Predicting DOC removal during enhanced coagulation

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Abstract
Langmuir‐based semiempirical models are used to predict DOC removal during alum and ferric coagulation.The concentration of dissolved organic carbon (DOC) remaining after enhanced coagulation can be predicted with a standard error of about 10 percent or 0.4 mg/L using a new model with inputs of coagulant dosage, coagulation pH, raw water UV254, and raw water DOC. Total organic carbon remaining after coagulation can be predicted with similar accuracy. The model may also be calibrated to a specific site, improving the standard predictive error to 4 percent or 0.27 mg/L (or ±10 percent for 90 percent confidence). Performance differences between equimolar dosages of alum and ferric coagulants in mediating DOC removal may be attributed to (1) equal or better removal of DOC using ferric at very high coagulant dosages, (2) equal or better removal of DOC using alum at lower coagulant dosages, or (3) differing acidity of coagulants, producing a performance advantage for the more acidic coagulant.
Funding Information
  • U.S. Environmental Protection Agency (R82-2462-010)