In recent years, effective methods for treatment of non-biodegradable substances have been required. 2-tertiary butoxy ethanol (ETB) is a non-biodegradable compound with tertiary and ether structure. Biological treatment of industrial wastewater containing the ETB was carried out experimentally in an activated sludge aeration tank.
In the case of treatment of wastewater containing the ETB as a single substrate, it was shown to accumulate a product in the aeration tank. The product was not accumulated by coexisting with the ETB and the other substrates in the influent wastewater. Under the condition of inlet substrate concentration and hydraulic retention time, removal efficiency of the ETB on coexisting with the ETB and biodegradable substrates was higher than that on coexisting with the ETB and non-biodegradable substrates.
The microorganisms which treated the ETB effectively were obtained by the step-shortening operation of hydraulic retention time.

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Regression models for the k and n values of the L=kQ^n-type pollutant runoff model (L : specific load, Q : specific discharge, k and n : constants) were developed. In the models, the independent variables are several watershed characteristics etc.
The relation between the k value and several watershed characteristics was analyzed using the data on 14 rivers with 17 stations as well as the n value. According to multi-regression analyses for the k and n values, it was found that (1) for the k value a correlation coefficient of a regression model was large even if discharged load was an only independent variable and (2) for the n value a correlation coefficient of a regression model was large when the k value or discharged load which had a strong correlation with the k value was included as an independent variable.
Regression models for estimating the k and n values were selected from the results and verified by observed data. According to the verification, the estimated k and n values ranged from half of the observed values to twice of those at most of the stations as well as the estimated load which was calculated by the estimated k and n values.

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As for a microbioassay of the vitamin B₁₂ by Lactobacillus leichmannii (ATCC 7830) an influence by salt is serious. Before desalt processing of samples should be done, when the measurement of vitamin B₁₂ in the sea water is done by the microbioassay. The method that vitamin B₁₂ was measured by the microbioassay after desalt processing by Bond-Elut^® was examined. First of all, vitamin B₁₂ was absorbed to Bond-Elut^®. The vitamin B₁₂ that was absorbed was extracted with 40% ethanol. This extract was measured with the microbioassay. An addition of KCN to samples was indispensable due to the stabilization of vitamin B₁₂. The coefficient of variation of this analysis method was 5.315.9%. In this method, the recovery of vitamin B₁₂ ranged from 92.7 to 116%.

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Effects of substrate concentration, specific surface area and hydraulic loading on the treatment efficiency in a submerged biological filter were investigated experimentally.
BOD removal efficiency was influenced by three factors, that is, substrate concentration of BOD (X₁), specific surface area (X₂) and hydraulic loading (X₃), and the multiple regression equation between BOD residual rate and these parameters was obtained as follows : Y = 4.66·X₁^0.546·X₂^-0.503·X₃^0.747 where Y was BOD residual rate. The multiple correlation coefficient of this equation was 0.94, and the predicted values of BOD residual rate were approximately in agreement with the observed values of that.
When 200 mg·l^-1 of BOD as substrate concentration and 50 m²·m^-3 as specific surface area were substituted in our equation, we found the relationship between hydraulic loading and the predictive value of BOD removal rate was nearly in accord with the tendency calculated by Horasawa's equation which was derived from data of actual plants. Consequently, our equation was effective to estimate the removal efficiency in the submerged biological filter.

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