Study On The Biological Sulfate Reduction Of Biological Flue Gas Desulfurization System

The initial conditions of sulfate reduction by anaerobic granule sludge were studied, in additon, kitchen wastes acidification liquid were used as carbon resource on the study of sulfate reduction. Besides, the process of biological sulfate reduction in expanded granular sludge bed (EGSB) in pilot-scale was studied.(1) Sulfate and sulphite from flue gas absorbed liquid were treated with by anaerobic granule sludge; Various factors affecting the removal of sulfate, of which initial concentration of SO₄^2-, initial COD/SO₄^2-, initial pH value, amount of sludge inoculums, and ferrous ion were investigated. The semi-continuous experiment was carried out with optimum conditions as 800 mg/L sulfate, COD/SO₄^2-of 3.0,initial pH value of 7.0, sludge inoculums of 31.10 gVSS/L, and ferrous ion.It indicated that the sulfate removal rate reaches above 70% under the above-mentioned conditions. And also the sulfate can be reduced preferably at low COD/SO₄^2-.(2) Kitchen wastes acidification liquid was used as carbon resource on the study of sulfate reduction with anaerobic granule sludge. It indicated that the accumulated and composition of organic acids might be changed with different initial pH; the accumulated organic acids from kitchen wastes after anaerobic acidification was the highest when pH was 5.0, of which lactic acid was the major composition; the sulfate reduction efficiency was the highest with lactic acid as carbon resource; sulfate reduction efficiency was the highest when kitchen wastes were anaerobic digested for 5 h prior to sulfate reduction, sulfate reduction efficiency improved with the increase of kitchen wastes acidification liquid addition.(3) Biological sulfate reduction was studied in a pilot–scale EGSB reactor. The results indicate that: the sulfate reduction efficiency decreased with the ratio of COD/SO₄^2- decreasing, but the electron flow of SRB increased 29.61%. At the low COD/SO₄^2- pattern, higher vup benefited for reaction, and the operating of reactor was more steady when vup was 4 m/h; the sulfate reduction efficiency and the efficiency of COD removal decreased with the shortening of hydraulic residence time (HRT). Sulfide reduced from sulfate had not restrained this system. The amount of sludge increased from 15 gVSS/L to 25 gVSS/L after the reactor operating process.