Sand filters have been shown to be an economic and effective solution for wastewater treatment in private households, although the removal of phosphorus (P) may be insufficient. However, P removal can be improved by adding a P-adsorbing material, such as biotite, into the sand filters. The physico-chemical characteristics and the microbial quality of the effluents of family-scale sand filters without adsorbing media (SF), sand filters with a biotite layer (B), and sand filters with a modular filter (MB) were followed for one year. Sand filters with a biotite layer displayed the highest capacity to remove nitrogen (N) and biological oxygen demand BOD₇. The efficiency of these filters did not depend on the age of the filter or the season. The P load of the effluent did not differ between sand filters with and without a biotite layer, but the modular sand filter failed to adequately reduce P. The treatment efficiency of sand filters without biotite decreased with increasing age. These private household sand filters can be a good way to treat domestic wastewaters, since these generally comply with the minimum requirements of a Finnish Decree (157/2017). However, enteric viruses (noro- and adenoviruses) were commonly found in the effluents, and the numbers of Escherichia coli were often above 10³ colony forming units (CFU) 100 mL⁻¹ (limit for the the EU Bathing Water Directive 2006/7/EC) for good water quality), signifying a risk of microbial contamination of nearby drinking water wells, as well as bathing and irrigation waters.

High-pressure processing (HPP) is a promising method for preserving food, for example by inactivating pathogens and spoilage microbes. However, there is still a lack of knowledge about the optimal processing parameters for different food products. The aim of this study was to assess the effectiveness of different pressures to inactivate Listeria monocytogenes in cold-smoked and warm-smoked rainbow trout (Oncorhynchus mykiss) ready-to-eat (RTE) fish products. L. monocytogenes ATCC 7644 was inoculated into sliced cold-smoked rainbow trout fillets and whole warm-smoked rainbow trout fillets. The fish samples were pressure-treated at three different pressures, either at 200, 400, or 600 MPa, at 4 ± 1 °C for 3 min in each pressure. Bacterial enumeration of the samples and control samples were analysed 1, 14, and 28 days after the HPP treatment by using serial dilution and the spread plate technique. Based on the study results, the most effective pressure was 600 MPa and the number of L. monocytogenes colonies, both in cold-smoked and in warm-smoked fish samples, was within the official limit of the Regulation (EC) No. 2073/2005 (100 cfu/g) even after 28 days of storage.

Sand filtration is a low-cost and easy solution for household wastewater treatment in areas lacking a centralized sewage system. However, there are only a few studies about the treatment efficiencies of nutrients and enteric microorganisms and their removal or filter mass reuse potential. Sand columns with different phosphorus adsorbents, gypsum, biotite, and peat were tested in laboratory-scale filters at 4 °C to assess their performance in variable conditions and their possibility to increase the efficiency of sand filters. The columns were fed with real municipal wastewater with variable wastewater flow and phosphate load at different stages of the experiments. Phosphate and total nitrogen concentrations were low in the effluent of all columns, and they were mostly rather similar. Waste gypsum was found to greatly increase the conductivity of the effluent. The numbers of enteric microorganisms in the effluents were low, and the used filter masses achieved good hygienic quality after the tests. Phosphate, ammonium, and nitrate concentrations were low in the used masses, evidently since the columns had operated only for 21–30 weeks. Sand filtration proved to be an effective method for wastewater treatment, but changing conditions should be considered when designing these filters. The masses have reuse potential as soil improvement.