Nutrient removal and fouling reduction in electrokinetic membrane bioreactor at various temperatures

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2009, 2011, 2012
Wei, Chunliang
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Water Science. & Technology
Water Research
Water Science & Technology
With the aim of mitigating membrane fouling, an electrocoagulation (EC) based electrokinetic membrane bioreactor (EMBR) was developed and operated with real municipal wastewater under low temperatures. Both batch tests and continuous EMBR experiments demonstrated the significant advantages in membrane fouling reduction over the conventional antifouling strategies, ushering its potential applications as an attractive hybrid MBR technology for decentralized wastewater treatment in remote cold regions. The main research observations and findings could be summarized as follows: (1). Effective membrane fouling mitigation at low temperatures was due to destruction of extracellular polymeric substances (EPS) and subsequent reduction of the biocake resistance. The transmembrane pressure (TMP) increased at a much slower rate in EMBR and the filtration resistance was about one third of the control MBR prior to chemical cleaning cycle; (2). A new membrane parameter, the specific fouling rate (SFR) was proposed, relating the fouling rate with permeate flux and temperature-dependent viscosity. Pore clogging and biocake resistances were quantified for the first time with the same membrane module and operating conditions as in regular MBR, rather than resorting to the use of batch filtration setups; (3). The floc size in EMBR did not increase as a result of the air scouring shear force and decrease in the extracellular polymeric substances (EPS); (4). When current intensity was less than 0.2 A, polarity reversal had minimal impact on electrode passivation reduction due to insignificant hydrogen yield, however, if current intensity was above 0.2 A, frequent polarity reversal (< 5 min per cycle) was detrimental to electrode passivation if no sufficient mixing was provided; (5). Viability of the microorganisms in the EMBR system was found to be dependent on duration of the current application and current density. The bacterial viability was not significantly affected when the applied current density was less than 6.2 A/m2; (6). Significant abiotic ammonification was found in electrocoagulation (EC). DO in the treated liquid was depleted within an hour, under the anaerobic condition in EC, nitrate was chemometrically reduced to ammonium following a two-step first order reaction kinetics. Aeration (DO > 2 mg/L) was shown effective in suppressing abiotic ammonification; (7). Magnetic resonance imaging (MRI) technology was used for the first time as an in-situ non-invasive imaging tool to observe membrane fouling status in an EMBR.
Membrane bioreactor, Electrokinectic, Wastewater treatment, Membrane fouling reduction
Water Sci. & Tech. 60:3159-3164
Water Research. 45 (16):5058-5062
Water Sci. & Tech. 65(4):737-42