Trihalomethane Removal by Coagulation Techniques in a Softening Process

摘要

Experimental work was conducted on both bench and pilot scale at the Daytona Beach Ralph F. Brennan water treatment plant to determine what combinations of coagulants and water pH could best remove trihalomethane precursor materials. The following conditions were evaluated with lime softening: Coagulation with: clay plus a cationic polymer, alum plus a non-ionic polymer, alum plus low pH, alum plus high pH, and experimental polymeric coagulant. A two-stage coagulation process, alum added at low pH (ca. 5.0) followed by settling, softening, and settling again, showed a slight improvement in precursor removal over single-step coagulation and over softening followed by low pH coagulation. Pilot scale performance (i.e. quality of finished water) tended to be poorer than full scale because of no sludge recirculation.