Biotransformation of dairy wash water

Wash water from milking parlours has a high BOD and cannot be discharged to a watercourse. The common practice of either storing the wash water together with livestock slurries, or direct low rate irrigation, has certain disadvantages, such as increased costs or causing soil and water pollution. Wash water can be biologically treated in a simple, farmer friendly system, and then recycled for floor washing or discharged into a drain without causing pollution. A six litre laboratory sequencing batch aerobic reactor (SBAR) was used for treatment of milking parlour wash water with 1.6 and 2.7 gBOD(5).L-1 and a between 3.2 and 5.1 gCOD.L-1. The SBAR produced the effluent with 16 to 85 mgBOD(5).L-1 and 3 to 62 mg filtrate BOD5.L-1. Concentrations of ammonium nitrogen and phosphate phosphorus in the effluent reached a maximum of 8 and 32 mg.L-1 respectively. A second treatment stage, using constructed wetland, indicated further removal of nitrogen and a decrease of BOD5 in the final effluent. A farm size treatment system is being commissioned to demonstrate and confirm the laboratory results.