Fluid bed biological nitrification and denitrification in high salinity wastewater

Wastewater from wet lime(stone)-gypsum flue gas desulphurisation (FGD) processes in coal-fired power plants contains nitrate. Where case selective catalytic reduction (SCR) of NO_x is applied the wastewater can also contain ammonia. For the removal of both nitrate and ammonia, biological processes are an attractive option. A bottle-neck for application of biological processes might be the high chloride concentration and relatively high temperature of the wastewater. Therefore research work was performed in fluid-bed reactors at pilot-plant scale for both biological nitrification and denitrification. Biological nitrification was studied up to 34 gCl⁻/l and nitrite was the main product formed. Biological denitrification was effective up to at least 45 gCl⁻/l. Both nitrate and nitrite were removed effectively.