Synthetic dairy wastewater treatment using a new horizontal-flow biofilm reactor

The aim of this study was to develop a simple biological system that would be suitable for the treatment of dairy parlour wash waters. A novel horizontal-flow biofilm system was designed, constructed and tested in the laboratory for organic carbon and nitrogen removal from a synthetic dairy wastewater with average filtered chemical oxygen demand (CODf) of 2947.7 mg L and total nitrogen (TN) of 295.5 mg L. The novel biofilm system consisted of two reactor units one on top of the other. Each reactor unit comprised a stack of horizontal plastic sheets placed above one another that were supported and separated by vertical plastic cone frustums, which were formed in the sheets during manufacture. The wastewater was pumped onto the top sheet of the top reactor unit at hourly intervals for a 5-minute period and flowed over and back along alternate sheets down through the 2 units. The top unit had 8 plastic sheets and 25 mm high frustums to cater for heavy biofilm growth, and the bottom unit had 17 sheets and 11 mm high frustums for thinner biofilm growth. The organic loading of 57 g CODf m(2)center dot d - based on the plan area of the system - was applied to the top reactor unit. When the reactor process reached pseudo steady-state, about 96% CODf, 71% TN and 100% ammonium nitrogen were removed. Low solids production occurred. The system was simple and easy to construct and operate.