Removal Of Taste Research Articles

Removal of Taste and Odor Compounds from Water: Methods, Mechanism and Prospects

In recent years, taste and odor (T&O) compounds in drinking water are becoming a serious problem, which has brought many challenges to drinking water treatment plants. Due to global concerns about the emergence of T&O compounds, researchers have proposed various water treatment technologies to ensure the quality of drinking water. In this paper, abiotic and biotic methods for the treatment of T&O compounds are reviewed, including process parameters, advantages and disadvantages, removal efficiency and mechanism. Geosmin (GSM) and 2-methylisoborneol (2-MIB) are the most common odorous substances with earthy and musty smells. The chemical and biological methods for the possible degradation pathways of these two compounds are summarized. Furthermore, suggestions and approaches are provided for efficient and safe strategies for T&O compound treatments and their future applications.

Removal of Taste and Odor Causing Compounds from Drinking Water Sources by Peroxone Process: Laboratory and Pilot Scale Studies

ABSTRACT Metabolites of some cyanobacteria and actinomycete species such as geosmin and 2-methylisoborneol (MIB) are generally the sources of earthy and musty odor in surface waters. Peroxone process, that is a combination of ozone (O3) and hydrogen peroxide (H2O2), has the potential to effectively remove these compounds. In this study, the removal of MIB with the peroxone process was investigated at both laboratory- and pilot-scale systems. Different H2O2:O3 ratios with 2 mg/L O3 dosage were applied for determining the optimum ratio of H2O2:O3 for MIB removal. The optimum H2O2:O3 ratio and contact time in the laboratory system were determined as 0.3 and 5 min, respectively, whereas they were 0.5 and 15 min for the pilot system, respectively. Although the performances of both systems were different at similar operating conditions, MIB removal efficiencies over 80% were achieved at the optimum conditions specific to laboratory and pilot scale.

페록손공정에서 수온변화 및 NaOH 주입에 따른 지오스민 및 2-MIB 제거특성 연구

페록손공정에서 수온변화 및 NaOH 주입에 따른 지오스민 및 2-MIB 제거특성 연구

Removal of taste and odor causing compounds by UV/H2O2 treatment: effect of the organic and inorganic water matrix

The occurrence of taste and odor in drinking water is the most common cause of consumer complaints. In this study, the effect of water matrix constituents (i.e. TOC, alkalinity, and NO3-) on the removal of geosmin/2-MIB with UV/H2O2 treatment was assessed. Experiments were carried out with a collimated beam apparatus equipped with a low and a medium-pressure (MP) UV lamp, with UV doses ranging from 300 to 1,200 mJ/cm2 with and without the addition of 4 mg/L H2O2. Results showed that the removal efficiency of geosmin/2-MIB with low pressure UV/H2O2 was inversely proportional to both the concentration of TOC and alkalinity in the synthetic water, as both parameters acted as scavengers of ⋅OH radicals. In the case of geosmin, the addition of 0.8 mg C/L of fulvic acid decreased the removal efficiency by 30%. The application of MPUV/H2O2 to water containing NO3- resulted in formation of NO2- which is also a ⋅OH radical scavenger. The presence of scavengers, in particular natural organic matter, causes significant increase in energy requirement due to the strong absorption properties for UV light and high reactivity with ⋅OH radicals.

Ozone/H2O2 AOP pilot testing at a waterworks with dynamic raw water characteristics in Singapore

In response to the national water strategies and pursuing to close the urban water loop with minimum concern, a proactive approach needs to be considered for future drinking water treatment process in Singapore. Ozone or ozone based advanced oxidation process (AOP) followed by granular activated carbon (GAC) can be one of the best available and cost-effective processes in implementing the national water strategies. Xylem Water Solutions and PUB jointly started a two-year ozone based AOP pilot study at a Waterworks in Singapore. The objective of the project is to study the effectiveness of ozone based AOP on the removal of taste and odour compounds and various emerging organic contaminants. In this paper, the first year results with six selected contaminants show that it is promising to employ ozone based AOP to remove the concerned organic contaminants.

Removal of Taste and Odor Model Compounds (2-MIB and Geosmin) with the NF Membrane

The objectives of this research were to identify seasonal variations of 2-MIB and geosmin which have been one of the biggest problems in the drinking water in the Han River in Korea and to evaluate the performance of the loose and tight NF membranes with respect to 2-MIB and geosmin rejection. Two kinds of NF membranes with different NaCl rejections were compared using a batch stirred cell to determine the membrane flux and the solute rejection for feed water. The results of the analysis of the occurrence characteristics of 2-MIB and geosmin, the major taste and odor material in the Han River water system show that the occurrence of 2-MIB continued from winter to spring (January–May) and through autumn (August–September), whereas geosmin occurred for about one to two weeks from summer to autumn (July–September) and spring (March–April). Following the rejection test of the taste and odor using the loose and tight NF membranes, it appeared that the two showed high rejection rates of 98% and above, irrespective of their concentration factor. The rejection of 2-MIB and geosmin increased with increasing shear rates for all of the NF membranes tested. Hydrodynamic operating conditions greatly affect the rejection of solutes in NF treatment. The rejection of taste odor compounds should increase with increased shear rates near the membrane surface. This suggests that the rejection will be further improved using dynamic membrane filtration.

