This document discusses the composition and treatment of dairy sludge. Dairy sludge contains nutrients but also contaminants from processing. It outlines several treatment methods: anaerobic digestion reduces volume while capturing biogas; composting and vermicomposting stabilize the waste; land application spreads nutrients but must consider groundwater; constructed wetlands use natural processes to treat wastewater; and lime stabilization pasteurizes sludge through a chemical reaction. The document provides details on how each treatment method works and its advantages and disadvantages. Overall it provides an overview of generating, treating and disposing of dairy industry waste.

1. Disposal Of Dairy Sludge

2. Composition of dairy sludge
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The dairy industry generate on an average 2.5-3.0 litres of waste
per litre of milk processed.
Generally this sludge contains large quantities of casein, lactose, fat
and inorganic salts, besides detergents, sanitizers etc. used for
washing.
Dairy sludge contain valuable nitrogen and phosphate although the
nutrient content of potassium is low compared with conventional
mineral fertilizers.
Dairy sludge has considerably higher fertilizer value than municipal
sludge.
Cheese factories have 50% more phosphorus than fresh milk
dairies.
Dairy sludge has lower levels of heavy metals or other harmful
components than sewage sludge.

3. The Various Treatments of Dairy
Sludge
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Anaerobic Digestion
Composting (vermicomposting)
Land Spreading
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Sea Disposal
Land Filling
Incineration
Constructed Wetlands
Lime Stabilization

4. Anaerobic Digestion
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Anaerobic digestion is the breakdown of organic material by a
microbial population that lives in an oxygen free environment.
AD treats waste by converting putrid organic materials to carbon
dioxide and methane gas (biogas can be used to produce electrical
power and heat).
The conversion of solids to biogas leads to much smaller quantities
of solids that must be disposed.

5. Advantages and Disadvantages of Anaerobic Digestion
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Advantages
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Reduction in the mass and volume of sludge
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Recovery of biogas
Reduced emissions of greenhouse gases
Disadvantages
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Relatively high capital costs
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Long retention times
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High polluted supernatant

6. Composting and Vermicomposting
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Composting is an accelerated biooxidation of
organic matter passing through a thermophilic
stage (45 to 65°C) where microorganisms
liberate heat, CO2 and water
Vermicomposting is also a biooxidation and
stabilization process of organic matter that, in
contrast to composting, involves the joint action
of earthworms and micro-organisms and does
not involve a thermophilic stage

7. Composting
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Systems of Composting:
-Windrow
-In-vessel
-Continuous vertical reactors
-Horizontal reactors

8. Vermicomposting
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Open systems based on beds or windrows on the
ground containing materials up to 18 inches deep
-this is labour intensive, process organic wastes
slowly
Batch reactors are containers raised on legs above
the ground
-these can use manual loading and collection or
completely automated and hydraulically driven
continuous flow reactors

9. Advantages of Vermicomposting
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Organic wastes can be broken down and fragmented
rapidly by earthworms, resulting in a stable non-toxic
material with good structure which has potentially high
economic value as a soil conditioner for plant growth
Vermicompost is a finely divided peat like materials with
excellent structure, porosity, aeration, drainage and
moisture-holding capacity
Vermicompost supplies a suitable mineral balance &
improves nutrient availability
It provides a great reduction in waste bulk density

10. Landspreading
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The dairy industry consumes 2 to 6m3 of
water per tonne of milk entering the plant
The effluent produced is either spread
directly on agricultural land or treated in an
on-site or local mixed wastewater treatment
plant
Dairy sludge contains high levels of nitrogen,
phosphorus, potassium and organic matter

11. 
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In the context of landspreading, the key
elements of groundwater protection are
-groundwater vulnerability
-groundwater resource underlying the
proposed spreadlands
-response to the perceived risk
Groundwater is most at risk where the
subsoils are absent or thin and in areas of
karstic limestone

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Regionally Important Aquifers must have a
consistent minimum of 2m of soil/subsoil
before landspreading takes place
Locally Important Aquifers & Poor Aquifers
must have a consistent minimum of 1m of
soil/subsoil before landspreading takes place
No landspreading if vulnerability of
groundwater source is classified as Extreme
or High within Inner Protection Area

13. Constructed Wetlands
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Man-made purpose built wetland
Specially designed to treat wastewater by using various
type of ecosystems and substrate to create the right
biological environment.
Built to treat various types of wastewater such as
Farm run-off, Industrial and Domestic wastes.

14. How Constructed Wetland work
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Sedimentation: plant stems reduces the flow of the
water,hence allow sediments in wastewater to be
deposited in the marsh.
Bacterial Action: the leaves draw oxygen through the
roots. Oxygen is released which allows micro-organisms
to thrive in the roots zone of the marsh. All microorganisms feed off the wastewater which plays a major
role in the water cleaning process.

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Filtration: soil, roots zone, plant litter help to filter the
pollutants.
Absorption: Attractive forces between particles in
wastewater draws them together and settles to base of
wetland.
Precipitation: of heavy metals to soil and plant
material.
Decomposition: Organic pollutants in the wastewater
are oxidised and reduced in the treatment process.

16. Advantages & Disadvantages of
Wetlands
Advantages
 Low energy cost.
 Provides growth for plant life.
 High level of treatment is achieved.
Disadvantages
 Large area of land is required
 No design and operating criteria in place.

17. Example of Constructed Wetland

18. Example of Constructed Wetlands in Ireland
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Tara Mines
objective was to treat water containing sulphate and
metals. Reduce sulphate content by 69%,64% lead &
98% Zinc.

19. Lime stablization
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Addition of lime to sludge material,
creates a high pH as a result.
Stabilisation occurs as a result of the
reaction between the lime & water.
Produces a exothermic heat pasteurizes
the sludge.

20. Legislation in regard to Disposal of
Dairy Wastes
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Waste Management Act 1996
Nitrate Directive.
Urban Wastewater Directive.
Sludge use in agriculture
Water Framework Directive.