We investigated the suppressive effects on filamentous bulking by addition of grinding flour of corn cob (corn cob flour abbreviated to CCF), agriculture waste, and the divalent metal ions. When 1000 mg.L−1 of activated sludge loading with 30 % of CCF was operated by a continuous process, we obtained a microbial coagulation of which nucleus was formed by CCF with good settling character and high density in spite of use the substrate of which the main element was glucose caused easily the filamentous bulking. This effect, further, was increased with addition of Ca2+ ion. From SEM observation, we found few filamentous microorganisms but cocci and short rods dominant on this surface of CCF which possessed good settling character, i.e., 20-30 ml·g−1 of sludge volume index (SVI) and 2-6 cnrmin.−1 of the interfacial settling velocity. It was characteristic that many Arcellasp., Protozoa, adhered to the surface of CCF with Ca2+. From these results, it was estimated that Ca2+, divalent metal ion, promoted the cross-linking act among cytoplasmic membranes charged negative and increased the affinity between CCF and microorganisms.

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