Disinfection of an Advanced Primary Effluent with Peracetic Acid and Ultraviolet Combined Treatment: A Continuous-Flow Pilot Plant Study

摘要

Disinfection of an advanced primary effluent using a continuous-flow combined peracetic acid/ultraviolet (PAA/UV) radiation system was evaluated. The purpose was to determine whether the maximum microblal content, established under Mexican standards for treated wastewaters meant for reuse-less than 240 most probable number fecal coliforms (FC)/100 mL-could be feasibly accomplished using either disinfectant individually, or the combined PAA/UV system. This meant achieving reduction of up to 5 logs, considering initial concentrations of 6.4·10~(+6) to 5.8·10~(+7) colony forming units/100 mL. During the tests performed under these experiments; total coliforms (TC) were counted because FC, at the most, will be equal to TC. Peracetic acid disinfection achieved less than 1.5 logs TC reduction when the C_t·t product was less than 2.26 mg·minimum (min)/L; 3.8 logs for C_t·t 4.40 mg·min/L; and 5.9 logs for C_t·t 24.2 mg·min/L. In continuousflow UV irradiation tests, at a low-operating flow (21 L/min; conditions which produced an average UV fluence of 13.0 mJ/cm~2), the highest TC reduction was close to 2.5 logs. The only condition that produced a disinfection efficiency of approximately 5 logs, when both disinfection agents were used together, was the combined process dosing 30 mg PAA/L at a pilot plant flow of 21 L/min and contact time of 10 minutes to attain an average C_t·t product of 24.2 mg-min/L and an average UV fluence of 13 mJ/cm~2. There was no conclusive evidence of a synergistic effect when both disinfectants were employed in combination as compared to the individual effects achieved when used separately, but this does not take into account the nonlinearity (tailing-off) of the doseresponse curve.