[Toxicity of leachate of different landfill ages and different seasons].

Leachates from 7 landfill of Wuhan, China were selected to determine the toxicity of leachates of different landfill age and different seasons, and relationships between physical-chemical parameters and toxicity of leachates were also study. Bioassays were conducted recording toxicity against Tetrahymena thermophila as median lethal concentrations (LC50 values) after 24h exposure and growth inhibition. The results show that LC50 values of leachates of different landfill age oscillate between 0.84% and 12.15%, and LC50 values increase and growth inhibitions do not decrease with increase of landfill age. No clear regularity is observed from LC50 values of leachates of different seasons, and LC50 values of leachates of summer are comparatively lower. Growth inhibitions of leachates of spring are the lowest. Physical-chemical parameters of leachates do not correlated with LC50 values, whereas growth inhibitions are dependent on COD, BOD5, NH4+ -N and concentrations of diethylhexyl phthalate (DEHP).

Monitoring bioaccumulation and toxic effects of hexachlorobenzene using the polyurethane foam unit method in the microbial communities of the Fuhe River, Wuhan.

Hexachlorobenzene (HCB) is a chlorinated aromatic hydrocarbon that was widely used for seed dressing in prevention of fungal growth on crops, and also as a component of fireworks, ammunition, and synthetic rubbers. Because of its resistance to degradation and mobility, HCB is widely distributed throughout the environment and is accumulated through food chains in different ecosystems. In this study, a preliminary investigation was carried out on the bioaccumulation and the toxic effects of HCB in the microbial (protozoan in particular) communities in the Fuhe River, Wuhan, a water body receiving industrial wastewaters containing HCB and other pollutants, using the standardized polyurethane foam units (PFU) method. Field samples were taken from eight stations established along the Fuhe River in January and August 2006. The concentration ratios of HCB in microbial communities and in water were 9.66-18.64, and the microbial communities accumulated 13.29-56.88 [ig/L of HCB in January and 0.82-10.25 microg/L HCB in August. Correlation analysis showed a negative correlation between the HCB contents in the microbial assemblage, and the number of species and the diversity index of the protozoan communities. This study demonstrated the applicability of the PFU method in monitoring the effects of HCB on the level of microbial communities.

[Study on technological characters of anaerobic-aerobic bioreactor landfill].

A technology of anaerobic-aerobic landfill bioreactor aimed at reusing landfill site is studied, and it's based on landfill bioreactor technology. A set of stimulating equipment is designed, and the technology characters are studied. In the anaerobic period, technological conditions are controlled by the means of leachate recirculation. The main experimental results are: pH, R1 rises to 6.7 - 7.8 in 6 weeks, and R2 is under 6.8 in 17 weeks; COD concentration of leachate, R1 declines to 10 617 mg/L in 13 weeks, while R2 rises to 60 000 mg/L in 5 weeks, and keeps stabilization in long time; the cumulating methane production, R1 reaches 44% in 8 weeks, while R2 almost cannot produce methane. The stabilization can be evaluated by pH of leachate, COD and BOD5/COD decreasing ratio, and cumulating methane production. They are main evidences to transform anaerobic period to aerobic period. In the aerobic period, odor and moisture are reduced by the means of aeration. The main experimental results are: ammonia concentration reduces to 1.16 mg/m3 in 19 days, and the odor concentration reduces to 19 in 23 days; the moisture of the wastes reduces to 26% in 14 days. The technological indexes to evaluate finishing of this period can be determined by the ultimately purpose of exploited wastes. Numerical modeling has been researched with the use of experimental data. The succession of microbes in the anaerobic-aerobic course is studied by RISA (ribosomal intergenic spacer analysis) analysis. There are 4 preponderant groups in this course, and some facultative anaerobes play important roles in the transition of anaerobic period to aerobic period.

[16S rDNA-RFLP analysis of structure and diversity of an aerobic microbial community degrading hexachlorobenzene].

Hexachlorobenzene is a chlorinated aromatic hydrocarbon that was widely used as a seed dressing for prevention of fungal growth on crops, and is also a component of fireworks, ammunition, and synthetic rubbers. Because of the bioaccumulation and persistence of hexachlorobenzene as well as its potential toxicity, hexachlorobenzene must be removed from environment. The potential for aerobic dechlorination of hexachlorobenzene by a hexachlorobenzene-adapted mixed culture was investigated. An aerobic microbial community which was able to grow at the presence of hexachlorobenzene was enriched from sediment from contaminated site after incubating about 2 months. During the growth of the mixed microorganisms on hexachlorobenzene, the accumulating consumption of oxygen, the microbial population curve and the release of Cl- were investigated. The data suggest the rapid degradation of hexachlorobenzene to support microbial growth and the aerobic decholrination of hexachlorobenzene was observed. The result showed that the mixed microorganisms were able to utilize hexachlorobenzene as sole carbon and energy source. It was shown that up to 55% of HCB could be degraded during 18 days incubation at 30 degrees C in mineral salts medium (pH 7.0) with 4.5mg/L HCB. The calculated rate of hexachlorobenzene biodegradation was 137.5 microg/ (L x d). The 16S rDNA genes were amplified from community DNA by using primers specific to bacteria and were subsequently cloned. The cloned 16S rDNA fragments were reamplified, and restriction analysis was performed following separate digestion with enzymes Hae III and Rsa I. Application of restriction fragment length polymorphism screening approach revealed 9 clusters, and 3 major clusters were sequenced. Nearly complete 16S rDNA sequence analysis show that the microbial community was dominated by Alcaligenes and Azospirillum groups. This is the first report describing aerobic dechlorination of hexachlorobenzene via dehalorespiration by a microbial community which was enriched from contaminated site. The microbial community can be used to degrade highly recalcitrant chlorinated pollutants.

[Studies of on-site night soil and kitchen garbage treatment].

The biological treatment technique of collection at source and disposition on-site of night soil and kitchen garbage were presented. By design project of overall technics, the lab-scale experiments were performed. It was revealed that water consumption of vacuum closestool was about 1 L/time. It consumed 0.4- 0.6L water to shred 1 kg kitchen garbage. Night soil covered 40%, kitchen garbage covered 60% in the influent. Water was controlled at about 93%, the C:N ratio was about 25:1, pH was between 6.2 and 7.3, the optical blend frequency was 6h/d and the overall solid retention time was 28 days in anaerobic digestion reactor. The COD removal rate of mixed supernatant was 91% in anaerobic baffled reactor. It was identified that these phosphorus strains and potassium strains were Bacillus. sp, and biological activated fertilizer was obtained by mixed these strains with digestion sludge which had been dehydrated and deodorized. These strains ability of forming phosphorus and potassium were determined, and the concentration of phosphorus increased 67.5%, potassium increased 33.4%.