PILOT-SCALE BIOLOGICAL SULFATE AND NITRATE REMOVAL UTILIZING PRODUCERGAS AS ENERGY-SOURCE

The discharge of effluents rich in sulphate and nitrate is of increasi ng concern, as the former leads to mineralisation of surface water, an d the latter is a plant nutrient. A process is described whereby sulph ate is reduced to sulphide under anaerobic conditions with producer ga s as substrate. Sulphide stripped off is then converted to elemental s ulphur by reacting it with biologically produced iron(III). The study consisted of laboratory batch and continuous experiments, as well as p ilot scale studies. Sulphate was reduced to sulphide at a rate of 1.2 g SO4 l(-1) d(-1) with H-2/CO as substrate, and 2.4 g SO4 l(-1) d(-1) with only CO as substrate. Nitrate was converted to ammonia in the ana erobic reactor. Sulphide was removed from 2 000 mg l(-1) (as SO4) to l ess than 90 mg l(-1). The iron(II), produced after reduction of iron(I II) with H2S, was oxidised biologically to iron(III). The volumetric r eaction rate was 5.5 g Fel(-1) d(-1).