Control Strategies for PAA Wastewater Disinfection at WWTPs with Variable Effluent Quality

The dose of peracetic acid that is required to control microbial concentration in wastewaters will depend on a number of factors, including: target microorganism, the disinfection contact time, and the characteristic quality of the wastewater effluent. Wastewater characteristics that impact peracetic acid oxidant demand, and hence disinfection performance, may include natural organic matter, reduced metals, biological oxygen demand, chemical oxygen demand and total suspended solids. For most treated municipal wastewater effluent, the quality of the wastewater is such that the peracetic initial oxidant demand is relatively low and stable over time. This allows PAA dose to be controlled using simple flow-pacing, once the oxidant demand is known. With recent advances in on-line, continuous PAA monitoring probes, feedback control based on effluent PAA residual could also be combined with flow pacing to provide robust and reliable PAA dose control.However, there are situations where wastewater effluent quality is highly variable, due to any number of factors, such as intermittent industrial discharges to the wastewater treatment plant. Changing effluent conditions can result in variable PAA demand; thus, more active control on PAA dosing may be required to optimize PAA performance in an effort to minimize operational costs.