seminar on biological wastewater treatment processes past, present and future dr. ajit p....
TRANSCRIPT
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Seminar on
Biological Wastewater Treatment Processes
Past, Present and Future
Dr. Ajit P. AnnachhatreEnvironmental Engineering ProgramAsian Institute of Technology
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Keywords Wastewater Biological Processes Treatment Processes Applications Ongoing Research Activities
Biological Wastewater Treatment
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1.Wastewater Domestic Wastewater
Industrial Wastewater Present State of Wastewater
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Domestic Wastewater over 80 % - untreated in Asian mega cities
major components- COD = 250-1000 mg/L Total N = 20-90 mg/L Total P = 4-15 mg/L effects of discharging into natural receiving bodies
oxygen demand by carbon and nitrogen
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Industrial Wastewater...Eg: Starch industry wastewater major component-COD = 10,000-20,000 mg/L
effects of discharging into natural receiving bodies - 20 m3/ton of starch- high COD - high suspended solids- cyanide exposure
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Industrial Wastewater...Starch industry wastewater factory with 300 T/d of starch
wastewater generation 6000m3/d
COD 14,000 mg/L
population equivalent 1000,000
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Industrial Wastewater present treatment method: Anaerobic ponds
typical loading rates:800-1000kg COD /ha/d
area requirement: 100 ha
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2.Biological Processes aim: any form of life- survive & multiply
need for energy & organic molecules as building blocks
made of C, H, O, N, S, P and trace elements
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Biological Processes... cell: derives energy from oxidation of reduced food sources (carbohydrate, protein & fats)
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MicroorganismsClassification: Heterotrophic- obtain energy from oxidation of organic matter (organic Carbon)
Autotrophic- obtain energy from oxidation of inorganic matter(CO2, NH4, H+ )
Phototrophic- obtain energy from sunlight
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Biochemical Pathways oxidation of organic molecules inside the cell can occur aerobic or anaerobic manner
generalized pathways for aerobic & anaerobic fermentation
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Biochemical Pathways Glucose
EPM Pathway
Pyruvic Acid ADP ATPEnergyLactic Acid TCA Cycle H+ Respiration H2O CO2 O2
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aerobic pathways contains- EMP pathways, TCA cycle, respiration
anaerobic pathways contains- EMP pathways
released energy stored as ATP molecules
excess food is stored as Glycogen
C6H12O6 + 6O2 +38 ADP + 38 Pi 6 CO2 +38 ATP + 44 H2O Biochemical Pathways
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Biological growth
- exponential growth (batch)
- Monod kinetics
- Haldane kinetics
under toxic conditions
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exponential growth
Biological growth...
= (X
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Monod kineticsBiological growth...
( = (m
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Haldane kinetics (under toxic conditions)
Biological growth...
( = (m
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3.Applications1. Carbonaceous removal - aerobic- anaerobic
2. Nitrogen removal- nitrification- denitrification
3. Sulfide removal- anaerobic SO4 reduction- aerobic HS- oxidation
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Biological Carbonaceous Removal aerobic- oxidation bacteria CHONS + O2 + Nutrients CO2 + NH3 + C5H7NO2 (organic matter) (new bacterial cells)+ other end products- endogenous respiration bacteriaC5H7NO2 + 5O2 5CO2 + 2H2O + NH3 + energy (cells)
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Biological Carbonaceous Removal anaerobic
Schematic of the Anaerobic Process
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Biological Nitrogen Removal nitrification-energyNitrosomonasNH4+ + 1.5 O2 NO2- + H2O + 2 H+ + (240-350 kJ) (1) NitrobacterNO2- + 0.5 O2 NO3- + (65-90 kJ)(2)
-assimilationNitrosomonas 15 CO2 + 13 NH4+ 10 NO2- + 3 C5H7NO2 + 23 H+ +4 H2O(3) Nitrobacter 5 CO2 + NH4+ +10 NO2- +2 H2O 10 NO3- + C5H7NO2 + H+(4)
- overall reaction
NH4+ +1.83 O2 + 1.98 H CO3- 0.021 C5H7NO2 + 0.98 NO3- + 1.04 1H2O + 1.88H2CO3
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Biological Nitrogen Removal factors affecting nitrification
* temperature
* substrate concentration
* dissolved oxygen
* pH
* toxic and inhibitory substances
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Biological Nitrogen Removal denitrification* assimilatory denitrification- reduction of nitrate to ammonium by microorganism for protein synthesis
