THE BENEFICIAL USE OF THE COD/TOC RATIO IN THE TREATMENT OF PAPER MANUFACTURING WASTEWATER

It has long been accepted that an empirical relationship exists between BOD, TOC and COD. Although this relationship must be determined for samples from each specific source, once established, wastewater treatment plants often use a correlation between TOC and BOD or COD and BOD for monitoring and process control. The relative ease of TOC and COD testing versus BOD, in addition to the much quicker feedback, allow both to be excellent tools for measuring water quality and overall plant performance.At each individual process within a wastewater treatment plant, specifically a paper manufacturing wastewater treatment plant, the benefit of determining a COD/TOC ratio is becoming evident. While both parameters are useful independently, the ratio of the two values, and the fluctuation of this ratio, is an excellent indicator of the organic loading and the overall health of an individual treatment process, or the system as a whole. This conclusion is supported by two key observations: (1) The two most common types of system upset can only be determined by using COD in conjunction with TOC. Neither parameter independently provides enough information to detect the upset or the source of the upset. And (2) The COD/TOC ratio calculated at the primary clarifier influent, the primary clarifier effluent and at the settling pond correlate more closely to final effluent BOD than either parameter independently. Monitoring each process within the plant, and determining a COD/TOC ratio at each unit process allows an operator to pinpoint potential problems, determine possible causes and adjust treatment in a timely and efficient manner.