How is wastewater treated in the dairy industry?
Raw milk is processed into pasteurized and sour milk, yoghurt, hard, soft, and cottage cheese, cream and butter products, ice cream, milk and whey powders, lactose, condensed milk, and various types of desserts.
The waste water in this industry varies significantly due to the different compositions, which are attributed to the product manufactured and the technology used to do so. Dairy effluents are notable for their high organic content, low nutrient value, relatively higher temperatures, wide pH range, and highly disinfected content. To reduce or eliminate the environmental impact of wastewater discharges, special purification and treatment steps are required.
Water is essential in the production of milk. It is used at every stage of the manufacturing process, including cleaning and washing, disinfection, heating and cooling. The large fluctuations in wastewater quality and quantity are very problematic in dairy plants because each milk product requires a separate technological line.
Composition of dairy wastewater
It includes pH, TSS, biological oxygen demand (BOD), COD, total nitrogen (TN), total phosphorus (TP), and fat, oil, and grease (FOG).
Processes of chemical precipitation and coagulation/flocculation
Some physical-chemical-biological processes, such as chemical precipitation and colloidal aggregation via coagulation-flocculation processes, are known to interact. Precipitation and coagulation-flocculation occur concurrently in most processes.
Chemical precipitation is the addition of chemicals to sedimentation to separate dissolved and suspended solids and is used for primary settling facilities. Phosphorus and heavy metal removal can also be accomplished. Many substances, such as alum, ferric sulphate, ferrous sulphate, and others, have been used as precipitants over the years. They are mostly used to treat metallic cations, anions, organic molecules, detergents, and oily emulsions.
Adsorption procedure
Adsorption has been discovered to be an appealing method for removing organic compounds from wastewater. Adsorbents come in a variety of forms, including activated carbon, synthetic polymeric, and silica-based adsorbents. Because of its low cost and ability to adsorb a wide range of organic compounds, activated carbon is most useful. Physical and chemical adsorption are the two types of adsorptions.
Membrane processes
Reverse Osmosis, microfiltration, ultrafiltration, Nanofiltration, dialysis and electro dialysisare all promising membrane processes. Membrane filtration is the removal or separation of particulate and colloidal substances from a liquid using a selective barrier that is typically 0.0001–1.0 m thick.
Several studies focus on membrane operations for the treatment of dairy wastewater. The use of membrane filtration technology provides numerous benefits to the consumers. The membrane technology is a novel non-thermal environmental friendly technology that minimizes the negative effects of temperature rise such as phase change, protein denaturation, and changes in sensory attributes of the product.
Electrochemical process
Electrolysis is the use of an electrical charge to degrade organic or inorganic substances. In an electrolytic cell with an anode and a cathode, oxidation and reduction reactions take place. When an electric current is applied to a cell, negative ions migrate to the anode and positive ions migrate to the cathode, and cations are reduced and anions are oxidized at both electrodes. Dairy treatment methods include electrocoagulation, electro flotation, and anodic oxidation.
Conclusion
Milk and dairy products are among the sources of industrial wastewater that pollute natural aquatic environments significantly. Wastewater is typically produced as a result of the dilution of milk or dairy products. In addition, detergents, disinfectant materials, machine oils, and cleaning cloth fibers are found in wastewater.
When dairy effluent is disposed of without treatment, it may result in adverse effects in fish growth, reproduction, and immunity in water bodies, harmful effect on beneficial microorganisms and plant growth due to decreased micronutrient solubility, serious health and hygiene problems, and eutrophication.
Various systems have been developed in various countries around the world to treat industrial wastewater from milk and dairy products. There are factors such as the initial investment and operating costs in the selection of treatment technologies as well as the presence of appropriate staff for the enterprise, and the need for treatment to ensure the regulations are followed. All of these are important considerations.
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