* dissimilatory denitrification- reduction of nitrate to gaseous nitrogen by microorganism- nitrate is used instead of oxygen as terminal electron acceptor- considered an anoxic process occurring in the presence of nitrate and the absence of molecular oxygen- the process proceeds through a series of four steps
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Biological Nitrogen Removal denitrification
* heterotrophic denitrification
- denitrifiers require reduced carbon source for energy and cell synthesis
- denitrifiers can use variety of organic carbon source - methanol, ethanol and acetic acid
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Biological Nitrogen Removal factors affecting denitrification
* temperature
* dissolved oxygen
* pH
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Biological Sulfate Removal * Sulfate removal cycle
anaerobicSO4 -- HS - S 0 (O2 deficient) (O2 excess)
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4.Treatment Processes pond treatment
activated sludge process
biofilm process
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- no biomass recirculation- high HRT- high land area- O2 transfer limitations- inadequate mixing- excess loading (anaerobic condition-H2S generation)Pond Treatment
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Activated Sludge ProcessFE
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Activated Sludge Process...- aerobic
- suspended-growth
- Design equations
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Activated Sludge Process... typical values of cell residence time (c )
- c for C removal ~ 3-10 days - c for N removal ~ 5-30 days
- loading rates ~ 2-3 kg COD/m3/d
- drawbacks: O2 requirements, inlet conc.
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Biofilm Processesadvantages of biofilm processes:
- higher process productivity (loading rates)- higher biomass holdup- higher mean cell residence time- no need for biomass recirculation- creates suitable environment for each type of bacteria- sustains toxic loads
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Biofilm Processes... types of biofilms: aerobic, anaerobic, anoxic
process of biofilm formation
- formation of diffuse electrical double layer due to electrostatic forces and thermal motion
- transfer of microorganism to surface
- microbial adhesion
- biofilm formation
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Biofilm Processes... biofilm operation
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Biofilm Processes... biofilm operation
- diffusion resistance
- inadequate supply of nutrients to inner
portions of Biofilm
- limitations on product out diffusion
- attrition of reaction conditions
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Biofilm Processes... biofilm operation as biofilm thickness increases effectiveness factor () decreases
average rate of substrate consumption
Effectiveness factor ( =----------------------------------------------
substrate consumption at biofilm surface
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Anaerobic biofilm processes
Conversion of Ethanol to Methane
Conversion Reaction
(Go (kJ)
Ethanol
CH2CH2OH (aq) + H2O (l) = CH3COO- (aq) + H+ (aq) + 2H2 (g)
+09.65
Hydrogen
2H2 (g) + CO2 (g) = CH4 (g) + H2O (l)
- 65.37
Acetate
CH3COO- (aq) + H+ (aq) = CH4 (g) + CO2 (g)
- 35.83
Net
CH2CH2OH (aq) = 3/2 CH4 + CO2 (g)
- 91.55
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Anaerobic biofilm processes... importance of H partial pressure
loading rates 10-15 kg COD/m3/d against 2-5 kg COD/m3/d in suspended growth processes
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Ongoing Research ActivitiesBiological Processes
aerobic anoxic anaerobic
nitrificationdenitrification SO42-- reduction
HS- oxidation detoxification
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Ongoing Research Activitiesaerobic
nitrification HS- oxidation
inhibition aniline modeling biofilm in ASP degradation processes in SBR ShabbirJega Sunil & Keshab Savapak Shabbir & Shabbir
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Ongoing Research Activitiesanaerobic
SO42--reductiondetoxification& modeling& modeling
Savapak Amara
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Ongoing Research Activitiesanoxic
denitrification
toxic chemicalsmembraneas C sourcebio reactor
Krongtong Tran
membrane processes Piyaputr
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Study of nitrification process inside a spherical biofloc particle based on biofilm kinetics.
determination of effectiveness factor for substrate consumption and thus the substrate removal rates.
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Mathematical model consists of a system of second order differential equations based on steady state material balance and appropriate boundary conditions.
