Performance of biological hybrid bioreactors containing both attached and suspended growth biomass was tested. Comparisons were made between the quantities of the two forms of biomass, their contributions to pollutants remediation and the performances of the hybrid bioreactors and conventional activated sludge process. Results showed that, in the hybrid bioreactors with 15-30% of polyurethane sponge, the total biomass could reach 4.36-5.2 gMLSS⋅l^-1 which was 36-82% times higher than that of the control (conventional activated sludge process) . COD removal rates of hybrid bioreactors could be 2.75-3.03 kg COD⋅m^-3⋅d^-1, 1.42-1.57 times of that of the control. Higher total nitrogen removal could be achieved in the hybrid bioreactors than in the control. Attached growth biomass in the hybrid bioreactors played an important role in upgrading treatment capability. The higher the influent organic load was, the higher contribution of attached growth biomass made to pollutant removal, and the higher advantages the hybrid bioreactors achieved.

View full abstract

The effect of mold, microbial pesticide Verticillium lecanii F126-12-3M on the egg-production of rotifera Philodina erythrophthalma, contributing to purification of wastewater was examined in batch culture experiment. The result indicated that the number of eggs was several times higher in the cultures with supernatant of mold than those of the control. It was found that there was a substance stimulating the production of eggs in the supernatant of mold culture. The supernatant of mold culture was found to be of importance for egg production. The egg of P. erythrophthalma, the reproduction of which was promoted by addition of mold culture, could survive under desiccation for five days. It was suggested that mass cultivation of P. erythrophthalma could be accomplished using this method.

View full abstract

In order to elucidate Nocardia (Gordona) amarae profiles in sequencing fed-batch culture of activated sludge, experimental invesitigations were carried out under various operational conditions e.g. sludge retention time (SRT), addition of N. amarae culture solution and change of carbon source. Growth of N. amarae in the aeration tank was confirmed corresponding to the component of influent substrate, being affecting SRT values. However, the possibility was suggested that the scum production was connected with some induced factors such as n-hexadecane, not being determined by N. amarae biomass only. It was concluded that SRT control was not necessarily effective after the scum production.

View full abstract

In order to investigate the condition of disinfection devices, the study was made at 75 domestic wastewater treatment plants about the relation between residual chlorine and the numbers of microorganisms in the chlorinated effluents, the change of bacteria flora during chlorination, and the factors necessary to detect the residual chlorine. The means for the chlorinated effluents were 1.5×10² CFU/ml of fecal coliforms, 5.8×10² CFU/ml of total coliforms, and 5.1 × 10⁴ CFU/ml of standard plate count bacteria. The means of the bacteria removal rate during the disinfection process were 69.6% for fecal coliforms, 79.8% for total coliforms, and 90.3% for standard plate count bacteria, respectively. When free residual chlorine was over 0.1mg/l, fecal coliforms and total coliforms were practically non-detectable. As for total coliforms in the chlorinated effluents, 34.7% of the surveyed plants were under 30 CFU/ml, but 5.3% were over 3.0×10³ CFU/ml which exceeds the effluent standard value.
In the secondary effluent in which standard plate count bacteria were 1.4×10⁴ CFU/ml, besides Enterobacteriaceae, Alcaligenes sp., Flavobacterium sp., Moraxella sp., and Pseudomonas sp. were detected. But in the chlorinated effluent in which free residual chlorine was 1.5mg/l, only Bacillus sp. was detected. The important factors controlling the detection of free residual chlorine were the presence of a flow equalization tank, the presence of a disinfection device to maintain a sufficient water depth, and the NH₄-N concentration in the inflow.

View full abstract

Two pilot plants applied to anaerobic-anoxic-oxic (A₂O) process with immobilized nitrifying pellets added in the oxic tank were operated supplying different influents, which one consisted of municipal wastewater mixed with so much supernatant returning from sludge treatment facilities and the other consisted of a major portion of municipal wastewater. The operating experiments were carried out comparing with a pilot plant applied to nitrified liquor recycling process with the same pellets added in the oxic tank supplying influent composed of a major portion of municipal wastewater. The influent to the pilot plants was different primary clarifier effluent, which was flown into municipal wastewater treatment works from combined sewer system.
As the results, declining S-BOD removed with T-P released in anaerobic tank could be expressed in the relation between T-P released and S-BOD removed / T-P released ratio, and the regression equation could be expressed as an exponential function. Namely, the bigger S-BOD removed / T-P released ratio increased progressively, the smaller T-P released produced.
And, the relationship between NO_X-N removed and S-BOD removed by denitrifying reaction in the anaerobic and anoxic tanks could be shown as the regression equation by two different straight lines having nearly the same gradient, of which were applied either for immobilized nitrifying pellets added A₂O process or for the same pellets added nitrified liquor recycling process. It was estimated that the S-BOD requirement to NO_X-N removed for the pellets added A₂O process was slightly higher than those for the pellets added nitrified liquor recycling process.

View full abstract

The survey was conducted to clarify the succession of the epilithic algal communities in two small streams (the River Tsunaki and the River Zaru) during Apr.1997-Apr.1998. The riverhead of two streams is almost same. The River Tsunaki is a branch of the River Hirose, a symbolic river in Sendai City, receiving the ozonated sewage effluent. While the River Zaru is a branch of the River Natori, receiving the effluents from housing developments.
The epilithic algae and water quality were investigated at eight sites (three in the R. Tsunaki and five in the R. Zaru) every month. The average of water temperatures were 11-18°C, velocities were 0.25-1.12m/s. The average concentrations of BOD were 0.7-1.2 (the River Tsunaki), 0.6-2.2 mg/l (the River Zaru) . The many nutrient concentrations were constantly high at the downstream site in the R. Tsunaki by the sewage effluent.
The average amounts of chl.α were 76-470 mg/m². The amounts of chl. α were tended to increase during winter. Among the algal species identified (77 species in the River Tsunaki) and (80 species in the River Zaru) Homoeothrix janthina, Stigeoclonium lubricum, Rhoicosphenia abbreviata, Nitzschia inconspicua and Cymbella minuta to dominated. At the site of rapid velocity the filamentous algae dominated, and at the sites of upper 0.5 m/s velocity the relative abundance of filamentous algae and the velocity related in high ratio (r=0.70) . And it was found that the epilithic algal communities in each river divided four groups during a year by cluster analysis bases on C_∏ similarity and the sewage effluent effected the epilithic algal communities.
The present results showed the efficiency of algal community for monitaring river environments.

View full abstract