The wastewater produced by Michigan milking facilities is harmful to the environment and costly to treat. A field demonstration of a subsurface treatment wetland in mid-Michigan has had continual success and has proven the capacity of constructed wetlands to effectively and affordably treat milking facility wastewater in colder climates. However, the wetland's design was inefficient and over-sized. Data from two lab-scale wetlands were collected and analyzed in order to create sizing and design criteria for a cost-effective design.As a result, design and sizing criteria were created for two types of wash water: manure contaminated and manure free. Several types of nutrients were monitored, including phosphorus, organic matter, total nitrogen, ammonia, nitrate, and pH. Since nitrogen levels in the manure contaminated wash water was three times larger than that in the manure free wash water, different designs were needed, though both designs were successful at treatment of COD and nitrogen. Phosphorus treatment was adequate, but temporary, as the wetland media lost capacity with time. Clogging potential was also taken into consideration. Although the change in hydraulic conductivity was indiscernible in the lab wetlands, the field site, which has been in operation over five years, was examined and no sign of clogging was found in sampling.
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