Water Quality Management- Principles of water quality
Water quality management involves understanding, monitoring, and regulating the chemical, physical, and biological characteristics of water to ensure its suitability for various uses, such as drinking, recreation, agriculture, and ecosystem health. Several principles guide water quality management:
Water Quality Standards: Establishing standards and guidelines for acceptable levels of contaminants and parameters in water bodies based on their designated use. These standards often include limits for pollutants such as heavy metals, nutrients, pathogens, and chemicals.
Pollution Prevention: Emphasising the prevention of pollution at its source through regulations, best management practices, and public education. This approach aims to minimise the introduction of harmful substances into water bodies and reduce the need for costly remediation efforts.
Monitoring and Assessment: Regularly monitoring water quality through sampling and analysis to assess current conditions, identify trends, and detect emerging issues. Monitoring helps authorities make informed decisions about water management strategies and prioritise areas for remediation or protection.
Integrated watershed management: Recognising that water quality is influenced by activities and land use practices within entire watersheds. Integrated watershed management involves coordinating efforts across multiple sectors to address pollution sources, manage runoff, and protect water resources holistically.
Treatment and Remediation: Employing treatment technologies and restoration measures to improve water quality in impaired or polluted water bodies. This may include physical, chemical, or biological processes to remove contaminants, restore habitat, or enhance natural filtration and purification mechanisms.
Public participation and Education: Engaging stakeholders, including communities, businesses, and policymakers, in water quality management efforts. Public participation fosters support for conservation initiatives, increases awareness of water issues, and encourages responsible behaviour to protect water resources.
Adaptive Management: Adopting flexible and iterative approaches to water quality management that allow for adjustments based on new information, changing conditions, and evolving priorities. Adaptive management emphasises continuous learning, experimentation, and collaboration to achieve long-term environmental sustainability.
Ecosystem Based Approaches: Recognising the interconnectedness of ecological processes and human activities in shaping water quality outcomes. Ecosystem-based approaches prioritise the preservation and restoration of natural habitats and functions to support healthy aquatic ecosystems and enhance water quality.
Water quality refers to the basic physical, chemical and biological characteristics of water that determine its suitability for life or for human uses. The acceptable quality of water varies with its intended use. The characteristics of water can be classified into three broad categories:
1. Physical Characteristics: temperature, colour, odour, turbidity and solids
2. Chemical Characteristics: pH, conductivity, salinity, hardness, BOD
3. Biological Characteristics: counts of specific organisms and groups of organisms
Physical Characteristics
Temperature: Temperature is a measure of the average energy (kinetic) of water molecules. It is measured on a linear scale of degrees Celsius or degrees Fahrenheit. Temperature is a basic water quality variable. It determines the suitability of water for various forms of aquatic life. Depending on the geographic location the mean annual temperature varies in the range of 10 to 21oC with an average of 16oC. Temperature affects a number of water quality parameters such as dissolved oxygen which is a chemical characteristic.
Colour: Colour in water is primarily a concern of water quality for aesthetic reason. Colored water give the appearance of being unfit to drink, even though the water may be perfectly safe for public use. Color of the water body can indicate the presence of organic substances, such as algae or humic compounds. In recent times, colour has been used as a quantitative assessment of the presence of potentially hazardous or toxic organic materials in water.
Taste and Odour: Taste and odour are human perceptions of water quality. Human perception of taste includes sour (hydrochloric acid), salty (sodium chloride), sweet (sucrose) and bitter (caffeine). Relatively simple compounds produce sour and salty tastes. However, sweet and bitter tastes are produced by more complex organic compounds. Odor is produced by gas production due to the decomposition of organic matter or by substances added to the wastewater.
Turbidity: Turbidity is a measure of the light-transmitting properties of water and is comprised of suspended and colloidal material. It is important for health and aesthetic reasons. Transparency of natural water bodies is affected by human activity, decaying plant matter, algal blooms, suspended sediments, and plant nutrients.
Solids: Total dissolved solids (TDS) is the term used to describe the inorganic salts and small amounts of organic matter present in solution in water. The principal constituents are usually calcium, magnesium, sodium, and potassium cations and carbonate, hydrogen carbonate, chloride, sulfate, and nitrate anions. The total solids content of water is defined as the residue remaining after evaporation of the water and drying the residue to a constant weight at 103°C to 105°C.
