Formation of disinfection by-products during the monochloramination of co-existing Microcystis aeruginosa and Cyclops metabolites

Microcystis aeruginosa and Cyclops exist together in their natural states. The formation of carbonaceous disinfection by-products (C-DBPs), including trihalomethanes, haloacetic acids, chloral hydrate (CH), and haloketones, as well as nitrogenous DBPs, including trichloronitromethane (TCNM), and haloacetonitriles, was investigated with respect to co-existing Microcystis aeruginosa and Cyclops metabolites under different conditions. The reaction conditions (monochloramine dosage and reaction time) and water quality conditions (pH, temperature, Cl/N, and Microcystis aeruginosa density) were evaluated. The formation of 1,1,1-trichloro-2-propanone (1,1,1-TCP) and TCNM followed an increasing and then decreasing pattern with increased monochloramine dosage and prolonged reaction time. The formation of C-DBPs (e.g., TCM, CH, DCAA, and TCAA) increased with increasing monochloramine dosage and reaction time. The formation of CH, dichloroacetonitrile, 1,1-DCP, and 1,1,1-TCP increased first and then decreased. The formation of TCM increased with increasing pH value and temperature. Additionally, the Cl/N mass ratio affected the formation of DBPs, and as a whole, a lower Cl/N ratio led to a decrease in the concentrations of the five most common DBPs. When the density of Microcystis aeruginosa was 10⁹ count/L, the formation of the tested DBPs reached a minimum.