Piggery Wastewater Treatment with Algae-Bacteria Consortia : Pilot-Scale Validation and Techno-Economic Evaluation at Farm Level

The efficiency of an outdoor pilot-scale raceway pond treating the wastewaters generated by a large-scale piggery farm in Northern Italy was evaluated. The biomass productivity over 208 days of experimentation was 10.7±6.5 g TSS·m-2·d-1, and ammoniacal nitrogen, orthophosphate, and COD average removal efficiencies were 90%, 90%, and 59%, respectively. Results were used to perform a comprehensive techno-economic analysis for integrating algae-based processes in farms of different sizes (100–10000 pigs). The amount of N disposed of on agricultural land could be reduced from 91% to 21%, increasing the fraction returned to the atmosphere from 2.4% to 63%, and the fraction in the biomass from 6.2% to 16%. For intensive farming, the release of 110 t N·ha-1·y-1 contained in the digestate could be avoided by including algae-bacteria processes. The biomass production cost was as low as 3.4 €·kg-1, while the cost for nitrogen removal was 7.6 €·kg N-1