Fundamentals of General and Pharmaceutical Hygiene - Dykyi I.L. 2003

Hygiene of Water and Water Supply
Hygienic assessment of drinking water quality and water supply sources

Water is one of the most critical environmental factors influencing all vital processes in the living Organism. The physiological significance of water for humans lies in the fact that it is a fundamental component of all biological Tissues. Essential physicochemical processes associated with body METABOLISM take place in an aqueous medium, including Hydrolysis, assimilation, dissimilation, diffusion, resorption, filtration, and others. Water also plays a vital role in the body's thermoregulation. Its hygienic importance is that it is indispensable both for maintaining personal hygiene and for ensuring cleanliness in medical and pharmaceutical facilities, as well as in industrial enterprises.

A significant amount of water is consumed for industrial needs, particularly in pharmaceutical manufacturing. The national economic importance of water is that drinking water is not merely a natural product, but also a manufactured one; it becomes potable only after numerous stages of transformation—extraction and transportation, achieving a state-regulated standard of quality, and maintaining control over that quality.

Specific requirements are imposed on drinking water quality, as substandard water can cause both infectious diseases (such as cholera, amoebic and bacillary dysentery, typhoid fever, paratyphoid, infectious hepatitis, and enteritis) and non-infectious conditions related to specific chemical compositions or reservoir contamination by various harmful substances (such as dental caries, fluorosis, Urov disease, and molybdenum Gout).

Drinking water must meet the following requirements:

1) be safe in epidemiological and radiation terms;

2) be harmless in its chemical composition;

3) possess favorable organoleptic properties.

In Ukraine, these requirements are regulated by the sanitary legislative document DSanPiN (State Sanitary Rules and Norms "Drinking Water. Hygienic Requirements for the Quality of Centralized Drinking Water Supply" No. 383 of December 23, 1996 (Table 12 of the Appendix).

Objective: to understand the hygienic requirements for drinking water quality, acquire skills in water analysis, provide a Hygienic evaluation of the obtained data, and develop measures to improve water quality.

QUESTIONS FOR INDEPENDENT PREPARATION

1. Physiological and hygienic significance of water; water supply norms.

2. Water as a vehicle for transmitting infectious diseases; characteristics of waterborne outbreaks.

3. The Role of water chemical composition in the onset of diseases; THE CONCEPT OF biogeochemical endemic diseases.

4. Principles of drinking water quality standardization.

5. Specifics of quality standardization for water from decentralized supply sources.

6. Organoleptic indicators of drinking water quality.

7. Indicators of epidemiological safety of water: coli-titer, coli-index, total bacterial count.

8. Toxicological indicators and indicators of radiation safety of water.

9. Methods for purification and disinfection of drinking water.

10. Methods of drinking water analysis.

11. Ongoing sanitary surveillance of drinking water sources.

Task 1. Determination of indicators of epidemiological safety of water

1.1. Determination of the total bacterial count of water

The microbial count of water is the number of microorganisms present in 1 mL of water.

The water tap is sterilized by flaming with an alcohol-soaked cotton swab, after which it is opened and water is allowed to run for 10 minutes. A water sample is collected in a sterile 500 mL bottle (if the water is chlorinated, 2 mL of a 1.5% sodium thiosulfate solution is added beforehand), carefully sealed with a sterile stopper, and transported to the analysis site, which is conducted following aseptic rules. Prepare 5 test tubes containing 9 mL of sterile water each. Using a sterile pipette, take 1 mL of the test sample, add it to the first test tube, mix thoroughly, transfer 1 mL to the next test tube, and continue this serial dilution to achieve 1:10, 1:100, 1:1000 dilutions, etc.

Then, 1 ml of water from each dilution is added dropwise into Petri dishes, poured over with 10 ml of meat-peptone Agar melted and cooled to 45 °C, and gently mixed. After the agar solidifies, the dishes are inverted, labeled (indicating the Location, time of sampling, and dilution), and incubated in a thermostat at 37 °C for 24 hours.

