Design and Evaluation of a Sequential Biological Treatment System for Dairy Parlor Wastewater in Southeastern Louisiana

Milking center wastewater from Louisiana grazing dairy operations is a prime candidate for biological treatments. The objective of this study was to evaluate the design and treatment performance of a replicated multiple stage treatment system. Each Dairy Wastewater Treatment Evaluation System (DWTES) replicate is composed of one anaerobic/facultative lagoon (ANL), one aerobic lagoon (AEL), and three constructed wetlands (WLD) placed in sequence. Two WLD (one in each replicate) were planted (PWLD) with pickerelweed ( Pontederia cordata ) and compared with WLD containing voluntarily grown vegetation/algae (CWLD). Approximately 23,000 L of untreated dairy waste and wash-water was pumped twice daily during milking times. Water quality monitoring began 1 June 2005 and ended 31 May 2006. Sampling was conducted at 0700 h bi-weekly at the terminal end in all stages. Among 20 water quality characteristics studied, efficiency of contaminant removal was highest (removal rates =67%) for COD, TSS, TKN, NH 3 -N, SO 4 , and log of ECC. Relatively low TKN concentration in raw wastewater (110 mg/L) resulted in removal rates higher than 85% in the system's effluent. Escherichia coli count was reduced by 4.5 orders of magnitude from 6.65 log MPN/100 mL at the inlet. Sequential anaerobic-aerobic-wetland wastewater treatment design could be a viable alternative for dairy wastewater contaminant abatement in Louisiana if legislation requires further treatment or if a farmer intends to reduce the amount/concentration of nutrients and/or contaminants that need to be recycled within the dairy operation.