Water Pollution Index: Understanding The Measure Of Aquatic Health

Water pollution indices are used to evaluate water quality and rank it according to its suitability for human consumption. The Water Quality Index (WQI) is one of the most popular and widely used methods, but it has limitations due to its unequal weighting of parameters. To address these limitations, a new concept called the Water Pollution Index (WPI) has been proposed, which is more flexible and easy to calculate. It takes into account the observed concentration (Ci) and standard permissible concentration (Si) of various physical, chemical, and biological parameters. Other indices such as the Heavy Metal Pollution Index (HPI) and the Integrated Water Quality Index (IWQI) also exist, each with its own strengths and weaknesses. These indices are essential for assessing water quality and pollution levels, especially in diverse geographical contexts.

Water Pollution Index

Water quality parameters

Physical Parameters:

• Temperature: Water temperature affects the solubility of oxygen and other gases, as well as the metabolic rates of aquatic organisms. Deviations in temperature can impact the ecological balance of water bodies.
• Turbidity: This measures the cloudiness or opacity of water caused by suspended particles. High turbidity can interfere with water treatment processes and affect aquatic life.
• Colour: The presence of colour in water can indicate the presence of organic matter, inorganic compounds, or pollutants.
• Odour: Unusual odours in water can result from bacterial activity, algal blooms, or chemical contamination.

Chemical Parameters:

• Dissolved Oxygen (DO): DO is crucial for the survival of aquatic organisms and can indicate the presence of pollution. High levels of organic matter or pollutants can deplete oxygen levels.
• Biological Oxygen Demand (BOD): This parameter measures the amount of oxygen consumed by microorganisms as they decompose organic matter. High BOD values indicate a high level of organic pollution.
• PH: The pH scale measures how acidic or alkaline water is. Deviations from a neutral pH (7) can have detrimental effects on aquatic life and water treatment processes.
• Conductivity: This measures the ability of water to conduct electricity, which is influenced by the presence of dissolved ions and salts. High conductivity can indicate mineral or salt pollution.
• Heavy Metals: The presence of heavy metals, such as lead, mercury, or cadmium, can pose significant risks to human health and the environment.

Biological Parameters:

• Coliform Bacteria: The presence of coliform bacteria, especially E. coli, indicates faecal contamination and can pose serious health risks.
• Algal Blooms: Excessive growth of algae can result in oxygen depletion, toxin production, and ecological imbalances.
• Aquatic Macroinvertebrates: The presence or absence of certain macroinvertebrates, such as insects and crustaceans, can indicate water quality as they are sensitive to pollution.

These parameters are used in various water quality indices, such as the Water Quality Index (WQI), Heavy Metal Pollution Index (HPI), and Comprehensive Pollution Index (CPI), to provide a quantitative assessment of water pollution. Each index integrates multiple parameters to produce a single numeric value that represents the overall water quality. These indices are valuable tools for monitoring and managing water resources, ensuring they remain safe and suitable for their intended purposes.

Water quality indices

The concept of WQIs was introduced in the 1960s by Horton, who developed a system for rating water quality through index numbers. Since then, various models and indices have been developed to assess water quality, such as the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) and the Freshwater Quality Index used by the Washington Department of Ecology's Stream Monitoring Program. These indices consider multiple variables and provide a single numeric result that expresses the overall water quality.

One example of a WQI is the West Java Water Quality Index (WJWQI), which is based on 13 crucial water quality variables: temperature, suspended solids, COD, DO, nitrite, total phosphate, detergent, phenol, chloride, Zn, Pb, mercury (Hg), and fecal coliforms. The WJWQI suggests 5 quality classes ranging from poor (5-25) to excellent (90-100).

It is important to note that WQIs are usually developed for specific regions and may not be generic. They also face challenges in converting large amounts of data into a single index, and different statistical approaches can be used to address these issues. Additionally, the selection of variables and the assignment of weights to each parameter can vary depending on the specific WQI model and the management objectives of the assessment.

Overall, WQIs provide a valuable tool for assessing and monitoring water quality, helping to identify areas of concern and guide efforts to improve water quality in rivers, lakes, and other water bodies.

