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

Abstract

Aim of the study The 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 methods The 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 conclusions It 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%.

Polyurethane Foams for Domestic Sewage Treatment

“…However, less rough surface of NF foam was not conducive to proper anchoring of the expanded biofilm and did not prevent its washing out of the carrier. As reported by Dacewicz [39], the excessive biomass accumulated in the lower part of the cylinders ( Figure 6) was washed away after 7 months of research. Moreover, the layer of sand in the third segment was covered with a surface scum that finally caused clogging of the filter.…”

“…The coefficient of grain-size uniformity d 60 /d 10 was 2.5. More detailed description of waste foams is presented in the papers by Dacewicz [ 33 ], Dacewicz and Chmielowski [ 34 ], Dacewicz and Jurik [ 35 ], or Chmielowski et al [ 36 ].…”

“…The fraction of each cross-section occupied by the open space (pores) and the fraction of each cross-section occupied by polyurethane were calculated for each image. The perimeter length per area was multiplied by the unit of thickness and the percentage of the constant cross-sectional area to obtain an estimate of the area per unit of volume [ 39 ].…”

“…Research on the use of brand new foams and waste foams for direct treatment of domestic sewage characterized by an increased content of ammonium nitrogen and a low C/N ratio, was carried out in two vertical flow filters. The structure of a single experimental filter was presented by Dacewicz [ 30 , 33 , 39 , 40 ] and Dacewicz et al [ 35 ]. The filters were operated automatically with a time controller.…”

“…The study investigated raw domestic sewage collected from a public institution located in Kraków. The experiment was conducted for 14 months at variable concentrations of pollutants supplied to the foam-sand filters [ 30 , 39 ]. The average value of COD and ammonium nitrogen in raw sewage amounted to 200 mg O 2 /L and 150 mg/L, respectively, while the C/N ratio ranged from 0.4 to 4.8.…”