Journal Article

Desalination of RO reject from textile industry: development and 4 E analysis of humidification dehumidification system using solar-assisted air heating

Bhale, Purnanand V., Wakchaure, Nilesh S., Pande, Rohan R.

2025

Overview

RO plants reject water from textile industries in landlocked regions containing high TDS, raising serious environmental concerns. The conventional desalination methods often rely on high-energy inputs based on fossil fuels. To address this concern, solar-assisted humidification dehumidification desalination (SA-HDH) was investigated as one of the promising options. This study investigates the development of a sustainable solar air-heated humidification–dehumidification desalination (HDH) process using a single-ended open evacuated tube collector (SEO-ETC). An experimental evaluation was conducted to assess the system's performance. The key parameters were analyzed, including freshwater production rate, energy efficiency, exergy efficiency, humidification rate, economic analysis, overall CO 2 mitigation, and the impact of solar radiation on performance. The current study was experimentally investigated at different mass flow rate ratios of M f R = 2, 2.5, and 3 by varying air flow rates in open and closed loop configurations. The finding shows a significantly higher humidification rate and freshwater yield in a closed-loop air circulation compared with open-loop mode. Also, it was observed that the increasing air temperature inlet to the humidifier positively impacts the system performance. The results revealed that the system performs better in the optimum value of M f R = 2.5 in a closed-loop configuration. The freshwater yield of 3.12 kg/m 2 -day (8.89 kg/kWh) was obtained at an M f R of 2.5 in closed-loop configurations. The energy and exergy efficiency in closed loop configuration at optimum M f R values were 26.41% and 3.09%, respectively. The overall CO 2 mitigation at optimum M f R was 182.6 tons for 20 years of considered systems life. The cost of freshwater of 0.018 $/kg (Rs. 1.5/kg) and the payback period of the SA-HDH system of 0.564 years were obtained at an M f R of 2.5 in closed-loop configurations, attributed to the higher freshwater yield.

• Publisher: Springer Berlin Heidelberg,Springer Nature B.V
• Subject: Air flow / Air temperature / Alternative energy sources / Carbon dioxide / Closed loops / Configurations / Dehumidification / Desalination / Efficiency / Energy resources / Engineering / Engineering Thermodynamics / Exergy / Groundwater / Heat / Heat and Mass Transfer / Heaters / Humidification / Humidity / Industrial Chemistry/Chemical Engineering / Mass flow rate / Productivity / Renewable resources / Saline water / Solar radiation / Textile industry / Thermodynamics / Water temperature / Water treatment