Wastewater Microbiology

Wastewater Microbiology - Wastewater Microbiology ESM 219...

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1 ESM 219 Wastewater Microbiology Wastewater Microbiology • Microbes are the catalysts in biological treatment, converting dissolved nutrients to biomass which is then separately disposed of • Harmful microbes are killed by disinfection prior to releasing the final effluent • Solids may be digested by anaerobic microbes, producing energy rich gas Wastewater constituents Major classes – Suspended solids (TSS, VSS, etc.) – Biodegradable organics (BOD, COD – Pathogens (bacteria, viruses, protozoa, etc.) – Nutrients (N, P, etc.) – Priority pollutants (EPA designated toxics) – Organics that don’t biodegrade (refractory) – Heavy metals (Cd, Zn, Pb, Hg, Cu) – Ions (pH; contribute to TDS e.g. Ca 2+ , Na + , SO 4 -2 ) – Temperature – toxicity Biochemical Oxygen Demand (BOD) • Establishes biological “strength” based on oxygen uptake by microbes during aerobic metabolism of organics in waste • 5-day (BOD 5 ) and 20-day (BOD 20 ) • Carbonaceous (CBOD) • Nitrogenous (NBOD) • Ultimate (UBOD) BOD •Standardized •Need: Incubator Bottles DO meter Dilution water Seed (opt.) Expressed in mg/L
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2 BOD Calculation Carbonaceous & Nitrogenous BOD Influent & Effluent BOD & TSS • Influent (M&E Tbl. 3- 13) – TSS 100 to 300 mg/L –BOD 5 100 to 300 mg/L • Effluent minimum 2 ° standards (avg 30-d) –TSS 30 mg /L 5 30 mg/L NOTE: BOD is always less (ca. 0.5) than COD Nitrogen & Phosphorus • Nitrogen – Urea mineralizes rapidly to NH 4 + –NH 4 + oxidizes to NO 3 - (NBOD) – Nitrifying bacteria use CO 2 -C (alkalinity) – Influent N ranges (mg/L as N) • Total: 20 – 70 • Organic: 8 – 25 • Ammonia: 12 – 45 • No nitrate or nitrite typically Nitrogen & Phosphorus • Phosphorus – Raw wastewater contains 4 – 16 mg/L as P – Effluent may restrict to less than 1 mg/L as P – Forms are • Orthophosphate: PO 4 3- , HPO 4 2- , H 2 PO 4 - , H 3 PO 4 • Polyphosphate (polymerized; important in biological phosphorous removal) • Organic phosphorous (low in raw wastewater) Biological Constituents • Many are human pathogens • Most occupy a role in the treatment process • They are: –Bac te r ia – Archaea – Fungi/yeast –P ro tozoa –Ro t i fe rs –A lgae – viruses
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5 Biological Nitrification: Stoichiometry • Ammonia oxidation (nitroso-bacteria) 2NH 4 + + 3O 2 2NO 2 - + 4H + + 2H 2 O • Nitrite oxidation (nitro-bacteria) 2NO 2 - + O 2 2NO 3 - • Overall: NH 4 + + 2O 2 NO 3 - + 2H + + H 2 O = 4.57 g O 2 /g N for complete oxidation Biological Nitrification • Molecular oxygen required is somewhat less from theoretical N oxidation (synthesis and CO 2 uptake co-occur) • Nitrifiers need constant concentration of NH 4 + • Recycle streams (dewatering!) rich in NH 4 + Nitrification • Nitrifiers get their C from CO 2 !!!
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This note was uploaded on 08/06/2008 for the course ESM 219 taught by Professor Holden during the Fall '07 term at UCSB.

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Wastewater Microbiology - Wastewater Microbiology ESM 219...

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