Recording results. The number of colonies grown on the nutrient medium (MPA) is multiplied by the dilution factor of the water from which this plating was made (10, 100, etc.).

According to the requirements of DSanPiN No. 383, the microbial number of water must not exceed 100.

1.2. Determination of the Coliform Index and Coliform Titer of Water (Membrane filtration Method)

The water coliform titer is the minimum volume of water in which coliform Bacteria (coliform group) are detected.

The water coliform index is the number of coliform bacteria per 1 L of water.

The determination of the coliform titer is carried out under aseptic conditions using a filtration apparatus, which is a filter holder with a membrane filter connected to a receiver. The filter holder consists of a funnel with a lid and a base with a porous plate on which the membrane is placed. Polymer nitrocellulose filters (No. 3) with a pore size of 0.45±0.02 µm and a diameter of 47 mm are used. Water filtration is carried out under a vacuum of 93.3 kPa.

Before taking a tap water sample, the tap is flamed with a torch, water is left to run for 10 min, and then 500 ml is collected in a sterile bottle. The test sample is passed through the filter, after which the filter is removed from the filter holder and placed bottom-side down in a petri dish with Endo agar. After incubation in a thermostat at a Temperature of 370 °С for 24 hours, the number of colonies typical of coliforms is counted — raspberry-colored with a metallic sheen (or without it). Belonging to coliform bacteria is confirmed by Gram staining (Gram-negative), oxidase testing (oxidase-negative), and the detection of glucose Fermentation, as described in the microbiology manual.

Recording results. The number of bacterial colonies corresponding to the aforementioned characteristics is multiplied by 2 to determine the content in 1 L, which corresponds to the coliform index, from the value of which the water coliform titer is calculated. For example, if the number of colonies is 5, then in 1 L there will be 5 × 2 = 10 (coliform index), and the coliform titer will be 1000 : 10 = 100.

Task 2. Organoleptic Analysis of Water

2.1. Determination of Water Odor

A 100 ml flask is filled up to ²/₃ with the test water sample, closed with a ground-Glass stopper, shaken thoroughly, and then the odor is determined by evaluating it qualitatively and quantitatively. Quantitatively, the odor is characterized as chlorine, earthy, hydrocarbon (petroleum), swampy, medicinal (iodoform), hydrogen sulfide, fishy, undefined, etc. Quantitatively, the odor is evaluated on a five-point scale (Table 5).

2.2. Determination of Water Aftertaste

The Oral Cavity is rinsed with a small amount of the test water sample (10 ml) without swallowing it, held for a few seconds, and the taste is determined, which is characterized as salty, bitter, acidic, sweet, or undefined. The aftertaste may be fishy, metallic, or undefined. The intensity of the aftertaste is determined according to Table 5.

Class="center">Table 5 Scale of Water Odor and Aftertaste Intensity

According to the requirements of DSanPiN No. 383, drinking water must not have an odor and aftertaste exceeding 2 points.

Task 3. DETERMINATION OF CHEMICAL Safety Indicators of Drinking Water

3.1. Determination of Ammonia Content

The detection of ammonia indicates fresh water contamination by organic matter of animal origin or the reduction of nitrates in the absence of oxygen.

Weigh 200 µg of sodium potassium tartrate, place it in a test tube, then add 10 ml of the test water sample and, after thorough mixing, add 0.2 ml of Nessler's reagent. After 5 min, evaluate the intensity of the coloration and determine The amount of ammonia in the water using Table 6. The amount of ammonia in drinking water must not exceed 0.1 mg/L.

Table 6 Approximate Ammonia Content in Water

3.2. Determination of Chloride Content

Place 100 ml of the test water sample and 1 ml of a 10% potassium chromate solution into a 250 ml flask, and titrate with silver nitrate (prepared by dissolving 4.8 g of AgNО₃ in 1 L of distilled water) until a yellow-brown coloration appears, while continuously mixing the sample.

The chloride concentration is calculated as follows.

