Pilot-scale treatment of 1,4-dioxane contaminated waters using 185 nm radiation: Experimental and CFD modeling

This work investigates the feasibility of a 185 nm advanced oxidation process (AOP) for the degradation of 1,4-dioxane from contaminated waters using a pilot-scale system operating at 6-30 L/min. Using synthetic and natural water samples with less than 20 L/min, the 185 nm pilot system was able to reduce 1,4-dioxane concentration from 100 ppb to below the WHO guideline limit (i.e., 50 ppb) with no need for an exogenous chemical oxidant/catalyst. The electrical energy-per-order (EEO) analysis of the system demonstrated the cost-effectiveness of the process for 1,4-dioxane removal with EEO values close to 0.8 kWh/m(3)/order. Further, 1,4-dioxane degradation rate decreased by 3%-13%, depending on the flow rate, when the raw water was spiked by a second micropollutant, atrazine, which competes for hydroxyl radicals. To provide an in-depth understanding of 1,4-dioxane removal, a mechanistic computational fluid dynamic (CFD) model was developed and validated experimentally. Sensitivity analysis of the operational variables underlined the significance of flow characteristics within the photoreactors as well as the natural organic matter (NOM) concentration of the water as the key factors controlling the degradation of 1,4-dioxane. The proposed model predicted the impact of the flow rates, center dot OH scavenging of atrazine and water matrix (NOM and alkalinity) on 1,4-dioxane degradation with less than 2% average absolute deviation, demonstrating its potential as a viable tool for the design, optimization, and scale-up of 185 nm AOP systems.