Beschreibung:
<jats:p>Increasing alkalinity can improve treatment at the best coagulant dosage.</jats:p><jats:p>Runoff can rapidly change coagulant demand and produce water that is difficult to treat by conventional coagulation processes. In cases in which alkalinity dropped below about 30 mg/L as CaCO<jats:sub>3</jats:sub>, adding supplemental OH<jats:sup>–</jats:sup> (using lime or sodium hydroxide)—and thereby markedly increasing alkalinity before adding coagulant—sharply reduced turbidity after sedimentation but increased coagulant demand. Coagulant demand was a linear function of increased alkalinity and raw water dissolved organic carbon, and it was not strongly influenced by turbidity or calcium concentration below about a pH of 7.8.</jats:p>