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. 2018 Sep 27;15(10):2124.
doi: 10.3390/ijerph15102124.

Biofouling Mitigation by Chloramination during Forward Osmosis Filtration of Wastewater

Takahiro Fujioka  1 , Kha H Nguyen  2 , Anh Tram Hoang  3 , Tetsuro Ueyama  4   5 , Hidenari Yasui  6 , Mitsuharu Terashima  7 , Long D Nghiem  8
Affiliations

Biofouling Mitigation by Chloramination during Forward Osmosis Filtration of Wastewater

Takahiro Fujioka et al. Int J Environ Res Public Health. .

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.

Keywords: chloramine; forward osmosis; membrane fouling; pre-concentration; wastewater treatment.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic diagram of the forward osmosis (FO) system.
Figure 2
Figure 2
Changes in flux during the pre-concentration of primary wastewater effluent using a FO membrane with and without chloramination (cross flow rate = 0.5 L/min and temperature = 20 °C).
Figure 3
Figure 3
Variation in (a) pH and (b) monochloramine concentration of the feed solution (FS) during the pre-concentration of primary wastewater effluent using a FO membrane. Feed pH was periodically adjusted to 7.5. NH2Cl concentration of FS was adjusted twice per day to achieve 8 mg/L.
Figure 4
Figure 4
Concentration factor during the pre-concentration of primary wastewater effluent using a FO membrane.
Figure 5
Figure 5
Conductivity in the FS during the pre-concentration of primary wastewater effluent using a FO membrane. Conductivity in the draw solution (DS) was maintained at 47 mS/cm for all tests.
Figure 6
Figure 6
Reduction in normalised flux and conductivity difference between the FS and DS (∆C) during the (i) first and (ii) second pre-concentration tests using primary wastewater effluent: (a) chloraminated and (b) non-chloraminated FO systems.
Figure 7
Figure 7
Photos of FO membrane surface (FS side) after 96 h of operation in the first pre-concentration test using primary wastewater effluent: (a) chloraminated and (b) non-chloraminated.
Figure 8
Figure 8
Images of FO membrane surface attained after the first pre-concentration using primary wastewater effluent: (a) chloraminated and (b) non-chloraminated FO systems.
Figure 9
Figure 9
Dead and alive bacterial counts in the chloraminated and non-chloraminated FO systems during the (a) first and (b) second pre-concentration tests using primary wastewater effluent. Error bars show the standard deviation of two replicate experiments.
Figure 10
Figure 10
Pure water flux before and after membrane fouling, and surface flushing at the second test using primary wastewater effluent.
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