Organoleptic Properties of Drinking Water

Smell and taste — up to 2 points. These properties are determined in the open and closed experiments on people with application of 1-5-point scale: point 0 means absence of smell and taste, point 1 — smell and taste is determined only by an odorator — a person with the increased sensitivity to smell and taste, 2 — a consumer does not pay attention to smell and taste, 3 — appreciable — causes a negative attitude to water, 4 — distinct — limits water consumption, 5 — very strong — water is unsuitable for drinking).

Colouring or chromaticity of water — up to 20 degrees. It is determined by a scale of ampoules containing a chrome-cobalt solution of different color.

Turbidity — up to 1.5 mg/l or transparency — 30 cm. It is determined with the help of special flasks — normally there must be the opportunity of reading a text through a 30-cm layer of water.

Temperature — 10-12ºC. If temperature is below, catarrhal diseases may occur, if it is higher, then оrganoleptic properties of water change.

Significance of Studying Organoleptic Properties of Water

· It is used for initial examination of water quality;

· Change of organoleptic properties is an indirect sign of organic pollution of water.

Chemical Parameters of Water, Their Influence on a Human Organism

These parameters are of great importance because their changes to increase or decrease may cause different diseases.

The dry residue or mineralization of water — up to 1000 mg/l (1 g/l). At higher values of dry residue (1400 mg/l and higher) changes of оrganoleptic properties of water, e.g. taste of water, take place.

According to degree of mineralization, the following classification of water is suggested:

· water of low mineralization — 1-2 g/l,

· water of high mineralization — 10 g/l and over (seawater contains 35 g/l).

At use of high mineralization drinking water (especially at sharp change of water on moving to other area) disorders of water-salt balance, retention of water in organism, dysfunctions of digestive and excretory systems, metabolic derangements occur. The increase of disease incidence of cardiovascular, urinary systems, urolithiases is statistically proved in these areas. With such water 25-100% of total amount of mineral substances of food ration gets in organism.

On the other hand, it is experimentally and clinically proved that waters with low mineralization(100 mg/l and less) are biologically deficient that results in increase of secretion and acidity of gastric juice, disturbance of water absorption in gastrointestinal tract, derangement of water-salt exchange, disorder of tubular reabsorption in kidneys, hypocalcemia, decrease of osmotic resistance of erythrocytes, etc.

 

The content of chlorides is up to 350 mg/l. They impart salt taste to water; in big concentrations they change water taste by more than 2 points. At increase of chlorides in water the derangement of water-electrolyte exchange and dysfunction of kidneys occur. Arterial hypertension, the so-called "salty hypertension" is encountered in the areas with salty water 4 times more often. At concentration of chlorides over 500 mg/l the inhibition of secretion and acidity of gastric juice occurs.

It is an indirect parameter of organic pollution of water with household sewage as there are a lot of chlorides in urine.

 

The content of sulfates is up to 500 mg/l. They impart bitter taste to water by more than 2 points. At their increase the inhibition of gastric secretion, disturbance of intestinal absorption, reflex diarrhea can occur.

It is also an indirect parameter of organic pollution of water as lots of sulfates are found in faecal masses.

 

General hardness of water is up to 10 mg–equivalent/l. It depends on content of calcium and magnesium ions. Hardness of wateris classified as eliminable (eliminated at boiling), non-eliminable (preserved in water after boiling) and common (the last is normalized by SS).

Classification of water according to general hardness:

· up to 3.5 mg-eq/l — soft water

· 3.5 — 7 mg-eq/l — water of average hardness

· 7 — 14 mg-eq/l — hard water

· over 14 mg-eq/l — very hard water.

In hard water it is difficult to do washing (expenditure of washing powder on binding salts), to cook food. Protein absorption is worsened as insoluble complexes with salts form. Problems of water supply arise as deposits on pipes form (eliminated hardness).

Nitrogenous Substances in Water (Ammonia, Nitrites, Nitrates)

Ammonia and nitrites should practically not be present in water, nitrates — up to 10 mg/l (converted into nitrogen). As these are the final links of protein disintegration, they give the possibility to judge about organic pollution: if only ammonia is revealed in water, then it is the recent pollution, only nitrates — the old one, all nitrogenous substances — the persisting pollution. It is an indirect parameter of organic pollution of water.

At increased content of nitrates and nitrites (caused by organic pollution of reservoir or water flushing of nitric fertilizers into it) a specific illness — water-nitrate methemoglobinemia — may develop which is especially dangerous for children of the first months of life.

 

Water oxidizability and biochemical consumption of oxygen (BCO). It is an important index of amount of organic substances in water as for their oxidation more О2 is required. Normally water oxidizability is 2-4 mg О2/l. The dynamics of water oxidizability for 5 or 20 days (BCO) is a criterion of oxygen regimen of reservoir which is studied for normalization of pollutants in reservoir water.

