in dairy wastewater can be oxidized to form highly toxic brominated disinfection byproducts (Br-DBPs), accounting for a significant portion of the total content of disinfection byproducts. Br-DBPs contribute to the cumulative risk quotient of disinfection byproducts in wastewater and their impact on aquatic organisms varies depending on the disinfection method used.