The hydraulic loading of biofilter (HL), temperature and C/N ratio - these factors influence on nitrogen and carbon removal efficiency from airport wastewater containing de-icing agents. The vast area of airports and significant fluctuations in atmospheric precipitation contribute to huge differences in wastewater flows discharged to treatment systems. The aim of the study was to determine the influence of the hydraulic loading on nitrogen and organic compounds removal in biofilters in low temperatures. The novelty of the paper results from low temperatures (0, 4 and 8 °C), specific wastewater and biofilter filling (light weight aggregates prepared from fly ashes from sewage sludge thermal treatment (FASST LWA). The study was divided into four series differing in the hydraulic loading (1.0, 3.0, 5.0, and 10.0 L·m−2·d−1). In each series, biofilters (filled with FASST LWA) were operated at the temperature of 0, 4, 8 °C and 25 °C. The organic carbon to nitrogen ratio was 0.5. The study showed the effective removal of nitrogen at low temperatures, even at high HL. The highest efficiency of nitrogen removal at the temperature of 0 °C (34.93 ± 4.54%) was obtained at 5.0 L·m−2·d−1. The hydraulic loading and temperature affected the efficiency of nitrogen and COD removal. The presented experiment demonstrated that the use of biofilters filled with FASST LWA may offer an effective and sustainable method for the treatment of airport de-icing wastewater.