 

The content of iron is up to 0.3 mg/l. Its source is a natural structure or water pipes. At high content of iron colouring of water changes.

 

The content of fluorine is 0.7-1.5 mg/l (in hot climate it may be 0.7 mg/l as more water is used, in cool climate — 1.5 mg/l). The reason of the abnormal content of fluorine in water is biogeochemical provinces and anthropogenic sources (superphosphate plants). At small content of fluorine in water caries may develop in people, at increased content — fluorosis (spotty damage of dental enamel, derangement of Са-Р exchange, fluoric cachexy, deformation and fragility of bones).

! Bacteriological Parameters of Water!

All over the world the following parameters of microbe pollution of water are used:

· total number of microorganisms in water

· the content of colibacillus (E.Coli) as a constant inhabitant of sewage and a relatively steadier microbe than others to disinfection of water shows efficiency of disinfecting water.

Total microbe number (TNM) — up to 100 per 1 ml — amount of microbe colonies at inoculation of 1 ml water in a Petri dish at 37ºС for 24 hours.

Coli index — up to 3 per liter — quantity of colibacilli per liter of water.

Coli titer — not less than 300 — quantity of water in 1 milliliter per 1 colibacillus.

Epidemiological Significance of Water

It is common knowledge nowadays that water factor plays a leading role in occurrence of number of infectious diseases, such as:

· enteric infections — typhoid, cholera, paratyphoid, dysentery, etc.

· anthropozoonoses — brucellosis, tularaemia, Siberian plague, leptospirosis,

· viral infections — hepatitis, poliomyelitis, adenoviruses,

· pathogenic protozoa — lamblias, amoebas, balantidia, etc.

· parasitic worms.

 

Signs of Epidemiological Hazard of Water

· direct — deterioration of bacteriological parameters of water, availability of pathogenic microbes;

· indirect — deterioration of organoleptic parameters, increase of amount of chlorides, sulfates, nitrogenous substances, water oxidizability.

 

Signs of water epidemic (epidemic by a water-way transmission) are the following:

· Quick mass episode of the same infectious diseases.

· Territorial relation of disease episode to the certain water source.

· After taking antiepidemic measures in the focus of infection (prohibition of using a water source, disinfection of water) a sharp decrease of disease incidence is observed, only separate cases are registered ("epidemic tail").

· Hot season presents better conditions for reproduction of causative agents, besides a person consumes a lot of liquid, hence acidity of gastric juice — barrier to microbes — is reduced.

Recommendations for Practical Classes on the Theme

Key Questions:

1.Physiological and hygienic significance of water.

2.Documents regulating quality of water and requirements to sources of water supply.

3.Rules of taking water tests for chemical and bacteriological researches.

4.Organoleptic parameters of water quality, methods of its research, norms.

5.Chemical parameters of water quality and diseases connected with their deviations.

6.Bacteriological parameters of water quality. Epidemic significance of water. Signs of water epidemics.

7.Chemical parameters of organic pollution of water.

8.Direct and indirect parameters of organic pollution of water.

9.Water-nitrate methemoglobinemia, its causes and prevention.

Learning Objectives and Their Concrete Definition

1. Determination of organoleptic parameters of investigated water:

temperature of water: 12-14ºС in norm is determined by a thermometer;

c) transparency of water: drinking water should be completely transparent, allowing through a layer of 30 cm to read a text of Snellen test type;

d) turbidity is determined by amount of suspension particles per 1 litre of water, they should be not more than 1.5 mg/l;

e) colour: drinking water should be colourless (not higher than 20º) by the scale of ampoules with chrome-cobalt solution;

f) taste and smell of water: they are determined at a room temperature (20ºС) and at heating of water up to 60ºС, taste and smell are estimated by a six-point system (0-5). Water with smell and taste of not more than 2 points is considered acceptable for drinking.

2. Qualitative evaluation of chemical substances in investigated water.

Determination of:

· pHof water is evaluated by litmus paper (in norm 6.5-8.5), that corresponds to colours from yellow to green.

· ammonia (NН3): to investigatedwater we add 3-4 drops of Nessler’s reagent, the appearance of yellow colouring indicates the presence of ammonia. In normal water NН3 should be absent.

· salts of nitric acid (nitrates): to 2-5ml of investigatedwater in a porcelain test add some crystals of diphenylamine, then some drops of sulfuric acid. The presence of nitrates is indicated by dark blue colouring. The norm of nitrates in water is up to 10 mg/l.

· salts of sulfuric acid (sulphates): to the tested water add some drops of hydrochloric acid, 2-3 drops of 10 % solution of barium chloride. The presence of white dreg quickly forming a precipitate indicates the availability of sulphates. Their norm in water is up to 500 mg/l.

· chlorides: the chloride salts form due to the presence of a silver solution (reaction of a silver mirror). To 5 ml of investigatedwater in a test tube add some drops of silver nitrate, the presence of chlorides is indicated by white dreg. The norm of chlorides is up to 350 mg/l.

