Biofouling Mitigation by Chloramination during Forward Osmosis Filtration of Wastewater.

Takahiro Fujioka,Kha Nguyen,Tetsuro Ueyama,Mitsuharu Terashima,Anh Hoang,Long Nghiem,Hidenari Yasui

doi:10.3390/ijerph15102124

Abstract

Pre-concentration is essential for energy and resource recovery from municipal wastewater. The potential of forward osmosis (FO) membranes to pre-concentrate wastewater for subsequent biogas production has been demonstrated, although biofouling has also emerged as a prominent challenge. This study, using a cellulose triacetate FO membrane, shows that chloramination of wastewater in the feed solution at 3–8 mg/L residual monochloramine significantly reduces membrane biofouling. During a 96-h pre-concentration, flux in the chloraminated FO system decreased by only 6% and this flux decline is mostly attributed to the increase in salinity (or osmotic pressure) of the feed due to pre-concentration. In contrast, flux in the non-chloraminated FO system dropped by 35% under the same experimental conditions. When the feed was chloraminated, the number of bacterial particles deposited on the membrane surface was significantly lower compared to a non-chloraminated wastewater feed. This study demonstrated, for the first time, the potential of chloramination to inhibit bacteria growth and consequently biofouling during pre-concentration of wastewater using a FO membrane.

Highlights

Anaerobic treatment is a promising platform for simultaneous wastewater treatment and biogas production [1,2,3]
Pre-concentration of wastewater by forward osmosis (FO) for 96 h resulted in a 35% flux reduction
Chloramination with a residual monochloramine of 3–8 mg/L in the FS led to a flux reduction of only 6% and this flux reduction was attributed to the increase in feed solution salinity

Summary

Introduction

Anaerobic treatment is a promising platform for simultaneous wastewater treatment and biogas production [1,2,3]. The anaerobic process transforms organic constituents in wastewater to methane gas, which can be used as a renewable fuel to offset the energy footprint of wastewater treatment [4]. Because the typical concentration of organic matter in municipal wastewaters is too low for anaerobic biological treatment, pre-concentration of wastewater (e.g., by 10-fold) is necessary for successful implementation of this process [1]. Studies have demonstrated the potential of forward osmosis (FO) as an effective technology for pre-concentrating wastewater for subsequent anaerobic treatment [5,6,7,8,9]. The FO membrane effectively retains most organic constituents [10,11,12], leading to the pre-concentration of the feed wastewater

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