Simulation and optimization of a lamella settler for cattle feedlot wastewater treatment and nutrients recovery. Experimental validation in the field.

Cattle concentrated animal feeding operations (feedlots), whose number has grown considerably in the last years, generate large volumes of wastewaters with a high organic load. The wastewaters are formed by rainfall-runoff of the accumulated manure and may contain hormones and antibiotics, which hampers the use of biological treatments. In this work, the feasibility of continuous separation of the suspended colloidal organic matter and nutrients to clarify the liquid and recover the solid is studied. A flocculation sedimentation system using a decentralized lamella settler is proposed, optimized and further tested in the field. Computational fluid dynamic (CFD) simulation is used to analyze the motion of the liquid and suspended inertial particles representing the formed flocs, for optimizing the settler. The simulations helped in the design of the bench-scale unit tested in the field. The clarified liquid was characterized to analyze its use for fertigation. The proposed treatment allowed excellent removal of organic matter (98% chemical oxygen demand, and almost complete turbidity) and phosphorus (95%). Organic nitrogen was partially removed (~70%) and ammonia nitrogen mostly remained in the liquid. Spectral characterization of the clarified liquid suggests that the remaining organic nitrogen is related to soluble protein-like compounds.