[Effect of simulated heavy metal leaching solution of electroplating sludge on the bioactivity of Acidithiobacillus ferrooxidans].

An Acidithiobacillus ferrooxidans strain WZ-1 was isolated from the tannery sludge in Wenzhou, Zhejiang Province in China. The cell of WZ-1 strain is Gram negative and rod-shaped, its 16S rDNA sequence is closely related to that of Acidithiobacillus ferrooxidans ATCC23270 with 99% similarity. These results reveal that WZ-1 is a strain of Acidithiobacillus ferrooxidans. The effects of Ni2+, Cr3+, Cu2+, Zn2+ and 5 kinds of simulated leaching solutions of electroplating sludge on the bioactivity of Fe2+ oxidation and apparent respiratory rate of WZ-1 were investigated. The results showed that Ni2+ and Cr3+ did not have any influence on the bioactivity of WZ-1 at concentrations of 5.0 g x L(-1) and 0.1 g x L(-1), respectively. WZ-1 showed tolerance to high levels of Ni2+, Zn2+ (about 30.0 g x L(-1)), but it had lower tolerance to Cr3+ and Cu2+ (0.1 g x L(-1) Cr3+ and 2.5 g x L(-1) Cu2+). Different kinds of simulated leaching solution of electroplating sludge had significant differences in terms of their effects on the bioactivity of WZ-1 with a sequence of Cu/Ni/Cr/Zn > Cu/Ni/Zn > Cu/Cr/Zn > Cu/Ni/Cr > Ni/Cr/Zn.

[Growth kinetics of aquatic worms feeding on activated sludge].

The growth kinetics of aquatic worms was investigated from juvenile to decline phase for 18 weeks by cultivating with activated sludge in batch test. Results showed that the growth of aquatic worms well fit Gauss function for cultivating 18 weeks. The maximum specific growth rate, growth yield of aquatic worms and sludge reduction rate was 0.41 d(-1), 0.32 and 25.5%, respectively. When the concentration of substrate and dissolved oxygen change from low to high, the relationship between the specific growth rate with dissolved oxygen, and substrate concentration meet the Monod equation. Compared with the dissolved oxygen, the substrate concentration had greater effect on the specific growth rate of aquatic worms, and aquatic worms can live in the environment with low dissolved oxygen. Furthermore, the breath test showed the oxygen uptake rate of aquatic worms was almost 6.39, 10.10, 11.31 and 5.74 mg x (L x g x h)(-1) from juvenile to decline phase, the dissolved oxygen demand of the rapid growth and mature stage was higher than juvenile and decline phase.

[Full-scale experiments of municipal sewage treated by symbiotic system consisting of tubifex and microbes].

A symbiotic system consisting of tubifex and microbe was formed when tubifex was incubated in the biological contact oxidation process,the tubifex attached to the outer layer of the carriers. When the density of tubifex was about 31.3 g/L, a recycling food chain between corpse of tubifex and excrement and wastewater and microbe and sludge was formed and it could reach balance. The large scale control experimental system for treating 20,000 m3 x d(-1) municipal sewage was carried out for a long time. The result showed that tubifex could improve water quality in the effluent. When the concentration in the influent of COD,NH4+ -N,TP and SS were 130-459, 14.21-27.46, 1.60-6.93, 60-466 mg x L(-1), respectively,the removal rates of COD and SS can be improved by 8.7% and 13.6%. However, tubifex can also increase the concentration of NH4+ -N in the system,but a proper operation can make the effluent concentration of NH4+ -N below 5 mg x L(-1) stably. The symbiotic system consisting of tubifex and microbe has very good phosphorus removal efficiency. The reactor has a high toleration to loading shock and it could keep the effluent quality stable.