Wastewater Treatment Solutions for Dairy Processing Industry

1. Introduction to dairy wastewater

Wastewater generated from dairy processing plants contains very high concentrations of organic pollutants due to its richness in proteins, lactose, fats, and microorganisms. This is a typical type of wastewater in the food industry, usually with BOD and COD concentrations many times higher than those of domestic wastewater. In addition, activities such as equipment washing, tank and pipeline cleaning (CIP) also generate large amounts of wastewater containing cleaning chemicals and unused milk residues.
If not properly treated, dairy wastewater can cause local oxygen depletion in receiving sources such as rivers, lakes, and canals, leading to the degradation of aquatic ecosystems, odor pollution, and serious impacts on surface water and groundwater. Therefore, investing in a standard wastewater treatment system is not only a legal requirement but also a sustainable environmental protection commitment of enterprises.

2. Composition and characteristics of dairy wastewater

2.1 Key pollution parameters

• COD (Chemical Oxygen Demand): ranges from 1,000–5,000 mg/L depending on time, indicating a high level of organic pollution.
• BOD (Biochemical Oxygen Demand): usually accounts for 50–70% of COD, showing good biodegradability but with high loads.
• SS (Suspended Solids): comes from milk residues, fats, and equipment cleaning residues.
• N–NH₄⁺ (Ammonium): originates from the decomposition of proteins, affecting the biological treatment process.
• Total Phosphorus: comes from milk and cleaning agents, posing a risk of eutrophication of water sources.
• Oil and Grease: from dairy products and equipment, which must be removed early to avoid inhibiting microorganisms.

2.2 Sources of wastewater generation

• CIP Washing (Clean-In-Place): an automatic process for cleaning pipelines and tanks – accounts for a large proportion of wastewater and contains cleaning chemicals.
• Floor, equipment, and production area cleaning: carries milk residues, oils, and surfactants.
• Production processes: including mixing, pasteurization, homogenization, packaging – generate surplus milk residues, cooling water, and washing discharges.
• Cooling – heating: generates condensate water and indirect wash water mixed with leaking milk.

3. Effective dairy wastewater treatment technologies

• Collection tank: Removes coarse waste such as plastic packaging, paper, and large milk residues to prevent pipe blockages and equipment damage.
• Grease trap: Wastewater enters the tank, fats and milk scum float to the surface and are skimmed off and collected separately before moving to the next treatment step.
• Equalization tank: Stabilizes flow and pollution concentrations. Aeration is used to prevent anaerobic fermentation causing odors and to partially treat fats and oils.
• Reaction cluster: Wastewater successively passes through reaction tanks 1 and 2 to perform coagulation and flocculation. PAC and polymer chemicals are dosed with agitators to enhance treatment efficiency before the wastewater flows to the DAF tank.
• DAF tank (Dissolved Air Flotation): Floats light flocs and residual oils using dissolved air, then collects them via scraper systems.
• Intermediate tank: Equipped with pH probes, level sensors, and agitators to ensure even mixing of wastewater with pH adjustment chemicals (NaOH, H₂SO₄). Neutralized wastewater is then pumped to the UASB anaerobic tank for further treatment.
• UASB tank (Anaerobic): Effectively reduces BOD, COD (80–95%) while generating methane gas (biogas) that can be utilized for electricity or heating.
• Anoxic tank: Performs denitrification and nitrite removal, releasing nitrogen gas through water and sludge recirculation from subsequent stages. Submersible mixers are installed to ensure thorough mixing, enhancing treatment efficiency before the wastewater flows to the aerobic biological tank.
• Aerotank (Aerobic): Aerobic microorganisms fully oxidize remaining organic matter, forming easily settled activated sludge in the next stage.
• Settling tank: Separates activated sludge from water. A portion of the sludge is recirculated back to the Aerotank, and the excess is further treated. Pathogenic microorganisms are destroyed, ensuring safe effluent that meets QCVN 40:2011/BTNMT standards.
• Disinfection tank: Disinfectants diffuse through cell membranes, destroying intracellular enzymes, killing microorganisms. Post-disinfection water is sent to an intermediate tank for further filtration.
• Intermediate tank + Sand filter: Water from the intermediate tank is pumped through a sand filter system to remove dirt using a filter media layer. Retained residues are backwashed and sent to the sludge holding tank; filtered water meets QCVN standards before being discharged into the general drainage system.
• Sludge holding tank: Sludge from the DAF and biological settling tanks is transferred here for decomposition, increasing solid content, reducing organic matter and sludge volume. The sludge is then pumped through a press and periodically handed over to licensed units for disposal.

Standard wastewater treatment process for the dairy processing industry according to QCVN

4. Advantages of applying Đại Nam’s solution

• Flexible technology by scale: Depending on the capacity and wastewater characteristics of each dairy plant, Đại Nam provides appropriate technological solutions: from small systems <50 m³/day to large scale >500 m³/day. As a result, customers always benefit from optimized investment costs and operational efficiency.
• Optimized power and chemical costs: Technologies such as UASB, MBBR, and improved Aerotank help reduce hydraulic retention time, save aeration energy, and use chemicals efficiently, avoiding waste in coagulation and flocculation.
• Compact design, easy operation: The system is designed in a modular form, saving construction space and suitable for the actual factory layout. The entire treatment process can be automated, reducing dependency on technical labor.