The long-term stable anaerobic treatment system at high organic loading rates for molasses wastewater has been investigated. Especially, the effectiveness of pretreatment, in which the molasses wastewater was evaporated under reduced pressure, has been evaluated. Furthermore, the competition between methane producing bacteria and sulfate reducing bacteria has been investigated.
A UASB reactor with an effective volume of 10m³ was used.
SO₄^2- and K⁺ concentrations in the molasses, which at high level have inhibitory effects on an anaerobic treatment, could he reduced to 80% or more by the pretreatment. Owing to the pretreatment, the treatment perfommance was excellent with 60-70% removal of COD_cr and 90% or more removal of BOD at the COD_cr loading rate as high as 25-30 kg·m^-3·d^-1,
The vial activity test results show that the methane producing activity is highly affected by the operating COD_cr loading rates of the reactor. The methane producing activity, operating at COD_cr loading rates of 10kg·m^-3·d^-1, has been compared with that of 28kg·m^-3·d^-1 rates, and a 2.4 times activity increase has been observed.
Of the total removed COD_cr, 94% had been used in the methane producing reaction and 4% in the sulfide producing reaction. Of the total electron flow, 92% was utilized by methane producing bacteria and 8% by sulfate reducing bacteria. It has been revealed that i) the methane producing reaction was actively undertaken, ii) the sulfide level in the reactor had hardly any inhibitory effects on the methne producing reaction, and iii) there was hardly any competition between methane producing bacteria and sulfate reducing bacteria.

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The tide fluctuates twice a day and the water content of the intertidal zone sediment changes with it. In order to assess the biodegradability of the sediment organics it is important to know the effect of water content on the rate of aerobic biodegradation in the sediment.
Biodegradability of organics in beach sands was measured over a water content range from 0 to 100% (g H₂O/g dry soil). The amount of CO₂ generated was used as an index of decomposition. This experiment was done four times changing carbon sources (Gracilaria powder, artificial sewage) and incubation conditions (still, shaken).
In all cases the rate of degradation became lower when the water content was less than 10%. And oxygen depletion seemed to affect the degradation rate when the sand was saturated with water.
When artificial sewage was used sand seemed to stimulate the degradation notably but in case of Gracilaria powder we couldn't detect such an effect. A possible explanation is that a particle like sand doesn't affect particulate organics such as Gracilaria powder so much.

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Mutagenicity after aqueous chlorination of amino acids in the presence of nitrite was investigated by the Ames Salmonella/microsome assay.
After aqueous chlorination of L-tryptophan and L-phenylalanine with higher concenration of chlorine, chlorination products from L-tryptophan showed to be mutagenic.
The behaviors of these mutagenic activities using strains highly detected nitroarenes and aminoarenes suggested that base-pair change and frame-shift mutagens such as nitroarenes are produced by aqueous chlorination of L-tryptophan in the presence of nitrite.
It was recognized that after aqueous chlorination of L-phenylalanine with lower concentration of chlorine in the presence of nitrite, base-pair change and frame-shift mutagens as well as nitroarenes may be produced.

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Groundwater contamination by cis-1,2-dichloroethylene (cis-DCE) is widespread as a result of transformation from tetrachloroethylene or trichloroethylene in natural environments. Under anaerobic conditions, cis-DCE can be biotransformed via reductive dechlorination to ethylene, which is an environmentally acceptable product. In order to develop anaerobic cis-DCE-dechlorinating enrichment cultures, five anaerobic reactors fed cis-DCE (0.46 mg·l^-1) with either acetate, propionate, glucose, yeast extract or hydrogen as a primary substrate (100 mgCOD·l^-1) were semicontinuously operated at 25°C. Among the five reactors, only acetate-fed reactor was unable to sustain dechlorination. Other four reactors developed to enrichment cultures capable of dechlorinating cis-DCE to ethylene at high rates. In propionate-fed, glucose-fed and yeast -extract-fed cultures, cis-DCE was almost completely dechlorinated to ethylene in four days, while dechlorination in hydrogen-fed culture was somewhat unstable. These results suggest that organic substrates which produce hydrogen during their anaerobic metabolism serve as effective electron donors for reductive dechlorination of chlorinated ethylenes. Dechlorination was sustained even in cultures fed cis-DCE with low concentrations (10 mgCOD·l^-1) of primary substrate, although steady-state conditions were not achieved Results of this study suggest that anaerobic bioremediation can be used for cleanup of groundwater contaminated by chlorinated ethylenes.

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Biological activated carbon (BAC) treatment of drinking water can remove trihalomethane (THM) precursors by adsorption and biodegradation, and also produce fresh THM precursors by bacterial activities. In this work, the changes in THM formation potential (THMFP) of the broth of mixed batch culture of bacteria were measured during the passage of culture time, the classification of THM precursors produced by bacterial activities was tried, and the biodegradability and adsorbability onto activated carbons of those precursors were investigated. The following was clarified.
The fresh THM precursors produced by bacterial activities in BAC involve the metabolic products released when bacteria are growing and the autolysis products released when they die. The former is easily biodegraded and is not contained in the BAC effluent. On the other hand, since the latter can be regarded to be non-biodegradable, it can flow out of BAC. Also, the latter is well adsorbed onto the activated carbon with mesopores of 1.5-10 nm in radius. The activated carbons with such pore-size distribution are considered to be effective for controlling THMFP of the BAC effluent.

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A laboratory scale biofilter was operated with synthetic wastewater to study the mechanism of organic removal in high-loading wastewater treatment. A reactor consists of 4 short stages was used with a total working volume 8.0l. The process was operated at 25°C with organic loading rate of 4.1-12.3 kgBOD·m^-3·d^-1, and dissolved oxygen concentration was about 3 mg·l^-1. With the result that 97% organics substrates was removed, MLSS was found being a low value about 950-1,830mg·l^-1 in average, slightly lower than that as in conventional activated sludge processes, and SRT was 0.75 day with a responsive higher gross yield coefficient of 58%. By the organic degradation rate tests, the microorganisms showed a greater activity. As the conclusion, it was proposed that it is the greater activity microorganisms being always maintained in the reactor, resulted from the frequent back washings, that made the high-loading wastewater treatment possible in biofilter.

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Denitrification rates were directly measured by acetylene inhibition technique in a reed bed receiving ground water with high nitrate concentration. Aboveground biomass of reed showed its seasonal maximum (30gN·m^-2) in July, when its rhizome reached 40cm and its root 60cm depth, respectively. Total organic carbon content was high in the surface sediment (0-15cm), ranging from 50 to 180mgC·g^-1 dry weight. Nitrate concentration in the pore-water varied between sampling dates; high nitrate concentrations of 10-40mgN·l^-1 were observed from surface to 15cm depth on some dates, whereas 1-10mgN·l^-1 was detected only in the 0-2cm layer on other dates. Denitrification rates on 24 April, 1992 ranged from 200 to 600ngN·cm^-3·h^-1 between surface and 15cm depth. The rates on other dates, however, were one to two orders less than those values, and denitrification was restricted to 0-5cm sections on most cases. Areal denitrification rates ranged from 1 to 1,200mgN·m^-2·d^-1, with an integrated annual value of 112gN·m^-2·yr^-1. Denitrification rates at greater depths (20-160cm) were very low or less than detectable limit in mid-July when the reed aboveground biomass reached its seasonal maximum.

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