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DAIRY INDUSTRY AND WASTE

MANAGMENT 

INTRODUCTION

Milk-producing animals have been domesticated for thousands of years. Initially

they were part of the subsistence farming that nomads engaged in. As the

community moved about the country so did their animals accompany them.

Protecting and feeding the animals were a big part of the symbiotic relationship

between the animal and the herder.

In the more recent past, people in agricultural societies owned dairy animals that

they milked for domestic or local (village) consumption, a typical example of a

cottage industry. The animals might serve multiple purposes (for example, as adraught animal for pulling a plough as a youngster and at the end of its useful life as

meat). In this case the animals were normally milked by hand and the herd size was

quite small so that all of the animals could be milked in less than an hour—about 10

per milker.

With industrialisation and urbanisation the supply of milk became a commercial

industry with specialised breeds of cow being developed for dairy, as distinct from

beef or draught animals. Initially more people were employed as milkers but it soon

turned to mechanisation with machines designed to do the milking.

Historically, the milking and the processing took place close together in space andtime: on a dairy farm.

SOME DAIRY PRODUCTS

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Skim milk 

The product left after the cream is removed is called skim, or skimmed, milk. Reacting

skim milk with rennet or with an acid makes casein curds from the milk solids in skimmilk, with whey as a residual. To make a consumable liquid a portion of cream is

returned to the skim milk to make low fat milk (semi-skimmed) for human consumption.By varying the amount of cream returned, producers can make a variety of low-fat milks

to suit their local market. Other products, such as calcium, vitamin D, and flavouring, arealso added to appeal to consumers.

Casein

Casein is the predominant phosphoprotein found in fresh milk. It has a very wide range of 

uses from being a filler for human foods, such as in ice cream, to the manufacture of  products such as fabric, adhesives, and plastics.

Cheese

Cheese is another product made from milk. Whole milk is reacted to form curds that can

 be compressed, processed and stored to form cheese. In countries where milk is legally

allowed to be processed without  pasteurisation a wide range of cheeses can be madeusing the bacteria naturally in the milk. In most other countries, the range of cheeses is

smaller and the use of artificial cheese curing is greater. Whey is also the byproduct of 

this process.

Whey

In earlier times whey was considered to be a waste product and it was, mostly, fed to pigsas a convenient means of disposal. Beginning about 1950, and mostly since about 1980,

lactose and many other products, mainly food additives, are made from both casein andcheese whey.

Yogurt

Yoghurt (or yogurt) making is a process similar to cheese making, only the process is

arrested before the curd becomes very hard.

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WASTE MANAGEMENT IN DAIRY INDUSTRY

•  

TYPES OF WASTE PRODUCED IN DAIRY INDUSTRY

1) Solid waste

2) Wastewater 

3) Air pollution

1. Solid waste

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Hardly any solid waste is produced by the dairy industry. The main solid wasteproduced by the dairy industry is the sludge resulting from wastewater purification. There are figures available about the amount of sludge production: inaerobic systems the sludge production is about 0.5 kg per kg of removed CODand in anaerobic systems about 0.1 kg per kg of removed COD.

2. Wastewater

Wastewater from dairy industry may originate from the following sources:

Milk receiving 

Wastewater results from tank, truck and storage tank washing, pipe line washingand sanitizing. It contains milk solids, detergents, sanitizers and milk wastes.

Whole milk products

Wastewater is mainly produced during cleaning operations. Especially whendifferent types of product are produced in a specific production unit, clean-upoperations between product changes are necessary. In developing countries, themain problem is pollution through spoilage of milk.

Cheese/Whey/Curd 

Waste results mainly from the production of whey, wash water, curd particles etc.Cottage cheese curd for example is more fragile than rennet curd which is usedfor other types of cheese. Thus the whey and wash water from cottage cheese

may contain appreciably more fine curd particles than that from other cheeses.The amount of fine particles in the wash water increases if mechanical washingprocesses are used.

Butter/Ghee

Butter washing steps produce wash water containing buttermilk.

Skim milk and buttermilk can be used to produce skimmilk powder in the factoryitself or itself or these materials may be shipped to another dairy food plant bytank truck.

The continuous butter production process materially reduces the potential wasteload by eliminating the buttermilk production and the washing steps (Harper et.

al ., 1971).

Milk powder 

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Environmental problems are caused by high energy consumption (= emission of CO2, CO etc.), by cleaning and by emission of fine dust during the dryingprocess.

Condensed milk/Cream/Khoa

Environmental problems related to the production of condensate and khoa aremainly caused by the high energy consumption during the evaporation process.

The main suspended solids mentioned in the literature are coagulated milk andfine particles of cheese curd.

Table 18 gives an overview of the waste production data for the dairy industry.

