Sensory Assessment of Water Quality

Preface


1 Introduction


1.1 General Aspects


1.2 The Nature of Sensory Assessment of Water Quality


1.2.1 Types of Senses for Water Quality Assessment


1.2.2 Human Olfaction


1.2.3 Human Gustation


1.2.4 Some Effects Related to Chemoreception


1.3 Perceptible Substances in Drinking Water


1.3.1 Historical Developments in the Netherlands


1.3.2 Substances Causing Turbidity of Water


1.3.3 Substances Causing Colour of Water


1.3.4 Compounds Causing Odor of Water


1.3.5 Mineral Substances Causing Taste of Water


1.4 Outline of the Work


2 Sensory Assessment of Drinking Water Quality by the Population of the Netherlands


2.1 Introduction


2.2 The Inquiry


2.2.1 The Questionnaire


2.2.2 Preparation and Realization


2.2.3 Characteristics of the Sample of the Population


2.3 Sensory Assessment of Tapwater Quality and Possible Causes of Quality Impairment


2.3.1 Visual Aspects


2.3.2 Temperature


2.3.3 Odor and Taste


2.4 Aspects Possibly Affecting Sensory Water Quality Assessment


2.4.1 Knowledge of Raw Water Source and Opinion on Water Taste Elsewhere


2.4.2 Odor of the Air at the Residence and at the Place of Work


2.5 Perceptible Water Quality Aspects and General Water Quality Assessment


2.5.1 Acceptability Rating of Water Quality


2.5.2 Safety Rating of Water Quality


2.6 Conclusions


3. Sensory Assessment of 20 Types of Drinking Water by a Selected Panel


3.1 Introduction


3.2 The Panel


3.2.1 Panel Selection


3.2.2 Factors Affecting Odor Sensitivity for O-Dichlorobenzene and Isoborneol


3.3 Stimulus Presentation, Test Conditions and Psychophysical Scaling


3.4 Selection and Sampling of 20 Types of Drinking Water


3.5 Taste and Odor Assessment of 20 Types of Drinking Water


3.5.1 Relation between Taste and Odor Rating of Drinking Water


3.5.2 Results of the Taste Rating


3.5.3 Results of the Taste Quality Assessment


3.5.4 Factors Affecting the Taste Rating by the Panel Members


3.6 Conclusions


4 Drinking Water Taste and Inorganic Constituents


4.1 Introduction


4.2 Taste Assessment of Individual Salt in Water Solutions by a Selected Panel


4.2.1 Stimulus Presentation and Test Conditions


4.2.2 Results


4.2.3 Discussion


4.3 Inorganic Constituents in 20 Types of Drinking Water and Taste Assessment


4.3.1 Levels of Inorganic Constituents in Drinking Water


4.3.2 Discussion


4.4 Conclusions


5 Drinking Water Taste and Organic Constituents


5.1 Introduction


5.2 Analytical Methods


5.2.1 General Remarks


5.2.2 Organochlorine Pesticides, Cholinesterase Inhibitors, Polynuclear Aromatic Hydrocarbons and Halogenated Volatile Compounds


5.2.3 Organic Compounds Concentrated by Means of Closed-Loop Gas Stripping and by Means of Amberlite-Xad Adsorption


5.3 Detected Types and Levels of Organic Constituents in 20 Types of Drinking Water


5.3.1 General Survey


5.3.2 Compounds Present in Drinking Water Derived from Ground Water


5.3.3 Compounds Present in Drinking Water Derived from Surface Water


5.3.4 Comparison between Tapwaters Derived from Surface Water and those Derived from Ground Water


5.4 Organic Substances and Drinking Water Taste


5.4.1 Screening Procedures to Select Taste Impairing Compounds


5.4.2 Compounds with C/OTC Ratios of 0.01 or More


5.4.3 Some Compounds Lacking OTC References


5.5 Conclusions


6 Sensory Assessment of Drinking Water Quality and Health Protection Aspects


6.1 Introduction


6.2 Sensory Water Quality Assessment and Water Consumption


6.3 Sensory Detectability and Chronic Toxic Effects of Compounds


6.4 Sensory Detectability and Acute Toxic Effects of Compounds


6.4.1 General Aspects


6.4.2 Natural and Industrial Compounds


6.5 Carcinogens and Accompanying Odorous Compounds


6.6 Conclusions


7 Further Study and Application of Water Quality Assessment


7.1 Introduction


7.2 Value of Sensory Water Quality Assessment


7.3 Application of Sensory Water Quality Assessment


7.3.1 Relation between Type of Water and Method of Taste or Odor Intensity Determination


7.3.2 Determination of Odor Intensity of Contaminated Waters


7.3.3 Determination of Taste of Drinking Water


7.4 Measures to Reduce Perceptible Contamination of Water


7.4.1 Causes of Impaired Taste and Smell of Water and Fresh Water Organisms


7.4.2 Prevention and Reduction of Taste Problems within Water Supply Systems


7.4.3 Abatement of the Presence of Taste and Odor Impairing Substances in Surface Waters


7.5 Final Considerations

Summary

List of Symbols, Abbreviations and Synonyms

Subject Index

References

Appendices


2.1 Survey of Z-Values for Associations between Ordinal Variables of the National Inquiry


2.2 Survey of H-Values for Associations between Ordinal and Nominal Variables of the National Inquiry


2.3 Some Results of the National Inquiry, Arranged According to 50 Communities in Combination with Some Water Quality Data


3.1 Survey of the Characteristic Data of the Group Used for Selecting the Panel Members and their Odor Sensitivity for Aqueous Solutions of Isobomeol and O-Dichlorobenzene


3.2 Correction Procedure for Changes in the Use of a Taste Rating Scale by a Panel


5.1 List of Organic Compounds Identified in 20 Tapwaters in the Netherlands in 1976


6.1 OTC/LD50 Ratios for Natural Organic Compounds in Water


6.2 OTC/LD50 Ratios for Industrial Organic Compounds in Water