Variation and removal of 2-MIB in full-scale treatment plants with source water from Lake Tai, China

Abstract

2-Methylisoborneol (2-MIB) is one of the most common taste and odor (T&O) compounds in waterbodies and causes complaints from drinking water consumers. This is a case study of two water treatment plants taking the raw water from Lake Tai, the third largest lake in China. The relationships between the 2-MIB concentration and algae density, light change and nutrients of the raw water for the most recent four years were comprehensively investigated. The yearly variation pattern of the 2-MIB concentration in the raw water is closely related to the algae cell density. Both values reached peaks in July or August with concentrations as high as ∼500 ng/L and ∼1000 × 104 count/L, respectively. For the diurnal 2-MIB variation, the concentrations increase from 5 to 6 am, reach a peak value at ∼12 p.m., and then gradually decrease and achieve the lowest value at night. These results further confirm that 2-MIB is highly related to algae cell activity (e.g., photosynthesis). In addition, 2-MIB exists both inside and outside algae cells (i.e., intracellular and extracellular or bound and dissolved 2-MIB, respectively), and the percentage of the extracellular/dissolved portion was as high as 60% during the study period. Conventional water treatment processes (usually referrings to coagulation sedimentation and sand filtration, CSF) in WTPs have extremely unstable 2-MIB removal efficiencies (from −20% to >95%), which is mainly related to the existing forms of 2-MIB. The intracellular/bound portion can be effectively removed by CSF, especially sand filtration, while advanced water treatment processes are required to remove the dissolved 2-MIB. An ozone-activated carbon process is recommended, and the 2-MIB removal rate can reach 100%. This research has great theoretical and engineering value for treating water containing T&O compounds.