| Waste lye containing high sulfide, discharged from petro-chemical enterprises, could do great harm to the environment if not eliminated effectively. However, the treatment costs was high for the conventional treatment methods, for example oxidation process, vapor distillation method, precipitation and traditional biochemical desulfuration process et al. What's worse, it couldn't achieve specified wastewater discharge standard. In this assay, in order to achieve the win-win aim of meeting the standard desired and waste control by waste, physicochemical process and biological treatment methods were conbined to treat the waste lye. Firstly, catalytic oxidation technique was used, producing a large quantity of high thiosulphate wastewater. Then together with high nitrate wastewater, they were treated by biological treatment process. Thiobacillus denitrificans, as a kind of autotrophic facultative bacteria, could oxidize sulphur compounds, such as hydrogen or various reduced sulphur compounds (H2S,S2-, S,S2O32-, S4O62-, and SO32-) into elemental sulfur or sulfate when nitrate was adopted as electron accepter and inorganic carbon compounds (CO2, HCO32-) as their carbon source for growth under anaerobic or anoxic environment.Through this way, nitrate was converted into nitrogen. Based on these special physiological characteristics, anoxic-anoxic-aerobic bio-contact oxidation process was used to treat wastewater containing high-strength thiosulphate and nitrate, for the purpose of providing scientific evidence and reference to projects.The experiment consisted of two phases.In phase one, the test operated at room temperature, and the other was at constant temperature 30℃.The results showed that it was entirely feasible to treat the wastewater containing high-strength thiosulphate and nitrate by anoxic-anoxic-aerobic bio-contact oxidation process, which successfully achieved the aim of removing thiosulfate, nitrate and organic matter simultaneously. What's more, the effluent could satisfy the first-class criteria specified in the Integrated Wastewater Discharge Standard (GB8978-1996).At room temperature(15-28℃),an initial thiosulphate concentration of 2500 mg L, which was also the final simulation level of Na2S2O3-5H2O (desired by practical engineering project),was used to start up the anoxic-anoxic-aerobic bio-contact oxidation reactor. After 24 days, the sludge acclimation was successfully completed. Then the nitrate loading rates was studied by decreasing the hydraulic retention time and increasing the the influent nitrate concentration. The results showed that when the hydraulic retention time was 24h and the influent thiosulphate concentration was 2500 mgNa2S2O3/L, the maximum nitrate loading rates was 0.728 kgNO3-N/m3·d. At the moment, the removal rates of NO3-N was as high as 98%.Through analyzing the operational effects of S/N ratio (S2O32--S/NO3--N), we know when it was between 2.37 and 3.50, the performance of biofilm system was optimal.At constant temperature 30℃by immersing the bio-contact reactor in a constant temperature bath, the effect of the influent ammonia concentration (NH4+-N) and the influent sodium bicarbonate concentration (gNaHCO3/gNO3--N) et al was also studied. The results showed that:(1)The utilization of NH4+-N in anoxic zones fluctuated wildly between 0.23mg/L and 30.09mg/L. By contrast, the utilization rates of NH4+-N in the effluence maintained at the level of higher than 99% because of heterotrophic nitrification in aerobic zones.However, in general, a certain amount of ammonia was still required in the bio-contact oxidation system. (2)It was of optimum at the influent sodium bicarbonate concentration of 1.11～2.41 gNaHCO3/gNO3--N.The microbes clinging to the packing materials were also experimentally studied. Thiobacillus denitrificans was the main bacteria in anoxic phase, which played an major role in the process of wastewater purification. In the aerobic phase, Nematode was the main bacteria. There were also a small amount of Nitrobacteria and a very minor amount of Thiobacillus denitrificans.
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