Starting-up and operating a full-scale activated sludge system for slaughterhouse wastewater

This research was conducted at the Frigofrontera wastewater plant which has screening, de-sanding, a grease trap and sedimentation as its primary treatment system, an activated sludge recirculation reactor for secondary treatment and a descending bed filter for tertiary treatment. Average treated flow is 1.38 L/s; the activated sludge reactor has a 144 m3 volume and 2-day cell retention time. Reactor oxygen levels are guaranteed by injecting air using high-efficiency equipment. Basic wastewater concentration parameters are: 5,242.13 mg / L BOD5; 9,039.75 mg / L COD and 2,972.69 mg / L SS. The treatment plant was started up during February 2006 and has been in constant operation since then. It has achieved 89.73% five-day biological oxygen demand (BOD5), 89.03% chemical oxygen demand (COD) and 94.09% soluble solid (SS) load removal efficiency. The sludge produced by the process is treated by screening where the solids are separated from wastewater. The liquid is returned to the sedimenters and solids are composted.