Milkhouse Wastewater Treatment
A modern milkhouse with milking machines that can be cleaned in place and drains that send wastewater to a treatment system. Photo courtesy Karl Hakanson.
Milkhouse wastewater treatment systems involve specialized technologies and processes to treat milking-related wastewater on dairy farms for water quality purposes. They are designed to treat milking center wastewater or wash water only, not waste milk from spills, bulk tank failures or directly from cows.
Milking center wastewater and wash water are generated when empty milking equipment and milkhouse floors are cleaned. Besides residual milk, the waste or wash water typically includes cleaning chemicals (detergents, sanitizers and acid rinses), water softener, recharge water and small amounts of manure, bedding, feed, grit and dirt.
The following treatment methods can be used alone or in combination. The first three are for milking center wastewater only; the last two can also be used for the liquid portion of milk-parlor wash water.
Chemical Batch Reactor or Flocculation System: Wastewater is treated with chemicals that coagulate and flocculate solids (form them into masses). The remaining liquid is sent to an infiltration or filtration system.
Bark Bed Method: Wastewater is distributed to an infiltration area covered with 18-24 inches of wood chips or shredded bark.
Aeration and Media Filtration: Wastewater is cycled first through a septic tank, then an aerobic treatment unit or re-circulating media filter, and finally a subsoil infiltration area, reducing the organic compounds in the wastewater to a level similar to that of household septic waste.
Irrigation Method: A primary tank delivers wastewater and/or the liquid portion of wash water to pasture or cropland via a pressurized irrigation system that operates year-round (even during freezing conditions).
Vegetated Treatment Dosing System: Wastewater and/or the liquid portion of wash water undergo primary treatment in two septic tanks, the second of which has a gravity-flow outlet to a separate dosing tank or chamber. The dosing tank uses a pump or other automatic siphoning device to deliver (via perforated plastic pipe) a dose of wastewater/wash water to the upper end of a sloping vegetated buffer once every three days at most.
Combination systems can provide additional benefits and flexibility but can also be more complex, mainly because different systems have different piping and pumping requirements. An example of a combination system might be using a bark bed in winter and irrigation in summer; this makes nutrients from some of the wastewater available for crop production while extending the useful life of the bark bed (because it is not used year-round).
Minnesota feedlot regulations, which mainly govern manure storage and handling, also apply to milkhouse wastes. (Minnesota Rules Chapter 7020 covers all water and/or precipitation that comes into contact with manure, litter, bedding or other material resulting from livestock production.)
Guidance from the USDA's Natural Resources Conservation Service
See contacts for specific programs that fund this practice in the side-by-side payment comparison or contact your local Soil and Water Conservation District