Pre-treatment and Valorization of Swine Farming Wastewater by Filtration with Arundo Donax Biomass

The growing increase in intensive swine production has huge environmental impacts. In addition to the high organic load and nutrients, swine effluents have large amounts of suspended solids, which hinder and limit several treatment technologies. Solid–liquid separation using filtration or centrifugation is often used as pre-treatment to reduce suspended solids, also reducing other critical parameters. In this work, pig farming effluents were filtrated using a biological filter composed of Arundo donax biomass and the filtrated effluents were characterized to evaluate removal of contaminants. Total suspended solids (TSS) initially at 336.5 mg/L were eliminated, and biomass filtration was also able to remove 48% of chemical oxygen demand (COD), 49% of total nitrogen (TN) and 87% of total phosphorus (TP). The Arundo donax biomass after the effluent filtration showed an increase of ash, carbon and hydrogen contents. Calcium (Ca), magnesium (Mg) and phosphorus (P) were the mineral components strongly reduced in the filtered effluent and concentrated in the filter biomass. Through this pre-treatment, the effluent reached a composition more compatible to valorization by anaerobic digestion or production of microalgae, without requiring extensive dilution. The biomass filter can be often replaced and recycled through composting, to obtain biofertilizers for agronomical applications. This pre-treatment approach promotes circular economy in swine production units.