Kinetic and process considerations on biological reduction of soluble and scarcely soluble sulfates

Discharging of sulfur compounds, which may occur in both liquid and solid p hases, can cause severe environmental pollution problems. Biological sulfat e removal processes are demonstrated to be suitable even for industrial eff luents or industrial derived sulfate-rich solutions. In this work a culture from anaerobic treatment plant has been employed to reduce soluble sulfate (Na2SO4) and scarcely soluble sulfate (CaSO4) using propionate as carbon s ource. The Pr-/SO42- inlet ratio influence on the process was studied anti when a complete selection of sulfate reducing bacteria (SRB) reached a rati o value equal to the stoichiometrical one, it was registered (about 1). A r emoval yield higher than 98% with a hydraulic retention time of 2 days was observed. The increased selection in SRB biomass allowed a sulfate reductio n rate of 0.7 kg(SO4)/m(3) per day which corresponds to a upsilon(max) of 3 .2 g(SO4)/g(vss) per day and to a K-s of 24.5 mg(SO4)/l. (C) 2000 Elsevier Science B.V. All rights reserved.