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Lecture 6

Lecture 6 Summary.docx

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BIOL 354
Bruce Greenberg

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BIOL354 – Environmental Toxicology I Spring 2012 Lecture 6: Sources and Fate of Contaminants Review: Gamma rays (3-10 mega electron volts); 3 stages of dose dependent radiation outcome: Haematopoietic effects; Gastrointestinal effects; Central Nervous System effects. Walkerton Accident (Local Farm Field Run-Off) - Few # of people died due to drinking E. coli contaminated well water - Chlorine was not added and many residents developed GI diseases - Currently, Walkerton has the best water treatment plan in Canada Pollutant Sources (2) 1) Accidental Release (Can’t be eliminated, maybe minimized) - Nuclear accidents (Chernobyl & Fukushima Daiichi), oil spills (Exxon Valdez & Deepwater Horizon) 2) International Release (Acknowledged as undesirable, no other methods, full extent of toxicity unknown) - Direct: Sewage effluents (municipal or industrial)  Land & Groundwater Entry  Intentionally applied pollutants (pesticides, fertilizers, manure – E. coli, Sewage sludge applied above surface)  Storage (septic) tanks needed to be cleaned out seasonally (leak into lands) - Indirect (Highly Dynamic): Automobile, exhaust, mines, landfill leachates, etc.  Road Salt, fertilizers, pesticides can leach into the soil -> can contaminate groundwater  May not be able to replace as of now, but should be applied WISELY  E.g. Dave Rudolph studies (Municipal – Nitrate & their effects on farm soil)  Sewage Treatment Plants -> Combined Sewer Overflows  Storm water/road run-offs (HIGHLY TOXIC)  Combined sewers – Older version, today most sanitary/storm are separated o Separated storm water systems are not treated in any way  Wet weather: Water overwhelms the dam, untreated water from both sewers flows out of the dam through the outlet pipe into lakes.  E.g. The lower Don River [Politicians] receives 27 CSOs & 19 storm sewers  E.g. Taylor-Massey Creek receives 13 CSOs & 6 storm sewers  Atmospheric Entry – Aerosols, gases, pesticides & chlorofluorocarbons  E.g. Volatile Organic Compounds (VOCs) – Fumigants: Mothballs (Gaseous)  E.g. Combustion/Incineration (Fuel, incomplete - PAH)(Acid Rain) o Major cause of atmospheric pollutions  Land & Groundwater Entry  Landfills to deposit waste – Leach into the soils/groundwater (VERY TOXIC)  Combustion – Particulates (ash) & volatiles – Absorbed into the land - Sewage Treatment Plants - Biological Oxygen Demand [BOD]: Oxygen required for the metabolic break down of decomposable organic matters (microbes, nutrients, pharmaceuticals etc.) - Chemical Oxygen Demand [COD]: Oxygen needed for the chemical reduction or oxidation of organic wastes (Oxidizing agents – Potassium dichromate etc.) - The Three Levels of Treatment  Primary: Solid removal by short period of settling process (filtration)  Secondary: Organic waste removal by chemicals (COD) or bacteria (BOD), use of “activated sludge” or “biological filter” units (constant shuffling to ensure contact)  Tertiary: Chemical removal of specific components (phosphate, nitrogen, ammonia) BIOL354 – Environmental Toxicology I Spring 2012 - E.g. Water Treatment Plant @ Guelph  Preliminary: Parallel detention ponds  Primary & Secondary: Biosolid & dissolved organic carbon removal  Tertiary: Nitrification (Ammonia/NH3 to Nitrate/NO3), filtration, chlorination (kill bacteria) & de-chlorination by sodium bisulphate (no Cl-residual) - Problems  Bacteria for decomposition can be killed by toxin/toxicants (e.g. Chemtura – Agent orange)  Residual sludge contains lipophilic contaminants, need to be properly disposed of  Highly biological active
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