Waste Water Treatment, Reuse and Disposal

The Dairy Industry in India has grown to a large size after independence. As we know, dairy industry is water intensive and uses water in the range of 3 to 4 liters for processing one litres of milk. Other food processing plants also use large volumes of water to process food products and to clean plant equipment. This results in generation of large volume of wastewater. This wastewater will be discharged into a big body of surface water. In areas where land is cheap, wastewater can be disposed of in surface irrigation systems. Whatever the means of disposal, wastewater should not affect the ecological balance of the large body of water.

In order to understand the environmental impact of dairy wastewater, it is useful to briefly consider the nature of milk. Milk is a complex biological fluid that consists of water, milk fat, a number of proteins (both in suspension and in solution), milk sugar (lactose) and mineral salts. The wastewater from a dairy plant carry these components and need to be removed before the effluent is disposed off.

To preserve the ecology of the natural water body, wastewater must be treated.Any substance or organism in wastewater that will pose a health risk to the public must be removed, destroyed, or reacted to make it harmless. In the same way, any substance or organism that could pose a threat to the ecosystem must be rendered harmless before the wastewater is introduced into the surface water. Suspended solids and particulates must be removed. Soluble solids must be diluted to a level where they will not hard the ecosystem. Nitrates and phosphates must be removed to stop excessive proliferation of fungi or algae in the water bodies. All natural surface waters are public property, and no one is allowed to pollute our common resources of water. To protect our environment, statutory regulations are made and objective of effluent treatment is to meet these legal requirements of environment protection.

It is imperative to reduce the waste to decrease the load on effluent treatment plant. It also makes a good business sense to reduce waste since waste is nothing but loss of product. Whey is a good example of this change in thinking. Whey disposal was considered as a problem. Now whey processing is considered as an attractive option to obtain high value nutraceutical products.Proper understanding of characteristics of wastewater, physical, chemical and biological unit operations and options available for use of treated waste water is essential for efficient management of dairy effluent system. Depending on these  characteristics, various unit operations will be selected for treatment purposes. We will discuss these aspects in this unit.

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