Oxygen Uptake Rate Of Activated Sludge Research Articles

Kinetics and fundamental mechanisms of starch removal by activated sludge: hydrolysis of starch to maltose and maltotriose is the rate-determining step

The mechanisms of hydrolysis and uptake of starch, a polymer in sewage, by activated sludge (AS) were investigated, taking into consideration the mechanisms of the maltose transport system, responsible for the uptake of hydrolysis products of starch, in Gram-negative bacteria. AS was acclimated to dextrin, and the molecular weight distributions of the substrates during dextrin removal are analyzed using a GPC method. The removal rates of substrates such as dextrin, various maltodextrins (maltotriose, etc.), maltose and glucose by AS, and the oxygen uptake rates (OURs) of AS during the removal of these substrates were compared. Low-molecular-weight saccharides such as glucose, maltose and maltotriose were undetectable in the substrates during dextrin removal. The removal rates of maltose and maltotriose were higher than those of dextrin and glucose, and the OURs of AS during the removal of maltose and maltotriose were higher than those for other substrates. Therefore, hydrolysis of starch to maltose (dimer) and maltotriose (trimer), and not to glucose (monomer), appears to be the rate-determining step during the removal of starch, although maltodextrins with molecular weights up to 1152 (maltoheptaose) appear to penetrate the bacterial outer membrane.

Kinetics and fundamental mechanisms of starch removal by activated sludge: hydrolysis of starch to maltose and maltotriose is the rate-determining step

The mechanisms of hydrolysis and uptake of starch, a polymer in sewage, by activated sludge (AS) were investigated, taking into consideration the mechanisms of the maltose transport system, responsible for the uptake of hydrolysis products of starch, in Gram-negative bacteria. AS was acclimated to dextrin, and the molecular weight distributions of the substrates during dextrin removal are analyzed using a GPC method. The removal rates of substrates such as dextrin, various maltodextrins (maltotriose, etc.), maltose and glucose by AS, and the oxygen uptake rates (OURs) of AS during the removal of these substrates were compared. Low-molecular-weight saccharides such as glucose, maltose and maltotriose were undetectable in the substrates during dextrin removal. The removal rates of maltose and maltotriose were higher than those of dextrin and glucose, and the OURs of AS during the removal of maltose and maltotriose were higher than those for other substrates. Therefore, hydrolysis of starch to maltose (dimer) and maltotriose (trimer), and not to glucose (monomer), appears to be the rate-determining step during the removal of starch, although maltodextrins with molecular weights up to 1152 (maltoheptaose) appear to penetrate the bacterial outer membrane.

Kinetics and fundamental mechanisms of protein removal by activated sludge: hydrolysis of peptone to amino acids is the rate-determining step

Most ninhydrin reactants in primary effluent are proteins (polymers), and activated sludge (AS) bacteria can only directly take up monomers such as amino acids (AAs) which are produced from proteins by hydrolysis. Whether the hydrolysis of protein to amino acids by AS is the rate-determining step in the removal of protein was examined by comparing not only the removal rate of peptone and a mixture of free AAs but also the oxygen uptake rates of AS during the removal of these substrates, as well as analyzing the time courses of the concentration of each AA during the removal of these substrates. The removal rates of the AA mixture by AS were higher than those of peptone, and the oxygen uptake rates of AS during AA mixture removal were higher than those during peptone removal. The composition ratios of AAs during peptone removal were almost constant, whereas those of AAs markedly changed during AA mixture removal. The important difference between the two substrates used in this study (peptone and an AA mixture) is whether or not peptide bonds exist in the substrates. It was therefore verified that the hydrolysis of protein to AAs by AS was the rate-determining step in the removal of protein from municipal sewage.

