Effect of BOD Loading on Solid–Liquid Separation Properties of Activated Sludge

活性汚泥による廃水処理において，廃水中の有機物量と活性汚泥量との比を表すBOD汚泥負荷の変動が活性汚泥の固液分離特性に及ぼす影響について検討した．活性汚泥の初期沈降速度は，BOD汚泥負荷の影響を大きく受け，汚泥の沈降性を表す指標であるSVIは，BOD汚泥負荷が増大するのに伴い，はじめ減少するが，やがて増加し，0.4 kg/(MLSS-kg·d)付近で極小値をもち，沈降性が最もよくなることが明らかとなった．一方，活性汚泥懸濁液の膜濾過挙動は，Ruthの定圧濾過速度式で記述でき，膜面上に形成されるケークの濾過比抵抗は，BOD汚泥負荷が0.4 kg/(MLSS-kg·d)付近で最も小さくなり， SVIと同様な傾向となった．また，活性汚泥ケークの圧縮性は極めて高く，操作圧力を大きくしても濾過性の向上には繋がらないことがわかった．活性汚泥の沈降および濾過特性は，活性汚泥フロックの面積平均径と相関があり，BOD汚泥負荷の変動により活性汚泥のフロック径が変化し，固液分離特性に多大な影響を及ぼすことが明らかとなった．

[1]  K. Kawasaki,et al.  Flux decline behaviors in dead-end microfiltration of activated sludge and its supernatant , 2007 .

[2]  Pierre Le-Clech,et al.  Fouling in membrane bioreactors used in wastewater treatment , 2006 .

[3]  Xia Huang,et al.  Effect of DO concentration on biofilm structure and membrane filterability in submerged membrane bioreactor. , 2006, Water research.

[4]  I. Chang,et al.  Correlation between dissolved oxygen concentration, microbial community and membrane permeability in a membrane bioreactor , 2006 .

[5]  Lei Ji,et al.  Influence of aeration on microbial polymers and membrane fouling in submerged membrane bioreactors , 2006 .

[6]  Renbi Bai,et al.  MEMBRANE FOULING AND CLEANING IN MICROFILTRATION OF ACTIVATED SLUDGE WASTEWATER , 2003 .

[7]  Hang-Sik Shin,et al.  Sludge characteristics and their contribution to microfiltration in submerged membrane bioreactors , 2003 .

[8]  G. Gu,et al.  Effect of acid and surfactant treatment on activated sludge dewatering and settling. , 2001, Water research.

[9]  K Brindle,et al.  The application of membrane biological reactors for the treatment of wastewaters. , 2000, Biotechnology and bioengineering.

[10]  Kazuo Yamamoto,et al.  Direct Solid-Liquid Separation Using Hollow Fiber Membrane in an Activated Sludge Aeration Tank , 1989 .

[11]  B. Ruth.  Studies in Filtration III. Derivation of General Filtration Equations , 1935 .

[12]  D. Sperry,et al.  Notes and Correspondence: A Study of the Fundamental Laws of Filtration Using Plant-Scale Equipment , 1921 .

[13]  K. Kawasaki,et al.  Effect of Suction Pressure and Aeration on the Hollow Fibre Microfiltration of Excess Activated Sludge , 2007 .

[14]  K. Kawasaki,et al.  The Effect of Operating Conditions on the Filtration Resistances of Microfiltration Type Hollow Fiber Membrane in Submerged Membrane Activated Sludge Process , 2004 .