Water quality assessment involves analyzing physical, chemical, and biological parameters. These factors interact to determine overall water health, affecting aquatic life, human use, and ecosystem function. Understanding these parameters is crucial for effective water management and pollution control.

Key aspects include temperature's impact on dissolved oxygen, nutrient levels leading to eutrophication, and the presence of contaminants like metals and bacteria. Interpreting water quality data involves comparing results to established standards and calculating indices to assess overall water health.

Physical, Chemical, and Biological Water Quality Parameters

Parameters of water quality assessment

• Physical parameters
  • Temperature influences dissolved oxygen levels warmer water holds less oxygen affects metabolic rates of aquatic organisms
  • Turbidity measure of water clarity influenced by suspended particles high levels reduce light penetration affects photosynthesis and aquatic plant growth clogs fish gills and affects their respiration increases water treatment costs
  • Total suspended solids (TSS) measure of solid particles suspended in water contributes to turbidity and water clarity
  • Conductivity measure of water's ability to conduct electricity indicates the presence of dissolved ions (salts, metals) high levels may indicate the presence of pollutants can affect the suitability of water for irrigation
• Chemical parameters
  • pH measure of water acidity or alkalinity scale ranges from 0 to 14 7 is neutral < 7 is acidic > 7 is alkaline extreme pH levels can be harmful to aquatic life affects the solubility and toxicity of metals and other pollutants
  • Dissolved oxygen (DO) amount of oxygen dissolved in water essential for aquatic life low levels can cause stress or death to aquatic organisms affects the breakdown of organic matter and nutrient cycling
  • Nutrients includes nitrogen compounds (nitrate, ammonia) and phosphorus compounds (phosphate) excess nutrients can lead to eutrophication (algal blooms, oxygen depletion, fish kills) nitrate in drinking water can cause methemoglobinemia in infants
  • Metals such as lead, mercury, cadmium can bioaccumulate in aquatic organisms pose health risks to humans through consumption of contaminated fish or water
  • Organic pollutants include pesticides, hydrocarbons can bioaccumulate in aquatic organisms pose health risks to humans through consumption of contaminated fish or water
• Biological parameters
  • Fecal coliform bacteria indicator of fecal contamination presence suggests potential pathogens (E. coli, Salmonella) indicates potential waterborne diseases (cholera, typhoid)
  • Algal growth excessive growth can lead to eutrophication certain algal species produce toxins harmful to humans and animals can lead to taste and odor issues in drinking water
  • Macroinvertebrate diversity indicator of long-term water quality and ecosystem health sensitive species disappear in polluted waters while tolerant species persist

Impacts of water quality parameters

• Temperature affects dissolved oxygen levels warmer water holds less oxygen influences metabolic rates of aquatic organisms (fish, invertebrates)
• Turbidity and TSS high levels reduce light penetration affects photosynthesis and aquatic plant growth clogs fish gills and affects their respiration increases water treatment costs
• Conductivity high levels may indicate the presence of pollutants (industrial discharges, agricultural runoff) can affect the suitability of water for irrigation (salt buildup in soil)
• pH extreme pH levels can be harmful to aquatic life (fish, amphibians) affects the solubility and toxicity of metals and other pollutants (increased bioavailability at low pH)
• Dissolved oxygen low levels can cause stress or death to aquatic organisms (fish kills) affects the breakdown of organic matter and nutrient cycling (slower decomposition)
• Nutrients excess nutrients can lead to eutrophication algal blooms, oxygen depletion, and fish kills nitrate in drinking water can cause methemoglobinemia in infants (blue baby syndrome)
• Metals and organic pollutants can bioaccumulate in aquatic organisms (fish, shellfish) pose health risks to humans through consumption of contaminated fish or water (neurological disorders, cancer)
• Fecal coliform bacteria presence indicates potential waterborne diseases cholera, typhoid, hepatitis A
• Algal growth excessive growth can lead to taste and odor issues in drinking water certain algal species produce toxins harmful to humans and animals (microcystin, saxitoxin)

Relationships among water quality factors

• Temperature and dissolved oxygen inverse relationship as temperature increases, dissolved oxygen decreases warmer water holds less oxygen
• Nutrients and algal growth excess nutrients (nitrogen, phosphorus) stimulate algal growth leading to eutrophication algal blooms, oxygen depletion, and fish kills
• Turbidity and photosynthesis high turbidity reduces light penetration limiting photosynthesis and aquatic plant growth affects primary productivity and food webs
• pH and metal solubility low pH increases the solubility and toxicity of metals (aluminum, lead, mercury) affects bioavailability and uptake by aquatic organisms
• Organic pollutants and dissolved oxygen breakdown of organic pollutants consumes oxygen leading to low DO levels affects aquatic life and nutrient cycling

Interpretation of water quality data

• Water quality standards and guidelines set by regulatory agencies (EPA, WHO) specific to the intended use of water drinking, recreation, aquatic life
• Comparing data to standards determine if water quality parameters exceed the established limits identify potential sources of pollution or contamination (point sources, nonpoint sources)
• Water Quality Index (WQI) integrates multiple water quality parameters into a single value provides an overall assessment of water quality calculated using the equation $WQI = \sum_{i=1}^{n} w_i q_i$ where $w_i$ is the weight of the $i$-th parameter and $q_i$ is the quality rating of the $i$-th parameter
• Interpreting WQI values range from 0 to 100 higher values indicate better water quality used to communicate water quality information to the public and decision-makers (policymakers, stakeholders)