Dr. Bajnóczy Gábor Tonkó Csilla
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Transcript of Dr. Bajnóczy Gábor Tonkó Csilla
Dr. Bajnóczy GáborTonkó Csilla
HIGH OXYGEN DEMANDING NON-TOXIC WASTEWATERS
BUDAPEST UNIVERSITY OF TECHNOLOGY AND ECONOMICS
DEPARTMENT OF CHEMICAL AND ENVIRONMENTAL PROCESS ENGINEERING
FACULTY OF CHEMICAL AND BIOCHEMICAL ENGINEERING
The pictures and drawings of this presentation can be used only for
education !
Any commercial use is prohibited !
HIGH OXYGEN DEMANDING NON-TOXIC WASTEWATERS
Contain significant amount of biodegradable organic matter,non-hazardous to aquatic life.
Main sources:
municipal wastewater
livestock
liquid manurefood industry
EFFECT OF HIGH OXYGEN DEMANDING, NON-TOXIC WASTES ON NATURAL WATER
high oxygen demandingwastewater flowsInto natural water
Dead organic matter in natural water (leaf, dead corpus, etc.) is decayed by bacteria using dissolved oxygen. The process is named mineralization and the final products carbon dioxide and water.
Number of aquatic bacteria is limited by the available organic matter
Increase of nutrientsfor the bacteria
number of decomposing
organisms increases significantly
oxygen consumption increases
↓dissolved oxygen in water
decreases
natural water:aerobic anaerobic
The process induced by non toxic organic materials in natural waters
PRODUCTS OF BIOLOGICAL DEGRADATION,AEROBIC AND ANAEROBIC CONDITIONS
Independently of water condition – aerobic or anaerobic – life is always present, only the living forms and the final product of organic metabolism differ (aerobic or anaerobic bacteria).
Aerobic conditions Anaerobic conditions
carbon
nitrogen
sulfur
phosphorus
carbon
nitrogen
sulfur
phosphorus
CO2
NH3 HNO3
H2SO4
H3PO4
CH4
NH3 amines
H2S
PH3 other phosphorus compounds
Flame in marsh.phosphorus hydrogen + air exothermic oxidation
The heat evolved ignites the methane
aerobic: oxygen is available ; anaerobic: lack of oxygen; anoxic: oxygen available only in form of eg.: nitrate, sulfate
BIOLOGICAL DEGRADATION OF ORGANIC COMPOUNDS
1. terminal oxidation of the carbon chain cytochrom-P450 (iron-containing enzyme) + oxygen in molecule
R – CH2 – CH2 – CH3 R – CH2 – CH2 – C - OH R – CH2 – CH2 – COOH
Simplified mechanism of the terminal oxidation and the formation of carboxyl group at the end of chain
2. step: β – oxidation enzymes playing significant roles in the process:
koenzyme – A : CoASH (reactive center: –SH thiol group)
hydrogen transfer enzymes: oxidized form reduced form
FAD FADH2
NAD+ NADH
O
R – CH2 – CH2 – C - OH
O
R – CH2 – CH2 – C - SCoACoASH
- H2O
O
R – CH = CH – C - SCoA
NAD+ NADH
OH O
R – CH – CH2 – C - SCoAH2O
water addition (Markovnyikov rule)
FAD FADH2
O O
R – C – CH2 – C - SCoA
O
R – C - OH
O
CH3 – C - SCoA+
instable compound in water decays immediately
H2O
acetil-koenzyme A
carbon chain is built backwards by the program of microorganism using this unit
In case of energy demand: citric acid cycle carbon
dioxide and water
BIOLOGICAL DEGRADATION OF ORGANIC COMPOUNDS
1. Long chain carbon compounds (number of carbon atoms > ≈ 32): poorly decomposable or remains intact.
This form is not favored by energetically This form has lower energy
?
?
microorganismdoesn’t find the end of
chain
Some bacteria have exocellular chain splittingenzymes. Short-term gains, the chain terminal
disappears in ball.
plastic degradation is very slow in nature
2. Branched carbon chain compounds: no or slow degradation
O
R – CH – CH2 – C – OH
CH3
O
R – CH – CH2 – C – SCoA
CH3
CoASH
- H2O
OH O
R – C – CH2 – C – SCoA
CH3
H2O
water addition (Markovnyikov rule)
FAD FADH2
O
R – C = CH2 – C – SCoA
CH3
O O
R – C – CH2 – C – SCoA
CH3
Motor oils contain mainly branched hydrocarbons, so the effect on environment is long-term.
