The Toxicity Studies Of Typical Beneficiation Wastewater Constituents By Nitrification Rate Method

Mineral processing wastewater is one of the main pollutants discharged in miningactivities. The heavy metals and flotation reagents remain in the wastewater and theyhave permant damage to the ecological environment and human health. Study on thetoxicity of the pollutants is very important，and it could provide an important basis forpollution control of mineral processing and the ecological risk assessment. To assess thebiological toxicity of the typical pollution components Cu，Pb and butyl xanthate inbeneficiation wastewater，the ammonia-oxidizing bacteria-rich activated sludge andammonia-oxidizing bacteria were used as test organisms. The NO2--N output,extracellular polymeric substances composition and dehydrogenises activity perspectivewere investigated. The main research results are as follows：Cu and Pb low concentration could induce the hormesis of ammonia oxidationprocess，but high concentrations of Cu and Pb inhibited the ammonia oxidation process.Butyl xanthate had toxic effect on ammonia oxidation process, and with increasingconcentration of toxic increase. The toxicity of the pollutants on the ammonia oxidationprocess followed by xanthate>>Cu> Pb. Combined toxicity type of Cu-Pb, Cu-xanthate and Pb-xanthate on the ammonia oxidation process is synergistic action.In the test concentration range of xanthate and Cu、Pb experimental concentrationexceeds the hormesis concentration，with the increasing of the concentration ofpollutants，the content of protein and polysaccharide in EPS and the dehydrogenisesactivity decreased，but the content of nucleic acid in EPS increased.Cu and Pb concentration on ammonia oxidation process was divided into three stages.The first stage was when the pollutant concentration was lower than1mg/L，pollutantspromoted cell secrete more polysaccharides and proteins to chelate Cu, Pb and reducedthe poison，at the same time, they improved the enzymatic reaction of system andpromoted the efficiency of ammonia oxidation process. The second stage is the pollutantconcentration is in the1mg/L-100mg/L range，Cu, Pb reduces the activity of ammoniaoxidizing bacteria and suppressed the ammonia oxidation process so as to increase itsbiological toxicity. The third stage was when the concentration of Cu and Pb was higherthan100mg/L，pollutants not only changed the ammonia oxidizing bacteria extracellularsecretion and enzyme activity, but also leaded to the death of bacteria and cell rupture.The effect of xanthate concentration on the ammonia oxidation process only had thesecond and the three stage. The result of toxicity test using ammonia-oxidizing bacteria-rich activated sludgemethod and ammonia oxidizing bacteria method is consistent. But the ammoniaoxidizing bacteria method was more sensitive than the ammonia-oxidizing bacteria-richactivated sludge on pollutant toxicity test.