Reference  (1) (2)

Average Range Average Range

Waste water prod. 2400 100 - 12400 2400 100 - 7100

BOD 6 0.2 - 71.2 5.5 0.2 - 7.1

SS (2.0) (0.06 - 10.8)

Nitrogen (0.15) (0.002 - 0.43)

Phosphorus (0.012) (0.007 - 0.16)

.

Type of product  Wastewater volume BOD

Average Range Average Range

(1)

Milk 3250 100 - 5400 4.2 0.20 - 7.8

Condensed milk 2100 1000 - 3000 7.6 0.20 - 13.3

Butter 800 0.85

Milkpowder 3700 1500 - 5900 2.2 0.02 - 4.6

Cottage cheese 6000 800 - 12400 34.0 1.30 - 71.2

(2)

Milk (canned) 320 - 1870 0.02 - 1.13Condensed milk 800 - 7290 0.17 - 1.48

Butter 800 - 6550 0.19 - 1.91

Natural cheese 200 - 5850 0.30 - 4.04

Cottage cheese 830 - 12540 1.30 - 42

(3)

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Milk 0.2 - 4.0

Cheese 0.9

Butter/milkpowder 0.3

Total 4000

The ranges in Table 19 also indicate that the production of wastewater is highlyinfluenced by management practices (see next paragraph). It is not possible toidentify particular waste producing practices. The way in which the water consuming and operation processes are carried out is indicative of themanagement quality. The major contribution to he waste load comes fromcleaning operations, which take place throughout the production process. Only inthe production process of (hard) cheese, is whey sewering one of the maincontributors to the waste load.

Waste generating processes of major significance include:

- Washing, cleaning and sanitizing of pipelines (metals), pumps, processingequipment, tanks, tank, trucks and filling machines (high N load); 

- Start-up, product change over and shut down of HTST and UHT pasteurizers;

- Breaking down of equipment and breaking of packages resulting in spillingduring filling operations;

- Lubrication of casers, stackers and conveyors

3. Air pollution

In dairy plants air pollution is mainly caused because of the need for energy. Inthe process gasses may be discharged such as CO2, CO, NOx and SO2.

Table 20 gives the emissions into the air as a result of gas- and oil-combustion.No figures are available about the emissions into the air resulting from the use of electricity.

Emissions of CFC’s and NH3 into the air may come about as a result of leakageand stripping of chilling machines when out of use.

Process: Air emission (kg/ton processed milk)

Heating by burning gas or oil CO: 0.03

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CO2: 92

Nox: 0.1

SO2: 0.05

Producing milkpowder Fine dust: 0.39

Cleaning VOC: 0.05

MANAGMENT OF WASETE PRODUCTS

The waste load, expressed as BOD depends to a large degree on the style of management. Table 21 gives an example of the relationship betweenmanagement practices and waste production in terms of BOD and the amount of wastewater produced. The table shows that a large quantity of processed milk

does not necessarily lead to higher waste loads or to higher levels of wastewater production.

Management practices cover a wide range of water consumption and processoperation activities. Well controlled processes reflect good managementqualifications, while bad practices are a reflection of poor management. Table 21shows the relationships. The qualification “fair” signifies that good as well as badpractises occur. With good management practices, values of BOD 1 kg/ton andproduced wastewater below 1 kg/kg may be reached. Poor management willresult in values greater than 3 kg/ton resp. 3 kg/kg.

For the evaluation of management practices, the following indicators are useful:

1. Housekeeping practices;

2. Water control practices; frequency with which hoses and other sources of water are left running when not in actual use;

3. Degree of supervision of operations contributing to either the volume of wastewater or to BOD coefficients;

4. Extent of spillage, pipe-line leaks, valve leaks and pump seals;

5. Extent of carton breakage and product damage in casing, stacking and cooler operations;

6. Practices followed during the handling of whey;

7. Practices followed in handling spilled curd particles during cottage cheesetransfer and/or filling operations

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8. The following of practices that reduce the amount of wash water from cottagecheese or butter operations;

9. Extent to which the plant uses procedures to segregate and recover milk solidsin the form of rinses and/or products from pasteurization start-up and product

change-over;

10. The procedures used to handle returned products;

11. Management attitude towards waste control.

Product  Milkprocessed

BOD Wastewater Management level 

(kg/day) (kg/ton) (kg/kg)

