Environmental and economic performances of incorporating Fenton-based processes into traditional sludge management systems

Municipal and industrial wastewater treatment plants produce a tremendous amount of sludge containing organic and toxic components. One of the advanced oxidation processes (AOP) - Fenton process has demonstrated great prospect in reduction of sludge organics and toxicity. Fenton pretreatment could ameliorate the sludge dewaterability and biodegradability for anaerobic digestion (AD) process, and enhance the sludge lower heating value for incineration process, thus stimulating sludge dewatering, reduction and energy recovery. However, doubts remain about whether the incorporation of the Fenton process into the traditional sludge management systems brings environmental benefits. Hence, a life cycle environmental impact calculation model was established for sludge with various organic contents (60%, 70%, 80%) under the effect of Fenton and US/UV/Electro-Fenton processes. Noteworthy mitigation of environmental load was observed for the Fenton process coupled with incineration system, which involves high dewatering demand. Conversely, as for the AD system with high biomass transformation rate, Fenton process failed to attain the assumed promotion of environmental benefit. Hydrogen peroxide (H₂O₂) prominently attributed to the weakness of Fenton process combined with AD (F-AD) scenario, compared with the AD scenario in terms of environmental impact. Summarily, the F-AD scenario acts as the preponderant system when weighing up the pros and cons of environmental impact, energy balance and life cycle cost. Contrary to the mainstream view, the proven technical advantages of Fenton process cannot compensate for the additional environmental loads in the life cycle of sludge. It provides valuable reflection for environmental managers and scholars that we should be more cautious in the application of cutting-edge technologies.