Degradation Of 2-methylisoborneol Research Articles

Comparative assessment of the degradation of 2-methylisoborneol and geosmin in freshwater using advanced oxidation processes

ABSTRACT Traditional methodologies of conventional drinking water treatment are unable to remove some chemical compounds, such as those that cause odor and taste in drinking water. The present work aims to evaluate the efficiency of advanced oxidations processes, using UV radiation, O3 and O3 + UV in the degradation of geosmin (GSM) and 2-methylisoborneol (2-MIB) in synthetic samples. The efficiency of the processes was monitored by Gas Chromatography coupled with Mass Spectrometry using solid phase microextration technique. Experiments were carried out for 45 min with samplings every 15 min. The degradation results showed that UV radiation alone was not efficient for the degradation of both compounds. The fasted decay was observed by the combined use of O3 and UV with an ozone concentration of 15.84 mg L−1. Under these conditions, the final concentration of GSM was below the limit of quantification, so that approximately 99% of the initial concentration was degraded, while 2-MIB was degraded by 95%. With the same O3 concentration without the use of UV radiation, 63% and 65.7% of MIB and GSM, respectively, were removed. Higher efficiency of the treatment was observed with a higher O3 concentration which allows a shorter reaction time.

Impact of copper sulphate, potassium permanganate, and hydrogen peroxide on Pseudanabaena galeata cell integrity, release and degradation of 2-methylisoborneol

Frequent off-flavor events caused by geosmin and 2-methylisoborneol have caused concern among consumers about the quality of potable water. Pseudanabaena galeata, a filamentous cyanobacterium, is a known producer of 2-methylisoborneol in lakes and reservoirs. The use of algicides to control cyanobacteria must consider the potential release of contaminants into the water. This is the first study to systematically investigate the effectiveness of copper sulphate (CuSO4), potassium permanganate (KMnO4), and hydrogen peroxide (H2O2) on the cell viability and integrity of Pseudanabaena galeata. Following algicide or oxidant treatment, the release and degradation of 2-methylisoborneol was also examined. It is evident that all of these chemicals can decrease Pseudanabaena galeata viability and damage cell membranes and the filamentous Pseudanabaena galeata was more susceptible to treatment by these three algicides than unicellular colonial Microcystis aeruginosa. Of the three compounds used, KMnO4 showed the stronger ability to compromise cell integrity and 5.0 mg/L KMnO4 could induce 91 ± 1.5% lysis of Pseudanabaena galeata within 2 h. It was found that H2O2 had the potential to degrade 2-methylisoborneol with 16.0 ± 0.4% degraded by 20.0 mg/L H2O2 within 8 h. In contrast, 2-methylisoborneol could not be degraded by CuSO4 (dosage: ≤ 1.5 mg/L; reaction time: ≤ 8 h) and KMnO4 (dosage: ≤ 5.0 mg/L; reaction time: ≤ 3 h) basically. Results showed that the oxidation capacity of H2O2 against Pseudanabaena galeata was enhanced under sunlight. The results will help drinking water utilities to better understand the risk of Pseudanabaena galeata lysis and 2-methylisoborneol release during raw water treatment.

Removal of 2-MIB and geosmin by electrogenerated persulfate: Performance, mechanism and pathways

In this study, the degradation of 2-methylisoborneol (2-MIB) and geosmin (GSM) was evaluated by electrochemical oxidation (EO) using boron-doped diamond (BDD) electrode. Both 2-MIB and GSM could be degraded efficiently in sulfate electrolyte compared to inert nitrate or perchlorate electrolytes, implying that in-situ generated persulfate may be responsible for contaminants degradation. The observed linear relationship between 2-MIB (GSM) degradation rates and persulfate generation rates further proved that the in-situ generated persulfate enhanced 2-MIB (GSM) degradation. Moreover, a divided electrolytic cell was employed to investigate the effect of cathodic reactions on contaminants degradation and persulfate generation, and results confirmed that both anodic and cathodic reactions participated in 2-MIB (GSM) degradation. High current density and low solution pH were found to be favorable for 2-MIB and GSM degradation. The degradation intermediates were identified and the possible pathways of 2-MIB and GSM degradation were proposed. This study indicated that the EO process with BDD anode could be considered as a potential alternative for the removal of 2-MIB and GSM.

Degradation of 2-methylisoborneol in drinking water by bauxite catalyzed ozonation

Raw mineral bauxites with and without thermal treatment were used as catalysts in a catalyzed ozonation process for the degradation of a typical taste and odour compound 2-Methylisoborneol (MIB). Compared with the sole ozonation or catalyst adsorption, raw mineral bauxite without further thermal treatment did not exhibit remarkable catalytic activity. But all bauxite catalysts with further thermal treatment exhibited some catalytic activity. Changing of the crystalline form during the thermal treatment played an important role in enhanced ozonation efficiency. Bauxite calcined at 450°C (Bauxite450), which is composed of γ-Al 2 O 3 , exhibited the most remarkable catalytic activity among all the bauxite catalysts with thermal treatment. Catalyzed ozonation with Bauxite450 could remove MIB effectively and reduce MIB concentration to below its taste and odour threshold concentration. The catalyzed ozonation of MIB followed an indirect oxidation mechanism by hydroxyl radical (·OH). This result was confirmed by tert -butyl alcohol inhibiting the catalytic activity and R ct value between the sole ozonation and catalyzed ozonation. As a natural mineral catalyst, bauxite with thermal treatment has supplied an economical and feasible choice for the catalyzed ozonation of MIB in drinking water.

