Full scale UV Advanced Oxidation Process with Sodium Hypochlorite for Potable Reuse Treatment – an economic attractive option

In a 12 month pilot trial at the Terminal Island Water Reclamation Facility in Los Angeles the most common AOP technologies were benchmarked regarding their efficiency and economics for the later 12 MGD (1,900 m3/h) expansion of the plant. Due to the favourable conditions of the water for the process combination of UV and hypochlorite characterized by a slight acidic pH and low organic content this process was implemented into the pilot program evaluating UV low pressure and UV medium pressure as the irradiation source. The results indicated a comparable performance with the classic UV / hydrogen peroxide AOP which sets the focus on the economic aspects. As hypochlorite dosing and storage infrastructure was already present at the Terminal Island WRF the selection of UV+ hypochlorite resulted in significant savings on the capital side. As peroxide is not consumed completely during the AOP quenching is necessary resulting in additional operational expenditures which are not present when UV + hypochlorite is applied as a residual chlorine concentration has to be maintained before the water is re-injected to the soil aquifer. These aspects resulted in the selection of UV + hypochlorite for the 1,900 m3/h indirect potable reuse train deploying two WEDECO K-reactors each equipped with 204 low pressure lamps with a total rated power of 134 kW providing a 100% redundancy plant layout.