Nick Nicholas is applications engineer and technical director for Gensis Water Technologies. Nicholas can be reached at [email protected].
The dairy industry utilizes significant amounts of water to turn its raw milk into various milk products. To create these dairy products, there is typically about 3 gallons of dairy wastewater per 1 gallon of marketable milk product. This industry is one of the most water intensive in the overall food and beverage sector, both in terms of effluent volume and composition.
Dairy processing facilities have two distinct options: either pretreat and pay discharge fees to release effluent to the municipal sewer system, or operate a decentralized modular treatment plant within the facility. There is no one size fits all solution for dairy wastewater treatment, however, there are several typical system configurations that can be used, and selecting the correct one can be a challenge of he variability of the quality of a dairy facility’s generated wastewater.
This water stream can contain a combination of carbohydrates, proteins and fats based on the milk product to be produced. Typical wastewater parameters in this source water include biological oxygen demand (BOD), total suspended solids (TSS), chemical oxygen demand (COD), color, and fats, oils, and greases. This inconsistent water quality needs to be taken into consideration by the treatment system process to be employed.
Dairy Wastewater Treatment Technologies Deployed
Source water effluent from dairy production operations require specific treatment prior to discharge in order to prevent damage to the environment. This is due in part to the elevated concentration of organic materials such as certain mineral contaminants, fats, oils and greases, proteins and carbohydrates.
Furthermore, cleaning processes generate wastewater containing detergents and cleaning agents that can increase COD and pH. There are different ways to reduce the suspended solids, BOD levels and COD levels, including aerobic biological processes in combination with other treatment methods such as bio-organic liquid flocculants, electrochemical treatment, filtration and disinfection that are utilized within a dairy wastewater treatment plant.
Stages of Dairy Wastewater Treatment
Typically, mechanical treatment such as centrifugal screen filtration is a primary treatment method deployed to filter out suspended solids.
Following this initial mechanical filtration stage, water is typically pumped to an equalization tank which has a typical capacity of four to 12 hours. These tanks are designed to create a more consistent flow rate and water quality. Air is typically supplied to equalization tanks to assist with reducing any odor issues as well as to provide initial oxidation of BOD, COD, TSS and fats, oils and greases.
Secondary treatment is typically accomplished through either sustainable chemical flocculant treatment with clarification or with integration of a coagulation process such as electrocoagulation treatment technologies to achieve the objectives of this stage in the treatment process.
Finally, post clarified effluent is typically treated using filtration systems and disinfection such as Genclean or ultraviolet light as required to meet the discharge approvals of the applicable regulatory agencies or to allow for water reuse protocols to be used for process water in the plant.
Dairy Industry Case Study
A dairy company producing organic milk and flavored milk products wanted to sustainably treat their process waste water in a new production facility to be in compliance with their local regulatory authorities. The levels of BOD, COD, TSS, and trace metals were required to be reduced to allow for sustainable discharge with minimal environmental impact to the municipal sewer system. Below are some of the requirements and their corresponding levels:
- Raw BOD levels: 1500 mg/L
- TSS: 770 mg/L
- pH: 6 to 12
- Color: 60 PCU
Genesis Water Technologies worked with the client’s project manager to essentially devise a split stream in which the water for the process cleaning would be directed to one equalization sump in which pH adjustment would be required and another equalization sump tank which contained the dairy wastewater.
Therefore, the CIP cleaning water from the first sump was pumped by a pump using a VFD to a pH neutralization system with an integration instrumentation to adjust chemical addition to neutralize pH prior to discharge.
The wastewater stream was pumped from the wastewater equalization sump tank to an aerated equalization tank with specialized jet aeration diffusers mounted on the bottom of this tank. The water would be aerated for about three to four hours prior to entering a lamella plate clarifier with integrated flash and flocculation tanks in which an NSF-certified Zeoturb liquid bio-organic flocculant would be introduced.
Post treated clarified water is then sent through a series of Natzeo backwash filtration systems prior to the clean water being pumped into the pH neutralization equalization tank. This treated water of neutral pH reduced the demand of chemical addition in the pH adjustment process, which optimized the systems operating costs.
The system solution was installed by the client with technical assistance provided by Genesis Water Technologies Inc. The optimal removal percentage efficiency results are listed below:
- Treated BOD levels: greater than 85% reduction from inlet water values
- Treated TSS levels: 95% reduction from inlet water values
- Treated Color levels: Colorless
Capital cost and operation cost were minimized in this process as the chemical feed skid had an adjustable rate dosing pump, which was able to be modulated to dose the correct amount of Zeoturb bio-organic liquid flocculant accordingly for this clarification process.
Due to the modulation of the dosage of the Zeoturb chemical feed system, the sludge production was minimized with a higher solids content. The sludge was sent to a sludge tank where a vacuum truck removed the sludge on a scheduled basis.
The chemical feed pump in the pH neutralization system was able to be upgraded to handle higher concentrations of sulfuric acid to reduce the chemical dosing cost to meet pH neutralization requirements.
The system passed inspection by the local regulatory agency and has been operating successfully within the water quality parameters set by the clients permit requirements to allow sustainable discharge of its process wastewater streams to the municipal sewer network with minimal environmental impact.