The quinone profiling technique was used to investigate the effects of zinc stress on the bacterial population structure of sewage activated sludge in laboratory-scale reactors. The quinone composition of sludges cultivated under different conditions with respect to the sludge retention time and zinc concentrations was determined by thin-layer chromatography, ultraviolet spectroscopy, reverse-phase high-performance liquid chromatography, and mass spectrometry. Numerical analysis of the quinone profiles showed that there were significant differences in the community structure between sludges cultivated with Zn²⁺ and without Zn²⁺. When the sludge was loaded with Zn²⁺, the sludge retention time was also an important factor affecting the quinone composition. The changes in the quinone composition from the normal sludge to the zin-stressed sludges resulted mainly from an increase in bacterial populations with ubiquinone-8 and a decrease in those with partially hydrogenated menaquinones.

View full abstract

Our laboratory wastewater namely medium-waste, Hg-trap-waste and ligand-waste were treated by the use of sedimentation method, Fe-powder column method and anion exchange resin method. Most of mercury in the medium-waste was adsorbed on suspended solid (SS) composed of Bacteria or Chlorella and a part of mercury was dissolved. The Hg-trap-waste contained no ligands and the ligand-waste contained Br^-, I^- and EDTA which complex Hg²⁺ strongly. By the addition of 0.05% of ferric chloride to the medium-waste, the mercury adsorbing on SS was efficiently precipitated but the dissolved mercury was not removed. Dissolved mercury in the Hg-trap-waste and medium-waste was well recovered by the Fe-powder column method. By the using of 5g of Fe powder, over 96% of dissolved mercury in 20l of these wastes was removed. When the anion exchange resin method was applied to the Hg-trap-waste and the ligand-waste, mercury in 100l of the Hg-trap-waste or in 50l of the ligand-waste was well removed with 10 ml of resin.
From above results, it is concluded that the Fe-powder column method is useful to remove dissolved mercury in laboratory wastewater containing ligands and the anion exchange resin method is effective as the secondary treatment.

View full abstract

The matrix solution behaviors of humic substances were studied by characterizing molecular weight distribution, hydrophilicity and others before and after batch tests of activated carbon treatment. Aquatic humic substances in peat water and pretreated peat water by alum coagulation were classified by size exclusion HPLC and Sep-Pak C-18 cartridge adsorption and extraction. The lower molecular weight and the less hydrophilic group has higher carbon adsorbability. Ideal adsorbed solution theory (IAST) using the Freundlich isotherm equation was used for the evaluation of adsorption isotherms of each classified groups of humic substances in batch adsorption experiments.

View full abstract

In Hinuma River, changes of periphyton biomass were observed weekly from September 1987 to March 1990 to evaluate the dynamics of the periphyton biomass in the river. Periphyton were sampled from artificial substrates which were 10cm×10cm unglazed clay tiles. The tiles were submerged in the river more than one month before sampling.
At the high periphyton biomass, the ratio of carbon per dry weight of periphyton was low because a significant amount of inorganic particles such as clay and silt was trapped in periphyton. However, the ratio of carbon : nitrogen : phosphorus remained constant regardless of the change of the biomass. From April to October the periphyton biomass was low due to losses by scouring due to frequent storm events. In November and December, the periphyton biomass became greatest because of steady low flow in the river. From January to March, the biomass did not increase significantly due to low temperature even though the rainfall was low.
The scouring was found to be a main factor in the dynamics of the periphyton biomass in the river. The amount of the periphyton biomass (as carbon) after scouring was proportional to the exponent of the maximum flow during the storm.

View full abstract

The performance and hydraulic characteristics of rock bed contact-purification of eutrophic coastal water were investigated in pilot-scale channels to determine the design and operating parameters (medium size, channel length, flow rate) for optimum rock-bed channel operation.
The results are summarized as follows :
1) 60-80% of SS and 8-17% of T-TOC in coastal water were removed after hydraulic retention time of 1-5 hrs.
2) The channels packed with rocks under 80mm were clogged by shellfish (Mytilus edulis etc) attachment in the short term. It is practical to use larger rocks (over 100-150mm) in order to prevent clogging and provide sufficient stability of contact-purification in the long term.
3) Detachment of biofilm was observed in the channels of high hydraulic loading and/or small rocks.
4) High deposit ratio was observed on the downstream area in the channel of high hydraulic loading. Detachment of biofilm significantly reduced the efficient purification length in channels, and moved the area downward.
5) The low loading treatment was expected to allow long-term purification without the rapid development of clogging.

View full abstract