| Dairies, cheese makers, and manufacturers of other dairy products must conform to special regulations. In the USA the regulation body is primarily the US Food and Drug Administration. The standards are set by an industry group called the International Dairymen's Association. The standards require members of the industry to observe strict rules of hygiene and cleanliness, especially in the production areas. Temperature control is essential, whether it be refrigeration control or higher temperature processes, such as in Pasteurization. Large quantities of hot water and cleaning chemicals are needed during cleaning operations. Wastewater from dairies is usually at a high temperature than ambient. For this and other reasons it is allowed to enter the communal drains only after pre-treatment. |
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In a typical dairy incoming milk is filtered, warmed, pasteurized and the cream removed. After this both milk and cream receive treatment according to the requirements of the final product. The machines, instruments and pipes involved in the process are kept clean in a well defined bacteriological cycle that runs automatically.
If this system breaks down the wastewater may receive additional load from food products like fats and proteins. The trend in the dairy industry is towards "Cleaning In Place", or CIP, and away from equipment that needs to be broken down to individual pieces for cleaning. CIP involves use of strong chemicals, including caustic soda, nitric acid, bleaching alkalis such as sodium hypochlorite and hydrogen peroxide. The temperature of these cleaning fluids is 80°C to 85°C (about 180°F). Concentrated chemicals purify the liquid obtained after cleaning so it can be reused at the beginning of the cleaning cycle.
Most dairies pre-treat their wastewater themselves. They make use of the fact that their wastewater is alternately acid and alkali. They pipe it into large tanks where the acids and alkalies neutralizes each other during a complete cycle. When the tank content reaches an appropriate pH value it is discharged into the communal drains. Other materials to treat the wastewater are sometimes added in these neutralizing tanks. Large dairies find it necessary to treat their wastewater to avoid overloading the communal installations.
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