Dairy Water purification Systems are used for the recycling of wastewater produced by dairies. The wastewater or dairy effluent is first passed through an oil removal system and then to a dairy water purification system where it undergoes a process of microfiltration, ultrafiltration, and/or reverse osmosis depending on the type of application. The final product is usually fresh, clean water destined for reuse in the dairy processes. This recycling reduces operational costs by significantly reducing the amount of fresh (potable) quality water that has to be sourced from external sources such as municipal supplies. It also eliminates potentially expensive wastewater treatment processes such as coagulation, sedimentation, and flocculation, which can contribute up to 40% of overall water treatment costs.
The initial purpose of Dairy Water purification Systems was to treat waste to be safely used to irrigate crops or for landscape irrigation purposes. The reuse of dairy wastewater is becoming more widespread in many parts of the world due to concerns about water scarcity, particularly given the high water content in milk and the large volumes produced by modern-day dairies. Freshwater represents, on average more than 90% of all water used by a dairy, and additional required supplies come from groundwater reserves and/or surface runoff captured from rainfall. In comparison, treated wastewater typically comprises only around 10% of all water used by a dairy, whilst treated effluent may only represent 0.5%. As such, any reduction or recycling of this valuable resource is highly beneficial to dairy farms.
Generally speaking, modern wastewater treatment systems are not designed to treat dairy effluents because of their relatively low pollutant concentrations. However, through reuse, onsite, this same effluent can be safely recycled – especially if it undergoes pre or post-treatment to remove possible contaminants that could cause damage to pump seals or foul membranes in membrane systems. For example, using a properly designed and operated grease removal system in combination with a microfiltration membrane can remove >97% of the oil content.
The majority (around 70%) of dairy wastewater treatment in North America is achieved through land application in irrigation ditches or spray irrigation. The land application provides an effective means for using treated wastewater to irrigate crops such as corn and alfalfa when used directly after microfiltration and/or reverse osmosis (RO). However, this method has been criticized due to concerns over high concentrations of phosphorous in effluents leading to eutrophication (i.e., water pollution), particularly during periods of excessive rainfall. Furthermore, modern dairy effluent typically contains elevated levels of nitrogen which results in increased leaching leading to groundwater contamination.
The reuse of dairy effluent for irrigation is becoming more common outside North America, particularly within regions of Australia and New Zealand, where water scarcity is a serious issue given the nature of the dairy industry. In addition, concerns over phosphorous levels have led to its prohibition from use on some crops such as potatoes in Scotland, and thus wastewater treatment systems are being designed accordingly. Wastewater recycling for irrigation usually takes place after further pre or post-treatment depending on local health standards (e.g., removal of BOD during oxygenation tanks) using processes such as aerobic digestion, coagulation/sedimentation/filtration (CSF), and Ultrafiltration (UF).
