DESIGN CRITERIA FOR THE TREATMENT OF MILKING FACILITY WASTEWATER IN A COLD WEATHER VERTICAL FLOW WETLAND

摘要

Wastewater produced by milking facilities is harmful to the environment if not properly managed but can be costly to treat. A field demonstration of a constructed, vertical flow, subsurface treatment wetland (also known as a vegetated gravel contactor) in mid-Michigan has had continual success for over five years. However, the wetland's design was not optimized. Data from two lab-scale wetlands that simulated the field installation were collected and analyzed in order to create sizing and design criteria. Nutrients, including phosphorus, organic matter, total nitrogen, ammonia, and nitrate, were monitored as well as pH and chemical oxygen demand. The design and sizing are dependent on the configuration of the milking facility, specifically if the wash water contains significant amounts of manure. Nitrogen levels in the manure-contaminated wash water were three times higher than in the manure-free wash water. Although the manure-free and manure-contaminated wash waters had similar levels of carbon, the manure-contaminated wetland had high nitrogen levels. As a result, the acceptable loading differed between the wetlands: the manure-contaminated wash water loading was determined by nitrogen removal, and the manure-free wash water loading was determined by carbon removal. Phosphorus treatment was adequate, but temporary, as the wetland media lost capacity with time.