Aerobic and media filter treatment systems for milk house wastewater on small dairy operations

Four different aerobic treatment systems were installed downstream of one or more septic tanks to treat milk house wastewater on nine dairy farms with between 41 and 130 cows. Seven farms had pipeline milking systems, one farm had a flat parlor and one had a milking parlor where parlor wash water entered the milk house wastewater treatment system. Two Biomicrobics FAST® systems, two NCS Nibbler® systems, three Pirana® units, and two Reactor Dynamics, Inc. DYNO2® units were installed. System performance was monitored over 1 to 2 years by measuring water use and collecting wastewater samples. Mean water flow rates and wastewater concentrations varied widely. Mean water flow rates through the eight milk houses with pipeline milking systems or a flat parlor ranged from 0.63 to 2.31 m³/d. After primary treatment in septic tanks, influent entering the aerobic treatments systems on the eight farms had average BOD5 concentrations from 296 to 2,650 mg/L and Oils and Grease (O&G) from 58 to 852 mg/L. The aerobic treatment systems on the eight farms had average discharge concentrations for BOD5 and O&G that ranged from 89 to 534 mg/L and 9 to 173 mg/L, respectively. Equipment and installation costs for the eight systems ranged from $6,700 to $16,500. The aerobic treatment units and recirculating media filters used were able to reduce organic levels in milk house wastewater to levels acceptable for final treatment and dispersal in soil treatment units. Small dairy producers with limited options can use aerobic treatment units and recirculating media filters as part of a milk house wastewater treatment system.