The majority of all biologically caused taste-and-odor outbreaks in drinking water characterized worldwide are caused by microbial production of (−)-geosmin [(−)-(4 S ,4a S ,8a R )-4,8a-dimethyloctahydronaphthalen-4a-ol] and (−)-2-methylisoborneol (2-MIB) {(1 R -exo)-1,2,7,7-tetramethylbicyclo

Biochemical and Ecological Control of Geosmin and 2-Methylisoborneol in Source Waters

A review on advanced oxidation processes for the removal of taste and odor compounds from aqueous media

Problems due to the taste and odor in drinking water are common in treatment facilities around the world. Taste and odor are perceived by the public as the primary indicators of the safely and acceptability of drinking water and are mainly caused by the presence of two semi-volatile compounds − 2-methyl isoborneol (MIB) and geosmin. A review of these two taste and odor causing compounds in drinking water is presented. The sources for the formation of these compounds in water are discussed alongwith the health and regulatory implications. The recent developments in the analysis of MIB/geosmin in water which have allowed for rapid measurements in the nanogram per liter concentrations are also discussed. This review focuses on the relevant treatment alternatives, that are described in detail with emphasis on their respective advantages and problems associated with their implementation in a full-scale facility. Conventional treatment processes in water treatment plants, such as coagulation, sedimentation and chlorination have been found to be ineffective for removal of MIB/geosmin. Studies have shown powdered activated carbon, ozonation and biofiltration to be effective in treatment of these two compounds. Although some of these technologies are more effective and show more promise than the others, much work remains to be done to optimize these technologies so that they can be retrofitted or installed with minimal impact on the overall operation and effectiveness of the treatment system.

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Treatment of taste and odor causing compounds 2-methyl isoborneol and geosmin in drinking water: a critical review.

Recirculation aquaculture systems (RASs) are increasingly considered as production systems of the future with a minimum ecological impact for the production of aquatic food. To maintain a good water quality and to produce quality and healthy fishery products, the systems depend on a diverse microbial community involved in different processes of water purification but also in unwanted effects. The article reviews the present knowledge on microorganisms in RAS, their relative distribution within the system compartments and their role in system performance. The system possesses different microniches in which microorganisms retrieve their preferential conditions for oxygen and nutrients. Ammonia and nitrite are oxidized under aerobic conditions into less toxic compounds. Anaerobic ammonium oxidizers in the biofilm oxidize anaerobically both ammonia and nitrites into less harmful dinitrogen gas. Heterotrophic bacteria mineralize organic matter derived from uneaten feeds, dead bodies and excreta of fish. Under conditions of high organic load and high C/N content, nitrifiers are overgrown by heterotrophs with negative effects to the nitrification process. For not yet understood reasons, the presence of off-flavour-producing microorganisms occurs also in RAS. Microbial management and management of inputs to the systems to prevent the proliferation of pathogens are discussed and possible management techniques of off-flavours are also presented. Research orientations are given to explore further the potential of heterotrophic bacteria in microbial management and intensive aquaculture production in systems other than RAS.

Microorganisms in recirculating aquaculture systems and their management

Assessment of the roles of reactive oxygen species in the UV and visible light photocatalytic degradation of cyanotoxins and water taste and odor compounds using C-TiO2.

Ozonation is an effective means for oxidation of two common earthy/musty odorants (MIB and geosmin) in drinking waters. Second order constants were experimentally determined between the two odorants with ozone and hydroxyl radicals (HO•). Geosmin was oxidized faster than MIB. Under most surface water treatment conditions, hydroxyl radical mediated reactions dominate over ozone reactions during MIB or geosmin oxidation. MIB and geosmin oxidation increases with greater ozone dose, higher pH, higher temperature or addition of H2O2.

Kinetics of MIB and Geosmin Oxidation during Ozonation

High-performance liquid chromatography with fluorescence detection for aqueous analysis of nanogram-level N-nitrosodimethylamine

N-nitrosodimethylamine (NDMA) is known to be highly carcinogenic and is present in drinking water, wastewater, and a variety of foods. Because of its presence in chloraminated water at nanogram per liter concentrations, NDMA has become an emerging issue for reclaimed water which may be used for aquifer recharge or irrigation. This research investigated the fate of NDMA in two soil column systems used to simulate subsurface transport. One column system was operated under aerobic conditions with increasing primary substrate concentration where the biodegradable organic carbon (BDOC) in reclaimed water was used as the primary substrate. The reclaimed water content in the influent was increased from 0 to 25% in the column to increase the BDOC concentration. Negligible NDMA removal was observed at 0% reclaimed water and increasing the primary substrate in the influent resulted in NDMA removal suggesting that biodegradation of NDMA might be a cometabolic process. The effects of redox conditions on NDMA fate was studied by operating a second column system with 100% reclaimed water under anoxic conditions and then changing the conditions to aerobic. It was observed that NDMA removal was similar under both aerobic and anoxic condition, however, much lower effluent concentrations were observed under aerobic conditions. Under anoxic condition, a normalized mass removal rate of 254 ng NDMA/mg DOC was observed which increased to 273-ng NDMA/mg DOC under aerobic conditions. The majority of NDMA and substrate removal occurred in the first of three columns in series column under both aerobic and anoxic conditions. Normalized mass removal rates of NDMA after the first, second, and third columns were 372, 30, and 20 ng NDMA/mg DOC, respectively. Since the majority of dissolved organic carbon was also removed in the first column, NDMA biodegradation was consistent with cometabolic activity. Batch tests verified the biodegradation removal potential of NDMA. Addition of a methylotrophic substrate, methanol and an aromatic substrate, toluene, did not increase NDMA removal.

Effects of Primary Substrate Concentration on NDMA Transport during Simulated Aquifer Recharge

High-performance liquid chromatography (HPLC) was applied for aqueous determination of Nnitrosodimethylamine (NDMA). A fluorescence derivatization technique was adopted to enhance detection using HPLC. Derivatization with dansyl chloride was optimized for excitation and emission wavelengths (340 and 530 nm, respectively), pH (9-12), and concentration of dansyl chloride (500 mg/L). An instrumental detection limit of 0.1 ng NDMA using a fluorescence detector was achieved. The NDMA in aqueous samples was extracted by continuous solid-phase extraction using 1.5 g Ambersorb 572. NDMA detection could be lowered to a concentration of 10 ng/L in both water and wastewater samples. The chromatographic peak for NDMA was distinct without interference from the complex matrix of wastewater effluents. Such selectivity of the HPLC method for NDMA determination is necessary for wastewater samples.

Brijesh Nalinakumari

Papers

Kinetics of MIB and Geosmin Oxidation during Ozonation

High-performance liquid chromatography with fluorescence detection for aqueous analysis of nanogram-level N-nitrosodimethylamine

Effects of Primary Substrate Concentration on NDMA Transport during Simulated Aquifer Recharge

High-Performance Liquid Chromatography for Determination of N-Nitrosodimethylamine in Water