Water
Pollution !!!
Environmental Engineering – 1 (CE339)
Lecture-4: Water Pollution—basic indicators
Outlines
Water pollutants
Nutrients
Salts
Temperature
Heavy metals
Pesticides
VOCs
POPs
Water pollutants
Organic matter (color)
Salts
Di-valents
Heavy metals
Nutrients (C, N, P, trace)
Sulfur (grey water)
Toxic chemicals (pesticides, industrial by-products)
Organic carbon (POPs, micro-pollutants)
Organic waste
Electroneutrality (OH-, H+)
Pathogens
Nutrients
• Nutrients are essential for world ecosystem
-Aquatic life ; Plant growth ; Human and animals
• Essential nutrients are Nitrogen, Phosphorous, Carbon (organic/inorganic),
trace elements, vitamins, etc.
• Un-optimized nutrients supply or distribution in water bodies lead many
environmental issues
• Lack of N & P hamper plant growth
• Excess N & P causes eutrophication—leading to low dissolved oxygen
• Freshwater lacks N & P
• Excess N & P due to fertilization
• Wastewater is rich is N & P, also organic carbon
Salts
• Most common salts are Na, Ca, Mg, K, Cl, SO4, HCO3–
• Salt concentration is critical
• Maintains the turgid pressure across the cell wall
• High salts concentration can cause cell rupture
• Concentration is measured as Total dissolved solids
• High Ca+ and Mg+ cause scaling, corrosion, odor and taste
• Excess of Cl- causes smell and poor taste
• Excess of iodine lead to thyroid disorder
• Excess of F- causes bone damage
• High Na+ hampers crop growth—sodicity
• Low HCO3 causes change in water pH
Temperature
• Impacts plant, aquatic, and human health
• Humans are adapted to specific temperature
• Fish survive at specific temperature (12-25 ̊ F) only
• Protein denature above 45 ̊ C
• Cells rupture at low temp (below 4 ̊ C)
• Directly proportional to dissolved oxygen—colder water can hold
more DO
• Seasonable variations affect water quality, concentrates salts
concentration, and fish death
Temperature
• Runoff (household, industry, rain) can impact water temp and
quality—mixing warm water with the freshwater
• Erosion leads to cloudiness of water, absorb more heat
• Metabolic rates and photosynthesis production
• Compound toxicity
• Dissolved oxygen and other dissolved gas concentrations
• Oxidation reduction potential (ORP)
• Conductivity and salinity
• Salted water holds less DO
Temperature and DO
• Day and night cycle regulates temp and DO
• Winter vs summer
• Algal blooms block light supply—DO decreases
• More GHG emissions in winter
Heavy metals
• Cr, Pb, Hg, Cd, As
• Released from household, municipal, and industrial sources
• Their high concentration present multiple health issues
Pesticides
• Insecticides, herbicides, rodenticides, fungicides
• They persist in the environment for a longer period
• Can affect non-target species
Volatile organic compounds
• Widely used in scents, paints, pesticides, cleaners, carpet
• Most-common groundwater pollutants (e.g., BTEX)
• Many are used as solvents and are carcinogens
• Vinyl chloride ( chloroethylene ) making PVC resins, also
carcinogenic
• Tetracholorethylene (PCE) solvent and CFC production
• Trichloroethylene (TCE) solvent and suspected human
carcinogen
• 1,2 dichloroethane (DCA) metal degreasing, high exposure
causes kidney , liver, damage
• Carbon tetrachloride (CT) household cleaning, fungicide,
very toxic
Persistent organic pollutants (POPs)
• Widely produced in chemical, pharmaceutical, medical, fertilizer
industry
• POPs are chemicals of global concern due to their potential for
long-range transport, persistence in the environment their
significant negative effects on human health
Electroneutrality
• Important parameter to reflect the fate of OH- and H+ ions
• Acidic or basic
• A unit change of pH has large impact—pH 4.0 water is 100
times more acidic than pH 6.0
• Most of the environmental species can’t survive below pH 3.0 or
above pH 11.0
• Sandy soil, rain, and snow are acidic
• Runoff (factories, household, agriculture sources) is a major
reason of pH change
• Deforestation lead to pH change
Take home message
Water quality is crucial for environmental, ecological, and human
health
Anthropogenic activities and the nature impact water pollution
Many factors impact water quality—pH, temperature and DO are the
most important
Water quality requirements vary across environmental recipients
(human, plant, animals, aquaculture)
