Application of a Double Layer Sand Filter With a Pur Foams Layer in the Treatment of Domestic Sewage With an Increased Content of Ammonia Nitrogen

Aim of the studyThe aim of the study was to determine the possibility of using PUR polyurethane foams as an upper layer of sand filter for the treatment of domestic sewage with an elevated concentration of ammonia nitrogen Material and methodsThe working of filtration beds factory-filled with a new stiffened filling or with mechanically ground PUR waste was compared.The efficiency of removal of the septic tank pre-treated organic and biogenic compounds as well as of total suspended solids and pathogenic bacteria from sewage with a hydraulic load varying from 31.8 to 229.2 mm 3 • mm -2 • d -1 was determined. Results and conclusionsIt was shown that after ten months of working, polyurethane and sand filters filled in the upper layer with pieces of polyurethane foam in casings, achieved high efficiency of organic substance removal (BOD 5 reduction by 88% on average and COD Cr by 66%).The use of polyurethane waste in the upper layer of the filter bed made it possible to remove N-NH 4 + ions by an average of 78%, whereas single-layer sand filters proved to be equally effective only in the first two stages of the research.It was found that the additional filling of vertical flow filters in the form of PUR foam clipping placed in casings provided favourable conditions for the development of both heterotrophic bacteria and nitrifying bacteria without the need for additional aeration.The applied upper layer of foams in combination with the lower layer of sand allowed for a very high removal of pathogenic bacteria: Escherichia coli on average 98.8%, while coliform bacteria on average 95.0%.