public health engineering - concepts regarding water

Quality control and checking Authorities• EPA – All water• FDA – bottled water• Water available for drinking may include contaminants that pose no

health risk

Temperature

• The temp. determines the kind of species that can thrive in the water• Thermal pollution leads to:• Loss of oxygen from water ( molecules agitated, loose, allowing oxygen to

escape)• fish population is affected

Dissolved Oxygen/BOD

• Measurement of oxygen present in water• Chemical and biological processed use up oxygen• Oxygen in water necessary for fish to thrive• Water with low BOD is considered healthier for human consumption

pH

• Hydrogen concentration in water• Affects how water reacts with different chemicals

TDS/TSS/Salinity

• Dissolved and suspended solids• Suspended solids affect turbidity of water.• Turbidity is the amount of haziness of water• Dissolved solids impact BOD and chemical properties of the water

TSS

TDS

Kidney damage, nervous system damage, Mutations, tumors

Abiotic and Biotic

• Abiotic factors are the non-living components of an ecosystem• SWATS - Soil, Water, Air , Temperature, Sunlight• Climate

• Biotic factors are the living components of an ecosystem• All living organisms

Why solids dissolve in water

• Hydrogen bonding in water allows many inorganic and organic substances to dissolve in water • Water molecules have a polar arrangement of hydrogen and oxygen

atoms allowing the charges on them to attract a multitude of other compounds.• Water contains both organic and inorganic as well as living and non-

living substances, not all of which are harmful.

Viruses vs bacteria

Virus BacteriaNon-living livingsmaller largerNeed host Don’t need hostVaccines prevent viral infection but don’t eradicate the virus

Antibiotics eradicate bacteria

Adenoviruses causing eye infectionsPolio, influenza

Salmonella typhi causing typhoid fever

Other pathogens

• Protozoa ( giarda lamblia, cryptosporidium) Causing diarrhea• Helminths (hookworms)

Sampling

• We take only a portion of water that represents in bulk the properties of the entire water body.• Saves money, time, energy and human effort.

Sample types

• Representative: represents properties of the constituents present in water in bulk amount.• Grab: Sample taken at any time and at any point within the water

body.• Composite: Grab samples mixed to produce a representative sample

Analytical protocol

• Sample collection• Storage and presentation• Preliminary treatment (drying,sieving,filteration)• Volumetric or weighing dilution (to prevent instabilities)• Sample extraction or digestion• Tests – chromatography or spectroscopy• Reporting results

Distribution of contaminants

Distribution type Description Random ScatteredUniform Homogenous distribution across entire

bodyStratified Layered distribution Patchy Scattered concentrations

Sampling approachesApproach Description

Judgemental Based on personal knowledge or experience or on preliminary test results or visual inspection

Random Samples collected randomly assuming distribution is homogenous

Stratified Random Sampling area divided into non-overlapping areas of homogeneous distribution (temporal or spatial)

Systematic Dividing sampling area into square or triangular grid and taking samples at nodes of each unit or at the same location within each unit.

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Factors affecting transpiration and evaporation• Temperature• Wind speed• Humidity• Solar radiation

Transpiration measurement

• Phytometer• A hermetically sealed vessel potted with certain plants• Weight measurements determine a plant’s need for water• Cannot simulate natural conditions

Zone of aeration and saturation

• Aeration: (vadose)• Contains small amounts of moisture. Acts as a zone of transmission rather

than storage.• Gravity water, capillary water and hygroscopic moisture (water held by strong

molecular forces)• Mositure cannot be tapped as a water supply source

• Saturation: (phreatic)• Pore spaces filled with water called groundwater• Aquifer is a stratum consisting of a substantial amount of groundwater.• Water table or phreatic zone serves as the interface between the two zones

Pumps types

1. Rotodynamic:1. Radial flow (Centrifugal)2. Axial flow(Propeller)3. Mixed flow(Centrifugal)

2. Displacement:1. Reciprocating (piston)2. Rotary (Cams or gears)

Others: Jet , airlift, diaphragm pumps

A negative static suction head isSometimes called suction lift

Sewers

• Shambles , Meat packing , waste dumped in streets• Storm sewers arose• Sanitary waste = domestic wastewater• Combined sewers• Sanitary sewers• Collecting sewers collect wastewater from households • Intercepting sewers or interceptors drain wastewater from collecting

sewers and allow this wastewater to flow to treatment plants

Infiltration and inflow

• Groundwater enters sanitary sewers is infiltration• Inflow is storm water enters sanitary sewers , Unintentional

collection.

• Flows of importance:• Peak• Min• Average

Manholes

• Need to be provided at:• Grade changes• Intersections of

pipes or sewers• A distance of 400 to

600 ft apart