Effects Of Copper On Anaerobic-Aerobic Biotreatment Of Swine Wastewater

So many researches have been done on the treatment of swine wastewater nowadays,but the effects of heavy metals on the treatment hardly been founded.As far as the treatment of swine wastewater was concerned,the commonly used technology was anaerobic treatment first and then aerobic ones.The neglect of the toxicity of heavy metals can lead to the failure uf the treatment.At present,the concentration of Cu in swine wastewater usually seriously exceeds the standard which caused by the widely used high-copper additives.So it's high time did some researches on effects of Cu on the biotreatment of swine wastewater.The experiment has not only optimized major operation parameter and found out the critical concentration during biotreatment system stably operated,but also the optimal operating conditions.The results are as following.There was almost no effect on COD removal efficiency during anaerobic digestion when the concentration of copper reached 5mg L^-1.However,when the concentration of copper increased further,COD removal efficiency decreased sharply.Besides,critical concentration of copper ion increased as temperature increased.The critical concentration of copper ion was 5.99mg L^-1 in anaerobic fermentation in normal temperature while 6.1mg L^-1 in intermediate temperature for concentration of COD in effluent is the most important criterion of livestock wastewater discharge standards.The results showed that total gas production reached maximum which was 650mL when concentration of copper was 5mg L^-1 and minimum which was 335mL when concentration of Cu was 20mg L^-1 in normal temperature.While it reached maximum which was 1018.5mL when concentration of copper was 0rag L^-1 and minimum which was 523mL when concentration of copper was 20mg L^-1 in intermediate temperature.The results showed that copper ion can promote the growth of methane bacteria when concentration of copper was below 5mg L^-1 and played a role as a component of prosthetic group and coenzym.Because the activities of methane bacteria and acid-producing bacteria both had been promoted in some degrees in normal temperature,so the gas production was much more than the groups in intermedia temperature.But as temperature increased, the tolerance of aerogen would decrease to some extents.VFA reached the maximum(8895mg L^-1) when concentration of copper ion was 0mg L^-1 in anaerobic fermentation in normal temperature.while the maximum was 9885mg L^-1 when concentration of copper ion was 0rag L^-1 in anaerobic fermentation in intermediate temperature.As far as VFA was concerned,the inhibition of Cu was not as regularly and obviously as COD removal efficiency and gas productivity were.It was because that once the concentration of copper ion was over the critical concentration,the methane bacteria would be restrianed and VFA would accumulated,but at the same time hydrolase and hydrogen-producing and acid-producing bacteria would be poisoned.Considering positive and negative aspects comprehensively,we could arrive at the conclusion above.During the whole fermentation in normal temperature,Ph varied from 7.3 to 8.2 while 7.3 to 8.3 in intermedia temperature.The inhibition of copper ion was not obvious.This indirectly proved that copper ion mainly did harm to methane bacteria but not acid -producing bacteria.The pH of groups in normal temperature was a little below groups in intermedia temperature..Maybe that was due to the activity of methane bacteria was low in normal temperature,velocity of gas-produing and acid-producing would out of balance in some time,this would lead to acid accumulation and restrained the dissolution and transformation of methane bacteria.Observed by microscopy,we found that the number of Methano brevibacter was dropped sharply while that of Methano sphaera was increased a little and the figure of bacteria was distortion.It proved that copper ion mainly did harm to methane bacteria and the tolerance of it was better than Methano brevibacter.Considering operating efficiency and cost comprehensively,the optimal operating condition to remove COD was determined period 540min,aeration after fill was 75min,aeration was 315min, settlement was 75min,decantation was 50min,idle was 25min.The optimal operating condition to remove nutrients was determined period 660min,fill was 60min,hypoxia was 60min,aeration was 420min,settlement was 60min,decantation was 60min.The inhibitory effects of cqopper ion on SBR system had been observed.The critical concentration of copper ion were 4.956 mg L^-1(according to copper ion discharge criteria) and 2.994mg L^-1(according to COD discharge criteria) in COD removal technique of SBR,while was 0.6813 mg L^-1 in nitrogen& phosphorus removal technique of SBR..The inhibitory effects of Cu on the COD removal efficiency was more significant than those on the removal efficiency of Cu²⁺ in effluent.Cu could decrease kinetics constant(K) but at the same time biodegradable COD concentration and biochemicalization of COD in piggery wastewater increased to some degree.DO was a very important parameter during aerobic biotreatment of piggery wastewater.The dynamic changing of DO content could be both described as three-section functions,which coupled with the growth of functional microorganisms and the mechanisms of main pollutants disposing very well in either operating condition.The results also showed that the risk of richness of Cu was not observed within the critical concentration of copper ion in which average concentrative coefficients was 0.0338.The content of Cu in sludge met the standard of pollutants control.