Research On Sulfate Wastewater Treatment

In recent years, the air, water and solid waste environment pollution caused bythe imbalance of sulfur gained more and more attention of people. Among them, thetreatment problem about organic wastewater with sulphate of high concentration hasalways diffcult to be solved. The traditional anaerobic treatment process accoreding tothis kind of wastewater could be a hard point because of primary competitive onsubstrate between SRB and MPB, and the inhibition caused by reduction products ofSRB.Desulfuration of organic wastewater containing sulfate was realized bytransforming the sulfate to elementary sulfur in a micro-aerobic condition resultedfrom intermittence aeration, in which fermentative acid ogenic bacteria （FAB）,sulfate-reducing bacteria （SRB） and sulphuroxidising bacteria kept symbiotic in thesame reactor.The results indicated that: through the tests about several important factors whicheffect the activity of SRB, we knew that, when the sulfate volumetric loading came upto4g/L· d, the best reduction rate was79.9%; when the influent water withSO₄^2-concentration1500mg/L, COD/SO₄^2-=1, the highest reduction rate occurred（96.6%）, and too much organic mightn’t obviously improved the reduction effect,instead would affect the microbial populations in the system. When inlet water withSO₄^2-concentration4000mg/L, set up COD/SO₄^2-ratio2:3and1:1, continuousoperating results showed, both the average COD removal rate were approximate, buthigher ratio of COD/SO₄^2-got the higher sulfate reduction effect; From the changes ofORP results within micro-aerobic condition, oxygen is the main factor which effectORP within the operating type of anaerobic sequencing batch was found, however,with continuous operating the system its ORP was also effected by sulfate loading andothers, which means that run in different ways, influence factors to the ORP value insystem are different.The results indicated, for an influent with COD/SO₄^2-=2000/1500mg/L, afterbeing processed in such a system with the aeration switching time of2s/2min andbiochemical time of10h, elemental sulfur concentration of448.2mg/L, the maximumproductivity of elemental sulfur of89.53%was achieved, with the minimum sulfate concentration of72.7mg/L, and a sulfate reduction rate of95.1%.The concentrationof sulfide in the system has little harm to microbe was gained by monitoring dataduring experiments; Under different sulfate volumetric loadings, the biggestproductivity of elemental sulfur are different with its own corresponding oxygen.When inflow with SO₄^2-concentration1500mg/L and2000mg/L respectively, theoxygen the volume of gas were2.0L/h and3.25L/h, the maximum productivity ofelemental sulfur of89.53%,81.82%. Continuous operating showed that theSO₄^2-concentration of effluent was stable, the average removal rate of sulfate reached82.7%. The ratio of different valence sulfur is quite different, the largest proportion iselemental sulfur78%; the smallest was sulfide5%; sulphite and sulphate respectivelyto total sulfur amount of6%and11%. The micro-aerobic process could transfer mostsulfate into elemental sulfur, and transformation ability is good.