Metrohm has provided large cheese producers with a method of 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 reuse in production.
This would potentially 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 value that varies from four to 12 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 was selected 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, a large on-line TOC system, coupled with the 1,200C furnace, made this an ideal choice.
At 1,200C, sodium chloride (salt) passes through the reaction chamber reducing the maintenance time required.
The second reason for using the Quicktoc is the high concentration of suspended solids in the sample.
The Quicktoc, using the LAR flow sampler, can handle high concentration suspended solids in a waste stream without pre-filtration.
This, in conjunction with the large bore tubing used for sample transfer and a method of delivering the sample into the reaction chamber, has proven to be a low maintenance and reliable method.
