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    Home > Chemicals Industry > Chemical Technology > Water quality physical and chemical indicators

    Water quality physical and chemical indicators

    • Last Update: 2021-06-19
    • Source: Internet
    • Author: User
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    Water quality indicators are the main basis for the monitoring, evaluation, utilization and pollution control of water bodies
    .


    When considering and studying the sewage and wastewater treatment process and final disposal plan, the first condition is to fully grasp the characteristics of the sewage and wastewater in terms of physics, chemistry and biology.


    The evaluation of water pollution status and pollution degree can be expressed by a series of indicators, which can be divided into three categories: the first category is physical and chemical indicators; the second category is organic pollution comprehensive indicators and nutrients; the third category is biological indicators
    .

    1.
    4.
    1 Physical and chemical indicators

    (1) Water temperature The physical and chemical properties of water are closely related to water temperature
    .


    The solubility of dissolved gases (such as oxygen, carbon dioxide, etc.


    (2) Chroma pure water is colorless and transparent
    .


    The clean water should be colorless when the water layer is shallow, and light blue-green in the deep layer


    (3) Turbidity Turbidity itself does not directly represent the nature of water, but comprehensively reflects the degree of turbidity of water, which is a sensory nature
    .


    The turbidity is related to the content of suspended substances and colloidal substances in the water


    (4) The peculiar smell of the smelling water comes from pollutants such as reducing sulfur and nitrogen compounds, volatile organic compounds and chlorine
    .


    Some organic and inorganic substances that produce odor in water are mainly due to the pollution of domestic sewage and industrial wastewater, the decomposition of natural substances, and the result of microbial or biological activities


    (5) Turbidity is caused by suspended substances such as sand, clay, organic matter, inorganic matter, plankton and microorganisms in the water.
    It is not only slow but also difficult to deposit
    .


    The turbidity caused by iron and manganese hydroxides in life is very harmful and must be removed by special methods


    (6) Transparency refers to the degree of clarity of the water sample.
    Clean water is transparent.
    When suspended substances and colloids exist in the water, the transparency will decrease
    .


    Generally, the transparency of groundwater is relatively high, and its transparency may be constantly changing due to different water supply and environmental conditions


    (7) pH value refers to the negative logarithm of hydrogen ion activity in water
    .


    pH=-lgH +


    (8) Residues Total residues are substances left in the vessel after water or sewage evaporates at a certain temperature after drying, including "non-filterable residues" (that is, all residues trapped on the filter, also called suspended matter) and " Filterable residue" (that is, all residue that passes through the filter, also called dissolved solids)
    .
    Suspended solids can affect the transparency of water bodies, reduce the photosynthesis of algae in the water, limit the normal movement of aquatic organisms, slow down the activity of the bottom of the water body, cause hypoxia at the bottom of the water body, and reduce the assimilation capacity of the water body
    .

    (9) Salinity Salinity is the total amount of inorganic minerals contained in the water.
    Frequent drinking of low-minerality water will destroy the balance of alkali metal and alkaline earth metal ions in the human body, causing disease, and excessively high mineralization in drinking water It will also cause calculi
    .
    Salinity is an important indicator for the determination of water chemical composition
    .
    It is used to evaluate the total salt content in the water and is one of the main indicators for the applicability evaluation of farmland irrigation water
    .
    It is often used to express the mass of the sum of main measured ions in natural water analysis
    .

    (10) Conductivity Conductivity is a digital representation of the ability of a solution to conduct current
    .
    The conductivity of pure water is very small.
    When the water contains inorganic acids, alkalis or salts, the conductivity increases
    .
    Conductivity is often used to indirectly estimate the total concentration of ionic components in water
    .
    The conductivity of the aqueous solution depends on the nature and concentration of the ions, the temperature and viscosity of the solution, and so on
    .
    Conductivity changes with temperature.
    When the temperature increases by 1℃, the conductivity increases by about 2%.
    It is usually specified that 25℃ is the standard temperature for measuring conductivity
    .

    (11) Oxidation-reduction potential For a water body, there are often multiple redox couples, which is a quite complex system, and its redox potential is the comprehensive result of the oxidation-reduction of multiple oxidizing substances and reducing substances
    .
    The oxidation-reduction potential is of great significance to the migration and transformation of pollutants in the water environment
    .
    The type, rate and balance of oxidation in the water body determine to a large extent the nature of the main solute in the water
    .

    (12) Acidity Acidity refers to all substances and can react with water, the role of a strong base, i.
    e.
    , release of H + or via hydrolysis to produce H + total amount of the substance
    .
    In the surface water, the pH value of the water body decreases due to the dissolution of CO 2 or the entry of acid-containing wastewater discharged from machinery, mineral processing, electroplating, pesticides, printing and dyeing, and chemical industries
    .
    Due to the corrosiveness of the acid, the normal living conditions of fish and other aquatic organisms and crops are destroyed, causing the death of fish and crops
    .
    Acid-containing wastewater can corrode pipelines, ships, and damage buildings
    .
    Therefore, acidity is an important indicator to measure changes in water bodies
    .

    (13) Alkalinity is the opposite of acidity.
    Alkalinity refers to all substances in water that can neutralize strong acids, that is , the total amount of substances that can accept protons H +
    .
    There are many sources of alkalinity in water.
    The alkalinity of surface water is basically a function of carbonate, bicarbonate and hydroxide content, so total alkalinity is regarded as the sum of the concentrations of these components
    .
    The alkalinity index is often used to evaluate the buffering capacity of water bodies and the solubility and toxicity of metals in it.
    It is a judgment index for the control of water and wastewater treatment processes
    .
    If alkalinity is formed by excessive alkali metal salts, alkalinity is an important basis for determining whether this water is suitable for irrigation
    .

    (14) Carbon dioxide Carbon dioxide mainly exists in the form of dissolved gas molecules in water, but there is also a small part of it reacts with water to form carbonic acid, which can react with alkaline substances in rocks, and can become precipitates from water through precipitation reactions.
    Remove
    .
    In the biochemical exchange between water and organisms, carbon dioxide occupies a unique position.
    The combined state of dissolved carbonate undergoes a homogeneous and multiphase carbonic acid reaction with the lithosphere and atmosphere, which plays an important role in adjusting the pH and composition of natural water.
    Plays an important role
    .
    The main source of carbon dioxide in surface water is the decomposition of organic matter in water and geology, as well as the respiration of aquatic organisms, and it can also be absorbed from the air
    .
    Therefore, its content can indirectly indicate the degree of organic pollution in the water body
    .

     

     

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