Environmental Engineering Water Pollution

Outline Water pollution categories Causes of water pollution Measurement of water pollution

Water pollution categories Sources of surface water pollution are generally grouped into two categories based on their origin. Point source pollution is a single identifiable localized source of air, water, thermal, noise or light pollution. The sources are called point sources because in mathematical modelling, they can be approximated as a mathematical point to simplify analysis. Pollution point sources are identical to other physics, engineering, optics and chemistry point sources.

Water pollution categories Non-point source pollution pollution refers to diffuse contamination that does not originate from a single discrete source. NPS pollution is often accumulative effect of small amounts of contaminants gathered from a large area. NPS Examples such as: discharges from vehicle emissions, construction site, Urban Runoff, forestry etc.

Causes of water pollution The specific contaminants leading to pollution in water include chemicals, pathogens, and physical or sensory changes such as elevated temperature and discoloration. Three main sources causing water pollution are:  Pathogens - Thermal pollution

Causes of water pollution Pathogens The most important biological organisms in water are pathogen These organisms are capable of infecting and transmitting diseases to human Pathogens are not native to aquatic system and usually require an animal host for growth and reproduction. Major groups of pathogens of interest in water supply and treatment are bacteria, viruses, protozoa, fungus and algae.

Causes of water pollution Pathogen Indicator The presence of pathogenic microorganisms is shown by indicator organisms. Their presence shows that pollution has occurred and suggests the nature, type and level of pollution. Indicator micro-organisms properties; Can be used for all type of waters, Always present when pathogen is absent, Easily experimented and give reliable results, Not be a pathogen itself

Causes of water pollution Thermal pollution Thermal pollution is the rise or fall in the temperature of a natural body of water caused by human influence. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers.

Causes of water pollution Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers. Elevated water temperatures decreases oxygen levels (which can kill fish).

Water Quality Water quality is a neutral term that relates to the composition of water as affected by natural processes and human activities. The quality of water also is related to its specific use, and usually measured in terms of the concentration of its constituents. Water quality measurements include physical, chemical, and biological parameters.

Water Quality Parameters Physical Parameters Chemical Parameters

Water Quality Physical Parameters Physical parameters define those characteristics of water that respond to the sense of sight, touch, taste, or smell. The six most commonly considered physical characteristics are suspended solid, temperature, taste and odour, colour

Water Quality Physical Characteristics a) Suspended solid – measured in mg/L Sources: (i) Inorganic compounds such as clay, silt, sand (ii) Organic compounds such as fine organic matter, human waste Effect: (i) Aesthetic (affect turbidity and transparency of water (ii) Health aspect (iii) Adsorption point/centre for chemicals and micro- organisms

Water Quality

Water Quality b. Turbidity – measured in NTU/FTU (nephelometric / Formazin turbidity units) Sources: (i) Inorganic compounds such as clay, sand (ii) Organic compounds such as plant fiber, human waste Effect: (i) Aesthetic (ii) Health aspect (iii) Adsorption point/centre for chemicals and micro- organisms

Turbidity – measured in NTU/FTU Water Quality Turbidity – measured in NTU/FTU

Water Quality (i) Inorganic compounds such as minerals, metals, c. Odour and Taste Sources: (i) Inorganic compounds such as minerals, metals, salts (all of them give taste to water but no odour) (ii) Organic compounds from petroleum and/or degradation of organic matters (odour and taste) Effect: (i) Aesthetic (ii) Health problem

Water Quality d. Temperature – measured in ˚C or ˚F Sources: (i) Effect from ambience (ii) Industrial activities such as cooling system Effect: (i) Disturb biological activities such as micro- organism and aquatic life (ii) Chemical properties such as the degree of gas solubility, density and viscosity

Water Quality Chemical Parameters The chemical characteristics of water are numerous.  Every substance that dissolves in water can be called a chemical water quality characteristic.  Chemical parameters are includes total dissolved solid, alkalinity, hardness, metals, organic compounds, and nutrients.

Water Quality Chemical Characteristics a) Total Dissolved Solid (TDS) Sources: (i) Inorganic compounds such minerals, metal and gases (ii) Organic compounds such as product from degradation of organic matter or organic gas Effect: (i) cause taste, colour and odour problem (ii) Health aspect (iii) small amount of TDS – water become corrosive Note: Recommended TDS concentration for drinking water supply is 500 mg/L

Water Quality b) Alkalinity Definition: the quantity of ions in water to neutralize acid or measure of water strength to neutralize acid - Main constituents are bicarbonate (HCO3- ),carbonate (CO32- ) and hydroxide (OH- ) ions. Sources: (i) Mineral dissolved in water and air (ii) Human activities such as fertilizers, detergent, pesticide etc. Effect: (i) Non pleasant taste (ii) Reaction between alkaline constituent and cation (positive ion) produces precipitation in pipe.

Water Quality Fertilizer Agriculture pesticide

Water Quality c) Hardness Definition: a measure of “multivalent” cations in water such as Ca2+, Mg2+, Fe2+, Mn3+ Sources: (i) Natural mineral on earth Effect: (i) Excessive soap usage (ii) Precipitate form on hardware (iii) Precipitate in pipe – temperature and pH increased Note: Recommended Iron concentration in Water Supply is 0.3 mg/L Desirable concentration of Mn in Drinking water is 0.01 – 0.05 mg/L

Effects on water supply Water Quality Effects on water supply Iron deposit on valve pipe

Water Quality d) Metals – non toxic and toxic Non Toxic Dangerous for health if the concentration is high Example: Ca2+, Mn2+, Fe2+, Zn2+, Al3+, + etc. Source: (i) Mineral, readily available from nature Effect: (i) Colour, odour, taste and turbidity (ii) Deteriorate health (at high concentration)

Water Quality d) Metals – non toxic and toxic Toxic Stored up in food chain Example: Pb2+, Hg2+, Cd2+ etc. Source: (i) Human activities such as mining and industries Effect: (i) Dangerous diseases such as cancer, abortion and deformation in new born baby Note: For Domestic Water Supply Metals level should be: Pb < 0.05 mg/L Hg < 0.02 mg/L Cd < 0.01 mg/L