Milk 181,600 0.3 0.4 excellent: 19, 25, 26

227,000 0.2 0.1 excellent: 19, 21, 26,27

113,500 0.7 1.0 good: 8, 10, 18, 20

68,100 7.8 5.2 poor: 1

Cottage cheese 272,400 2.0 0.8 good: 8, 15, 16

135,200 1.3 4.7 good: 8, 17

295100 71 12.4 poor: 2

Milk, cottagecheese

454,000 4.1 1.2 good: 2, 19

211,110 1.8 1.1 good: 21, 22

408,600 3.3 1.1 fair: 8, 9

454,000 8.6 2.0 poor: 8, 3, 4

Milk, butter 135,200 0.9 0.8 good: 23, 24, 28

Whey powder 227,000 0.2 5.9 good-fair: 11, 12, 13

Milk powder, butter 90,800 3.0 2.5 fair: 14, 7, 3

Source: EPA, 1971

SOME TABLES PROVIDED BY CENTRAL POLLUTION

CONTROL BOARD

Table 1 : Number and Locations of Agro-based industries

S. No. IndustrySegment

Total No. of Units

AnnualProcessing/

ProductionCapacity

Locations

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1. Dairy 96 5.5 x 10.66

KilolitreUttar Pradesh,Maharashtra, Gujarat,

Tamil Nadu,

Rajasthan

2. Edible Oils &  

Vanaspati

725 4.5 x 106 tonne Maharashtra, Andhra

Pradesdh, Gujarat, MadhyaPradesh, Uttar Pradesh

3. Fermentation 225 2 X 106 Kilolitre Uttar Pradesh, Maharashtra,

Andhra Pradesdh, MadhyaPradesh, Karnataka, Tamil

Nadu

4. Food & FruitProcessing

204 - Maharashtra, Tamil Nadu,Andhra Pradesdh, Karnataka,

West Bengal

5. Pulp & Paper 89 1 x 106 tonne andrapradesh

T able 2: Water Consumption, Wastewater.Generation and Organic

Pollution Load in Agro-based IndustrieS. No. Industry Specific Water

Consumption(Cubic

meters)

Waste Water

generation,Cubic Metre

Pollution load

(in terms of Kg of BOD)

1. Dairy(Integrated)(per kilo litre of milk)

8.7 6.0 11.0

2. Edible Oils & Vanaspati

(per tonne oil)

3.0 2.0 7.5

3. Fermentation

(i) Brewery(per Kilo litre of beer)

(ii) Distillery(per kilo litre of alcohal)

(iii) Maltry(per tonne of grain)

11.5

130.0

8.5

9.5

90.0

3.5

24.0

600.0

2.0

SUGGESTION FOR DAIRY WASTE CONTROL BY

EPA

1. Instruction of plant personnel concerning the proper operation and handling of dairy processing equipment. Major losses are due to poorly maintainedequipment and to negligence by inadequately trained and insufficientlysupervised personnel.

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2. The carrying out of a study of the plant and the development of a materialbalance to determine where losses occur. Modification and replacement of ill-functioning equipment. Where improper maintenance is the cause of losses, aspecific maintenance programme should be set up.

3. The use of adequate equipment for receiving, cooling, storing and processingof milk, so as to take care of the maximum volume of flush production and of special products. All piping, around storage tanks and other areas, should bechecked on mis-assembly and damage that may lead to leakage.

4. Accurate temperature control on plate, tubular and surface coolers to preventfreeze-on, which may result in loss of products.

5. Elimination of valves on the outlet sides of internal tubular or plate heaters andcoolers and maintenance of plates and gaskets in good repair so as to eliminatewaste due to blown or broken gaskets

6. Installation of suitable liquid level controls with automatic pump stops, alarms,and other devices at all points where overflows could occur (storage tanks,processing tanks, filler bowls etc).

7. Keeping in good order of vats, tanks and pipelines so as to eliminate andreduce to a minimum the number of leaky joints, gaskets, packing glands androtary seals.

8. Proper design and installation of vats and tanks at a level high enough abovethe floor for easy drainage and rinsing if hand cleaned. Tanks should be pitched

to insure draining.

9. Correct connections on plate type heat exchangers so as to avoid milk beingpumped into the water side of the exchanger or water being pumped into the milkside.

10. Provision and use of proper drip shields on surface coolers and fillers so asto avoid that products reach the floor. Avoidance of cheese vats, vat processorsor cooling tanks being overfilled so that no spillage occurs during productagitation. The liquid level in cheese vats should be at least three inches belowthe top-edge of the vat.

11. Avoidance of foaming of fluid dairy products, since foam readily runs over processing vats and other supply bowls and contains large amounts of solids andBOD. The use of air tight separators, proper seals on pumps and proper lineconnections to prevent inflow of air when lines are under partial vacuum, willavoid foam production.

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12. Turning off of water hoses when not in use. Use should be made of hosesequipped with automatic shut-off valves so as to avoid excessive water usage.

REFERENCES

1)CPCB URL

2)EPA URL

3)WIKIPEDIA URL

4)ANSWERS URL

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