• Journal of Korean Society of Environmental Engineers
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• v.38 no.6
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• pp.323-328
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• 2016

Pressurized membrane used for side-stream MBR process requires fouling control strategy both for normal and abnormal operation conditions for stable operation of the facilities. In this study, $85m^3/day$ of pilot-scale side-stream MBR process was constructed for the evaluation of fouling mitigation by air bubble injection into the membrane module. In addition, fouling phenomena at abnormal operation conditions of low influent and/or loading rate were also investigated. Injection of air bubble was found to be effective in delaying transmembrane pressure (TMP) increase mainly due to scouring effect on the membrane surface, resulting in expanded filtration cycle at a high flux of $40L/m^2{\cdot}h$ (LMH). At abnormal operation condition, injection of PACl (53 mg/L as Al) into the bioreactor showed 19% reduction of TMP increase. However, inhibition of nitrifying bacteria by continuous PACl injection was observed from batch experiments. In contrast, injection of powdered activated carbon (PAC, 0.6 g/L) was able to maintain the initial TMP of $0.2kg/cm^2$ for 5 days at the abnormal conditions. It may have been caused from the adsorption of extracellular polymeric substances (EPS), which was known to be excessively released during growth inhibition condition and act as the major foulants in MBR operations.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.6
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• pp.405-415
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• 2021

MMBR system has been suggested as a promising system to resolve harvesting problems induced from low settling efficiency of microalgae. And recently, a lot of research on reducing fouling at the MMBR system has investigated focused on EPS in many cases. EPS of microalgae mainly consists of polysaccharides and protein components, and is produced through photosynthesis and nitrogen-carbon metabolic pathways. Especially, P-EPS is one of major compounds which occur membrane fouling phenomenon, as its hydrophobic protein components cause floc formation and cake layer accumulation. And it is already known that almost every microalgae can metabolize P-EPS or Chl-a when nitrogen sources as a substrate is insufficient or exhausted situation. With the above backgrounds, uptake rates of P-EPS or Chl-a by Scenedesmus quadricauda according to the type of carbon source and nitrogen concentration were evaluated in order to verify correlation between carbon source vs P-EPS production, and indeed Scenedesmus quadricauda uses P-EPS or Chl-a when the amounts of nitrogen sourc es in the feed is not satisfied. As a result, it was shown that P-EPS and Chl-a production were increased proportional to nitrogen concentration under organic carbon condition. And especially, the amo unts of P-EPS and Chl-a in the cell were diminished with the nitrogen source becomes insufficient or exhausted. Because P-EPS accelerates fouling at the MMBR system, P-EPS degradation by Scenedesmus quadricauda in order to get nitrogen source may contribute to reducing fouling. About a affects of N-consumed Chl-a to the MMBR fouling, more survey is needed. On the contrary, considering the purpose of MMBR system of this study, i.e. harvesting useful high value microalgae efficiently feeding adequate industrial process wastewater, it seems like difficult to maintain satisfied metabolic activity and to harvest with high yield rate using nitrogen-poor MMBR feed.

• Journal of the Korea Organic Resources Recycling Association
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• v.30 no.3
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• pp.23-28
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• 2022

In order to investigate the degree of sewage sludge dewaterability using Fe(II)/Na₂S₂O₈, STTF, SCST, water content, TS, VS, TB-EPS as carbohydrate and Protein were measured. The dosage of Na₂S₂O₈ was varied from 0.4 to 0.7 mmol/gVS and molar ratio of Fe(II)/Na₂S₂O₈ was varied from 0.5 to 0.7 mol/mol. According to the increase of the dosage of Na₂S₂O₈ and Fe(II)/Na₂S₂O₈ molar ratio, STTF and SCST increased from 1.00 to 15.00 and 4.51, respectively. Water content decreased to 82.6%. TB-EPS as carbohydrate and protein decreasing rate also increased to 37.16% and 57.34%, respectively. Especially, Na₂S₂O₈ 0.6 mmol/gVS and Fe(II)/Na₂S₂O₈ 0.6 mol/mol condition, water content dercreased to 83.1%, STTF and SCST increased to 13.64 and 4.19 which showed the cost effective improvement of dewaterability. It is considered that SO₄^- radical generated by Fe(II)/Na₂S₂O₈ degraded EPS and converted bound water to free water.