Dairies, cheese makers and manufacturers of other dairy products are usually subject to special regulations. These oblige them to observe strict rules of hygiene and cleanliness, especially in the production areas. Temperature can be a problem, as some production processes use higher temperatures. Large quantities of hot water and cleaning materials are needed for cleaning. Wastewater from dairies is therefore often at a somewhat high temperature. For this and other reasons it is allowed to enter the communal drains only after pre-treatment.
A typical dairy process operates as follows. Incoming milk is filtered, warmed, pasteurized and decreamed. 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 I a well defined bacteriological cycle that runs automatically. If this system breaks down even partially the wastewater may receive additional load from food products like fats and proteins.
The installation as a whole is "CIP”*, with strong chemicals that include 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 used 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 liquid neutralizes itself during a complete cycle. When the tank content reaches an acceptable pH value it discharges 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.
* cleaning in place |