3. Aromatic compounds: aromatic ring slowly, but biologically degradable
OOH
OH
COOH
COOH
CH3 – COOH
O O HO – C – C – CH2 - COOH
+
cytochrom
P-450
COOH
OH
cytochrom
P-450
4. Highly condensed aromatic ring: not degradable
Carcinogenic compounds containing highly condensed aromatic rings decay a few hours in atmosphere (sunshine), but toxic effect takes a long time in water and soil.
ORGANIC MATTER CONTENT OF WATER,BOD AND COD
BOD (Biological Oxygen Demand)
The oxygen quantity in a unit of water, necessary for the biological oxidation of organic matter during 5 or 20 days, at 20 °C
Unit of BOD5 or BOD20 [mg oxygen/dm3]
BOD5 necessary oxygen quantity for the biological oxidation of organic carbon compounds
BOD20 necessary oxygen quantity for biological oxidation of organic carbon and nitrogen compounds
degradation of nitrogen compoundsstarts later
organic nitrogen-containing compounds
desamination
NH4+ + 1,5 O2 H2O + 2 H+ + NO2
-
NO2- + 0,5 O2 NO3
-
NH3
Nitrosomonas
Nitrobacter
In aqueous medium
slow
fastday
BOI
ORGANIC MATTER DEGRADATION IN NATURAL WATERS approximated by first-order reaction
BOD t = BOD0 *(1 – e -kt)BOD t: residual oxygen demand at the t time, BOD 0: total biological oxygen demand at the beginning t=0k : air supply constant at a given temperature
Air supply constant
water type k [day-1] 20°C
Little lakes, dead branches 0,1 – 0,23Slow flow 0,23 – 0,35Large, slow water flow 0,35 – 0,46Large, normal water flow 0,46 – 0,69Fast flow 0,69 – 1,15
Conversion to other temperature: k(T) = k(20°C)*1,024T-20
COD (Chemical Oxygen Demand)
The oxygen quantity in a unit of water, necessary for the chemical oxidation of all dissolved or suspended organic matter by a strong oxidizer (potassium dichromate or
potassium permanganate). The final product of the oxidation : CO2 and H2O.
Unit of COD [mg oxygen/dm3]
Relationship between BOD and COD
BOD < COD General relationship, the chemical oxidizer disintegrates all organic compounds, but the microorganisms are choosy.
BOD = COD Water sample contains only biologically degradable organic compounds.
BOD << COD Water sample may contain toxic compounds or only small amount of biologically degradable organic matter.
SIMPLIFIED AEROB BIOLOGICAL WASTEWATER TREATMENT
Accelerated biological degradation of organic matters by activated sludge in continuous aerobic fermenting tanks.
anoxic basin: a.) pre-degradation of organic matters b.) ammonification (organic nitrogen → ammonia) c.) denitrification of recycled purificated wastewater (nitrate → nitrogen)
aerobic basin: a.) air supply b.) oxidation of organic carbon c.) ammonia (formed in anoxic basin) oxidation to nitrate d.) increase of sludge mass
AEROB BIOLOGICAL WASTEWATER TREATMENT
SIMPLIFIED ANAEROB BIOLOGICAL WASTEWATER TREATMENT
Accelerated biological degradation of organic matters by activated sludge in continuous anaerob fermenting tanks.
COMPARISON OF WASTEWATER TREATMENT TECHNOLOGIES
organic matter content of waste water (100%)
carbon contentIn form of
carbon dioxide (~50%)
carbon contentof sludge
~50%
carbon content of drain water
~ 1%
organic matter content of waste water (100%)
carbon content of biogas 90-95 %methane : carbon dioxide ~ 50-50 %
carbon content of drain water
~ 1-5%
carbon content of sludge~1-5%
AEROB ANAEROB
- well known technology - lesser-known technology- aeration: energy intensive - large body of water –> warming problem- sludge disposal problem (heavy metals) - less sludge formation- sludge fermentation → biogas - fuel gas formation- sludge incineration - sensitive to toxic matter (ash content: < 60%) - COD > 2000 mg/dm3
(organic matter: > 25%) - higher capacity (water content: < 50 %) - 1 kg organic matter ~ 1 m3 biogas