TOC/COD in Cheese Production

Large Cheese producers are looking for a reliable COD measurement to optimise the production of cheese and reduce the surcharges in the wastewater treatment. The idea is to separate the high strength waste from the low strength waste. The low strength waste could be sent directly to the sewer without treatment.

The high strength waste could be diverted to where it could separated and recover the milk products for re-use in production. This idea would potentiallly save thousands of pounds in sewage surcharges and yield more products from the same amount of milk.

There are several things in this process that makes this a difficult measurement. The untreated wastewater in cheese production has very high concentrations of salt, milk fat, raw milk and high levels of suspended solids. In addition the waste stream also has a pH that varies form 4pH to 12pH due to the clean in place (CIP) processes. To make this idea pay off there would have to be a reliable/repeatable systems with minimal maintenance.

It has been determined that a correlation could be made between COD and TOC in this application. It is also possible to use TOC to monitor CBOD (carbonatious Biological Oxygen Demand). The only way to perform the correlation in this application is high temperature combustion in a range of 100 – 10,000mg/l TOC.

The LAR QuickTOC from Metrohm is chosen for a number of reasons, first because of the high concentrations of salt in the process, a system with a large reaction chamber and very high temperature was needed. The LAR reaction chamber is the largest of any on-line TOC system, coupled with the 1200°C furnace made this the ideal choice. At 1200°C Sodium Chloride (salt) passes through the reaction chamber reducing the

maintenance time required.

The second reason is the high concentration of suspended solids in the sample. The QuickTOC using the patented LAR flow sampler can handle high concentration suspended solids in a waste stream without prefiltration. This in conjunction with the large bore tubing used for sample transfer and an innovative method of delivering the sample into the reaction chamber proves to be the lowest maintenance and the most reliable method.