Removal of taste and odour from potable water by ozone and Powdered Activated Carbon (PAC)

The paper presents experimental evidence that selection and addition of an appropriate type of Powdered Activated Carbon (PAC) and alternatively or in combination ozonation of the water can be very effective in removal of both geosmin and 2-MIB from surface waters intended for supplying potable water. According to the experimental results, it was shown that the adsorptive capacity of the carbon is about five times greater in the case of geosmin when compared with 2-MIB. Furthermore, addition of ozone at doses in the range 1-3 mg/L for a period of 5-10 min can reduce odour to levels below threshold odour value.

Photocatalytic removal of taste and odour compounds for drinking water treatment

Photocatalytic degradation of geosmin and 2-methylisoborneol (MIB), which are two taste and odour compounds commonly found in drinking water supply sources, was investigated using an immobilised TiO2 photoreactor. It was found that the degradation of geosmin and MIB followed similar pseudo-first-order kinetics with reaction rate constants being approximately 0.025 min−1 for typical geosmin and MIB concentrations of 250 and 500 ng/L. The normalised formal quantum efficiency was calculated to be in the range of 162–182 L/mol. Influence of additives (i.e. sodium bicarbonate and alcohols) on the degradation process was also investigated. It was found that there was a small reduction in the degradation rate constants of geosmin and MIB with increasing sodium bicarbonate concentration. At 50 mg/L sodium bicarbonate the degradation rate constants decreased by approximately 5%. Similarly, for methanol and ethanol concentrations up to 35 and 50 mg/L, respectively, these constants were found to also decrease. While addition of sodium bicarbonate and alcohols was seen to have relatively small negative effects on the photocatalytic degradation performance, the magnitude of their influence was consistent with the hypothesis that the degradation mechanism of geosmin and MIB was predominately that of attack involving HO∙ radicals.

Removal of taste and odor model compound (2,4,6-trichloroanisole) by tight ultrafiltration membranes

Taste and odor causing organic compounds of concern to the general public are produced at low concentrations (i.e., ng/L) in surface water. Bench-scale membrane filtration experiments were conducted with 2,4,6-trichloroanisole (TCA), which is of special interest as a model compound due to its very low odor threshold level (i.e., 10 ng/L). Four different tight ultrafiltration (UF) membranes, with different molecular weight cutoffs (MWCO) and hydrophobicities were investigated. The removal of TCA decreased with increasing permeability for all of the UF membranes tested. Relatively hydrophobic UF membranes, even those with higher MWCO and permeability values, exhibited much higher TCA removal efficiencies than relatively hydrophilic UF membranes, both in the presence and absence of hydrophobic natural organic matter (Suwannee River NOM). The adsorption of TCA onto the membrane surfaces/pores through the hydrophobic interaction was found to be important for the efficient removals of TCA by hydrophobic UF membranes, especially those with greater hydrophobicities. The removals of TCA by the tight-UF membranes were affected by two major mechanisms: (1) a convection mechanism for the transmission of TCA through the membrane pores and (2) the adsorption of TCA onto the membrane surfaces/pores through hydrophobic interactions.

Removal of geosmin and 2-methylisoborneol through biologically active sand filters

The removal of taste and odour compounds from drinking water is a constant challenge to water authorities. Although adverse odours do not present a risk to human health, their presence often leads to a misconception that the water is unsafe for drinking. 2-Methylisoborneol (MIB) and geosmin are the most common causes of earthy/musty odour, and are not easily removed by conventional treatment processes. MIB and geosmin can be removed through biologically active sand filters. Experiments were conducted using laboratory sand filter columns using sand taken from South Australian water treatment plants. Sand with a well-established biofilm taken from a 26 years old filter was capable of removing MIB and geosmin to below detection limit after 11 days of operation at an Empty Bed Contact Time (EBCT) of 15 min. Sand without an established biofilm removed 60% geosmin and 40% MIB after 154 days of operation at 15 min EBCT.

