Valorization of waste from dairy farm using low-cost wastewater treatment technologies

Abstract

The main objective of this thesis was to develop a low-cost valorization system to treat and recover nutrients, water and energy from wastewater produced in the Uruguayan dairy farms. The characteristics of the sector in Uruguay refine the technologies to be applied, being the anaerobic digestion the key for the valorization system. The effluent characterization and the study of the codigestion of this wastewater with crude glycerol were done to predict the behaviour in a full-scale system. A lab-scale reactor was used to model the stoichiometry and the kinetic of the anaerobic digestion process. Lowcosts secondary and tertiary treatments were implemented to achieve the fertilization standards and the recycle of the effluent. Consequently, the 52 % of the groundwater for cleaning process in the dairy farm was saved by this recycle. The results obtained in the lab-scale experiments allowed to design a full-scale system for a medium-scale farm. Economical profitability evaluation of the valorization system was done based in the lab-scale results and the full-scale design. The codigestion of the effluent of the farm with crude glycerol increased the energy production in 87 % considering the initial condition. The complete lab-scale system had high removal efficiencies of the influent fluxes in the water line, as 99.1 % of the Chemical Oxygen Demand (COD), 99.9 % of the Total Suspended Solids (TSS), 95.9 % of the Total Nitrogen (TN), 98.1 % of Total Phosphorous (TP) and 4 Log of the Faecal Coliforms (FC). Therefore this low-costs system could be an interesting valorization system for the small- and medium-scale dairy farms.