Bioluminescent Bacteria-based Water Quality Comprehensive Toxicity Studies

Our country has entered high pollution period at present, the safety situation of water environment is stern. Especially the kinds of contaminants are various, and the toxicology and environmental health thresholds of many contaminants are indeterminate. Only depending on traditional physicochemical properties cannot meet the request of water environment security management anymore. Luminescent bacteria test has been widely applied to many water bodies'toxicity test because of many advantages such as simple detection method, sensitive reaction to toxicities, short test cycle, similar physicochemical property and enzyme system as advanced animals, and reliable data obtained in a short time and so on.Luminescent bacteria test is a sensitive method to detect heavy metals' toxicity. The toxicity order for the heavy metals'detected by Microtox Model500toxicity detector is:Pb> Hg> Zn> Cu> As> Cr> Cd> Ni, and the toxicity result of15mins is more correct than5mins. This paper compared and analyzed the EC10value of the heavy metals with the highest emission concentration in the discharge standard and the V grade surface water environment quality standard, and found that the toxicity standard of Pb,Cu and Zn are stricter, and would be applied as limit emission standard in sensitive water bodies and outlets. The toxicity standard of Cd,As and Ni are more commodious, and could be used as preliminary detection means to help physicochemical analysis to limit this three contaminants'emission. The toxicity standard of Hg and Cr are looser than water quality standard and stricter than discharge standard, and could be used as outlets'limit emission standard.Luminescent test has some disadvantages also, for example, some nutrients in the wastewater have an impact on test results, and make the relative luminous inhibition rate negative, that means promote bio-luminescence. My paper analyzed impact manner and degree of the different nutrients through basic theory test. The results of the experiment indicated that NH4Cl,NaNO3,NaNO2and NaH2PO4could impact the luminous property of the luminescence bacteria, and the influence is different according to the nutrients and concentration, and different in different substrate also. For example, in solo nutrients test, NaNO3, NaNO2and NaH2PO4inhibit luminous property, and the inhibit action enhances with the concentration increase. But NH4Cl, NaNO2and NaH2PO4promote bioluminescence in a wide range of concentration, and this promote action is differ with concentration in the test with ZnSO4as substrate.In the detection of water quality and toxicity of outlets, I found that, they have certain correlation, and the differences exist at the same time. Individual indexes meet the request of the surface water environmental quality, but their toxicity or the joint toxicity with other pollutants is still obvious. In addition, the luminous property of luminescent bacteria can be affected by the nutrients, and the real toxicity detection result would be influenced, so it is very necessary to use different assessment methods to assess water quality or apply different bioassays to test water toxicity. Luminescent bacteria test is more suitable in such outlets'water toxicity test that the concentration of toxic substances such as heavy metals are higher while the nutrients concentration are lower.