Soap and detergent manufacturing generates waste water that is highly contaminated with organic compounds, significant concentrations of oil, grease, and surfactants. These compounds are a concern for receiving waters due to the formation of foam, and potential toxicity to microbial habitats and wildlife. Process water treatment typically involves dissolved air flotation, chemical coagulation-sedimentation, and biological treatment by activated sludge process.
Due to the hazardous nature of the Dichromate COD Method, and recent restrictions on Dichromate and Mercury, a soap and detergent manufacturing facility in Sri Lanka purchased a PeCOD® Analyzer for effluent monitoring. The Laboratory (L100) PeCOD® Analyzer was used for grab sampling at multiple locations in the plant to obtain rapid and reliable results. Figure 1 compares photoelectrochemical Chemical Oxygen Demand (peCOD) COD and Dichromate COD at the final effluent. Samples were filtered through a 1.5 micron filter prior to analysis, however the suspended particles presented a positive interference with the dichromate method which lead to an over-estimation of COD. Soluble Chemical Oxygen Demand was a more accurate measure of contamination for this sample matrix, based on the ratio of total dissolved and total suspended solids.