| In recent years, our industrial wastewater emissions is overgrowing, andpollution has become a increasingly serious phenomenon. There are a wide range ofpollutants in industiral wastewater; these pollutants play a role jointly in the organism,show complex interactions and cause the body’s comprehensive toxicity. Biologicaltoxicity test method can not only reflect the comprehensive toxicity of water samplesand the testing process is relatively simple, especially the acute toxicity test is shorterand low cost, so the biological testing has a greater advantage in evaluating watersamples toxicity and the impact of toxic substances in wastewater on the treatmentsystem. This study optimized the experimental conditions of luminescent bacteriaacute toxicity test and carired out the related research of biological acute toxicitythrough the optimized method. With a view to play an active role in determining thekey monitoirng pollutants and enterpirses for the wastewater treatment plant,strengthen the formulation of emissions standards, and guiding the direction ofenterpir’ses production mode. The main contents are as follows:(1) At present, our standard methods of the luminescent bacteira acute toxicitytest,"Determination of water acute toxicity, luminescent bacteria"(GB/T15441-1995), are not detailed on some experimental conditions and procedurerequirements, while the luminescent bacteira and instrument adopted in the study aredifferent from GB, thus through the experiment to improve the test conditions. Threeconditions, pH, reaction time, and bacteiral density, were studied to expound theirimpact on the luminescent bacteira light-emitting. Blank test determined that whenthe system pH is in the range of5.5-8.0，pH fluctuations will not produce luminescent bacteira light-emitting inhibition, beyond this range will significantly inhibit thelight-emitting. Therefore in the determination of luminescent bacteira acute toxicity,not including the pH influence, there is no need to adjust the pH when the system pHin the5.5-8.0range. React ant’s half inhibitory concentration EC50of15min，20minand50min，reaction time，are0.105mg/L，0.068mg/L and0.050mg/L, the reactionin20min can be basically stable. Therefore, optimize the reaction time to20min. Thel’uminous intensity can show bacteiras density, when the blank luminous intensity are4600，3200，2200and1500mV, the EC50of HgCl2are0.125,0.117，0.107and0.104mg/L separately. The results indicated that when the cell density is too large,luminescent bacteira will present a lower sensitivity to the toxicity substances, whilethe cell density is too low can also cause a large deviation results, so determine theblank luminous intensity should be controlled between1200?3200mV.(2)Use the improved luminescent bacteria toxicity test method to evaluatethe toxicity level of inflow and the toxicity reduction along the processes of Swastewater treatment plant. The light-emitting inhibition rate of inflow is from75%to96%, toxicity level is IV level, a highly toxic level; influent COD fluctuations ismore than four times a day and the enterpirses wastewater discharge is intermittent.The toxic inflow has a large impact on biological treatment systems, and consideirngthe safe and stable operation of wastewater treatment plant, the inflow toxicitymonitoring is very necessary. The luminous efficiency of wastewater treatment planteffluent is between104%and108%, indicating that the acute toxicity of wastewaterto luminescent bacteira has been basically cut down, and the effluent is safe to bedischarged; this can also be a way to monitor the normal operation of the wastewatertreatment plant biological treatment systems.(3)After the treatment of acid hydrolysis section, wastewater luminescentbacteria bio-acute toxicity enhanced, luminescent bacteria light-emitting inhibitionrate increased more than50%, and then atfer process in CASS section, wastewaterlight-emitting inhibition rate reduced below zero，toxicity has almost been cut down.The data showed that heavy metals have been cut in acid hydrolysis section, but theamount of ammonia, SCOD and UV254are increased. As the luminescent bacteira are not sensitive to ammonia, changes of ammonia will not cause the luminescentbacteira light-emitting change significantly. Therefore we assume that the toxicity ofacid hydrolysis section effluent increased due to the increase of organic toxicants.(4) In order to investigate the source of wastewater treatment plant influenttoxicity, we selected15typical enterpirses in the Industiral Park as research objects toscreen the key enterprises and key monitoirng pollutants. Six samples were fromtannery enterpirses, three of their raw water light-emitting inhibition rate exceeded50%, the two fur tanning enterprises (W5, W6) effluents are the two highest degree oftoxicity level, virulent level, the light-emitting inhibition rate of luminescent bacteiraeven reached100%; enterpirse W5total toxicity mission load is equivalent to19.85kg, Hg, exceeded the other five samples from10to100times, it is the keytoxicity-emission enterpirse, the average concentration of Zn in its effluent is up to48mg/L, Zn can be considered as a typical pollutant, and there should be asupervision and management on enterpirse W5and Zn. Seven samples from textileenterpirses, only two of their raw water light-emitting inhibition rate exceeded50%,toxicity levels are grade II，the intoxication level. Differences in emission load andthe toxic equivalency of7enterpirse are not significant, monthly toxicity emissionloads are in the range of0.61?5.85kg, not like the tannery wastewater, there is noespecially outstanding toxicity-emission enterprises. The differences in toxicity loadare determined by a number of factors such as production processes, raw mateiralsand wastewater pretreatment processes. |
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