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Soybean peroxidase (SBP), (EC 1.11.1.7) can be readily extracted from soybean seed hulls. This study reports on the direct use of soybean seed‐hull extracts for the bioremediation of phenolic wastes. The crude SBP extract from the hulls, like pure soybean peroxidase, is catalytically active in a broad range of pH and temperatures. As SBP is gradually released into the aqueous solution from seed hulls, the direct use of soybean seed hulls can reduce SBP inactivation by H2O2 and enhance the utilization efficiency of SBP through the slow release of the enzyme from the seed hulls. However, large doses of soybean seed hulls were found to be ineffective in phenol removal. Gradual additions of H2O2 in combination with the SBP released from the hulls were applied to optimize the bioremediation. Since the crude extract contains a mixture of multiple soybean proteins, soybean seed hull slurry required a higher concentration of H2O2 to remove the phenolic substrates than did the purified enzyme. Under the experimental conditions, 80 % of phenol (10.6 mM), 96 % of 2‐chlorophenol (3.9 mM), 95 % of 2,4‐dichlorophenol (3.1 mM), and 94 % of mixed phenol and chlorophenols were removed using soybean seed hulls in a single batch reactor. These results demonstrate that soybean seed hulls, compared to purified SBP, may be a more cost‐effective alternative in the enzymatic removal of phenolic compounds through polymerization reactions.

The roles of various mixed liquor constituents in the membrane filtration of activated sludge were investigated. Bench-scale filtration tests with four mixed liquor fractions (whole mixed liquor, mixed liquor supernatant, filtrate I (<8.0 μm), and filtrate II (<0.45 μm) or the soluble fraction) were carried out at different permeate fluxes. It was found that due to its high contents of organic carbon compounds, macromolecules and small supra-dissolved particles, which were most likely to adsorb onto and/or clog in the membrane structure, the soluble fraction (<0.45 μm) of mixed liquor ranked first in terms of its contribution to the total mixed liquor fouling, followed by the colloidal fraction (0.45-8.0 μm) and the unsettleable microfloc fraction (>8.0 μm). In particular, the study revealed that large flocs were able to exert dual effects on membrane filtration. Depending on the hydrodynamic conditions, they could either act as membrane foulants causing fouling via particle deposition and cake formation, or serve as "moving filters" entrapping soluble and colloidal substances and thus alleviating the fouling. A "steric hindrance effect" mechanism was postulated to explain the positive effect of large sludge flocs on membrane filtration.