Nitrate removal from wastewater generated in wet Flue Gas Desulphurisation Systems (FGD) in coal-fired power generation using the heterotrophic denitrification method

The article presents an assessment of the possibilities of using the heterotrophic denitrification process to remove nitrates from wastewater produced in wet flue gas desulphurisation (FGD) installations and also its optimization in the scope of basic technological parameters. This kind of wastewater is characterized by high salinity (even up to 40,000 g/m³), high temperature (up to 50°C) and low biodegradability, which is expressed by the biochemical oxygen demand (BOD5). The experimental rig consisted of a storage tank and a bioreactor in the form of a bed with an apparatus for measuring basic parameters (temperature, pH, nitrate nitrogen). After an initial adaptation period, a high degree of nitrate nitrogen removal from wastewater (exceeding 95% reduction) was obtained with a reaction time of 180 minutes during the denitrification rate test (NUR). It was also determined that the optimal loading range of the active surface of the bed of 300 m²/m³ should be between 1.5–2.5 gN-NO₃/m²·d. The results of the study show that when the required conditions for the development of microorganisms are provided, it is possible to fully adapt the denitrification biomass to the adverse composition of wastewater from wet FGD unit.