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Water standards

Water standards

It is a criterion that defines the quality of water to be suitable for various uses, such as drinking water, utility water, water for industry, or agriculture. These water standards aim to prevent impacts on health and the environment.



Types of Water Standards


1. Drinking Water Standards

Drinking water must have safe quality, free from harmful substances and pathogens that are dangerous to health. Common standards for drinking water include

  • World Health Organization (WHO):
    • Establish drinking water quality that emphasizes safety, such as controlling the levels of chemicals and microorganisms.
  • Drinking Water Standards of Thailand (TIS 257-2551):
    • Establish various criteria such as
      • Pathogens: No E. coli or coliforms allowed in the water
      • Chemicals: For example

    ​ ​ ​- Ammonia not exceeding 1.5 milligrams/liter

    ​ ​ ​- Lead content not exceeding 0.01 milligrams/liter

    ​ ​ ​- Residual chlorine not exceeding 0.2–0.5 milligrams/liter

        • Physical properties: Water must be clear, colorless, odorless, and tasteless.

    2. Water Use Standards

    Water used for daily activities such as bathing, washing dishes, or washing cars. The general standards for water use include:

    • Water Quality Standards for Consumption (Ministry of Public Health):
      • It doesn't need to be as clean as drinking water, but it must be free of harmful substances.
      • Must be clear, without turbidity or foul odor
      • The pH value is between 6.5–8.5
      • Turbidity not exceeding 25 NTU

    3. Wastewater Standards

    Wastewater discharged from industrial plants or community sources must be treated before being released into the environment. Wastewater standards in Thailand are set by the Pollution Control Department (PCD), such as:

    • pH value: 5.5–9.0
    • Turbidity: Should be low to prevent sediment accumulation
    • BOD value: Not exceeding 20 milligrams/liter
    • COD value: Not exceeding 120 milligrams/liter
    • Heavy metal content: such as lead, zinc, or cadmium must be below the specified limits

    4. Water Standards for Agriculture

    The water used in agriculture, such as for irrigating plants or raising animals, should have appropriate quality to prevent the accumulation of toxins in food, such as:

    • pH value: Ranges from 6.0 to 8.5
    • Salt concentration (TDS): Should not exceed 450–2,000 milligrams/liter
    • Heavy metal content: such as cadmium or lead must be below the specified limits
    • No chemical residues: such as pesticides

    5. Water Standards in Industry

    Water in industry must be suitable for its use, such as cooling water, water in the production process, or wastewater treatment:

    • pH value: Depends on the production process, such as 6.5–8.5 for cooling water
    • Hardness: Should be low to reduce the formation of scale in machinery
    • Suspended solids (TSS): Must be low to reduce damage to equipment

    Key Criteria in Water Standards


    clear drinking glass with water

    1. Physical properties

    • Clarity: The water must be clear, without any turbidity or suspended particles.
    • Odor and taste: Drinking water must not have any unusual odor or taste.

    2. Chemical Properties

    • pH value: Must be within the appropriate range, such as 6.5–8.5
    • Toxins: Such as lead, cadmium, and arsenic must be below the specified limits.

    3. Biological properties

    • No pathogens: such as E. coli bacteria or coliforms
    • No parasites: such as roundworms or flukes



    The Importance of Water Standards


    1. Protecting public health: Preventing illnesses caused by water-related diseases such as cholera, diarrhea, or chemical contamination
    2. Reduce environmental impact: Treating wastewater before discharging it into natural water sources helps maintain balance in the ecosystem.
    3. Improving quality of life: Clean water helps communities have better hygiene

    clear water close-up photography

    Why use chlorine in water?