Pilot-scale evaluation of FO-RO osmotic dilution process for treating wastewater from coal-fired power plant integrated with seawater desalination

Abstract

An osmotic dilution process of forward osmosis (FO) and reverse osmosis (RO) was applied at pilot-scale to integrate wastewater treatment with seawater desalination in a coal-fired power plant. FO was osmotically driven by seawater used as cooling water. FO-treated wastewater was diluted with seawater and then further processed by RO. Seasonal variation in water flux, fouling behavior and reversibility, and energy consumption in both FO and RO were systematically evaluated during 5 months of pilot operation. The FO water flux, which declined due to the organic fouling induced by the wastewater from the coal-fired power plant, was readily recovered by physical cleaning. The integrated FO-RO dilution process was able to reduce the RO fouling potential through FO treatment of wastewater, significantly decreasing SDI value to 1.5 +/- 0.1. This study also reported energy consumption data, to our knowledge for the first time, at pilot scale operation of FO-RO dilution process, and showed that total energy consumption for desalinating the diluted feed, including wastewater reclamation by FO, was 15% less than that of typical seawater desalination by RO. The results of this FO-RO pilot study demonstrated that sustainable FO-RO operation can be achieved in the treatment of power plant wastewater owing to easy fouling control, low energy consumption, and superior final water quality.