Management of slurry in Gran Canaria with full-scale Natural Treatment Systems for Wastewater (NTSW). One year’s experience in livestock farms.

Abstract

The objective of this work is to describe the performance of three full-scale Natural Treatment Systems for Wastewater (NTSW) operating with livestock farms (1,200-1,500 pigs) during one year. Slurry management is performed within these systems, which are operated under normal conditions of livestock farms, and based on elements such as, first generation biodigesters, subsurface flow constructed wetlands (SSFCW) and facultative ponds. The facilities, located in The Island of Gran Canaria, have allowed us to study viable alternatives of management of effluents from livestock farms with a low-cost based treatment and also to validate these systems according to the removal rates, behavior under changes of load and/or flow, low cost energy and operation. Chemical oxygen demand (COD) removal efficiency obtained was between 70-90%. Likewise, it have been possible to compare the operation of first-generation cascade flow digesters (<76% COD removal) versus complete mixing digesters (<50% COD removal) and facultative ponds when combined with SSFCW, removed a higher percentage of COD compared with ponds (92%). Finally, it has been verified that when the NTSW combine different elements, they have better COD removal and better response to load and/or flow changes.