Combination of activated carbon/ultrafiltration as pre-treatment for seawater reverse osmosis plants

Abstract

Seawater Reverse Osmosis (SWRO) is a common technology to treat seawater to comply high freshwater demand. Currently, the main issue of seawater/brackish water as the potential sources for drinking water is vulnerable to organic pollutants. An effective pre-treatment is crucial to maintain the efficiency of SWRO for sustainable operation. Optimization of the process could be performed by a hybrid membrane combination using commercial Activated Carbon (AC) with based material coconut shell/coal and Ultrafiltration membrane (UF). For hybrid process, the activated carbon was continuously dosed into the pilot scale filtration employing PES Hollow Fiber membrane with active area of 4 m² and average pore size of 10 nm that represents a real operation filtration process (i.e., filtration flux, filtration time, backwashing, and cleaning in place), and was performed until 8 filtration cycle sequence. This study investigated membrane performance with combination technique PAC/UF and GAC/UF in Pilot scale experiments within resistance membrane and retention membrane. Combination of Activated Carbon/Ultrafiltration showed synergistic effects in the removal of organic content for COD 40%-96%, UV-VIS 43%-92% and Turbidity 73%-99%. High removal of organics pollutants (COD, UV-VIS and Turbidity) was attributed to small average pore distribution of Activated Carbon (<10 µm) that increase adsorption process. Moreover, hybrid Activated Carbon/UF adsorption kinetics can reduce filtration times to achieved optimal retention. Related to membrane performance, hybrid AC/UF resulted in less permeability declines almost double in first two filtration cycle and slightly less permeability decline until fifth cycle in comparison with single UF process. Better membrane performance can furtherly be explained from less irreversible fouling in case of AC/UF. Combination AC/UF enhanced the control of Irreversible fouling and resulted in better filtration performance as well as higher organic substance removal. Therefore, hybrid AC/UF could be seen as an effective system as pretreatment for SWRO.