Whey-ste Not: An Insight into Dairy Farm Waste Operations
Wastewater Holding Tank
Dairy farms are notorious when it comes to wastewater treatment. The high fat, oil, and grease (FOG) content fashioned in the dairy-making process can easily disrupt treatment operations. High concentrations of calcium, being a main ingredient in dairy, can build up on the inner surfaces of pipelines and other equipment, slowing the movement of waste solids, causing increasing changes in the hourly flow, and decreasing the overall efficiency. Generally, processing equipment is cleaned multiple times daily, causing the circadian activity to be grueling and time-consuming. Beyond that, the cleaning chemicals sometimes contain toxic compounds.
Creating a Processing Process
Dairy plant wastes are biodegradable and, after a certain amount of treatment, can be added to the local municipal wastewater system. The multi-step treatment process involves pumping the wastewater into equalizer tanks to reach a certain pH, removing solids, and using either irrigation or biological treatment to create high quality effluent to be disturbed to municipal sewage systems.
Darigold, a dairy plant in Boise, Idaho, had to deal with this problem1 on a large scale in 2009. Adding an expansion for cottage cheese production, the plant had to find a solution to increasing their chemical oxygen demand (COD)2 five-fold. High concentrations of COD translate to a higher difficulty in biologically degrading substances, and in the case of Darigold they needed to build a system that could degrade a considerably larger amount of material. Darigold faced the issue with installing a low-rate anaerobic digester which, over a long retention time and aerobic polishing system, ensured that the FOG in the wastewater and sludge would be properly digested. Darigold’s process removes 96-98% of the COD load, and the wastewater is discharged as a high-quality effluent into the local sewer district while the anaerobic biosolids are used as liquid fertilizer.
No Need to Waste Dairy Waste
For other dairy plants, on-site irrigation3 is a viable option. Usually this option is only available for dairy plants that have a large parcel of land and are not closely surrounded by neighbors. After treatment, the processed wastes can be fed through a pipeline or moved via truck to the fields and distributed so that no ponding takes place on the land. In some cases, dairy plants partner with nearby farmers to dispose of the nutrient-rich waste process on the farmland. Overall, the treatment and removal of dairy waste can be dealt with in a variety of ways depending on available resources.
Reclaimed wastewater can be used as fertilizer