Studty On Speciation And Distribution Of Heavy Metal During Worms Predation Sludge Process

The broader application of the activated sludge process in domestic and industrial treatment plants has amplified sludge management problems. As the environmental and legislative requirements on the discharge of excess sludge have been strengthened, about 60% of the total operation cost is accounted for the cost of sludge storage, transport, digestion and disposal. This has given an impetus to develop strategies and technologies for excess sludge reduction in biological wastewater treatment processes. Compared with other strategies, micro-fauna predation with the advantages such as energy saving and no secondary pollution, has begun to receive increasing attention.During energy transfer from low to high trophic levels in a natural food chain, energy is lost due to inefficient biomass conversion. Therefore using the proper predator and under optimal conditions, the total loss of energy will be maximal and the total biomass production minimal.Therefor, there are heavy metals in sewage and sludge. By using technology to deal with excess sludge ,heavy metals could have toxicaction to worms which may influence the treatment process.In order to know the effect and influence of heavy matals to worms,we choose copper, zinc and lead to find out during different exprosure time ,their toxic effects to Limnodrilus hoffmeisteri .The result shows that together with the metal concentration is higher and the exposure time is longer , the toxic effect to microfauna is inceasing ,and represents conspicuous relation of concentration-effect and time-effect, with the toxicity Cu²⁺ >Zn²⁺ >Pb²⁺. From the research we know ,the actual concentrations of the three kind of typical heavy metals in wastewater and sludge have little effect on the survival of Limnodrilus hoffmeisteri safety.This study determined the biological sludge reduction system threshold of heavy metal concentration for survival of worms, and preliminary analysis the effect of heavy metals migration during worms preying process ,in order to provide research foundation on sludge reduction by using worms .