Feasible Study On Bioluminescence And Nitrification Inhibition For Wastewater Toxicity Test

With more attention paid to the environmental problems and more knowledge about nature and mankind obtained by mankind, usual water-quality indexes can not meet the request of environmental protection anymore. Instead, bioassays are playing a more and more important role in the field of environment research. Although many kinds of bioassays have been used in environmental protection, tests using microorganisms were chosen more often than other kinds of tests because of its advantages such as rapid growing speed, short generation time, lower test cost, similar physicochemical property and enzyme system as advanced animals, and reliable data obtained in a short time. Bioluminescent and nitrification inhibition test have been used widely, but they still have some disadvantages. This paper is aimed at these two commonly used assays for better understanding of them and modifying the nitrification inhibition assay for more convenient procedure and correct results.When using the bioluminescent test (Photobacterium phosphoreum), some nutrients in the wastewater can influence the results, and make the relative luminescence more than 100%. The results of experiment indicated that such nutrients as CH₃COONa,C₆H₁₂O₆ and NH₄Cl could enhance the lighting of the bacteria and make the results lower than the real toxicity; the influence of different nutrients on the different toxicants was different; and the same nutrient with different concentration also had different effects; the results also could be influenced by the different components of nutrient mixture. Besides, NaCl used in the test would not influence the results of the test.When doing nitrification inhibition test with the nitrifying sludge, results of the test could be distorted because of mutual influence of the two strains of nitrobacteria (Nitrosomonas and Nitrobacter). It was proved with experimental data that the Nitrosomanas could be enriched from nitrification sludge as follows: the nitrification sludge from municipal wastewater treatment plant could be used for the inoculation; the substrate contained NH₄Cl 1.15g/L, NaHCO₃ 0.50g/L, K₂HPO₄·3H₂O 0.21g/L, MgSO₄·7H₂O 0.125 g/L, NaCl 0.125g/L, FeSO₄·7H₂O 2.5 mg/L; the cultivation...