Aerobic purification of dairy wastewater in continuous regime Part I:: Analysis of the biodegradation process in two reactor configurations

The removal of organics and nitrogen species is postulated in many water quality regulations. In the dairy industry, milk, water and detergents are discharged to wastewater treatment plants as a result of routine operations. In general, the treatment applied has been aerobic. This work is focused on the study of the biodegradation of a synthetic dairy wastewater (4000 mg/L COD, COD/TKN ratio of 4 and pH around 11.5) in continuous regime. Two different reactor systems thermostated at 30degreesC were used. The first system was a single reactor with a working volume of 80 L. The second one was a three-stage reactor cascade with a total working volume of 30 L. In general, high organic matter removals (exceeding 96.8%) were achieved with the two systems. However, the performance of the systems showed much variability in relation to the biomass settling properties, resistance to filtration and tendency to produce viscous bulking and foaming phenomena associated with the specific characteristics of the wastewater and operational conditions. (C) 2004 Elsevier B.V. All rights reserved.