Techno-enviro-economic investigations on self-sustainable solar powered blackwater treatment system

Abstract

In this work, a sustainable way of blackwater treatment using solar energy is proposed and analyzed. This proposed system is designed for a small scale treatment capacity of 55 kg/day wastewater and 2.4 kg/day semisolid waste. The mixture of wastewater and semisolid waste (blackwater) is separated and passed through distillation and drying circuits powered by solar collectors making the system self-sustainable. The viability of the proposed system is assessed by thermodynamic, environment and economic aspects using a developed mathematical model for varying solar radiation and ambient conditions of Chennai, India. Upon year around analysis, this system is found to deliver a maximum average distillate yield of 15.54 kg/day and 20.82 kg/day showing the distillate efficiency of 28.25% and 37.85% under two modes of operation, normal and evacuated. The final moisture ratio and moisture content of semisolid waste can be reduced to a minimum of 0.028 and 6.82% wet basis. The environmental analysis performed shows effective net CO2 mitigations of about 68.49 tons and 95.31 tons under NM and EM operation during its lifetime of 20 years. From the economic analysis, the system payback period is reduced further with a decrease in the financed interest rate and an increase in distillate production cost when operated under EM. The system performance upon deployment in various water-stressed regions worldwide is analyzed and presented in an atlas that shows the proposed system's potential.