The efficiency and mechanism of γ-alumina catalytic ozonation of 2-methylisoborneol in drinking water

The efficiency and mechanism in degradation of 2-methylisoborneol (MIB) as a taste and odour compound in drinking water were studied under the condition where γ-alumina catalysed ozonation. As a result, γ-alumina can show distinct activity in enhancing the efficiency of ozonation of MIB. Tert-butyl alcohol had a remarkable effect on the removal efficiency of catalytic ozonation of MIB. The surface charge status, surface hydroxyl group status of γ-alumina, and pH values of the solution can be linked together. When the pH value of the solution was near the pHzpc of γ-Al2O3, there was observable activity in the catalysed ozonation process. Rct, which denoted the relative concentration of hydroxyl radical (·OH), was much higher in the catalysed ozonation process than in the ozonation process. This result further illuminated that γ-Al2O3 can promote ozone decomposition to produce ·OH. Finally, the effect of rP/I on catalysed ozone decomposition and ozone decomposition was investigated.

Seasonal occurrence and degradation of 2-methylisoborneol in water supply reservoirs

Methylisoborneol (MIB) and geosmin are cyanobacterial metabolites that occur at nanograms per liter levels in surface water supplies and are responsible for many taste and odor complaints about the aesthetics of drinking water. This study evaluated three water supply reservoirs with bottom-release (hypolimnion) outlet structures in Arizona. MIB concentrations were always higher than geosmin concentrations, but both followed similar seasonal trends. MIB concentrations increased from spring to late summer, and stratified vertically with depth in the water column; the highest concentrations were always in the upper 10 m of the water column. Thermal destratification in the autumn increased MIB concentrations released from the outlet of reservoirs and impacted downstream utilities for several months. By winter of each year MIB concentrations were non-detectable. Mass balance analyses on MIB indicated that in-reservoir reactions were more important in changing MIB concentrations than conservative hydraulic “flushing” of the reservoir. Maximum net loss rates for MIB in the field ( R F , max ) were on the order of 0.23–1.7 ng/L-day, and biodegradation appeared more important than volatilization, photolysis or adsorption. Using lake water in laboratory experiments, bacterial biodegradation rates ( R L ) ranged from 0.5–1 ng/L-day and were comparable to R F , max values. Based upon these rates, MIB concentrations in a reservoir would decrease by approximately 30 ng/L over a period of 1 month. This was the magnitude change in MIB concentrations commonly observed after autumn thermal destratification of the reservoirs.

Degradation of 2-Methylisoborneol by Aquatic Bacteria

2-Methylisoborneol (MIB) is a musty- or muddy-smelling compound which occurs in some natural waters and which is difficult to remove by conventional water treatment methods. Bacterial degradation of MIB was examined in batch culture experiments. Cultures able to metabolize MIB were enriched in a mineral salts medium supplemented with milligram-per-liter levels of the compound and were inoculated with water and sediment samples from reservoirs where MIB is seasonally produced. Bacteria from degrading cultures were isolated on R2A agar and identified as predominantly Pseudomonas spp. Degradation occurred only in cultures consisting of three or more different bacteria. MIB supported growth as the sole added carbon source at 1 to 6.7 mg/liter. MIB was also degraded at microgram-per-liter levels in sterile filtered lake water inoculated with washed bacteria and in synthetic medium supplemented with various sugars or acetate. Complete degradation of MIB took from 5 days to more than 2 weeks. Enrichment with isoborneol, a structural analog of MIB, failed as a preenrichment for MIB degraders. Isoborneol at 20 to 40 mg/liter readily supported bacterial growth, whereas MIB at 12 to 20 mg/liter took months to degrade. The relative recalcitrance of MIB compared with isoborneol may be a result of the additional methyl group in MIB.

Bacterial Degradation of 2-Methylisoborneol

2-Methylisoborneol (MIB) is a musty-odored compound occurring in natural waters that is difficult to remove by conventional water treatment methods. Biodegra-dation may be an alternative for its removal from drinking water. Studies were undertaken to determine the conditions enhancing MIB degradation and to isolate and identify the bacteria responsible. MIB degraders were enriched using mg/l levels of the compound, in a defined mineral medium, inoculated with water and sediment samples from reservoirs where MIB is seasonally produced. Cultures that degraded MIB were isolated and enumerated. Degradation occurred only in mixed cultures. MIB supported growth as sole carbon source at 1-6.7 mg/l. MIB at 10 µg/l was also degraded in sterile lake water inoculated with washed bacteria. The degradation of MIB at both µg/l and mg/l levels took from 7 days to more than 2 weeks.