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Direct and complete phosphorus recovery from municipal wastewater using a hybrid microfiltration-forward osmosis membrane bioreactor process with seawater brine as draw solution Guanglei Qiu, Yi Ming Law, Subhabrata Das, and Yen Peng TING Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/es504554f • Publication Date (Web): 28 Apr 2015 Downloaded from http://pubs.acs.org on May 5, 2015
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Environmental Science & Technology
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Direct and complete phosphorus recovery from municipal wastewater
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using a hybrid microfiltration-forward osmosis membrane bioreactor
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process with seawater brine as draw solution
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Guanglei Qiu∗, Yi-Ming Law, Subhabrata Das, Yen-Peng Ting∗
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Department of Chemical and Biomolecular Engineering, National University of Singapore, 4
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Engineering Drive 4, Singapore 117585, Singapore
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∗ Corresponding author. Tel.: +65 65162190; fax: +65 67791936;
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E-mail:
[email protected] (Y.P. Ting);
[email protected] (G. Qiu)
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ABSTRACT
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We report a hybrid microfiltration-forward osmosis membrane bioreactor (MF-FOMBR)
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for direct phosphorus recovery from municipal wastewater in the course of its treatment. In
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the process, a forward osmosis (FO) membrane and a microfiltration (MF) membrane are
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operated in parallel in a bioreactor. FO membrane rejects the nutrients (e.g. PO43-, Ca2+, Mg2+,
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etc.) and results in their enrichment in the bioreactor. The nutrients are subsequently
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extracted via the MF membrane. Phosphorus is then recovered from the nutrients enriched
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MF permeate via precipitation without addition of an external source of calcium or
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magnesium. The use of seawater brine as a draw solution (DS) is another novel aspect of the
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system. The process achieved 90% removal of total organic carbon and 99% removal of
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NH4+–N. 97.9% of phosphate phosphorus (PO43-–P) was rejected by the FO membrane and
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enriched within the bioreactor. >90% phosphorus recovery was achieved at pH 9.0. The
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precipitates were predominantly amorphous calcium phosphate with a phosphorus content of
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11.1–13.3 %. In principal, this process can recover almost all the phosphorus, apart from that
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assimilated by bacteria for growth. Global evaluation showed an overall phosphorus recovery
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of 71.7% over 98 days.
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TOC Art
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INTRODUCTION
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Phosphorus is a pollutant but is also an important non-renewable resource. The world
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phosphorus reserves will run out in a few decades, while its demand continues to rise.1 One
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way out of this problem is to recycle phosphorus from various phosphorus-containing waste
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streams. Municipal wastewater is a hidden treasure for phosphorus, from which 15–20% of
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the world’s phosphorus demand can be satisfied by its recovery.2
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Calcium phosphate precipitation is one of the most promising phosphorus recovery
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processes. Similar to struvite, calcium phosphate is a very important phosphate mineral.1
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Since it is the effective composition of phosphate rocks, it can be more readily accepted by
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the phosphate industry without limitation.3,4 However, the economic application of a
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phosphorus recovery process usually requires a liquid phase containing high phosphorus
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content (typically, >50 mg/L 3,4), which is not directly suited to municipal wastewater (which
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typically has phosphorus concentrations of
