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Seminar on
Biological Wastewater Treatment Processes
Past, Present and Future
Dr. Ajit P. AnnachhatreEnvironmental Engineering ProgramAsian Institute of Technology
Keywords Wastewater Biological Processes Treatment Processes Applications Ongoing Research Activities
Biological Wastewater Treatment
1.Wastewater Domestic Wastewater
Industrial Wastewater Present State of Wastewater
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
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
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
Industrial Wastewater present treatment method: Anaerobic ponds
typical loading rates:800-1000kg COD /ha/d
area requirement: 100 ha
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
Biological Processes... cell: derives energy from oxidation of reduced food sources (carbohydrate, protein & fats)
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
Biochemical Pathways oxidation of organic molecules inside the cell can occur aerobic or anaerobic manner
generalized pathways for aerobic & anaerobic fermentation
Biochemical Pathways Glucose
EPM Pathway
Pyruvic Acid ADP ATPEnergyLactic Acid TCA Cycle H+ Respiration H2O CO2 O2
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
Biological growth
- exponential growth (batch)
- Monod kinetics
- Haldane kinetics
under toxic conditions
exponential growth
Biological growth...
= (X
_946447430.unknown
Monod kineticsBiological growth...
( = (m
_946447421.unknown
Haldane kinetics (under toxic conditions)
Biological growth...
( = (m
_957724922.unknown
3.Applications1. Carbonaceous removal - aerobic- anaerobic
2. Nitrogen removal- nitrification- denitrification
3. Sulfide removal- anaerobic SO4 reduction- aerobic HS- oxidation
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)
Biological Carbonaceous Removal anaerobic
Schematic of the Anaerobic Process
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
Biological Nitrogen Removal factors affecting nitrification
* temperature
* substrate concentration
* dissolved oxygen
* pH
* toxic and inhibitory substances
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
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
Biological Nitrogen Removal factors affecting denitrification
* temperature
* dissolved oxygen
* pH
Biological Sulfate Removal * Sulfate removal cycle
anaerobicSO4 -- HS - S 0 (O2 deficient) (O2 excess)
4.Treatment Processes pond treatment
activated sludge process
biofilm process
- no biomass recirculation- high HRT- high land area- O2 transfer limitations- inadequate mixing- excess loading (anaerobic condition-H2S generation)Pond Treatment
Activated Sludge ProcessFE
Activated Sludge Process...- aerobic
- suspended-growth
- Design equations
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.
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
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
Biofilm Processes... biofilm operation
Biofilm Processes... biofilm operation
- diffusion resistance
- inadequate supply of nutrients to inner
portions of Biofilm
- limitations on product out diffusion
- attrition of reaction conditions
Biofilm Processes... biofilm operation as biofilm thickness increases effectiveness factor () decreases
average rate of substrate consumption
Effectiveness factor ( =----------------------------------------------
substrate consumption at biofilm surface
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
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
Ongoing Research ActivitiesBiological Processes
aerobic anoxic anaerobic
nitrificationdenitrification SO42-- reduction
HS- oxidation detoxification
Ongoing Research Activitiesaerobic
nitrification HS- oxidation
inhibition aniline modeling biofilm in ASP degradation processes in SBR ShabbirJega Sunil & Keshab Savapak Shabbir & Shabbir
Ongoing Research Activitiesanaerobic
SO42--reductiondetoxification& modeling& modeling
Savapak Amara
Ongoing Research Activitiesanoxic
denitrification
toxic chemicalsmembraneas C sourcebio reactor
Krongtong Tran
membrane processes Piyaputr
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.
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
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
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.
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
Chart1
0.99130.99130.99130.99130.99130.99130.99120.99120.99120.99110.99080.99030.9890.9870.98050.970.9548
0.97560.97560.97560.97560.97560.97560.97560.97560.97550.97530.97470.97360.96990.9630.93070.87670.8245
0.93590.93590.93590.93590.9360.9360.9360.93610.9360.93590.93520.93360.92560.89840.81360.74140.6844
0.85560.85560.85570.85580.85580.85590.8560.85610.85630.85640.85610.8550.84540.79940.70310.63180.5783
0.659080.659140.659210.659260.659310.659380.65930.659430.659710.659910.660210.659640.651410.601010.513750.454820.41238
0.52640.52640.52650.52650.52660.52670.52680.52690.52710.52730.52750.52710.52010.47560.40190.35350.3192
0.37190.37190.3720.3720.37210.37210.37220.37230.37250.37270.37280.37260.36760.33330.27880.24390.2194
0.28670.28670.28680.28680.28680.28690.2870.2870.28720.28730.28750.28740.28340.25610.21320.1860.167
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)
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
00000000000000000
00000000000000000
00000000000000000
00000000000000000
00000000000000000
00000000000000000
00000000000000000
00000000000000000
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
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)
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
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
Ongoing Research Activities
EMBED Visio.Drawing.4
_957776719.vsd
THE END