Biodiesel waste as source of organic carbon for municipal WWTP denitrification

This paper presents the results of experiments to test biodiesel waste (glycerine – g-phase) as an organic carbon source for the removal of nitrate in a WWTP denitrification process. Investigation of g-phase was first centered on g-phase utilization as an external source for denitrification under laboratory conditions and consequently, after positive results from the laboratory investigation, g-phase was applied in the denitrification process in the WWTP Vrútky (35,000 PE). This WWTP had insufficient nitrogen removal via denitrification. Denitrification was insufficient due to an influent with a low BOD5/N ratio (1.7:1) entering into the activated sludge tank. Laboratory experiments and calculations showed that, to reach Ntotal concentration under 10 mg l−1 in effluent, a biodiesel waste dose of 500 kgCOD d−1 was necessary. Glycerol phase (g-phase) dosing into the denitrification tank increased denitrification efficiency by 2.0-5.0mgNO3–Nl-1 per 100 l of g-phase dose into the denitrification tank.