Treatability of U.S. Environmental Protection Agency contaminant candidate list viruses: removal of coxsackievirus and echovirus using enhanced coagulation

Enhanced coagulation was evaluated for removal efficacy of coxsackievirus and echovirus (Contaminant Candidate List [CCL] enteroviruses), poliovirus, four potential surrogate bacteriophages, and dissolved organic carbon (DOC). Viruses and DOC were effectively removed using enhanced coagulation, with removals generally improving as dose increased and pH decreased. Optimal enhanced coagulation conditions of 40 mg/L FeCl3 and pH between 5 and 6.5 resulted in a maximum removal of 3.0 logs of coxsackievirus B6, 1.75 logs of echovirus 12, 2.5 logs of poliovirus 1, 1.8 logs of fr, 1.3 logs of phi-X174, 0.36 logs of MS2, 0.29 logs of PRD1, and 41% DOC. Bacteriophages fr and phi-X174 appear to be the most representative surrogates for the physical removal of coxsackievirus, while MS2 and PRD1 are more conservative. For echovirus, MS2 and PRD1 appearto bethe most appropriate surrogates. The relative removal profiles of the enteroviruses (greatest removal of coxsackievirus followed by poliovirus and then echovirus) suggest that studies of the physical removal of poliovirus may be extended to the CCL enteroviruses. These results contribute to evaluations of the CCL and regulatory status of coxsackievirus and echovirus and aid in building a database of the treatment efficiencies of enteroviruses and their surrogates.

Efficacy of removal of CCL viruses under enhanced coagulation conditions

The focus of coagulation as a water treatment process is shifting to accommodate recent regulatory additions that strive to balance the risks between microbial and chemical contamination of drinking water. In this work, enhanced coagulation using increased ferric chloride dose and/or pH adjustment was evaluated for removal efficacy of viruses on the United States Environmental Protection Agency (USEPA) Contaminant Candidate List (CCL), their surrogates, and dissolved organic carbon (DOC). Jar tests demonstrated that optimal DOC removal was achieved using 40 mg/L FeCl3 at a pH between 5 and 6. Under these conditions, bench-scale testing resulted in a maximum removal of 2.58 log units of adenovirus type 4, 2.50 log units of feline calicivirus, 2.32 log units of MS2, 1.75 log units of PRD1, 1.52 log units of phi-X174, 2.49 log units of fr, and 56% of DOC. The trend in virus removals (MS2 and fr > PRD1 and phi-X174) was consistent between bench- and pilot-scale testing; however, pilot-plant removals exceeded bench-scale removals. Feline calicivirus was more efficiently removed than the bacteriophages, thereby suggesting potential for the bacteriophages as suitable surrogates, with MS2 and fr being more representative and PRD1 and phi-X174 (which were removed to a lesser extent) more conservative. The bacteriophages do not appear to be appropriate surrogates for adenovirus.