General Background

Glanbia Plc, Ballyragget, Co. Kilkenny, Ireland
The traditional methods for measuring dairy effluent strength were Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). The problem with both these methods is that they take significant time to give results. BOD analysis takes 5 days and COD analysis takes a few hours (at best). A further disadvantage of the COD method is that every COD sample results in hazardous waste.

At Glanbia Plc, the need for continuous, online monitoring to control the level of spillage losses in their dairy plant prompted the decision to replace these traditional methods with TOC analysis.

Solution
Six BioTector 970s are currently installed in the Glanbia dairy plant. Three units are used to monitor the fallout from the milk processing plants, one to measure the waste loading of the bio-tower and two are used to monitor the final effluent.

Excellent COD correlations have been obtained from each of the four waste-monitoring BioTectors installed at Glanbia. On average, the COD to TOC correlation factor for untreated dairy waste is 2.99.
To quote Eamon Ryan, Asst. Environmental Manager at Glanbia plc: “Having established the conversion factor to convert TOC to COD, we virtually had on-line COD monitoring and this information could be fed back to a PC in the central control room. Operators would monitor spillage rates and set a target, in line with acceptable losses. At the whey processing plant alone, reductions were above expectations, with an average decrease of 37% being achieved”.

“While the benefits include better solids recovery, energy savings and reduction of waste, it has also relieved pressure on the treatment plant”.