Water Quality and Toxic Metal Effects

Hydrology Overview

• Hydrology is the study of water and its movement through various pathways within the hydrological cycle.
• It's applied by engineers to compute river flows, water movement in soils, and evaporation rates.

Water Properties

• Water is a clear, odorless, and tasteless liquid essential for most plant and animal life.
• Under chemical nomenclature, its scientific name is dihydrogen monoxide, but this name is rarely used.
• Water's intrinsic color is a slight blue hue, but in small quantities it appears colorless.
• Water vapor, however, is essentially invisible as a gas.
• Water is a universal solvent, dissolving salts, sugars, acids, alkalis, and some gases (especially oxygen and carbon dioxide).
• Substances that dissolve in water are known as hydrophilic (water-loving).
• Substances that do not mix well with water are known as hydrophobic (water-fearing), examples being fats and oils.

Boiling Point and Density

• The boiling point of water varies depending on barometric pressure.
• At the top of Mt. Everest, water boils at 68°C, while at sea level, it boils at 100°C.
• Water's maximum density occurs at 3.98°C.
• When cooled further, it expands to become ice, which accounts for 9% greater volume than the liquid form. This allows ice to float on water, as seen in icebergs for instance.

Water Trivia and Facts

• Only 3% of Earth's water is fresh water.
• Over 90% of the world's fresh water supply is stored in Antarctica.
• The average adult human body contains 37 liters of water.
• The human brain is comprised of 75% water.
• Dehydration results if a human does not absorb enough water.
• Water (in the three forms of liquid, gas and solid) is the only substance found naturally on Earth.
• In a 100-year period, a water molecule spends 98 years in the ocean, 20 months as ice, 2 weeks in lakes and rivers, and less than a week in the atmosphere.
• Frogs absorb water through their skin.
• Mauna Kea, an inactive volcano in Hawaii, is taller than Mount Everest when measured from its base on the ocean floor.

Hydrology Applications

• Hydrology is the study of the movement of water and its use in various processes like;
• Calculating river flows from rainfall.
• Studying water movement in soils.
• Determining evaporation rates.

Groundwater Supply

• Groundwater is both a direct and indirect supply of water.
• In the zone of aeration (near the surface) soil pore spaces hold both air and water, with moisture held on soil particles by capillary forces.
• Below the aeration zone, is the zone of saturation, where pores are filled with water and is commonly referred to as groundwater.
• A stratum containing substantial groundwater is called an aquifer.
• The surface of this saturated layer is known as the water table.
• Unconfined aquifers are underlain by an impervious stratum.
• Confined aquifers are trapped between two impermeable layers.

Surface Water Supplies

• Surface water supplies are less reliable than groundwater sources.
• Water quantities fluctuate widely over time and are easily polluted.

Water Quality

• Water in its natural evaporation state is nearly pure in composition.
• Human activities such as industrial and domestic waste, agricultural chemicals and other contaminants add to water impurities during its passage through the hydrologic cycle.
• Water quality encompasses its physical, chemical, biological, bacteriological or radiological characteristics for acceptability assessment.
• Classifications typically include potable (fit for drinking), palatable (pleasant taste), contaminated (unfit for drinking due to substances present), and infected with pathogenic matter.

Physical Water Quality Parameters

• Suspended solids: are inorganic material (clay, silt) and organic material (plant fibers, biological solids, algae, bacteria) or other solids resulting from human use of water bodies.
• Total solids (organic and inorganic combined): measured by evaporating a sample to dryness and weighing the residue.
• Dissolved solids: pass through a filter paper. This is determined by Total solids - suspended solids
• Turbidity: a measure of the extent to which light is scattered by suspended matter in water. It is not a direct measure of suspended solids.
• Color: can be apparent (due to suspended solids) and true (due to dissolved solids)
• Measuring color typically involves comparing it with standardized colored materials or using spectrophotometric techniques common amongst industries.

Taste and Odor

• Substances that produce odor in water usually also impart a taste - Mineral substances give taste without odor.
• Sources include minerals, metals, salts, biological reactions, and organic substances (like petroleum products and decomposition of organics like H2S).
• Measurement involves human sensory assessment (TON) or spectrophotometric techniques.
• A TON of 3 is a recommended limit for drinking water.

Temperature

• Water temperature is an important parameter affecting biological species activity and chemical reactions in natural water systems.
• The temperature of surface waters governs the biological species present and their rates of activity.
• Temperature affects the solubility of gases in water.
• Sources of temperature variation in water bodies include ambient temperature, and industrial waste heat dissipation which can alter the temperature of receiving streams.
• Impacts: lower temperatures lead to lower biological activity.
• Fish are affected by temperature and dissolved oxygen levels.
• Increased rates of biological activity at elevated temperatures also lead to accelerated growth of algae, which can cause eutrophication.

