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Dairy Industry Wastewater Treatment

The wastewater produced in the dairy industry is due to land washing and CIP operations and contains high levels of fat, COD and BOD, as well as suspended particles (TSSs) that are completely refined in the treatment of dairy wastewater. Dairy industry wastewater treatment is carried out in the first stage by physical, chemical methods and secondly by biological methods that depending on the nature and type of products such as milk, yogurt, dough and cheese. The use of anaerobic, aerobic, fat-stuck methods and advanced is the requirement of dusts wastewater treatment.
 
dairy industry wastewater treatment by activated sludge

The Process of Dairy Industry Wastewater Treatmen

The production of wastewater at the dairy plant is due to the washing of equipment, land, machinery and milk lines and other dairy products. Dairy products are a very good environment for the growth of all types of microorganisms, enzymes, and bacteria due to their high levels of fat, carbohydrates and high protein. Thus, washing dishes and dairy machinery is very important.

The amount of wastewater produced in the dairy factory depends greatly on the process of production and the type of products. The most important dairy products are milk, dough, yogurt, butter and cheese. Generally, the raw material of the entire dairy industry is milk and for each ton of raw milk entering the plant, about 4 to about 10 cubic meters of wastewater is produced.

Nowadays, with the use of industrial machinery in the production of dairy products and mechanized production process, the need for washing at the situation or the same CIP equipment is very importance. A proper and principled CIP operation will result in the remaining milk and its products that is entirely out of tanks, cabins, pipes and production and packaging. It also prevents the growth of organisms and bacteria. CIP operations or washing in the site are performed locally with acidic or bases solution. In general, rinsing has the following steps:

1) Rinsing with cold water
2) Rinsing with high-temperature of caustic soda
3) Washing with water
4) Rinsing with nitric acid or chloride
5) Final washing with water

In each dairy factory depending on the nature of the production and type of machinery, a combination of several washing with different materials is used. However, in the design of dairy wastewater treatment, the major amount of sewage is generated by CIP operations.

The Essence of the Dairy Industry Wastewater

The first step in designing and implementing a wastewater treatment unit in the dairy industry is to identify the nature or quality of sewage. Sewage industries dairy is rich in soluble fat and insoluble. The appearance of high amounts of carbohydrates, lipids and proteins is one of the most important features of dairy industry wastewater. The chemical oxygen demand of the COD and its biological BOD are very high and it has a lot of suspension solid particles. Generally, a dairy factory with milk production, yogurt and dough can be considered as the design criterion for the sewage treatment.
 
Parameter Amount
COD 3500-3500 mg/l
BOD  2000-1200 mg/l
TSS 960 mg/l
Oil & Grease 350-200 mg/l
pH 7-10
                                        
As you can see in the analysis, the presence of high levels of fat and TSS in dairy wastewater requires the use of physical and chemical purification methods before using biological methods. Biological purification units such as anaerobic and aerobic units cannot remove high levels of fat from large carbon chains and these fats disrupt the functioning of the system. Therefore, it is necessary to use fat removal methods and TSS in dairy wastewater treatment is essential.

 
  Dairy Industry Wastewater Treatment package

Dairy industry wastewater treatment process

In a simple classification, the wastewater treatment of the dairy industry and the dairy factory consists of two parts which include the removal of the physical fat and solid suspended solids (TSS) and the second part is the biological removal of COD and BOD agents by aerobic and anaerobic units. As it was mentioned, if fat and oil were introduced into the biological units of dairy wastewater treatment, these systems would be in trouble and their function is disrupted. For this purpose, pretreatment methods are used to remove fat. Also due to high concentrations of COD, it is essential to use of several biological units in the form of a series. It should be noted that the maximum COD concentration inputs to aerobic units cannot exceed 2000 mg / lit.

In total, the dairy industry wastewater treatment units are as follows:

1. Uniform equipment and lubricants: Due to the use of acid and bases solutions in the production line, the unit is homogenized and its pH and flow are uniform. In a simple grease, fat and insoluble oil in an insoluble wastewater comes down to the surface due to its lightness and is collected by a raft.

2 Advanced fat degradation units and deleted particles: In these units, soluble fats as well as solid suspended solids are removed physically or chemically. The most important methods are DAF fat burner, coagulation and chemical clotting, electrical coagulation and fat burner is CPI.

3. Anaerobic units for dairy wastewater treatment: Due to the high concentration of COD, it is not possible to enter the dairy factory directly into the aerobic unit because it reduces the efficiency of the unit and increases the amount of sludge produced. Therefore, anaerobic methods based on the production of gas by anaerobic bacteria are used. The most important methods for anaerobic treatment include UASB, UABR, UAFBR, SGSB.

4. Dairy industry sewage treatment of aerobic units: These units are the last step in removing COD and BOD from sewage and using air injection with fine bubbles, a portion of the sewage is sprayed and refined. The most important aerobic units include extensive aeration, climbing MBBR, PBBR or IFAS. At the last stage, the treatment of dairy industry wastewater is deposited in which sludge formed due to high density is deposited and removed from the system.

Wastewater Treatment of Dairy Industries with Specific Products

As we know, the raw material of the whole dairy factory is milk. But very wide variety of products can be produce such as cheeses, cream, pizza cheese, puff powder and ice cream.
It should be noted that the quality of wastewater depends on the type of product produced, as well as on how the CIP is used; thus, all systems of dairy industry wastewater treatment cannot be considered simultaneously.
In the following table, the quality of the dairy industry waste is classified according to the type of products.
Diary product  The concentration of COD (mg/l)
Milk, yogurt and dough 3500-3000
Types co cheese 8000-7000
Ice-cream 1100-1000
Puff powder 7000-6000
 

Applications of Dairy Industry Sewage Treatment

Now, the most important environmental problem in our country is the problem of water scarcity, so the use of renewable resources such as wastewater and its return to the environmental cycle is one of the most urgent and inevitable issues in this regard. Using wastewater treatment system for dairy industry can be used in three ways according to economic resources and production capacities:

1. Use of refined wastewater treatment plant for dairy industry for irrigation, especially farming and obtaining environmental certification.

2. Use of refined wastewater treatment for dairy industry for disposal in surface water or underground waters and returning water to the environmental cycle.

3. Designing and manufacturing dairy wastewater treatment and supplementary units in order to restore water to the beginning of the dairy production line.

 
 Dairy Industry Wastewater Treatment by UASB process

Advantages and Features of the Dairy Industry Wastewater Treatment System

The use of the most up-to-date standards in the design and construction of dairy wastewater treatment systems is the most important feature of these systems in Designing and Engineering Company. Perform accurate analyzes of the dairy factory's raw sewage and calculate and design it with regard to all the parameters of the economy, engineering and obtaining environmental certification are other features of the dairy industry sewage treatment.
The structures used in the treatment of dairy wastewater are based on the type of volume and the size of the metal or concrete.