Chemical Characteristics
pH: pH is a measure of how acidic or basic (alkaline) the water is. It is defined as the negative log of the hydrogen ion concentration. The pH scale is logarithmic and ranges from 0 (very acidic) to 14 (very alkaline).
Electrical Conductivity: The conductivity of water is an expression of its ability to conduct an electric current as a result of breakdown of dissolved solids into positively and negatively charged ions. The major positively charged ions are sodium (Na+), calcium (Ca+2), potassium (K+ )and magnesium (Mg+2).
Salinity is a measure of the amount of salts in the water. Because dissolved ions increase salinity as well as conductivity, the two measures are related. The salts in sea water are primarily sodium chloride (NaCl). However, other saline waters owe their high salinity to a combination of dissolved ions including sodium, chloride, carbonate and sulfate.
Alkalinity: The alkalinity of natural water is generally due to the presence of bicarbonates formed in reactions in the soils through which the water percolates. It is a measure of the capacity of the water to neutralize acids and it reflects its buffer capacity. It may also be attributed to the presence of carbonates and hydroxides. Alkalinity is important for fish and aquatic life because it protects or buffers against rapid pH changes.
Hardness: Hardness is a natural characteristic of water which can enhance its palatability and consumer acceptability for drinking purposes. The hardness of water is due to the presence of calcium and magnesium minerals that are naturally present in the water.
The following is a measure of hardness (expressed in mg/l as CaCO3):
Soft: 0 - 100 mg/l as CaCO3
Moderate: 100 - 200 mg/l as CaCO3
Hard: 200 - 300 mg/l as CaCO3
Very hard: 300 - 500 mg/l as CaCO3
Extremely hard: 500 - 1,000 mg/l as CaCO3
Major ions in Water: There are various kinds of trace ions in water supply that influence chemical nature and account for the bulk of natural water mineral content. Most of the dissolved, inorganic chemicals in freshwater occur as ions.
Heavy Metals: Heavy metal refers to any metallic chemical element that has a relatively high density and is toxic or poisonous at low concentration. The some major examples of heavy metals are mercury (Hg), cadmium (Cd), arsenic (As), chromium (Cr), nickel (Ni), copper (Cu), cobalt (Co) and lead (Pb) etc.
Dissolved Oxygen: Dissolved oxygen is the amount of gaseous oxygen (O2) dissolved in an aqueous solution. It gets into water by diffusion from the surrounding air, by aeration (rapid movement), and as a waste product of photosynthesis. The oxygen in dissolved form is needed by most aquatic organisms to survive and grow.
Biochemical Oxygen Demand (BOD)
Biochemical oxygen demand the amount of dissolved oxygen required by aerobic biological organisms to degrade the organic material present in a water body at certain temperature over a specific time period. It widely used as an indication of the organic quality of water and thus representing the pollution load. It is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days (BOD5) of incubation at 20°C.
Chemical Oxygen Demand
Chemical Oxygen Demand (COD) determines the quantity of oxygen required to oxidize the organic matter present in water body under specific conditions of oxidizing agent, temperature and time. COD is an important water quality parameter as it provides an index to assess the effect discharged wastewater will have on the receiving environment.
Biological Characteristics
Microbial Contamination: Microbial contamination is one of the major concerns of water quality. Many types of microorganisms are naturally present in the water such as
Protozoans -Amoeba, cryptosporidium, giardia
Bacteria – Salmonella, typhus, cholera, shigella
Viruses –Polio, hepatitis A, meningitis, encephalitis
Helminths –Guinea worm, hookworm, roundworm
Fecal Matter
Total Coliform and Fecal Coliform
Total coliform bacteria, fecal coliform bacteria, and E. coli are all considered indicators of water contaminated with fecal matter. Contaminated water may contain other pathogens (micro-organisms that cause illness) that are more difficult to test for. Therefore these indicator bacteria are useful in giving us a measure of contamination levels. E. coli is a bacterial species found in the fecal matter of warm blooded animals (humans, other mammals, and birds).
