The rate of yearly increase of dairy production in the US is +2.8%
Dairy processing is usually considered the largest industrial food wastewater source.
The effluents originating from various dairy production technologies are not discharged simultaneously, thus forming a stream with wide qualitative and quantitative variations.
Dairy effluents are distinguished by their relatively increased temperature, high organic content and a wide pH range, which requires special purification in order to eliminate or reduce environmental damage.
Intensive effluent volumetric variations in time are commonly observed. Daily and hourly changes are the consequence of washing the equipment and floors as the final step in every process cycle. Seasonal variations can be attributed to a higher dairy plant load in summer than in winter.
Dairy processing effluents mostly include milk or milk products lost in the technological cycles (spilled milk, spoiled milk, skimmed milk and curd pieces); starter cultures used in manufacturing; by-products of processing operations (whey, milk and whey permeates); contaminants from the washing of milk trucks, tanks, cans, equipment, bottles and floors; reagents applied in CIP procedures, cooling of milk and milk products, for sanitary needs, in equipment damage or operational problems; and various additives introduced in manufacturing.
Typically, dairy wastewater is white in color (whey is yellowish-green) and has an unpleasant odour and turbid character.
Due to their high organic content, represented mainly by rapidly assimilable carbohydrates and slowly degradable proteins and lipids, dairy wastewater is characterised by high BOD and COD values varying from 0.1 to 100 g/L
Dairy manufacturing has a strong impact on the environment, producing large volumes of wastewater with high organic and nutrient loading and extreme pH variations. This requires the application of effective and cheap wastewater treatment procedures which ensure freshwater preservation
Sewage treatment plants are dimensioned to treat a certain quantity of organic substances and also to be able to deal with certain peak loads. However, one organic substance – fat – presents particularly difficult problems. Besides it’s high BOD (cream with 40% fat has a BOD of about 400,000 mg oxygen/L while skim milk has 70,000 mg/L), fat sticks to the walls of the mains system, as well as causing sedimentation problems in the sedimentation tank as it rises to the surface.