Different drinking water production schemes to treat authentic algae-laden source water: Removal of 2-methylisoborneol in different forms

2-Methylisoborneol (2-MIB) is a typical and common off-flavor pollutant in drinking water, which is produced by cyanobacteria and other microorganisms. 2-MIB exists in several forms, such as intracellular, extracellular; and a fraction of 2-MIB is in free form, while the remaining fraction is combined with coexisting organic matters, which complicates the study of 2-MIB removal mechanisms in drinking water production. This research used raw water containing 2-MIB to investigate the effect of combination processes on the removal of 2-MIB (in different forms) and the coexisting organic substances. With conventional processes alone (coagulation, sedimentation and filtration (CSF)), the removal ratio of 2-MIB was 49.4%, which was due to the removal of intracellular 2-MIB. The removal ratio after CSF increased to 80.0–89.4% when powdered activated carbon (PAC) pretreatment (doses of 10, 20, and 50 mg/L) was applied. The fraction of 2-MIB adsorbed by PAC was in the extracellular free form. For preoxidation, the combination of KMnO4 and CSF (KMnO4-CSF) was more effective than H2O2-CSF and NaClO-CSF but less effective in removing dissolved organic carbon (DOC) than the other two methods. H2O2 exhibited the best overall removal of 2-MIB and DOC after CSF. NaClO caused the release of a large amount of intracellular 2-MIB. The removal ratio of 2-MIB by nanofiltration (NF, ∼300 Da) alone was ∼ 87%, and the total removal ratio with PAC, CSF, and NF was as high as 98%. The findings are of particular significance for selecting the combined drinking treatment processes (e.g. PAC-CSF-NF) when odorous compounds are present in high concentrations.