[Characteristics of 4-chlorophenol degradation by a soil bacterium Acinetobacter sp].

The bacterium capable of degrading 4-chlorophenol (4-CP) was enriched and isolated from agricultural soil. It was gram-negative, rod-shaped bacterium, and identified as Acinetobacter sp. based on the analysis of the 16S rRNA gene fragment. It was able to utilize 4-CP as a sole carbon source. The degradation mechanism of 4-CP by this isolate was proposed as a modified ortho-cleavage pathway, the activity of chlorocatechol 1,2-dioxygenase was markedly induced. The bacterial isolate grew well and exhibited a high degradation efficiency when the initial concentration of 4-CP was between 2-8 mmol/L. It was able to survive in the presence of 4-CP at higher concentrations (up to 8 mmol/L). Not only 4-CP, but also 2-chlorophenol, 3-chlorophenol, phenol, and 2,4-dichlorophenol, were also growth substrates for the isolate. The results of co-substrate supplementation illustrated the suitable conditions of the isolate to improve growth rate and 4-chlorophenol biodegradation efficiency. The results suggested that the isolate had a potential use for bioremediation of the site contaminated with 4-chlorophenol.

Effect of salinity variations on the performance of activated sludge system.

OBJECTIVE: To investigate the influence of salinity variations on the performance of activated sludge systems, treating domestic wastewater. METHODS: The completely mixed reactor was used and operated in a batch-wise mode. The activated sludge taken from the Gaobeidian Wastewater Treatment Plant was used as a seeding sludge. Total organic carbon (TOC), oxygen uptake rate (OUR) and suspended solids (SS) were used as parameters to characterize the performance of the treatment systems. TOC was measured using a TOC-analyzer (TOC-5000, Japan). The OUR value was measured with a dissolved oxygen meter (YSI model-58). SS was measured gravimetrically. RESULTS: The TOC removal efficiency and the OUR value of activated sludge were not deteriorated when the NaCl shock concentration was less than 0.5 g/L. However, when the NaCl shock concentrations were up to 10g/L and 20 g/L, the OUR of activated sludge was reduced by 35% and TOC removal efficiency was dropped by 30%, compared with the control experiment without NaCl shock loading. CONCLUSION: The effect of NaCl shock loading on the activated sludge wastewater treatment system is dependant upon the NaCl concentrations and the degree of influence can be inferred through the change of substrate utilization rate at different shock NaCl loadings.