Water Quality Criteria and Indicators
Drinking water quality in the Russian Federation is strictly regulated by normative documents (specifically, SanPiN 2.1.4.1074-01). According to modern standards, water is tested against dozens of parameters.
Key standards for centralized systems:
- Organoleptics: odor and taste must not exceed 2 points, chromaticity — no more than 20 degrees, and turbidity — up to 1.5 mg/L. The presence of water organisms visible to the naked eye and any surface film is strictly prohibited.
- Chemical composition: total mineralization is permitted up to 1000 mg/L. It is important to control hardness (7–10 mEq/L) and the content of specific elements. For example, iron is normed at 0.3 mg/L. Exceeding the fluorine concentration (> 1.5 mg/L) leads to damage to bone tissue and tooth enamel — fluorosis, while heavy metal salts (lead, cadmium) cause acute and chronic poisoning.
- Microbiology: total and thermotolerant coliform bacteria, as well as coliphages and Giardia cysts, must be completely absent. The total microbial count is limited to 50 bacteria per 1 mL.
Classification of Water Sources
All water supply sources are divided into underground, surface, and atmospheric. The need for water treatment (aeration, filtration, coagulation, or disinfection) directly depends on their quality class.
- Underground waters: formed by multi-meter filtration of precipitation through rock. Groundwater (accumulating on the first aquitard layer, easily polluted), unconfined and confined interstratal (artesian) waters are distinguished. The latter lie deep beneath aquitard layers, are not directly replenished from the surface, and are considered the purest, often requiring no treatment.
- Surface waters: rivers, lakes, reservoirs. They are accessible and possess enormous reserves, but are easily contaminated, contain few salts and many microorganisms. Their purity is assessed by the flora and fauna living in them — this indicator is called saprobity (from Lat. sapros). Water can be abstracted for the centralized water supply only from zones of active self-purification: oligosaprobic (clean water zone) or beta-mesosaprobic.
- Atmospheric waters: rain and snow. Characterized by minimal mineralization. Within large cities, they are not used for household needs due to the high risk of contamination by industrial emissions.
Water Supply Systems and Their Protection
Depending on the method of resource delivery to the consumer, systems are divided into centralized (with water supply to the point of consumption), decentralized (without direct supply, e.g., public wells), and autonomous (for individual use).
For decentralized supply, the following are most commonly used:
- Shaft wells: dug to a depth of 10–15 meters. Require strict adherence to sanitation: distance from landfills and cesspools at least 20–25 meters, presence of elevated walls (75–80 cm), a cover, and a special "clay cap" around the shaft to protect against rotting and runoff. Water is retrieved only with a public bucket.
- Drilled wells: deep vertical shafts with casing pipes protecting the walls from collapse. Water is abstracted through perforated filters at the bottom. Wells are better protected against external factors; however, if the wellhead or joint tightness is compromised, there is a serious risk of contamination of the entire underground water basin.
To ensure the safety of any water intakes, sanitary protection zones (SPZs) are established. They consist of three belts: Belt I — strict regime zone (directly at the water intake), Belts II and III — territories with restrictions on economic activity.
Briefly: answers to topical questions
Which infectious diseases are predominantly waterborne?
A multitude of bacterial, viral, and protozoan infectious diseases are transmitted via water. These include:
- Acute intestinal infections — dysentery, enteritis, enterocolitis, typhoid fever, paratyphoid A and B, cholera.
- Viral infections — infectious hepatitis A, hepatitis E virus, poliomyelitis, adeno-, rota-, and enteroviral infections.
- Bacterial zoonotic infections — tularemia, leptospirosis.
- Protozoan infections — diseases caused by protozoa.
What methods of drinking water disinfection are used at water treatment plants?
Reagent and non-reagent methods of drinking water disinfection are used at water treatment plants.
- Reagent methods — chlorination (including double chlorination, chlorination with chlorine dioxide, and pre-ammoniation) and ozonation.
- Non-reagent methods — ultraviolet irradiation, ultrasound, and other physical methods.
The most common method is chlorination with chlorine gas, while ozonation is considered the most promising method.
The three pillars of water quality: Safe (infections and radiation), Harmless (chemical composition), Optimal (taste, color, odor).
Class and exam questions
Why is it unacceptable to use rainwater in a large city?
In megacities, atmospheric precipitation is heavily polluted by industrial and motor vehicle emissions; therefore, its use for household purposes is not recommended.
From which zones of a surface water body is water abstraction permitted for the water supply system?
Water intake organization is permitted only in the purest zones with active self-purification processes: oligosaprobic and beta-mesosaprobic.
Why is a "clay cap" created around a shaft well?
It performs two functions: protects the wooden walls from rotting and serves as a barrier preventing contaminated surface water from entering the well shaft.
What else to study on this topic
- Acute and chronic effects of heavy metal salts (lead, cadmium, mercury) on the body.
- Indicator organisms (hydrobionts) for each of the four saprobity zones.
- Specifics of regimes in Belts I, II, and III of sanitary protection zones (SPZs).
- Water treatment methods (aeration, coagulation, filtration) depending on the source class.
- Evolution of domestic hygienic water quality standards from 1937 to the present day.
Master the entire topic in the "Hygiene" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Hygienic Requirements for Drinking Water" and 530 more pages of the subject
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Other topics in "Chapter 2. Ecological and Hygienic Problems of the Hydrosphere and Water Supply"
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.