Decentralized electro-sanitation system as proof of concept to treat urine produced in long-distance bus

Abstract

Long-distance transportation provides in-vehicle access to essential sanitation to the passengers. However, generated yellow and black waters may not be correctly managed prior sanitary effluent discharge. Processes that can handle decentralized effluent treatment can be considered alternatives to traditional chemical treatment systems. In this study, decentralized electrochemically-driven treatment is presented as a proof of concept. A compact electrochemical reactor design considering the boundary conditions and requirements for decentralized sanitary treatment for long-distance bus transportation has been accomplished. Treatment of synthetic urine effluents was conducted under filter-press reactor with continuous flow in a closed upward recirculation reactor containing a carbon felt (CF) cathode and a dimensionally stable anode (DSA: Ti/Ru0.36Ti0.64O2). The experimental design allowed the assessment of operational variable impacts on reduction of urea concentration, and consequent estimate of the total organic carbon abatement. The results revealed that synthetic urine solution diluted from toilet water flushing (TOC = 402 mg L−1) can be effectively treated under application of low current densities of 18 mA cm−2 in 300 min (average time of on-road service). Real-time monitoring of parameters revealed a decrease in pH from 6.98 to 3.49, and a gradual increase in temperature from 25.3 °C to 32.0 °C at the end of the process. Those physico-chemical changes can be useful to inhibit urea hydrolysis. Thus, the results encourage the application of electrochemical technology in decentralized effluent treatment systems to enhance and enable ecologically correct sanitation actions in portable urinary collectors, such as those used in bus road transport.