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The aim of the study was to assess the possibility of using polyurethane foams (PUF) as a filling of a foam-sand filter to directly treat domestic sewage with increased content of ammonium nitrogen and low organic carbon to nitrogen ratio (C/N). The study compared performance of two types of flexible foams: new, cylinder-shaped material (Novel Foams, NF) and waste, scrap foams (Waste Foams, WF). The foams serving as a filling of two segments of a foam-sand filter were assessed for their hydrophobic and physical properties and were tested for their cell structure, i.e., cell diameter, cell size distribution, porosity, and specific surface area. The study accounted also for selected application-related properties, such as hydrophobicity, water absorption, apparent density, dimensional stability, amount of adsorbed biomass, and the possibility of regeneration. Cell morphology was compared in reference foams, foams after 14 months of the filter operation, and regenerated foams. The experimental outcomes indicated WF as an innovative type of biomass carrier for treating domestic sewage with low C/N ratio. SEM images showed that immobilization of microorganisms in NF and WF matrices involved the formation of multi-cellular structures attached to the inner surface of the polyurethane and attachment of single bacterial cells to the foam surface. The amount of adsorbed biomass confirmed that the foam-sand filter made up of two upper layers of waste foams (with diameters and pore content of 0.50–1.53 mm and 53.0–63.5% respectively) provided highly favorable conditions for the development of active microorganisms.

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Innovative geotextiles built from meandrically arranged thick ropes were produced. For the production of the geotextiles, the strips of woollen nonwoven were used. The segments of the geotextiles were installed on the bank of a drainage ditch. The behaviour of the geotextiles during 1 year was observed. It was demonstrated that the geotextiles installed in the ditch provide immediate protection of the bank. In the soil-covered wool, the process of slow biodegradation was initiated. Because of a low biodegradation rate at the end of the growing season, when the protective vegetation was not well developed, the geotextiles maintained their protective potential. In the following months, the biodegradation led to further destruction of wool fibres. During the biodegradation, the organic compounds rich in nitrogen were released into the soil. In spring, at the beginning of new growing season, the compounds acted as effective fertilizers, promoting the growth of protective vegetation. The vegetation growing on the bank provided an effective protection and took over the protective function of the geotextiles.

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