Comparing UV and Chlorine for Wastewater Disinfection

Five municipal utilities in Colorado evaluated wastewater disinfection alternatives as part of the process to construct, expand, or upgrade their wastewater treatment facilities. Four of the five cases involved existing wastewater treatment facilities (WWTFs), three of which had historically used gaseous chlorine for disinfection. The fourth had historically used ozone. The fifth case involved an entirely new wastewater treatment facility with no prior disinfection history. The treatment system design capacities ranged from less than 3 million gallons per day (mgd) to over 60 mgd based on peak hourly design flow rate. The capital costs of disinfection facilities varied widely in relation to the lifetime operation and maintenance (O&M) costs for the systems. Capital costs depended largely on the character of existing structures. O&M costs were primarily a function of chemical and energy costs. In all cases, both economic and noneconomic factors were considered in the analysis; and in each case the factors, and the way they were perceived, were different. Four of the five utilities selected ultraviolet (UV) light as their preferred method of wastewater disinfection. One utility selected gaseous chlorine. In every case the O&M costs for UV disinfection were estimated to be substantially lower than the O&M costs for the other alternatives evaluated.