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Wastewater Treatment

Wastewater Treatment. Water Pollution. Water Pollution Any chemical , biological , or physical change in water quality that has a harmful effect on living organisms or makes water unsuitable for desired uses Point source Specific location (ex. drain pipes, ditches, sewer lines)

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Wastewater Treatment

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  1. Wastewater Treatment

  2. Water Pollution • Water Pollution • Any chemical, biological, or physicalchange in water quality that has a harmful effect on living organisms or makes water unsuitable for desired uses • Point source • Specific location (ex. drain pipes, ditches, sewer lines) • Non-point source • Cannot be traced to a single site of discharge (ex. atmospheric deposition, agriculture/industrial/residential runoff)

  3. Laws • Clean Water Act • 1972 – Federal Water Pollution Control Act Amendments • EPA required technology-based effluent standards and permits for all discharges from point sources • 1977 – Clean Water Act Amendments • New technology based program for toxic pollutants • 1987 – Water Quality Act • Control toxic hot spots and non-point sources

  4. Laws • Major Provisions of the CWA • National Goals • Elimination of pollution discharges • Research and Grant Programs • Clean up for Chesapeake Bay and Great Lakes • Construction Grants • Sewage treatment plants • Standards and Enforcement • Effluent limitations • Permits and Licenses • National Pollutant Discharge Elimination System permit • General Provisions • Citizen suits and judicial review

  5. Prevention and Reduction • Prevent groundwater contamination • Reduce non-point runoff • Reuse treated wastewater for irrigation • Find substitutes for toxic pollutants • Work with nature to treat sewage • Monitoring • Separate sewage and storm lines • Proper disposal of waste materials • Practice four R’s of resource use (refuse, reduce, recycle, reuse)

  6. Water Treatment • Why treat water? • To eliminate organic and inorganic wastes • Organic • Fecal matter – coliform test (bacteria found in intestines in warm blooded animals, ex. E. coli) • Drinking water 0 colonies / 100 mL • Water treatment 2000 colonies / 100 mL • Swimming 200 colonies / 100 mL • Inorganic • Mercury and phosphates

  7. Water Treatment • Water comes from watersheds, lakes, streams, rivers, etc. • 1. Sedimentation • Sediments out only large particles • 2. Flocculation • Flocculation chemicals are added • Aluminum sulfate (alum) • Bind organic matter – form clumps called flocs • 3. Filtration • Typically made of sand  blocks organic matter • Over 99% of microbes now removed • 4. Chlorination • Kills any remaining microbes • Less than 30 minutes • Treats pipes from water treatment  storage  home • Prevents biofilms from forming

  8. Sewage Treatment • Removes organic matter and is measured by Biochemical Oxygen Demand (B.O.D.) • How much B.O.D. is needed to break down organic matter • More sewage means more B.O.D. • Primary Sewage Treatment • Physical process • Secondary Sewage Treatment • Biological process • Tertiary (Advanced) Treatment • Series of specialized chemical and physical processes to remove specific pollutants left in the water after primary and secondary treatment.

  9. Sewage Treatment • Primary Treatment • Screening and Grit Chamber • Remove large floating objects and allow solids such as sand and rock to settle out • Primary Settling Tank • Suspended organic solids settle out as sludge • What is removed? • Removes 60% of suspended solids • Removes 30-40% of the B.O.D. organic wastes • Pathogens, phosphates, nitrates, salts, pesticides, and radioactive isotopes remain

  10. Sewage Treatment • Secondary Treatment • Aerobic • 1. Activated Sludge Aeration • Oxygen pumped in; more oxygen means more breaking down • B.O.D. decreases 75-95% • 2. Trickling System • Round vats with rotating sprayers • Decreases B.O.D. 85% • Anaerobic • 1. Sludge tank/bioreactors/anaerobic sludge digestor • Comes in layers (gas, scrum, supernatant, actively digesting sludge, stabilizing sludge) • Anaerobic microbes digest solid portion and give off methane and carbon dioxide • Stabilized sludge can be used as fertilizer • 30 days

  11. Primary and Secondary Sewage Treatment • http://www.youtube.com/watch?v=GV-DoisLwm0

  12. Sewage Treatment • Primary and Secondary Treatment Overview • 95-97% B.O.D. removed • 70% of most toxic metal compounds and synthetic chemicals removed • 50% of nitrogen removed • 5% of salts dissolved • Radioactive isotopes, organic substances (pesticides), and pathogens remain

  13. Sewage Treatment • Tertiary (Advanced) Treatment • Special filters to remove phosphates and nitrates • Chlorination • Bleaching to remove water coloration and disinfect to kill disease-carrying bacteria and some viruses • May have harmful health effects such as the increase risk of cancer, miscarriages, and damage to the nervous, immune, and endocrine systems • Ozone and ultraviolet (UV) light may be used, but cost more and are not as effective • Ex. Peru stopped chlorination, but resumed after a 1991 cholera outbreak which infected more than 300,000 people and caused at least 3,500 deaths

  14. Sewage Treatment Overview

  15. Greensburg Sewage Treatment • http://www.ggsa.us/ • Greater Greensburg Sewage Authority (GGSA) • Greater Greensburg Wastewater Treatment Plant (WWTP) • Treats 6.75 million gallons of wastewater per day • Preliminary screening, grit removal, primary sedimentation combined carbonaceous and nitrogenous BOD5 removal in a conventional activated sludge system, final sedimentation, chlorination, and dechlorination. • Gravity thickening for primary sludge, mechanical concentrators for waste activated sludge, two-stage anaerobic digestion, and mechanical dewatering. • Approximately 9,800 customers

  16. Overview • U.S. Federal Law • Requires primary and secondary treatment for all municipal sewage treatment plants • Exemptions from secondary treatment possible if there is an excessive financial burden • According to EPA, two-thirds of sewage treatment plants have violated water pollution regulations, many of them minor • 500 cities failed to meet federal standards for sewage treatment plants • 34 East Cost cities only screen out large floating objects from their sewage before discharging into coastal waters

  17. Overview • Network of Pipes • Some cities have separate pipes for carrying runoff of storm water • 1,200 U.S. cities have combined sewer lines for these two systems (cheaper) • Heavy rains or too many users can cause Combined Sewer Overflow (C.S.O.) • Discharge untreated water directly into surface water • According to EPA, at least 40,000 overflows per year in the United States • EPA estimate that 7.1 million get sick each year from swimming in CSO or storm-water runoff contaminated waters

  18. Sludge • Sewage Treatment produces Sludge • Contains bacteria-laden solids and toxic chemicals and metals • 9% is placed in digesters and converted to compost • 36% fertilizes farmland, forests, degraded land, etc. • 55% dumped in conventional landfills • Solutions? • Ban release of toxic and hazardous wastes from water • Eliminate the use and waste of toxic chemicals • Waterless composting toilet systems • Wetlands to treat sewage

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