Water pollution sources

Water pollution is a critical issue that jeopardizes human health and safety. It is caused by various sources, including both point sources and non-point sources. Point source pollution refers to contamination originating from a single, specific location, while non-point source pollution comes from diffuse sources. Here are the key sources of water pollution:

Point Sources:

• Wastewater Treatment Facilities: These facilities treat and process billions of gallons of wastewater daily, reducing pollutants like pathogens, phosphorus, nitrogen, heavy metals, and toxic chemicals. However, aging infrastructure and overwhelming volumes can lead to the release of untreated wastewater, contributing to water pollution.
• Industrial Discharges: Factories, refineries, and other manufacturing facilities can discharge untreated or partially treated effluents containing toxic chemicals, heavy metals, and other pollutants directly into water bodies.
• Sewage Systems: Leaking septic systems and inadequate sanitation infrastructure can contaminate water sources with harmful microorganisms and chemicals, posing significant health risks.
• Chemical and Oil Spills: Accidental or illegal releases of chemicals and oil from industrial, transportation, or storage facilities can have devastating impacts on water quality.
• Illegal Dumping: Unregulated disposal of hazardous wastes, chemicals, and other pollutants into water bodies or near watershed areas contributes to point source pollution.

Non-Point Sources:

• Agricultural Activities: Agriculture is the leading cause of water degradation globally. The use of fertilizers, pesticides, and animal waste in farming contributes to nutrient pollution, with excess nitrogen and phosphorus causing algal blooms that harm aquatic ecosystems and drinking water sources.
• Fossil Fuel Power Plants: Air pollution from burning fossil fuels can indirectly contaminate water sources. Pollutants released into the air can fall back onto land and water, impacting both surface water and groundwater.
• Urban Runoff: Stormwater runoff in urban areas can carry various pollutants, including oil, grease, chemicals, and litter, into nearby water bodies.
• Natural Sources: Water quality can also be influenced by natural processes, such as volcanic eruptions, algae blooms, and wildlife waste.

It is important to note that the impact of these sources can vary based on geographical location, season, and the specific parameters of the water body in question. To effectively address water pollution, it is crucial to identify the sources, implement proper waste disposal practices, and adopt sustainable water management strategies.

Water pollution tracking

One commonly used approach is the Water Quality Index (WQI), which integrates multiple water quality parameters into a single numeric result. This index considers various physical, chemical, and biological factors that influence water quality. These parameters can include temperature, biological oxygen demand, total suspended sediment, dissolved oxygen, and conductivity. By measuring and analysing these factors, scientists and researchers can gain insights into the overall health of a water body.

Another popular method is the Heavy Metal Pollution Index (HPI), specifically designed to address metal pollution in water. This index takes into account factors such as the unit assigned weight, the number of metal ions, observed metal concentrations, and the maximum permissible levels of metal ions for safe water. The HPI is particularly relevant in industrial or urban areas where metal pollution is a significant concern.

In addition to these indices, organisations like the Canadian Council of Ministers of the Environment (CCME) have developed their own water quality indices. The CCME-WQI, for example, is a complex method used to assess water quality in different seasons. It focuses on values that exceed standard guidelines, helping to identify water bodies that require immediate attention due to high pollution levels.

To facilitate water pollution tracking, various tools and resources are available. The National Water Information System, for instance, provides access to water-resources data collected from approximately 1.5 million sites across the United States. This system offers online access to surface water, groundwater, and water quality data. Additionally, the National Environmental Public Health Tracking Network, led by the CDC, aims to enhance surveillance and improve understanding of how environmental contaminants impact human health.

Water purification

The World Health Organization (WHO) reported that, as of 2019, billions of people worldwide lack access to improved drinking water. This lack of access contributes to 1.8 million deaths annually from diarrhoeal diseases associated with inadequate water, sanitation, and hygiene. These deaths are preventable through simple water purification techniques and safe storage practices.

Filtration is another essential water purification technique, utilising filters with varying pore sizes made from materials such as sand, gravel, or charcoal. These filters effectively remove germs, including parasites, bacteria, and viruses, as well as dissolved particles like dust and chemicals. Advanced filtration methods, such as ultrafiltration, employ filters with very small pores, allowing only water and tiny molecules to pass through. Reverse osmosis is a specialised filtration technique that removes additional particles from water, often used in water treatment plants for recycled water or saltwater.

Disinfection is a critical step in water purification, utilising disinfectants like chlorine to kill pathogens (viruses and bacteria). Chlorination, an established technique, is particularly useful in emergencies when other methods are unavailable. When disinfecting water, it is essential to hold the treated water in a storage unit, such as a tank or clear well, to ensure the completion of the disinfection process. Chlorine tablets or liquid can be added to water, but tablets require dissolution in heated water. Individuals with thyroid problems should exercise caution and consult a doctor before adding chlorine to their drinking water due to its potential association with low thyroid issues.

While less common, solar purification and the addition of iodine are alternative water purification methods. Additionally, deionization using UV light and distillation are effective techniques that fall under the category of water purification rather than simple filtration. Distillation involves heating water to evaporate and then collecting and condensing the steam back into liquid form, leaving impurities behind.

Frequently asked questions