Treatment of taste and odor material by oxidation and adsorption

Abstract

Massive blooms of blue-green algae in reservoirs produce the musty-earthy taste and odor, which are caused by compounds such as 2-MIB and geosmin. 2-MIB and geosmin are rarely removed by conventional water treatment. Their presence in the drinking water, even at low levels (ng/L), can be detected and it creates consumer complaints. So those concentrations have to be controlled as low as possible in the drinking water. The removals by oxidation (O3, Cl2, ClO2) and adsorption (PAC, filter/adsorber) were studied at laboratory and pilot plant (50 m3/d) to select suitable 2-MIB and geosmin treatment processes. The following conclusions were derived from the study. Both of the threshold odor levels for 2-MIB and geosmin appeared to be 30 ng/L as a consequence of a lab test. For any given PAC dosage in a jar-test, removal efficiencies of 2-MIB and geosmin were increased in proportion to PAC dosage and were independent of their initial concentration in raw water for the tested PAC dosages. In comparison of geosmin with 2-MIB, the adsorption efficiency of geosmin by PAC was superior to that of 2-MIB. The required PAC dosages to control below the threshold odor level were 30 mg/L for geosmin and 50 mg/L for 2-MIB at 100 ng/L of initial concentration. Removal efficiencies of odor materials by Cl2, ClO2, and O3 were very weak under the limited dosage (1.5 mg/L), however increased ozone dosage (3.8 mg O3/L) showed high removal efficiency (84.8% for 2-MIB) at contact time 6.4 minutes. According to the initial concentrations of 2-MIB and geosmin, their removal efficiencies by filter/adsorber differed from 25.7% to 88.4%. For all those, however, remaining concentrations of target materials in finished waters were maintained below 30 ng/L. The longer run-time given for the filter/adsorber, the higher the effluent concentration generated. So it is necessary that the run-time of the filter/adsorber be decreased, when 2-MIB or geosmin occurs in raw water.

Occurrence of odor problems in drinking water of major cities across China

“…Although the results of this study do not represent the highest levels of 2-MIB in each source water, the relatively high detection rates and mean values suggest that 2-MIB may be a serious problem during warm seasons for many surface DWTPs. Among the 111 DWTPs, only five have adopted the ozone-biological activated carbon and powdered activated carbon (PAC) technologies that are effective for removing 2-MIB and geosmin [22][23][24]. So PAC dosing should be applied to those conventional DWTPs whose source water was detected with relatively high levels of 2-MIB.…”

Simultaneous removal of multiple odorants from source water suffering from septic and musty odors: Verification in a full-scale water treatment plant with ozonation

“…Though the O 3 -BAC process has been proved to be effective in the removal of odors (Cook et al, 2001;Newcombe and Cook, 2002), most of the previous studies have mainly been limited to the earthy odorants including 2-MIB and geosmin (Srinivasan and Sorial, 2011;Antonopoulou et al, 2014). Ozonation and associated advanced oxidation processes (O 3 /H 2 O 2 , UV/O 3 , UV/O 3 /H 2 O 2 ) have been proved to be effective for the removal of 2-MIB and geosmin (Atasiet et al, 1999;Ho et al, 2002;Jung et al, 2004;Liang et al, 2007;Andreadakis et al, 2010;Mizuno et al, 2011). It is possible that different types of odorants may coexist in some source waters.…”

Fate of geosmin and 2-methylisoborneol in full-scale water treatment plants

“…These variations in intracellular to extracellular ratio of T&O compounds and their producers influence the treatment performance. This is because, while the removal efficiency of conventional chemical-physical (coagulationflocculation, clarification and filtration) and disinfection treatment processes for the removal of extracellular geosmin and MIB is very low, at less than 20% (Jung et al, 2004;Persson et al, 2007;Newcombe et al, 2010;Srinivasan and Sorial, 2011), their removal within the intact cells as intracellular compounds is highly efficient. Cell damage during the treatment processes including hydraulic stress from pumps or pre-oxidation, and subsequent release of intracellular T&O compounds to cause further treatment issues, is therefore a major risk (Peterson et al, 1995;Schmidt et al, 2002Schmidt et al, , 2009).…”