Energy, exergy, economic and environment analysis of standalone forward osmosis (FO) system for domestic wastewater treatment

Abstract

Energy, exergy, economic and environmental analysis is applied to a novel FO system. The system is designed to achieve minimal/zero liquid discharge with low specific energy consumption. Up to 43 % recovery is obtained with desired output in terms of salinity of diluted draw solution and concentrated feed solution. The specific energy required to produce diluted draw and concentrated feed solutions for the proposed application is as low as 0.0285 kWh/m3. In this study, DS-Lumen/AL-DS mode shows specific energy savings of 49.5 % in performed cases compared to FS-Lumen/AL-FS mode using a less flow rate of draw solution. The process design is done to reach the appropriate salinity level at the system outlet. The feed solution connection is in the series between membranes, which helps to dilute the draw solution, while the draw solution connection is in parallel between membranes to achieve desired salinity level at the outlet. The influence of the feed and draw solution temperature and flow rate on the membrane performance is observed. Capital and operating costs of the membrane and other costs, such as tank and chemical solution costs, are significant contributors to the total cost. The specific solution (total output of FO system) cost is estimated at 0.23 $/m3. Environmental analysis suggests that the deployment of solar energy as an energy source of the system reduces 93.06 % of CO2 emissions compared to fossil fuel (coal).