Study On The Toxicity Effects Of Heavy Metals On Microbial In Biological Nitrogen And Phosphorus Removal System

During using activated sludge to make sewage disposal, a little amount of heavymetal is a very necessary nutrients for the microbes to grow and component for bothmicrobes and their enzyme. However, over height of concentration of heavy metal willpoison and even kill the microbes. In the end, it will do harm to the effect of sewagetreatment. Heavy metal can do some impactions to the microbes in two main ways:firstly, restrain the respiration; secondly, deprive the activation by combining with theactive or non-active centre of the enzyme and lower its activity. This paper is under themicrobial enzyme system and the respiratory rate mechanism of inhibition by heavymetals. The activated sludge microbial electron transport system (ETS) activity, specificoxygen uptake rate (SOUR) and ammonia uptake rate (AUR) are using as the primarydetection means in this paper. From theory and application, the influence of copper,cadmium, mercury and zinc on nitrogen and phosphorus removal systems will beinvestigated, and the domestication of nitrogen and phosphorus removal system oncopper zinc is conducted. The results show that:(1) Compared with the aerobic heterotrophic bacteria, nitrifying bacteria are moresensitive to heavy metal toxicity. Four kinds of heavy metal toxicity on nitrifyingbacteria is: Hg2+＞Cu2+＞Cd2+＞Zn2+.(2) Improve the sludge concentration could promote microbial dehydrogenaseactivity, SOUR and AUR; beneficial for microorganism to resist heavy metal toxicity.The COD load, pH and DO have significant correlation with Heavy metal toxicity.Generally speaking,the increasing of DO is synergy with heavy metal toxicity.(3)Four kinds of heavy metal toxicity on biological phosphorus removal system is:Hg2+＞Cu2+＞Cd2+＞Zn2+.INT-ETS activity is suitable for characterization of the heavymetal ions toxicity on the anaerobic microorganisms, and TTC-ETS activity is suitablefor aerobic microorganisms, in the inhibition of heavy metal ions.(4) The toxicity of copper and zinc ions on phosphate accumulating bacteria have ahysteria, and the impact of removal on total phosphorus has significant correlation withthe copper or zinc accumulation in vivo micro-organisms. The ability of microorganisms resisting toxicity of copper and zinc ions is increased duringdomestication.(5) The inhibition of copper and zinc ions to TTC-ETS activity of Acclimatedsludge is significantly higher than INT. The ETS activity of domestication microbial hasnot been improved stably during domestication of copper, but not zinc.(6) The capacity of Microorganisms to adsorption copper and zinc ions in theenvironment has significant correlation with the accumulation of copper and zinc invivo micro-organisms. The copper in vivo micro-organisms is easily re-released to thewater when the concentration of copper ions is very low, while zinc was the opposite.