Dairy Facility Wastewater Treatment

How to Prevent Odors in Dairy Wastewater

Facilities that are processing dairy are one of the highest consumers of water in the agricultural industry.  Most of the process and wastewater is generated from the sanitation processes, such as the cleaning of floors, piping and process equipment. Sanitation wastewater is often contaminated with extremely alkaline cleaning chemicals and detergents such as sodium and calcium hypochlorite.  As much as 6 gallons of water is used to produce a single gallon of final product.


Whey, casein proteins, lactose, salts and fats, oils, and greases (FOG) make up the rest of the dairy wastewater.  Milk products will change from the acidic side as the milk sugars ferment to lactic acid.   As you can imagine, the pH of dairy wastewater can vary tremendously based on the proportion of more acidic milk products to more alkaline cleaning chemicals at any given moment.


Wastewater from dairy operations will be high in suspended solids (TSS) and have a BOD5 ranging from 2,000-3,000 mg/L (which is 10 times the strength of domestic wastewater), and in the event of a spillage, the BOD can go even higher.  The high level of suspended solids must be digested or they will settle to the bottom of the lagoon as sludge and create issues later.


One of the main reasons that lagoon/pond wastewater treatment is the most popular choice for dairies is that the long retention times offer the capacity to accept varied levels of influent and shock loads without jeopardizing the quality of treatment.  Batch production in the dairy industry leads to inconsistent flow and shock loadings make it difficult to treat the wastewater without a mechanism of flow equalization in the design.


Is it me, or is it worse this year?


Most of the U.S. experienced an unusually harsh winter this year, which destroyed some of the lagoon’s resident microbial population.  BOD-consuming bacteria are temperature sensitive, with every 10 degree reduction in temperature reducing their activity by half.   Increases in sunlight and the warming air temperatures of spring will cause lagoons to de-stratify.  De-stratifying occurs when the overall temperature equalizes in the lagoon, which will lift the settled solids from the bottom and release the accumulated odorous gases that had been trapped at the bottom.  This process is commonly referred to as lagoon or pond turnover.  When you take into account the exceptionally high BOD and TSS levels found in a typical dairy lagoon – the lagoon turnover can be extremely unpleasant in the Spring and early Summer months.  Establishing a healthy, well established bacterial colony supplied with sufficient dissolved oxygen (DO) is the best preventative treatment. Otherwise, BOD loads get out of control, resulting in permit violations and objectionable odors by facility staff and the surrounding residents.


Zinkan offers a blend of natural biological bacterium cultures to use as part of your daily preventative maintenance program that will help to ensure a well-established bacterial colony and prevent issues such as odors from arising. 


In order to keep BOD levels and odors in check, a wastewater lagoon needs a good mix of beneficial bacterium cultures, proper mixing and aeration. Robust mixing throughout the water column keeps solids in suspension, where they come in contact with BOD-consuming bacteria instead of settling as sludge.


High BOD levels require high DO levels. Without sufficient dissolved oxygen levels, bacteria resort to anaerobic digestion, which is inefficient and creates odors. Fine bubble aeration, with its high surface area bubbles, provides the most efficient oxygenation to support the bacteria and increase consumption rates.