Electrical Conductivity

• Measures how well water can conduct electricity.
• High conductivity indicates high contaminant content.
• Potable and ultra-pure water has extremely low conductivity.
• Electrical conductivity is reported in micromhos per centimeter (µmhos/cm) or microsiemens per centimeter (µS/cm).

Hardness

• Hardness is a term used to express the properties of highly mineralized water.
• Mainly caused by the presence of calcium and magnesium ions.
• These ions are present as bicarbonates, sulfates, and sometimes chlorides and nitrates.
• Groundwater is typically harder than surface water.
• The sum of calcium and magnesium ions is a measure of Total Hardness.

Fluorides

• Seldom found in surface waters but appears in ground water in some regions.
• Toxic to humans and animals in high concentrations but beneficial at low concentrations.
• Levels: 1.0 mg/L helps prevent dental cavities, 2.0 mg/L can cause tooth discoloration, >5 causes bone fluorosis, 1.5 mg/L is a limit in drinking water.
• Bone fluorosis leads to osteoporosis.

Metals

• Metals dissolve somewhat in water.
• Excessive amounts of heavy metals can pose health hazards.
• Toxic heavy metals include cadmium, lead, chromium, etc. and their exposure can lead to nervous system breakdown, kidney damage, mutation, and tumor induction.
• Non-toxic metals include calcium, magnesium, sodium, iron, manganese, aluminum, copper, and zinc.

Nutrients (Nitrogen and Phosphorus)

• Essential nutrients for the growth and reproduction of plants, animals and aquatic species.
• Nitrogen and phosphorus regulate plant and animal growth and reproduction.
• Sources include animal wastes, chemical fertilizers, and wastewater discharges. Runoff from agricultural lands and industrial activities also contribute significantly to nutrient levels in water bodies.
• Excessive nitrogen can cause nitrate poisoning in babies (blue baby syndrome), and phosphorus affects water quality by causing eutrophication (algal blooms).

Organics

• Come from natural sources (decay products of organic solids) or result from human activity (wastewater discharges and agricultural practices).
• Two categories of dissolved organics: biodegradable and non-biodegradable.
• Biodegradable organics consist of starches, fats, proteins, alcohols, acids, aldehydes, and esters, and can be easily used as food by micro-organisms.

Dissolved Oxygen

• A key indicator of water pollution.
• Higher concentration of dissolved oxygen indicates better water quality.
• Actual dissolved oxygen varies depending on pressure, temperature, and salinity of water body.
• Drinking water with very little or no oxygen can have an undesirable taste.

Biochemical Oxygen Demand (BOD)

• Measure of the organic material in water.
• Amount of dissolved oxygen needed by aerobic biological organisms to break down organic material over a specified time period correlated with the amount of organic matter in water body.
• High BOD in water indicates higher organic waste and potential pollution issues.

Chemical Oxygen Demand (COD)

• Measures all organic substances, both biodegradable and non-biodegradable, based on the amount of strong oxidizing chemicals needed.
• COD values are typically higher than BOD values for the same sample, as COD considers both biodegradable and non-biodegradable organics.

Radioactive Substances

• Potential sources include nuclear power plants, industries, medical research, and uranium mining.
• Decay of radioactive substances releases beta, alpha and gamma radiation.
• Exposure can cause genetic and somatic damage to living tissues, including harmful effects on both human and animal health and reproductive capability.
• Radon gas is naturally found in groundwater and is a cause for concern as it's volatile and can be inhaled during water use activities such as showering, and drinking.

Maximum Allowable Level (MAL)

• Standards commonly used to regulate specific chemicals and substances present in drinking water, with each chemical or substance having its prescribed limit.

Biological Water Quality Parameters

• May cause water-borne diseases and water contact diseases.
• Pathogens are biological organisms in water capable of infecting and transmitting diseases to humans.
• Pathogens require a host for growth and reproduction and often survive in water for long periods of time.
• Common water-borne pathogens include bacteria, viruses, protozoa and helminths

Additional Terms

• Endemic: refers to a disease prevalent in a specific population.
• Epidemic: an outbreak of an infectious disease spreading widely within an area
• Pandemic: if the outbreak of an infectious disease spreads widely worldwide
• Epidemiology: studies the causes of a disease spreading in a community.
• Microbiology: the study of microorganisms and their activities.