Example. Titration required 12 ml of silver nitrate. It is known that 1 ml of this solution precipitates 1.2 mg of sodium chloride. Based on this, we set up the proportion:

1.0 ml — 1.2 mg

12 ml — x mg

x = 14.4 mg

In 1 liter: 14.4 10=144 mg/l.

The chloride content in drinking water must not exceed 250 mg/l.

Task 4. Determination of residual chlorine in drinking water as an indicator of disinfection efficiency (rapid method)

An indicator of the efficiency of water chlorination is the content of active chlorine, which must be present in the water after its contact with chlorine for 30 minutes.

Before taking a sample, tap water is allowed to run for 2 minutes. 100 ml of the test water sample is poured into a conical flask, 5-6 drops of a 10% potassium iodide solution are added, followed by the same amount of freshly prepared 0.5% starch solution, and the flask is thoroughly swirled.

The content of residual free chlorine in the water is determined by the intensity of the blue coloration (Table 7).

Table 7 Residual chlorine content in water

The permissible content of residual free chlorine in drinking water is 0.3-0.5 mg/l.

PROTOCOL TEMPLATE

Topic of the practical session.

1. Determination of water epidemiological safety indicators.

1.1. Determination of the total bacterial count of water.

Water sampling location ... .

Water dilution ... .

Culture medium ... .

Number of inoculated Petri dishes ... .

Incubation conditions (temperature ... , time ...).

Number of colonies ... .

Final result (taking into account the water dilution factor) ... .

Permissible count in 1 mL ... .

1.2. Determination of the coli index and coli titer of water (membrane filtration method).

Water sampling location ... .

Volume of the water sample under study ... .

Filter characteristics (number ... , pore size ... , diameter ... .

Water filtration was carried out under a pressure of ... kPa.

After filtration, the filters were placed on a nutrient medium ... .

Culture conditions (temperature ... , incubation time ... ).

Number of coliform colonies ... .

Calculation of the coli index ... .

Calculation of the coli titer ... .

Permissible values for the coli index ... , coli titer ... .

2. Organoleptic water analysis.

2.1. Determination of water odor.

Volume of the water sample under study ... .

Characteristics of odor ... .

Odor intensity in points ... .

Standard limit in points ... .

2.2. Determination of water taste.

Characteristics of Water taste ... .

Taste intensity in points ... .

Standard limit in points ... .

3. Determination of chemical safety indicators of water composition.

3.1. Determination of ammonia content.

Source of the water sample ... .

Water sample volume ... .

Amount of Rochelle salt ... µg.

Amount of Nessler's reagent ... mL.

Color intensity of the solution:

a) when viewing the test tube from the side ... ;

b) when viewing the test tube from above ... .

Result. Ammonia content in the tested water sample ... mg/L.

Permissible content ... mg/L.

3.2. Determination of chloride content.

Source of the tested sample ... .

Water sample volume ... .

Amount of 10% potassium chromate solution ... .

Volume of silver nitrate spent on titration ... mL.

Calculation of chloride concentration in 1 L of water ... .

Result. 1 L of the tested water sample contains ... mg/L of chlorides.

Permissible chloride content in drinking water ... mg/L.

4. Determination of residual chlorine in drinking water as an indicator of disinfection efficiency (rapid method).

Location of water sampling ... .

Water sample volume ... .

Amount of 10% potassium iodide solution ... .

Amount of 0.5% starch solution ... .

Color intensity of the solution ... .

Result. Amount of residual chlorine in water ... mg/L.

Conclusion. Based on the conducted Sanitary and hygienic studies, it has been established that the total bacterial count of the water is ... in 1 mL, which (does not) meet the hygienic requirements, coli titer is ... , which (does not) meet the hygienic requirements, odor is ... points, which (does not) meet the hygienic requirements, taste is ... points, which (does not) meet the hygienic requirements, ammonia content is ... mg/L, which (does not) meet the hygienic requirements, chlorides are ... mg/L, which (does not) meet the hygienic requirements, residual free chlorine is ... mg/mL, which (does not) meet the hygienic requirements. This water (cannot) be used as drinking water.

Recommendations.