Water quality index: What are the various factors affecting it
What's the story
The water quality index is a tool that measures water purity by analyzing the physical, chemical, and biological factors.
The index provides a convenient way to assess the suitability of water for different uses, such as drinking, recreation, and aquatic life support by considering multiple water parameters such as PH value, turbidity, etc to provide a single value.
Physical indicators
Key physical indicators
The physical indicators of the water quality from any source include temperature, conductivity, taste, Total Suspended Solids (TSS), turbidity, odor, color, and Total Dissolved Solids (TDS).
Water temperature is one of the most crucial factors as it affects the metabolism, growth, and reproduction of marine and aquatic life.
Many marine species can survive only within a certain temperature range.
chemical indicators
Chemical indicators detect water quality?
Among the chemical indicators most important is the Biological Oxygen Demand (BOD).
It is essentially a measure of the amount of oxygen required to remove waste organic matter from the water in the process of decomposition.
Higher BOD indicates more oxygen is required to decompose waste in water thus leaving water with low oxygen, signifying lower water quality.
biological factors
Biological factors lead to eutrophication in water
Higher nutrient levels in water like phosphorus and nitrogen can promote the growth of algae, leading to eutrophication thus affecting its quality.
Eutrophication enriches water with nutrients more than required which causes algal bloom or green scums.
These dense mats of vegetation exacerbate eutrophication by depleting it of oxygen thereby affecting marine life. Further, eutrophication is also caused by human activities.
microplastics
Microplastics - Critical factor in assessing water quality
Apart from the above-mentioned indicators, the presence of nanomaterials like microplastics (less than five millimeters in size) can significantly affect water quality in various ways.
Microplastics in aquatic environments have become a growing concern due to their persistence, widespread distribution, and potential negative impacts on ecosystems.
After a recent study found bottled water containing 240,000 plastic particles, the importance of the factor increases manyfold.
Human Factors
Anthropogenic factors
Human-induced factors like industrial discharge, agricultural runoff, and improper wastewater disposal of solid and hazardous materials leach harmful substances into water thus contributing to water pollution.
Mining activities and marine and inland oil spills together lead to water pollution thus adversely affecting the water quality index in many ways.
Growth in population leads to higher urbanization affecting water sources.
Assessing purity
General range for water quality
Typically, the acceptable range of PH is between 6.5 and 8.5. Dissolved oxygen levels above 5mg/l are generally considered healthy.
The temperature and nutrient levels vary based on the water body. Elevated levels of either of the two may lead to eutrophication suffocating and killing the species thus further deteriorating the water quality as the decay of the dead will consume more oxygen.