5. Surveillance of drinking water quality. Water quality – criteria and standards. Water sampling for physical, chemical and bacteriological examination. Purification of water. Disinfection of water. Water pollution.

Water – hygienic, health, and ecological significance. Hygienic requirements for the quality of drinking water.

1. Hygienic Significance:

• Water is essential for personal hygiene (bathing, washing hands, cleaning), which prevents infectious diseases.
• Safe water reduces waterborne diseases like cholera, dysentery, hepatitis A, and typhoid.
• Adequate water supply is crucial for food preparation and sanitation, minimizing contamination and infection risk.

2. Health Significance: Water maintains physiological functions such as blood volume, nutrient transport, and body temperature regulation. Safe water prevents infections and exposure to harmful chemicals like heavy metals and nitrates. Balanced minerals in water, such as calcium, magnesium, fluoride, and selenium, support overall health and antioxidant systems like glutathione peroxidase.

Calcium in Hard Water and Kidney Stones

• Hard water contains calcium (Ca²⁺) and magnesium (Mg²⁺).
• Magnesium may protect against kidney stones by binding oxalate in the gut, reducing calcium-oxalate stone formation.
• High calcium intake, whether from very hard water or diet, can increase urinary calcium, which may promote calcium-oxalate kidney stones in susceptible individuals.
• Key point: For most people, normal hard water levels are safe, but very high calcium levels can contribute to stone formation.

3. Ecological Significance: Water is crucial for aquatic ecosystems, supporting plants, fish, and wildlife. It ensures safe irrigation for agriculture, supports industrial processes, and helps maintain environmental balance. Clean water preserves rivers, lakes, wetlands, and groundwater, contributing to biodiversity and natural nutrient cycles.