Summary:

The two-stage technological system for the treatment of domestic sewage, characterized by an elevated concentration of ammonium nitrogen, consisted of a settling tank and a vertical flow multi-layer filter bed with a sponge-sand filling was analyzed. In the upper part of the filling in the form of spongy polyurethane foams there was the removal of hardly decomposable organic compounds and ammonium nitrogen without the need for additional aeration. In the lower layer of quartz sand, the removal of orthophosphates and pathogenic bacteria took place. After 400 days of operation, multi-layered filter beds achieved high average removal efficiency under variable hydraulic load conditions. The upper 30 cm layer of waste foams used, combined with the 60-cm bottom layer of sand, proved to be very effective in the removal of ammonium nitrogen and organic compounds. The degree of N-NH-4+, CODCr and BOD5 elimination was at 91.6, 77.4 and 91.7% respectively. The 30-cm upper layer of waste foams used combined with the 60-cm lower layer of sand allowed for removal of Escherichia coli in 98.9% on average, whereas coliform bacteria - in 95.0%.