Most industrial wastewater treatment plants use chemical oxygen demand (COD) or total organic carbon (TOC) rather than the BOD5 test. Due to the length of time required to complete the BOD5 test (five days), BOD results provide historical data only and do not facilitate rapid water quality assessment for optimal process control. The highly variable chemical composition and strength of industrial wastewater requires a much more rapid method for measuring the organic concentration, hence the use of the two hour COD test or the 30 minute TOC analysis. Municipal wastewater plants operate with much greater consistency (less variation) in the strength of the influent organic loading which allows the municipality to wait five days to determine the organic concentration entering the plant.