High Sulphate-high Cod Concentration Waste Water Anaerobic Treatment Research

Many industrial waste water usually contains sulfate, and most of them higher than 3000mg/L, such as resin producting wastewater, molasses wastewater, pharmaceutical wastewater and so on. This acidic waste water containing sulfate without been treated directly flows into the Waterbody, so that the receiving Waterbody would been acidificated, and endanger aquatic life; cause potentially corrosive, damage the soil structure, decrease the crop yields. The traditional approach is conventional aerobic treatment, avoiding the impact of sulfate. However, the low aerobic capacity to handle high-strength wastewater requires a lot of structure, investment is very large, which is result in waste of resources.This subject selects chemical pus anaerobic biochemical treatment and two anaerobic biochemical treatment to treat high sulfate high COD artificial wastewater (COD/SO₄^2- between 3 and 4), and try the feasibility study to treating pharmacy producing wastewater (COD/SO₄^2-around 3.5). Main research contents and results include the following aspects:(1) In chemical pus anaerobic biochemical treatment test ,the best operation conditions of chemical sulfate removal was found by controling the lime milky dosing and pH, stirring intensity, reaction time, crystallization temperature, Ca-S ratio and other conditions: crystallizating pH value is 7.0, stirring intensity is 60 r/min, the timing of crystallizating reaction is about 1.5 h, crystallization pre-heat temperature is 80℃, Ca-S ratio is 1.0 and add some gypsum crystals as a crystalline core. The COD reduction is 20% 25%, with the SO₄^2- reduced 85%～90% after physico-chemical treatment. The COD/SO₄^2- of wastewater is above 10 after physico-chemical pre-treated, which significantly reduce the adverse effects of anaerobic biological treatment, and the remaining sulfate can be ignored to the anaerobic biochemical treatment effects. The volume load of the next anaerobictreatment is above 9.0kgCOD/(m³·d), and COD removal rate reaches 85%.(2)Two-connected anaerobic biochemical test, The sulfate-resistant activated sludge in the first one was domesticated by gradually raising the influent COD and SO₄^2-volume load. When the reactor operated with the influent sulfate concentration at 3300mg/L, and the system volume load at the 11.9kgCOD/(m³·d) and 3.3kgSO₄^2-/(m³·d), the system sulfate removal rate maintained at over 80%, while COD removal rate is about 30% and the effluent COD/SO₄^2- ratio is above 10.The first anaerobic effluent, where the sulfide concentration is about 320mg/L³55mg/L, was adjusted pH to 6.0, and stripped by nitrogen, then the sulfide concentration reduces to 50mg/L⁷0mg/L.(3) This subject chooses the pharmaceutical wastewater to try, which quatity is similar to the artificial wastewater, and the result is similar too. The research found that, when the COD/SO₄^2-of the influent wastewater is between3 and 4, the volume load of the first anaerobic reactor can be stabilized at 3.3kgSO₄^2-/(m³·d), and the removal rate is about 80%,after 3-month of acclimation, which chose digested sludge as the inoculation sludge.(4) The domestication of SRB should choose the high COD/SO₄^2- ratio(about6.0 8.0) wastewater to start ,which is to resume the activity of inoculated sludge, then use the COD/SO₄^2- ratio between 2.0 3.0 wastewater to enhance the domestication. The volume load can be up to 3.0kg SO₄^2-/(m³·d), and the SO₄^2-removal is about 80% after 2～3months cultring.This paper examined the feasibility of using physico-chemical method plus anaerobic and two connecting anaerobic treatment with different inoculated sludge(digested sludge and granular sludge) to treat high COD high sulfate wastewater(COD/SO₄^2- between 3 and 4), and the conclusions will give some reference for the design, commission and operation of new related projects.