Improving the Sustainability of Wastewater Treatment Through Solar-Assisted Multiple Effect Evaporators

India’s current water use is around 600 BCM of which 60% is sourced from surface water bodies and 40% from ground. Consumption wise 89% is used by the agricultural sector, 7% by domestic, and 4% by industries. While agricultural sector water use can be considered to be a part of the water cycle, establishing techno-economic treatment systems and wastewater reuse facilities is essential for domestic and industrial sectors. Three stages of wastewater treatment systems are available—primary, secondary, and tertiary. Each stage provides varying qualities of treated water, with the tertiary systems providing the best water quality with total dissolved solids less than 50 parts per million (ppm) permitting its reuse in agriculture and industrial sectors. In India, only primary and secondary treatment systems are widely available. Tertiary systems are retrofitted now, to reuse water. Treated water reuse increases water security by preventing water pollution and decreasing stress on water bodies due to excessive water withdrawals. Preventing water pollution, treating water, and its reuse is vital; similarly, deployment of low-carbon sustainable technologies for water treatment is imperative. Else water pollution prevention efforts would reshape as air pollution issue. Energy consumption by a treatment system correlates to the air pollution potential. Primary, secondary, and tertiary treatment systems consume 2, 3, and 6 kWh/m³ electrical energy, respectively, in addition, the tertiary systems also require thermal energy which is about a kg steam for every 3 kg effluent to concentrate the waste (Tamil Nadu Water Investment Company Ltd. (TWIC), 2014). Environmental policies are therefore necessary to ensure the use of only sustainable treatment systems. Multiple effect evaporators are the widely used tertiary treatment system. It uses steam as a source of heating medium to evaporate wastewater. Steam used in MEE is of process heat quality with temperatures 150–200 °C and 10 bar pressure. The present chapter would discuss how conventional wastewater treatment systems could source their energy requirements sustainably and the policy implications surrounding such a promotion.