Application of a double layer sand filter with a pur foam layer in the treatment of domestic sewage with an increased content of ammonium nitrogen

Abstract

Aim of the study: The aim of the work was to determine the possibility of using polyurethane sponges as the upper layer of a sand filter for the treatment of domestic wastewater characterized by elevated concentration of ammonium nitrogen. Material and methods: The work of filters filled with a new stiffened filling and mechanically disintegrated PUR wastes was compared. The efficiency of removal from sewage pre-treated in the septic tank of organic and biogenic compounds, as well as of the total suspended solids and pathogenic bacteria with hydraulic load ranging from 31.8 to 229.2 mm3∙mm-2∙d-1 was determined. Results and conclusions: It was shown that after ten months of operation, filters filled with polyurethane waste, which were additionally placed in casings, achieved a high average efficiency of BOD5 removal at the average level of 88%. The average efficiency of removal of COD for variable hydraulic load was 65.6%. The use of polyurethane wastes allowed the removal of N-NH4+ ions at an average level of 77.6%. It was found that the additional filling of vertical flow filters in the form of PUR foam clipping placed in casings provided favorable conditions for the development of both heterotrophic bacteria and nitrifying bacteria without the need for additional aeration. The applied upper layer of foams combined with the lower layer of sand allowed for very high removal of indicator bacteria: Escherichia coli in 98.8% and coliform bacteria in 95.0%.

Keywords

• waste
• sand filter
• domestic wastewater treatment
• polyurethane foams