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, NH3-N, SO4, and log of ECC. Relatively low TKN concentration in raw wastewater (110 mg/L) resulted in removal rates higher than 85% in the system\u27s 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. © 2010 American Society of Agricultural and Biological Engineers