Interferência do processo de coagulação na remoção de compostos orgânicos causadores de gosto e odor em águas de abastecimento mediante a aplicação de carvão ativado em pó

O carvão ativado em pó (CAP) tem sido empregado no tratamento de águas de abastecimento para a solução de problemas de gosto e odor, podendo sua aplicação ser efetuada antes ou depois da mistura rápida ou juntamente com o coagulante. Tendo em vista as dúvidas existentes entre a interferência do processo de coagulação na eficiência do processo de adsorção, foram conduzidos ensaios de jarros simulando-se diversos cenários de aplicação de dosagem de coagulante e CAP. Concluiu-se que, para as mesmas dosagens de CAP e coagulante aplicadas, independentemente do seu ponto de aplicação, não foram observadas diferenças significativas na remoção de compostos causadores de gosto e odor, o que indica que, sob as condições testadas, o ponto de aplicação de CAP, antes ou depois da aplicação do coagulante, possui muito pouca importância na eficiência do processo de adsorção.

Influences on the removal of tastes and odours by PAC

Geosmin and 2 methylisoborneol (MIB) are earthy/musty odour compounds produced as secondary metabolites by some cyanobacteria and actinomycetes. At levels as low as 5–10 ng l −1 in drinking water they can result in consumer complaints, and consequently their removal from potable water is a priority for many suppliers. In water treatment plants where taste and odour episodes are common, the homogenous surface diffusion model (HSDM) can be used to estimate powdered activated carbon dose requirements under a range of conditions including inlet concentration and plant flow rates (controlling PAC contact time). Water quality, in particular dissolved organic carbon concentration and character, can affect the required doses of PAC, as can the addition of chemicals such as alum and chlorine. There is significant scope for the more cost-effective utilisation of powdered activated carbon for the mitigation of taste and odours, as well as a wider range of other micro-contaminants, using tools such as the HSDM, in conjunction with knowledge of the effects of water quality and water treatment processes.

Assessment of membrane processes for taste and odour removal

The occurrence of tastes and odours (T&O) in potable water is considered one of the main problems by the drinking water companies. Thus, several treatment processes have been developed over the years to control T&O, including air stripping, activated carbon and oxidation using ozone. However, little information is available in the literature on the use of membranes for T&O removal. Therefore, the objective of this paper is to present potential of membrane processes for the removal of taste and odour-causing compounds. Several membranes were tested including ultrafiltration (UF), UF combined with powdered activated carbon (PAC), nanofiltration (NF) and low pressure reverse osmosis (LP RO) membranes. Combination of UF with PAC was found to be effective for T&O control. The use of NF or LP RO is still unclear in the objective of T&O control.

Pre-treatment with dissolved air flotation considering an integrated process design

The raw water from Lake Zegrzynski is difficult to treat and requires a high chemical dosing rate of coagulant for the reduction of organic matter in order to comply with EU standards. The high degree of reduction calls for an efficient coagulant, but also an optimal chemistry such as correct dosing amount and an optimal flocculation-pH. The paper describes different removal efficiencies of organic matter, particularly with respect to pH in flocculation. During the warm season, the raw water can also suffer from large amounts of plankton that are difficult to remove to a satisfactory degree. In a two-step chemical treatment concept, with Dissolved Air Flotation (DAF) and the pulsator process, the plankton content in the final outlet water is reduced to very low levels. It follows that eventual peaks of plankton in the raw water cannot be detected in the final outlet water. Ozone is added for removal of taste and odour originating from the presence of plankton. In the pre-treatment step prior to the ozonation, a great deal of the organic matter is removed, which reduces the necessary ozone dosage. The Municipal Water Company of Warsaw City has decided to consider an additional pre-treatment step to the existing water treatment plant at Wieliszew. For that purpose, and bearing in mind an integrated process design, the company has performed pilot-scale experiments with DAF installed prior to a process line identical with the existing full-scale plant. The experimental flow is about 10 m3/h.

Removal of Taste and Odour Compounds by Conventional Granular Activated Carbon Filtration

Abstract In recent years, musty-earthy tastes in drinking water have become a seasonal problem (September to November) for communities that draw their water from the upper St. Lawrence River. The source of the problem is attributed to the presence of geosmin and 2-methylisoborneol (MIB) at concentrations ranging from 5 to 60 ng/L. In 1997 and 1998, the Cornwall Water Purification Plant added granular activated carbon (GAC) to conventional gravity filters to control taste and odour compounds. We report on a study to test the efficiency of these conventional GAC-capped filters to reduce geosmin and MIB concentrations in finished water as a function of filter age, initial chlorine residual and contact time. GAC–capped filters removed on average 60% of the MIB and 80% of the geosmin from the source water after 2 and 12 months of filter operation. However, testing after 24 months operation showed reduced efficiency. Amounts removed ranged between 13 and 20% (15% average) for MIB and 50 to 57% (54% average) for geosmin in these filters. Testing also suggested that filter efficiency was greater with longer contact times and with higher chlorine residuals (in the range 0.1 to 0.6 mg free Cl2/L). In addition to carbon age, chlorine residual and contact time, flow channelization and slow release of the taste and odour compound load (particularly MIB) from the GAC bed may affect apparent filter efficiency.

