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Abstract
The integration of forward osmosis (FO) and biological process, known as the osmotic membrane bioreactor (OMBR), may be viewed as beyond the state of the art for used water treatment and water reclamation. While it is known that the OMBR is able to produce good product water quality in terms of total organic carbon (TOC) removal, limited information is available on the removal of organic micro-pollutants in relation to process performance under the concentrated environment. In this study, a novel OMBR system was continuously operated over 73 days, during which pharmaceuticals were dosed on two occasions into the system. It was found that while pharmaceutical removal was high (>96%), other process parameters in the form of TOC, mixed liquor suspended solids (MLSS) and extracellular polymeric substances (EPS) were unmistakably affected. The major portion of TOC that permeated the FO membrane was found to be low-molecular weight neutral compounds which were associated with the impaired biological process. Microbiological analysis confirmed shifts in microbial populations occurred due to the increased salinity and dosage of the pharmaceuticals. The study demonstrated the importance of the biological process for optimal OMBR system performance, and paves the way for further research in this direction.
ACKNOWLEDGEMENTS
This study is supported by the Singapore National Research Foundation through the Environment and Water Industry Program Office under the projects EWI RFP 08/01 and MEWR C651/06/177. The authors thank and acknowledge all members of this project for discussion on this study. Special thanks are also due to: Hydration Technologies Innovations for the provision of the FO membranes, DOC-LABOR DR. HUBER for the professional service and the complimentary LC-OCD analysis for the second batch of samples, Drs. Zhang Lifeng, Hu Ruikang, and Qian Xiaoqing from the Water Research and Analytical Laboratory (WRAL) of PUB for their generous help with the pharmaceutical analyses, and project students of the Nanyang Technological University and Republic polytechnic for their assistance in the lab works. Winson C.L. Lay gratefully acknowledges EWI and PUB for the PhD scholarship support.
Notes
a All pharmaceutical compounds were obtained from Sigma-Aldrich.
b (Citation12,Citation41).
c (Citation41).
d (Citation42).
e (Citation11,Citation59).
f (Citation60).
g (Citation14).
*The remaining dissolved organic carbon (DOC) fractions were not reported and amounted to 88 ppb-C, which corresponded to about 2.9% of the total DOC concentration in D2.
