Options for Handling Milking Center Wastewater?
Dairy Pipeline: February 2000
Gerald M. (Jerry) Jones
Extension Dairy Scientist, Milk Quality and Milking Management
Are there options to handling milking center wastewater? If you are not discharging wastewater directly to liquid waste storage and applying it at rates that do not exceed actively growing crop needs, you may be in violation, regardless of herd size and especially after July 1, 2000. No dairy can discharge wastewater into a stream. Milking center wastewater may contain organic matter, nutrients such as nitrate and phosphate, chemicals, grit, and microorganisms coming from manure, detergents, rinse water, feed, hoof dirt, and waste milk. If not properly managed, it can contaminate groundwater or surface water with ammonia, nitrates, phosphorus, detergents, or disease-causing microorganisms. Herds with 200 dairy cows (which equals 300 animal units), and may be fewer if waste from heifers goes into liquid storage, must have a VPA permit by July 1, 2000, or be subject to a fine. All farms, no matter what size herd, should have a minimum of approximately 120 days storage for liquid waste (parlor wash down, tank and pipeline washwater and preferably lot runoff). Ideally, all farms would have 180 days of storage. If not a liquid manure system, then smaller herds will need something for wastewater. Forget about a septic system; it is not encouraged for wastewater and you probably can not get EPA to permit it! They are not designed for dairy farms and may fail. Organic matter in milk is not degraded in septic tanks. This keeps leach lines saturated and, under an anaerobic environment, milk fat seals the soil and the lines. One option is a shallow concrete settling basin or pond. Approximately 95% of the heavier solids would be trapped and settle. These may need to be cleaned out every month or so to prevent clogging. Liquid waste or wastewater, whether from slurry or parlor waste, should be applied to crops, hay, or pasture at appropriate rates and times. Storage for waste handled as a semi-solid or solid is also required for dairies over 200 cows, not for dairies under 200 cows. But environmentally and economically it would be beneficial to all farmers to have storage. Even the settling basin needs to be big enough to store 120 days worth of wastewater to avoid application during times when the fields are frozen or saturated from rain. New storage systems built for VPA permit holders or dairies receiving cost-share money must meet USDA technical specifications. Other possible options include hauling the wastewater to a treatment plant or to waste storage on another permitted farm. Farms with less than 300 animal units, where they are properly managing their wastes, don't need a permit, but they still cannot discharge into a stream. In managing wastewater, manure and excess feed solids would need to be scrapped from milking center floor before wash down. Water also can be reduced by cut back or eliminating washing of teats and udders at milking. Many herds have gone to doing this combined with predipping, but udders and teats need to be reasonably clean when cows enter the milking parlor and clean and dry when the milking unit is attached. Look into other feeding systems so that concentrate isn't fed in the parlor. And one other thing, sewage from toilets or restrooms must be handled in a separate treatment (septic) system as it may contain disease-causing organisms. It can not be combined with milking center discharge.