Model is solved numerically using a computer program developed in Macsyma 2.3, which uses 4th order Runge-Kutta method for solving system of ODEs
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Assumptions:Spherical bioflocDouble substrate limited kinetics based on Michaelis - Menten equationSteady State conditions.Constant Kinetic and Diffusional parameters, and biomass density inside the floc.Evaluation of concentration profile for the substrates inside a spherical biofloc
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Substrate : Oxygen and Ammonia-nitrogen Material Balance Equation:Mass transfer limitations due to diffusional resistances and biochemical reactions taking place inside the biofloc are considered.
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Boundary Conditions:Depend on, Degree of penetration Partial or Full Limiting Substrate Substrate-1 (Oxygen) Substrate-2 (Ammonia)Case : Full Penetrationat r = 1.00 ,s1 = 1.0, s2 = 1.0 at r = 0, s1 = s1,0, s2 = s2,0, ds1/dr = 0, ds2/dr = 0
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Chart1
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0.52640.52640.52650.52650.52660.52670.52680.52690.52710.52730.52750.52710.52010.47560.40190.35350.3192
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0.1
0.125
0.15
0.2
0.25
0.3
0.4
0.5
0.75
1
1.5
2
3
4
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8
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Biofloc diameter (mm)
Effectiveness factor (h)
Fig. Variation of effectiveness factor with the size of biofloc and bulk DO to bulk NH4+ conc. ratio for constant bulk DO conc = 4 mg/l
Sheet1
4
406080100150200300400
0.10.99130.97560.93590.85560.659080.52640.37190.2867
0.1250.99130.97560.93590.85560.659140.52640.37190.2867
0.150.99130.97560.93590.85570.659210.52650.3720.2868
0.20.99130.97560.93590.85580.659260.52650.3720.2868
0.250.99130.97560.9360.85580.659310.52660.37210.2868
0.30.99130.97560.9360.85590.659380.52670.37210.2869
0.40.99120.97560.9360.8560.65930.52680.37220.287
0.50.99120.97560.93610.85610.659430.52690.37230.287
0.750.99120.97550.9360.85630.659710.52710.37250.2872
10.99110.97530.93590.85640.659910.52730.37270.2873
1.50.99080.97470.93520.85610.660210.52750.37280.2875
20.99030.97360.93360.8550.659640.52710.37260.2874
30.9890.96990.92560.84540.651410.52010.36760.2834
40.9870.9630.89840.79940.601010.47560.33330.2561
60.98050.93070.81360.70310.513750.40190.27880.2132
80.970.87670.74140.63180.454820.35350.24390.186
100.95480.82450.68440.57830.412380.31920.21940.167
Sheet1
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00000000000000000
00000000000000000
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0.1
0.125
0.15
0.2
0.25
0.3
0.4
0.5
0.75
1
1.5
2
3
4
6
8
10
Biofloc diameter (mm)
Effectiveness factor (h)
Variation of effectiveness factor with the size of biofloc and bulk DO to bulk NH4+ conc. ratio for constant bulk DO conc = 4 mg/l
Sheet2
Sheet3
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Ongoing Research Activities
Cyanide Degradation in Ananerobic Processes
_957784459.doc
Feeds Tank
Water
Seal
Biogas
10 cm dia.
300 cm tall
Acrylic tube
Sampling Port
Effluent Outlet
Gas Solid Liquid
(GSL) Separator
Sludge Blanket
Glass Beeds
Wash-out
Biomass
Settler
Effluent
Gas Measurement Unit
U
Feed Pump
(peristaltic)
Recirculation Pump
(peristaltic)
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Ongoing Research ActivitiesFludized Bed for Sulfide Oxidation ProcessUASB for Sulfide Removal
Fluidized Bed For Sulfide Oxidation Process
Recycle
pH electrode
Aeration
Tank
Effluent
Air
Nutrients
Na2S/NaHCO3
Solution
HCl (NaOH)-pump
Sand
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Ongoing Research Activities
Bio-Chitosan Membrane Reactor for Denitrification
Feed Side
NaNO3 Solution
C = 50 (mg NO3-- N/L)
V = 3.5 (L)
Weir
Denitrifying Bacteria
Sampling Point
Recycle Pipe
Feed Tank
NaNO3 Solution
C = 50 (mg NO3-- N/L)
V = 4.0 (L)
Influent
Permeate Side
V = 3.5 (L)
Sampling Point
Chitosan Membrane Stirrer
Magnetic Stirrer
Feed Pump
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Ongoing Research Activities
EMBED Visio.Drawing.4
_957776719.vsd
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THE END