Removal of Taste‐ and Odor‐Causing Compounds by Biofilms Grown on Humic Substances

Laboratory experiments showed that biodegradation of taste‐ and odor‐causing compounds by biolfilms grown on natural humic materials is feasible. Although the mineralization of peat fulvic acid (PFA) was relatively low (about 10 percent), long‐term application of the PFA resulted in a significant amount of biofilm mass in the reactor and allowed the secondary utilization of trace levels of taste and odor compounds. These results suggest that biofilms grown on natural organic materials can play an important role in removing taste and odor compounds during water treatment. Examples of drinking water treatment processes that allow good biofilm accumulation are granular activated carbon, sand filters, river bank filtration, submerged fixed‐bed reactors, and fluidized‐bed reactors.

Treatment Application Points for Activated Carbon

This article begins by discussing the influence of softening chemicals, lime and soda ash, on the adsorption of taste and odor compounds by activated carbon. Although removal of taste and odor compounds is the primary function for activated carbon, additional benefits include: adsorption of such compounds as organic insecticides, herbicides, and detergents, which are relatively inert to chemical oxidation; removal of color and improvement of coagulation; and, reduction in substances having chlorine demand.

Comparison of Tests for Activated Carbons

The task of preparing specifications for activated carbon suitable for the removal of tastes and odors from water is a formidable one, because it is a material with properties entirely different from those of other treatment chemicals with which the water-works industryis familiar. To prepare such specifications in a manner satisfactory to both the user and the manufacturer, has required an enormous amount of careful work by the Sub-Committee on Activated Carbons. Of the two methods which are now available for measuring the primary property of activated carbons, viz., their capacity for removing tastes and odors from water, one, the phenol test, is an indirect method, and the other, the threshold odor test, is a direct one. Extensive work has been done on the phenol test, to ascertain and correct sources of error, and to establish the magnitude of reasonable experimental error, now accepted as ±10 per cent. Work on the threshold odor test has now reached a point at which similar reliance is possible on that procedure as a method of evaluating adsorptive capacities of carbons. Demonstration of this reliability is based upon demonstration that in adsorbing odors from water, carbons follow the fundamental adsorption equation of Freundlich,

Removal of Taste and Odor from Municipal Water Supplies

Since the spring of 1931 the Ontario Department of Health has conducted an extensive experimental investigation into the problem of tastes and odors in municipal water supplies. The results accomplished are summarized in tables 1 and 2. Laboratory and plant-scale experiments were performed. The success of each treatment is shown by the sign affixed. Plus indicates that the treatment was successful; minus, that no good was accomplished; and plus-and-minus, that only partial improvement was obtained. At Chatham chloramine was effective in preventing algae growth, and thereby also was effective in reducing the taste to a considerable extent. At Wallaceburg chloramine prevented the formation of the taste-producing chlorphenol by reducing the activity of the chlorine. The details of these two experiments will be given by others. They illustrate the two uses of chloramine treatment; first, in preventing taste by preventing algae growth, and second, in preventing the formation of taste producing substances by reducing the activity of chlorine. Chloramines cannot be expected to remove tastes already present in the water. The use of granular activated carbon received considerable attention at Chatham, Haileybury, Kirkland Lake, Lindsay, and Timmins. The carbon was used in the form of small filter beds through which water was passed. The amount of water obtained before a noticeable taste was secured was not large. At Chatham the experiment was discontinued before the carbon was saturated. At Haileybury the filter was used only during short periods of extremely offensive taste. At Kirkland Lake and Timmins, unfiltered water was used. This probably reduced the life of the carbon. At Timmins, color was removed as well as taste and odor. At Lindsay, clear and colorless tap water was used. The yield of tasteless water was 18,000 gallon per cubic foot. This is evidently too low to make

Modern Practice in the Removal of Taste and Odor

Journal AWWAVolume 9, Issue 5 p. 766-782 Article Modern Practice in the Removal of Taste and Odor1 Norman J. Howard, Norman J. Howard Bacteriologist in Charge; Filtration Laboratories, Toronto, Canada.Search for more papers by this author Norman J. Howard, Norman J. Howard Bacteriologist in Charge; Filtration Laboratories, Toronto, Canada.Search for more papers by this author First published: 01 September 1922 https://doi.org/10.1002/j.1551-8833.1922.tb12417.xCitations: 5 1 Presented before the Philadelphia Convention, May 19, 1922. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume9, Issue5September 1922Pages 766-782 RelatedInformation