fermentation test (phenol red). john snow’s cholera spot map
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Environmental MicrobiologyEnvironmental 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 waterNew York City: 20 years later
http://www.kingcounty.gov/environment/wastewater/CSO/FAQ.aspx
American waste amounts: (per person per day)
150 gal water120 gallon of waste
5lbs trash
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
1. Determine O2 levels 2. Incubation with microbes (5 days/20°C)3. Determine O2 levels 4. Calculate difference between 1 & 3
BOD Organic
Matter (waste)
B.O.D. Effects
Raw sewage BOD: 300 to 400 mg/literNatural 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
Multi-series process (US)• 1° treatment
• 2° treatment (4 methods)• Advanced Treatment
Large Scale Wastewater Treatment
Effluent (treated liquid) is discharged in body of water
Sludge (solid) is further treated in anaerobic digester and disposed of
• 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
Anaerobic Sludge Digestion
2° Treatment
• Eliminates most of remaining BOD
• Microbial degradation of organic material
• 4 different options
1. Activated sludge- commonly used Aerobic microbes (grown in flocs)Requires innoculation & aerationResedimentation(save floc, treat sludge)
2. Trickling filter- smaller treatment plants Spray sewage over biofilmof aerobic microbes
2° Treatment Methods
• 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 processesPhysical, chemical or biological processesIncreased expense over 1° and 2 ° treatmentIncreased 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
Performed before effluent is discharged• Chlorine• Ozone• Ultraviolet light
Disinfection
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
Salmonella typhimurium
Vibrio cholerae
Leigeonella species
Clostridium botulinum
Escherichia coli
Rotavirus Hepatitis A
Polio virus
Giardia lambliaEntomoeba histolytica
Cryptosporidium parvum
1. Sedimentation
2. Flocculation of organic material
3. Filtration Removal of microorganisms
Chemical absorption
4. Disinfection
Drinking Water Treatment Process (US)
Test for indicator organisms: coliforms
Drinking Water Testing (US)
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.
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