Influence of temperature and C/N ratio on nitrifying and denitrifying bacteria of biofilters treating wastewater from de-icing airport runways

One of the key elements in the operational management of airports is effective de-icing of surfaces. The run-off of precipitation water loaded with pollutants from de-icing is a considerable and costly problem. The aim of our research has been to evaluate the applicability of biofilters filled with light expanded clay aggregate (LECA) generated from incineration of sewage sludge and now serving as a matrix for the development of microorganisms. The tested biofilters treated precipitation water polluted with agents used to de-ice airports. The solution was tested on a laboratory scale, in a range of temperatures from 0 to 25°C, and at concentrations of pollutants from airport de-icing expressed as COD and varying from 503.30 to 3827.50 mg O₂·L^-1. The tested filling allowed nitrifying as well as denitrifying bacteria to grow and develop even at low temperatures. Biofilters provide simultaneous nitrification and denitrification, as well as removal of organic compounds, even at 0°C. Biofilters based on the granulate prepared from fly ash from sewage sludge thermal treatment can be a cost-efficient and low-maintenance technology to treat airport surface runoff.