· iron: to investigatedwater add 2-3 drops of nitric acid and then 2-3 drops of ammonium thiocyanate solution. The presence of salts of iron is indicated by the orange-red colouring, its intensity depending on concentration of salts of iron. Their norm in water is up to 0.3 mg/l.

Algorithm of Students’ Practical Work

The first stage. Testing the initial level of students’ knowledge and skills.

The second stage. Active participation in discussion of key questions of the theme.

The third stage. Independent work on determination of some organoleptic and chemical parameters of water.

The fourth stage. Problem solving and final testing on the theme.

Self Test

1. Name the basic groups of parameters of drinking water quality.

*A. organoleptic

*B. chemical

*C. bacteriological (microbiological)

D. toxicological

E. helminthologic

 

2. The transparency of drinking water is determined by a text of standard test type (named after the author)

A. Heiner

B. Giss

C. Herbar

D. Stocks

*E. Snellen

 

3. The qualitative reaction to chloride content in water is:

*A. reaction with silver nitrate

B. reaction with nitrate solution

C. reaction with sulphuric acid

D. reaction with nitric acid

E. reaction with natrium chloride

Final Testing on the Theme

1. In an hour after feeding a baby with a milk formula, the following symptoms of disease developed in it: cyanosis of lips, mucous membranes, face, then nausea, increased salivation, pain in the stomach, vomiting, diarrhea. The called in pediatrician stated the phenomena of cardiopulmonary decompensation in the child. In the course of investigation it was established that water from a well was taken to prepare milk formula. What diagnosis was established by the doctor?

A. nitrate intoxication

B. food toxicoinfection

C. staphylococcus toxicosis

D. food poisoning with heavy metals

E. sulphate intoxication

2. For water supply of the city the water is used containing: fluorine — 2.0 mg/l, nitrates — 43 mg/l, chlorides — 250 mg/l, iron — 0.2 mg/l, residual chlorine — 0.5 mg/l. Identify the disease which may develop in population at use of water with the given chemical structure:

A. dental caries

B. thyrotoxicosis

C. methemoglobinemia

D. fluorosis

E. endemic goiter

3. The chemical analysis of water from a well has indicated the presence of increased concentration of nitrates, iron and sulphates. What parameter of water quality can testify to recent pollution of water by organic substances of an animal origin?

A. nitrates

B. ammonia

C. nitrites

D. sulphates

E. chlorides

Problem Solving

1. In people of a city district the non-uniform colour of teeth was marked. On incisors the white spots and cross brown strips were observed. Drinking water from a deep borehole was suspected in occurrence of these symptoms. What microelement of water components could have caused the disease?

2. The mountain lake is situated outside the inhabited locality. There is wood around it, lakeside is sandy, stony. The analysis of water revealed the following: taste, smell — 1 point, ammonia and nitrites are absent, colour — colourless, nitrates — 40 mg/l, transparency — 40 cm, chlorides — 50 mg/l, coli titer — 300, microbe number — 65. Give a sanitary estimation of water.

3. Disease incidence of caries among the inhabitants of town N. makes up 89 %. It is established that water contains 0.1 mg/l of fluorine. What preventive measures should be carried out?

Standard Answers:

1. Fluorine

2. Water is suitable for drinking

3. Fluorination of water.

 

Theme No 8.

Hygiene of Water Supply. Methods of Improving Water Quality

Hygienic Characteristics of Water Supply Sources

There are 4 types of water supply sources:

v Surface water (open reservoirs) — rivers, lakes, water basins;

v Underground water:

Ø subsoil water is in the ground above the impervious layer — wells, springs;

Ø middle water — between the impervious layers — artesian wells;

v Atmospheric water (meteoric water) — accumulation of atmospheric precipitation,

v Desalination of seawater.

Hygienic Characteristics of Open Reservoirs

These are big supplies of water which are easily accessible. Their drawback is that they are easily exposed to pollution for natural and anthropogenic reasons. Their chemical and microbe structure is inconstant that requires daily supervision of water quality.

Ways of Autopurification of Open Reservoirs

· Dilution in big water masses

· Sedimentation

· Biochemical oxidation by microflora

· Adsorption by hydrobionts

· Bactericidal effect of UVR in top layers — up to 50 cm

· Neutralization.

Estimation of Pollution Degree in Open Reservoirs

Methods ofestimation ofpollution degree in open reservoirs are as follows:

v Comparison of water parameters with SS or maximal permissible concentration — analytical monitoring;

v Medical-hygienic monitoring includes observation of changes of health parameters in people using water from the given reservoir;

v Ecological monitoring is carried out with application of hydrobiological parameters:

Ø sensitive — indicatory organisms, e.g. trout;

Ø organisms–filtrators, e.g. mussels — by accumulation of pollutants in them;

Ø qualitative and quantitative characteristics of hydroecosystems.