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Explore wastewater treatment processes, focusing on advanced methods, their effects on the environment, and comparison between India and the US. Learn about the significance of wastewater treatment in maintaining water quality.
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Environmental Microbiology:Treatment of Waste Water and Polluted Habitats 08/09/11
Waste Water & Sewage • A little history • Ancient Romans • Modern sewage system • London: pipes and high pressure water • New York City: 20 years later American waste amounts: (per person per day) 150 gal water 120 gallon of waste 5lbs trash http://www.kingcounty.gov/environment/wastewater/CSO/FAQ.aspx
Sewage Treatment Purpose: • Eliminate potential pathogens and toxins • Decrease nutrient content (reduce microbial growth) • Reduce B.O.D. Biochemical oxygen demand (BOD): Amount of oxygen required for microbial decomposition of organic matter in sample • Determine O2 levels • Incubation with microbes (5 days/20°C) • Determine O2 levels • Calculate difference between 1 & 3 BOD Organic Matter (waste)
B.O.D. Effects Raw sewage BOD: 300 to 400 mg/liter Natural water BOD: 5-10mg/L If you dump raw sewage into “receiving water”, the dissolved O2 can be quickly depleted by microbes http://www.theepochtimes.com/news/4-5-12/21351.html “200 million liters of sewage and industrial waste, much of it untreated, ooze into the Ganges from Varanasi” -Richard Stone, Science 2011
Large Scale Wastewater Treatment Multi-series process (US) • 1° treatment • 2° treatment (4 methods) • Advanced Treatment Effluent (treated liquid) is discharged in body of water Sludge (solid) is further treated in anaerobic digester and disposed of
1° Treatment • Filter & settle steps remove • ~50% of solids & 25% of BOD
Anaerobic Sludge Digestion • Anaerobic organisms act on solids (sludge) • Various populations act sequentially Organic matter organic acids, CO2, H2 Organic acids acetate, CO2, H2 Acetate, CO2, H2 methane • Remaining sludge dehydrated • Disposal: incineration, landfill, fertilizer
2° Treatment • Eliminates most of remaining BOD • Microbial degradation of organic material • 4 different options
Aerobic organisms degrade organic material to • C02 and H2O
2° Treatment Methods • Activated sludge- commonly used Aerobic microbes (grown in flocs) Requires innoculation & aeration Resedimentation(save floc, treat sludge) 2. Trickling filter- smaller treatment plants Spray sewage over biofilm of aerobic microbes • Bacteria • Fungi • Algae • Protozoa • Nematodes
2° Treatment Methods continued • 3. Lagoons- shallow ponds where photosynthetic organisms create aerobic environment (treatment takes months) • 4. Artificial wetlands • Similar to lagoons • Aerobic & anaerobic • environments • Involves bacteria, • algae, plants, • sedimentation • Habitat generation
Advanced Treatment Physical, chemical or biological processes Increased expense over 1° and 2 ° treatment • Removal of ammonia, nitrates and phosphates • Ammonia stripping: Liberates gaseous ammonia from water • Denitrification: use of bacteria (creation of N2 gas) • Chemical precipitation: phosphate removal
Disinfection Performed before effluent is discharged • Chlorine • Ozone • Ultraviolet light • Purpose: reduce numbers of microorganisms and viruses
Septic Tanks (Rural Areas) Collection in large tank • Settling of sludge • Anaerobic degradation Outlet to drainage field • Aerobic oxidization of organic material Potential Problems: Improper aeration Improper drainage Presence of pathogens Toxic conditions
Water-borne disease Giardia lamblia Entomoeba histolytica Cryptosporidium parvum Salmonella typhimurium Vibrio cholerae Leigeonella species Clostridium botulinum Escherichia coli Rotavirus Hepatitis A Polio virus
Waste and Water in Underdeveloped countries Pit latrine verses Composting toilets Macha, Zambia
Drinking Water Treatment Process (US) • Sedimentation • Flocculation of organic material • Filtration Removal of microorganisms Chemical absorption 4. Disinfection
Drinking Water Testing (US) Test for indicator organisms: coliforms • MPN Index: • Maximum for drinking water: 0/1000ml • (depends on collections per month) • Example: If collect 40 samples: <5% can be positive • If exceed positives/month must be reported
Activity Read through “Ailing Ganges” article and identify similarities and differences (3 total) between waste-water treatment in India and in the US.
