Public Health Engineering - Concepts Regarding Water


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Water Resources, contamination, sampling, Quality testing

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Public Health Engineering - Concepts Regarding Water

  1. 1. Quality control and checking Authorities • EPA – All water • FDA – bottled water • Water available for drinking may include contaminants that pose no health risk
  2. 2. 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
  3. 3. 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
  4. 4. pH • Hydrogen concentration in water • Affects how water reacts with different chemicals
  5. 5. 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
  6. 6. Kidney damage, nervous system damage, Mutations, tumors
  7. 7. 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
  8. 8. 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.
  9. 9. Viruses vs bacteria Virus Bacteria Non-living living smaller larger Need host Don’t need host Vaccines prevent viral infection but don’t eradicate the virus Antibiotics eradicate bacteria Adenoviruses causing eye infections Polio, influenza Salmonella typhi causing typhoid fever
  10. 10. Other pathogens • Protozoa ( giarda lamblia, cryptosporidium) Causing diarrhea • Helminths (hookworms)
  11. 11. 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.
  12. 12. 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
  13. 13. 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
  14. 14. Distribution of contaminants Distribution type Description Random Scattered Uniform Homogenous distribution across entire body Stratified Layered distribution Patchy Scattered concentrations
  15. 15. Sampling approaches Approach 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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  17. 17. Factors affecting transpiration and evaporation • Temperature • Wind speed • Humidity • Solar radiation
  18. 18. Transpiration measurement • Phytometer • A hermetically sealed vessel potted with certain plants • Weight measurements determine a plant’s need for water • Cannot simulate natural conditions
  19. 19. 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
  20. 20. 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
  21. 21. A negative static suction head is Sometimes called suction lift
  22. 22. 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
  23. 23. Infiltration and inflow • Groundwater enters sanitary sewers is infiltration • Inflow is storm water enters sanitary sewers , Unintentional collection.
  24. 24. • Flows of importance: • Peak • Min • Average
  25. 25. Manholes • Need to be provided at: • Grade changes • Intersections of pipes or sewers • A distance of 400 to 600 ft apart