Performance investigation of the double-stage solar air evaporating separation system for saline wastewater treatment

Abstract The traditional evaporating separation system applied in the wastewater treatment field cannot meet the both requirements of low energy consumption and zero waste-liquid discharge. Therefore, a novel two-stage solar air evaporating separation system for saline wastewater treatment which adopts low air temperature for concentration and high air temperature for separation is investigated experimentally in this paper. The results unveil that the system can effectively adapt to the variation of solar radiation intensity in a single solar day by utilizing the two-stage switching method, and the average evaporation efficiency (EE) of the system in the concentration stage is obviously higher than that in the separation stage. Seasons and weather have a great influence on the system EE, while the concentration of circulating wastewater has a relatively small influence. In addition, the influence of different heat collection modes is also obvious. Compared with the air alone heat collection, the EE of the simultaneous heat collection system can be improved by 31.7%. Moreover, this system has certain advantages in the EE and the power consumption rate (PCR) compared with the traditional evaporation separation system. The average EE and PCR in July summer sunny days are 5.99 kg/kWh and 0.156 kWh/kg respectively.