Kinetics and fundamental mechanisms of protein removal by activated sludge: hydrolysis of peptone to amino acids is the rate-determining step

Most ninhydrin reactants in primary effluent are proteins (polymers), and activated sludge (AS) bacteria can only directly take up monomers such as amino acids (AAs) which are produced from proteins by hydrolysis. Whether the hydrolysis of protein to amino acids by AS is the rate-determining step in the removal of protein was examined by comparing not only the removal rate of peptone and a mixture of free AAs but also the oxygen uptake rates of AS during the removal of these substrates, as well as analyzing the time courses of the concentration of each AA during the removal of these substrates. The removal rates of the AA mixture by AS were higher than those of peptone, and the oxygen uptake rates of AS during AA mixture removal were higher than those during peptone removal. The composition ratios of AAs during peptone removal were almost constant, whereas those of AAs markedly changed during AA mixture removal. The important difference between the two substrates used in this study (peptone and an AA mixture) is whether or not peptide bonds exist in the substrates. It was therefore verified that the hydrolysis of protein to AAs by AS was the rate-determining step in the removal of protein from municipal sewage.

Effects of Various Disinfectants on Oxygen Uptake of Activated Sludge Microorganisms.

This paper describes the results concerning the effects of various disinfectants on the oxygen uptake rate (OUR) of activated sludge (AS). To start with, in vitro inhibitory effects of four test disinfectants : STERIHYDE[○!R], HYAMINE-T[○!R], ISODINE[○!R] and HYPAL No.20[○!R], on OUR of two kinds (AS-A ; Kamaboko fishcake industrial waste water and AS-B ; local municipal sewage) of AS were determined by the previously mentioned method. The IC50 values of thirty-three kinds of typical disinfectants were measured for AS-A, respectively. GRINCE[○!R], termed 2, 4, 4'-trichloro-2'-hydroxydiphenyl ether (0.3% Irgasan DP 300), and Irgasan DP 300 alone, inhibited most strongly by the IC50 values of 6 mg/l, respectively, and followed by Cetylpyridinium chloride (20 mg/l), OSVAN[○!R] (58 mg/l), HYAMINE-T[○!R] (58 mg/l), Potassium permanganate (60 mg/l), Thimerosal (65 mg/l) and Benzethonium chloride (80 mg/l). However, with Phenol, Suponated cresol, Resorcin, Silver nitrate, Medical soap, Bronopol and Acrinol, the concentration of these disinfectants which results in the IC50 value were over 1000 mg/l. In addition, the toxic effects on OUR of AS in the presence of an equivalent mixture of two disinfectants tend to become stronger than that of the disinfectant alone. Namely, the additive effects of OUR-inhibition seemed to exist (For example ; Saponated cresol-STERIHYDE[○!R], HIBITANE[○!R]-GRINCE[○!R] etc.).

Method for Estimating the Toxicity of Chemicals to Activated Sludge. III. Effects of Commercial Detergents on Oxygen Uptake Rate.

The inhibitory effects of twenty-five commercial detergents on the oxygen uptake rate (OUR) of activated sludge (AS) were investigated by the use of the oxygen electrode method. The commercial detergents are used for many application, such as laundry detergents (Sample No. 11-13), dish-washing detergents (Sample No. 21-25), household cleaners (Sample No. 31-39), fabric softeners (Sample No. 41-42), bleaching agents (Sample No. 51-54) and scouring cleansers (Sample No. 61-62). The IC50 values of the commercial detergents tested here were measured to be 670-2100, 720-2900, 660-22000, >25000, 1800-2300 and >2500 or >25000 mg/l, respectively, for No. 11-13, No. 21-25, No. 31-39, No. 41-42, No. 51-54 and No. 61-62. Surfactant is one of the major compounds in commercial detergents, and the IC50 values of the surfactants of LAS, SDS, AE, AOS, AES, AO, sodium palmitate, sodium laurate and sodium oleate were 250, 190, >2500, 150, 530, 100, >2500, 410 and >2500 mg/l, respectively. On the other hand, the builders such as sodium silicate, sodium carbonate, sodium sulfate, enzyme and fluorescent agents had little adverse effect on the OUR of AS. Therefore, it was revealed that the major inhibitory compounds in commercial detergents were not builders but surfactants.