These are factors that affect water quality.

What Are the Factors and Indicators That Affect Water Quality?

These are factors that affect water quality.

• Atmospheric pollution: Environmental air pollution with gasses such as carbon dioxide, sulfur dioxide, and nitrogen oxides mix with water particles in the air to produce polluted rain, sometimes referred to as acid rain. Acid rain then pollutes water systems.
• Runoff: Runoff refers to the flow of excess water across the surface of the land and into waterways. As the water flows, it can pick up agricultural and industrial pollutants such as litter, petroleum, chemicals, fertilizers, and other toxic substances which then contaminate water.
• Erosion and Sedimentation: Soil erosion increases the amount of sediment which enters the water. This can contribute to the degradation of water quality because toxic chemicals or naturally occurring but unhealthy elements can become attached or adsorbed to sediment particles and then be transported to bodies of water.

These are water quality indicators and parameters that reflect the impact of natural and artificial processes.

• Turbidity: Turbidity refers to the cloudiness of water and is a measure of the ability of light to pass through it. Turbidity is caused by different suspended materials in water such as organic material, clay, silt, and other particulate matter. High turbidity is aesthetically unappealing and increases the cost of water treatment. Particulate matter provides hiding places for harmful microorganisms, shields them from disinfection processes, and absorbs heavy metals and other harmful chemicals.
• Temperature: Temperature has indirect influences on water quality. It influences the palatability, viscosity, solubility, and odor of water. It affects the disinfection and chlorination processes, biological oxygen demand (BOD), and the way heavy metals behave in water.
• Color: Color reflects the concentration of vegetation and inorganic matter in water. Although it has no direct influence on the safety of water, it makes water aesthetically unappealing.
• Taste and Odor: Taste and odor affect the aesthetic qualities of water. They are determined by the presence of natural, domestic, or agricultural foreign matter in water.Total Solids (TS): In water two types of solids are present, Total Dissolved Solids (TDS) and Total Suspended Solids (TSS). Solids represent the amount of minerals (good or bad) and contamination present in water. When harmful solids are present, it affects the quality of water by affecting turbidity, temperature, color, taste, odor, electrical conductivity, and dissolved oxygen content.
• Electrical conductivity (EC): Electrical conductivity indirectly measures the ionic concentration of water by measuring its ability to carry or conduct an electrical current. Higher conductivity means more solids are present in the water.
• pH: pH measures how acidic or basic water is. Excessively high or low (<4 or >11) pH is detrimental for the use of water as it alters the taste, effectiveness of its chlorine disinfection process, and increases the solubility of heavy metals in water making them more toxic.
• Hardness: Hardness is a property of mineralized water, and it measures the concentrations of certain dissolved minerals, particularly calcium and magnesium. Hard water can cause mineral buildup in hot water pipes and cause difficulty in producing lather with soap. Very hard water (>500 mg/L of CaCO3) can even have laxative properties.
• Dissolved oxygen (DO): Dissolved oxygen is an indirect measure of water pollution in streams, rivers, and lakes. The lower the concentration of dissolved oxygen, the worse the water quality. Water with very little or no oxygen tastes bad to most users.
• Biochemical oxygen demand (BOD): Biochemical oxygen demand indirectly measures the degree of microbial contamination, and is primarily used as a measurement of the power of sewage water. As microorganisms metabolize organic substances for food, they consume dissolved oxygen (DO) in water. As such, BOD is an indirect indicator of organic material in water.
• Chemical oxygen demand (COD): Chemical oxygen demand measures the oxygen necessary to oxidize all biodegradable and non-biodegradable substances in the water.
• Toxic inorganic substances: Toxic inorganic substances measure the concentrations of metallic and nonmetallic compounds such as arsenic, silver, mercury, lead, cadmium, nitrates, and cyanide. The parameters regarding toxic inorganic substances are essential for assessing the quality of water, as their presence, sometimes even in trace amounts, poses a danger to public health.
• Toxic organic substances: Toxic organic substances refer to compounds such as insecticides, pesticides, solvents, detergents, and disinfectants that degrade water quality and pose a danger to human health.
• Radioactive substances: Radioactive substances decay to emit beta, alpha, and gamma radiation, which has numerous detrimental effects on human health. Radiation primarily affects hematopoietic, gastrointestinal, reproductive, and nervous systems; and is highly carcinogenic. Water quality parameters therefore commonly monitor the concentrations of alpha particles, beta particles, radium, and uranium.
• Bio-indicators: Biological parameters of water quality analyze the presence or absence of various bacteria, algae, viruses, and protozoa.

How to Treat Water and Improve Its Quality

Treatment of water to improve its quality such that it is suitable for subsequent use by humans can require physical, chemical, or biological processes. Some degree of “treatment” occurs even in nature, however higher water contamination levels require sophisticated engineering processes. The following are some of the major processes by which water can be treated and purified.

• Distillation involves evaporation and condensation of water to produce to leave behind only pure water. Though volatile organic substances that evaporate at or below the boiling point of water can remain and may require other treatment processes to remove. Distillation is used to produce desalinated water or when water with special qualities is needed.
• Gas Exchange and Aeration adds oxygen to water and removes dissolved gasses such as carbon dioxide and hydrogen sulfide. Gas exchange helps reduce unpleasant tastes and odors and helps the oxidation of iron and manganese, making the metals more easily removable.
• Coagulation and Flocculation can occur naturally or be aided by adding coagulants such as aluminum sulfate or other synthetic polymers. Coagulation causes colloidal and suspended particles that impart turbidity, odor, or taste to water to come together and form large “flocs” that settle easily during the purification process and can be physically removed by passing the water through sediment beds or filters.
• Sedimentation uses engineered water purification facilities in which water flow is minimized such that gravity allows water-borne particulates including bacteria to settle and be captured in a sediment layer. This process is aided by coagulation and flocculation, as larger particulate matter settles faster.
• Filtration can first occur naturally as water percolates through the soil. However, in engineered water purification facilities, water is passed through granular media or membranes which capture fine particulate matter. Filtration is important for removing very fine particles including any floc particles that escape the earlier sedimentation tank.
• Adsorption involves passing water through special media such as activated carbon, both in granular form as filters and in powdered form as an additive to water, which then adsorbs water contaminants. This process is used to remove unpleasant tastes and odors and a wide variety of organic chemical contaminants that may have made it through the previous phases of purification.
• Ion Exchange passes water through natural and synthetic resins that remove specific ion contaminants. The most common products are zeolites that remove calcium and magnesium (the main components which make water hard) and replace them with sodium.
• Disinfection processes destroy pathogenic microorganisms that may cause water-borne disease. The most widespread disinfection procedure for water purification is chlorination, with UV light treatment and ozonation (O₃) common.