Environmental Health X. Rodents and Insects Shu-Chi Chang, Ph.D., P.E., P.A. Assistant Professor 1 and Division Chief 2 1 Department of Environmental Engineering.
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Environmental Health X. Rodents and Insects Shu-Chi Chang, Ph.D., P.E., P.A. Assistant Professor 1 and Division Chief 2 1 Department of Environmental Engineering 2 Division of Occupational Safety and Health, Center for Environmental Protection and Occupational Safety and Health National Chung Hsing University Friday, May 11, 2007
Individual household disposal systems 30-35% of Americans depend on on-site subsurface disposal system Septic tank Process Drain field Aerobic system Others: biological toile, composting toilet, incinerating toilet, oil- flushed toilet, and vacuum toilet.
Liquid wastes – a broader perspective Point sources Non-point sources Effects Drinking water pollution DO consumption Fish and shellfish may be injurious Eutrophication Can block sunlight and destroy coral reef
Water pollution regulations Federal Water Pollution Control Act (1956) Best available control technology Secondary sewage treatment standards EPA can enter and inspect industrial sources of pollution Water Quality Act (1987) Permits Measurement Quantity of contaminants SS Nutrients Chlorine Acidity and alkalinity Treatment indicators Organic matter: oxygen demand Nutrients and toxic chemicals Other measurements DO BOD and COD
Treatment of municipal sewage Three stages Primary Settling tank to remove sand, grit, and small rocks Remove 50% of solids and 30-50% BOD Secondary Trickling filter (70-80%BOD removal), activated sludge process (90%BOD removal), or biological stabilization pond Tertiary Coagulation, flocculation, sand filter, and disinfection
Treatment of industrial wastes Physical processes Remove suspended oils, greases, and emulsified organics Remove dissolved materials Recover acid Chemical processes Addition of acids Addition of coagulants Ion-exchange resin Oxidants Biological processes Predigestion Oxidation Others Deep-well injection Non-point sources
Land disposal of treated wastewater Advantages Returning nutrients back to soil Reclamation and preservation of open space or wetland. Allows development of new wetlands Creating an ideal environment in which natural biological, physical, and chemical processes can stabilize the wastes Recharging the groundwater Saving Standards for wastewater for recycling and reuse. Sludge disposal: fertilizers or landfill. Heavy metals tend to be concentrated.