Browsing by Author "Zhou, Qiangwei"

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    Impact of hydraulic retention time and organic matter concentration on performance of side-stream aerobic granular membrane bioreactor
    (2019-07-16) Tavana, Arezoo; Wong, Ron Chik Kwong; Zhou, Qiangwei; Khoshnazar, Rahil
    Widespread membrane bioreactors (MBRs) application has been limited due to an undesirable yet inherent phenomenon named membrane fouling. Membrane fouling can be defined as unfavorable attachment of organic and inorganic matter inside (pore clogging) or onto (cake layer) membrane pores. Aerobic granulation biotechnology has become a promising substitute for activated sludge process (ASP) by offering advantages including high biomass retention, good settleability, high resiliency to high strength wastewater and shock loading and strong and round shape structure. Aerobic granulation technology is attributed to cell-to-cell interaction between microorganism consisting physical, chemical and biological phenomena. An integration of aerobic granulation technology (AG) and membrane bioreactors (MBRs) leading to the advent of aerobic granulation membrane bioreactor (AGMBR) method, has been able to suppress fouling rate. It was believed that large particle size, high density and more compact and dense structure of granules can significantly control and reduce membrane fouling compared to conventional MBRs method which are operated by activated sludge. However, granules instability in long term operation is a detrimental obstacle which is followed by delayed irreversible (i.e., irrecoverable) fouling in AGMBR application. Operational parameters majorly contributed to granule formation and membrane fouling. Hence, optimum selection of operational factors plays significant role in granules stability leading to fouling control in AGMBR application. This study investigated the effect of hydraulic retention time (HRT) and chemical oxygen demand (COD) concentration on membrane fouling in aerobic granular membrane bioreactor (AGMBR) in a systematic approach. Changes in HRT (7, 10, and 15 h) and COD (500, 1000 and 1500 mg/L) were applied in five operational phases, corresponding to different organic loading rates (OLRs), to determine the most significant parameters to control membrane fouling for enhanced AGMBR performance. Membrane fouling was associated with two critical points: initial flux reduction (primary fouling) and maximum transmembrane pressure (TMP) (secondary fouling). Membrane permeability loss was significantly intensified with increase in HRT from 7.5 to 15 h and COD from 500 to 1000 mg/L (OLR of 1.6 kg COD/m3.d). The highest polysaccharide content of loosely bound EPS (0.41 mg PS/mg VSS) and soluble microbial products (SMPs) (27 mg PS/L) occurred alongside poor AGMBR performance at this phase. Variations in membrane fouling was accompanied with considerable changes in Flavobacterium, Thauera and Paracoccus populations. Membrane performance deteriorated with reduction in Flavobacterium and Thauera relative abundances, while system recovery coincided with Paracoccus proliferation. Generally, OLR diminution from 3.6 kg COD/m3.d (phase I) to 1.6 kg COD/m3.d (phase IV) resulted in severe granules breakage alongside intensified membrane fouling. HRT and HRT and COD interaction were identified as the most significant parameters in controlling membrane fouling.
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    ItemOpen Access
    Treatment of emerging contaminants in wastewater using an aerobic granular sludge sequencing batch reactor
    (2019-04-24) Kent, Jordan; Tay, Joohwa; Zhou, Qiangwei; Achari, Gopal
    Abstract (abridged): The presence of emerging contaminants in municipal wastewater is a concern since traditional biological technologies often have limited removal of micropollutants. This study evaluated the treatment capability of aerobic granular sludge for 17α-ethinylestradiol, 4-nonylphenol, and carbamazepine using a sequenced batch reactor. This study was comprised of two main stages. The first stage established and optimized the performance of an aerobic granular sludge bed… The second stage was divided into two experiments, the first quantified the amount of each contaminant adsorbed onto the aerobic granule sludge, the second introduced the contaminants into a sequenced batch reactor for a bioreactor operating study…. In summary this study found that aerobic granular sludge had good removal of 17α-ethinylestradiol and nonylphenol but poor removal of carbamazepine, a compound known to be resistant to biodegradation. Adsorption was an effective removal mechanism, but adsorption capacity was quickly saturated. At the lower concentrations commonly-detected adsorption could be a reliable and long-term means of removal. The macronutrient removal by the aerobic granular sludge was resilient and effluent quality did not deteriorate in the presence of these three emerging contaminants. Granule properties were not affected by the presence of the two emerging contaminants that are readily biodegradable. Carbamazepine, however, appeared to interfere with the mechanism of granulation leading to a decrease in the average particle size of the sludge. While the treatment of the emerging contaminants showed only slight increases in removal efficiency compared to conventional activated sludge, the reduced operating cost and facility footprint continue to make aerobic granular sludge an attractive option for municipal wastewater treatment.