Studies on biochemical oxygen demand and chemical oxygen demand at different stages of processing of milk products.

摘要

Contributions of different stages of processing of milk products to the final effluent load (EL) in terms of biochemical oxygen demand (BOD) and chemical oxygen demand (COD) were carried out. Effluent samples at different stages of product manufacturing, such as butter churn, ice cream freezer, curd milk pasteurizer, etc., were collected and analysed for BOD and COD, as well as for fat, protein and ash contents to know which stage of processing elaborates maximum EL and the constituent responsible for increased EL. The BOD and COD values were found high for samples collected from curd sacheting machine (9213 and 14 840 mg/litre, respectively), butter churn (12 740 and 32 288 mg/litre, respectively), ice cream freezer (9234 and 19 220 mg/litre, respectively), and butter melting vat (5726 and 14 830 mg/litre, respectively) from different sections (i.e., curd, butter, ice cream, ghee, respectively). High BOD and COD values of effluent sample collected at butter churn are attributed to higher fat losses (10 120 mg/litre). It is possible to minimize EL by taking some preventive measures at the above stages such as fat recovery from the butter churn, collection of curd milk from the pipeline, and overhead tank from the curd filling machine and using it for bulk selling and complete emptying of ice cream freezer or use of first rinse for ice cream mix preparation, which will not only help in minimizing the product losses but also help in maximum recovery of nutrients and this will reduce the cost of production by reducing the cost of effluent treatment and problems associated with the discharge of effluent..