MEV 015: Unit 03 - Water Quality and Its Impact

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Unit 3: Water Quality and Its Impact

3.1 Introduction

Water is essential for all life forms, and its quality directly affects human health, agriculture, aquatic ecosystems, and overall environmental balance. However, increasing human activities and industrialization have led to the contamination of water bodies, making it necessary to monitor, assess, and manage water quality effectively.

3.2 Objectives

The aim of this unit is to help learners understand what water quality means, what factors affect it, and how to assess and manage it. By the end of this unit, learners will be able to explain the concept of water quality, identify key water quality parameters, understand pollution effects, and learn about water quality standards, indices, and assessment methods.

3.3 Concept of Water Quality

Water quality refers to the physical, chemical, and biological characteristics of water that determine its suitability for different uses such as drinking, irrigation, industrial processes, and sustaining aquatic life. Good water quality means water is clean, safe, and free from harmful substances.

3.3.1 Different Processes Affecting Water Quality

Several natural and human-made processes affect water quality. These include industrial discharges, agricultural runoff, sewage, and waste dumping. Natural processes like erosion, sedimentation, and the mixing of surface and groundwater also influence water quality.

3.3.2 Effect of Hydrogeochemistry on Water Quality

Hydrogeochemistry refers to the chemical interactions between water and the rocks or minerals it passes through. These interactions can dissolve or add minerals to water, changing its composition. For example, water passing through limestone areas may contain high levels of calcium and magnesium, affecting its hardness.

3.3.3 Weathering Processes and Water Quality

Weathering of rocks also influences water quality. When rocks break down due to rain, wind, or temperature changes, they release minerals and other substances into water. This process can change the pH, salinity, and overall chemical nature of water, sometimes making it unsuitable for use.

3.4 Water Quality Parameters

To evaluate the quality of water, different parameters are measured and analyzed.

3.4.1 Physico-chemical Parameters

These include physical and chemical properties like temperature, pH, turbidity, color, conductivity, hardness, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), and presence of harmful substances such as heavy metals or toxic chemicals.

3.4.2 Biological Parameters of Water Quality

These parameters involve the study of microorganisms like bacteria, viruses, algae, and other biological indicators. For example, the presence of coliform bacteria (especially E. coli) indicates contamination from human or animal waste, making water unsafe for drinking.

3.5 Water Quality Standards and Guidelines

To ensure water is safe for different uses, national and international agencies set water quality standards. These standards specify the maximum allowable limits for different parameters. In India, the Bureau of Indian Standards (BIS) and Central Pollution Control Board (CPCB) set such limits. The World Health Organization (WHO) also provides global guidelines which countries can refer to while framing their national policies.

3.6 Effects of Water Pollution

Water pollution has serious impacts on both human health and the environment. Contaminated water can spread diseases like cholera, typhoid, and hepatitis. It also harms aquatic life, reduces agricultural productivity, and damages ecosystems. Industrial pollution, chemical spills, and heavy metal contamination can make water toxic and unfit for any use.

3.7 Water Quality Index (WQI)

Water Quality Index is a tool that helps in summarizing complex water quality data into a single number or category to indicate the overall quality of water in a particular area. It simplifies decision-making and helps people understand whether the water is safe for drinking, bathing, or other uses.

3.7.1 Categorization of Water Quality Indices

WQIs can be of various types, depending on their use — such as drinking water quality index, surface water index, groundwater index, etc. Each type uses different parameters and criteria depending on the purpose.

3.7.2 Basic Procedure of Water Quality Index (WQI) Development

To develop a WQI, scientists select important parameters (like pH, BOD, DO, etc.), assign weights based on their importance, and calculate a final score using a mathematical formula. This score is then compared to a scale that tells whether the water is excellent, good, poor, or polluted.

 

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