l22 sludge stabi - MIT OpenCourseWare · PDF fileAdapted from: WEF. "Wastewater Treatment...
Transcript of l22 sludge stabi - MIT OpenCourseWare · PDF fileAdapted from: WEF. "Wastewater Treatment...
METHANE
CO2
Carbohydrates
Proteins
Lipids
Glucose
PO4-3
Acetic
Propionic
Lactic + Cell
Cells
Hydrolysis
Extracellular
Enzymes
Acid Producers Methanogens
ORGANIC
ACIDS
SOLUBLE
ORGANICS
COMPLEX
ORGANICS
Phosphorylated Organics
Amino Acids
Fatty Acids
Stabilized Organics
MICROBIOLOGICAL PATHWAY OF ANAEROBIC DIGESTION
Figure by MIT OCW.
Adapted from: WEF. "Wastewater Treatment Plant Design. Water Environment Federation." Alexandria,
Virginia, 2003.
Figure by MIT OCW.
Adapted from: Sawyer, C. N., P. L. McCarty, and G. F. Parkin. Chemistry for Environmental Engineering
and Science. 5th ed. Boston, MA: McGraw-Hill, 2003.
25,00010,000500025001000500250
10
20
30
40
50
6.0
pH = 6.2
6.4
6.66.8
7.0 7.2
7.4
7.6
7.8
8.0
8.2
8.4
8.6
8.8
Bicarbonate Concentration as CaCO3, mg/L
0
Relationship between pH, bicarbonate concentration, and carbon dioxide concentration at 35oC and 1 atm.
CO
2 in
Dig
este
r G
as, P
erce
ntag
e
Limits of Normal Anaerobic Treatment
SUBSTANCE MODERATELY INHIBITORY
CONCENTRATION, mg/L
STRONGLY INHIBITORY
CONCENTRATION, mg/L
Na+ 3500 - 5500 8000
K+ 2500 - 4500 12000
Ca++ 2500 - 4500 8000
Mg++ 1000 - 1500 3000
Ammonia-nitrogen (pH dependent) 1500 - 3000 3000
Sulfide (un-ionized gas) 200 200
Copper (Cu) 0.5 (soluble)
50-70 (total)
Chromium VI (Cr) 3.0 (soluble)
200-250 (total)
Chromium III 180-420 (total)
Nickel (Ni) 2.0 (soluble)
30.0 (total)
Zinc (Zn) 1.0 (soluble)
Toxic and Inhibitory Concentrations of Selected Inorganic Materials in Anaerobic Digestion
Figure by MIT OCW.
Adapted from: WEF. Wastewater Treatment Plant Design. Water Environment Federation, Alexandria,
Virginia, 2003.
SCUM
Feed sludge treatment plant
Digester gas
Digested solids
SUPERNATANT
ACTIVE LAYER
STABILIZED SOLIDS
Effluent to
LOW-RATE ANAEROBIC DIGESTION
Figure by MIT OCW.
Adapted from: WEF. Wastewater Treatment Plant Design. Water Environment Federation, Alexandria,
Virginia, 2003.
Figure by MIT OCW.
Adapted from: Reynolds, T. D., and P. A. Richards. Unit Operations and Processes in
Environmental Engineering. 2nd ed. Boston, MA: PWS Publishing Company, 1996, p. 582.
Hatch
Overflow
Gas dome
Roller
Gas line
Composition roof hatch
Ceiling plate (1/4 in.)(6.5 mm)
Sludge inlet pipe
Concrete support
Supernatantwithdrawal
Supernatant gas
Freeboard
16
Sludge in
Sludge in
Gas line
Digested sludge out
Sludge to recycle
Side water depth (swd)
Section Through an Anaerobic Digester with a Floating Cover
Landing bracket
Figure by MIT OCW.
Adapted from: Reynolds, T. D., and P. A. Richards. Unit Operations and Processes in
Environmental Engineering. 2nd ed. Boston, MA: PWS Publishing Company, 1996, p. 584.
Drive
Compressor
B
Gas
Gas
Compressor
A
DC
Gas recycle & draft tube Gas recycle & gas injection
Gas
GasDrive
Impeller & draft tube Impeller
TYPES OF MIXING SYSTEMS FOR ANAEROBIC DIGESTERS
Platform to other
digesters Ele
vat
or
Pip
e ar
ea
Pipes
Platform
Feed
Mixer
Hopper
Supernatant
withdrawal
Scum door
8.8
m21 m
Gas
37o
20 m DIA. Piping to
withdrawal
bottom sludge
spargers
Tower
EGG-SHAPED ANAEROBIC DIGESTER
Figure by MIT OCW.
Gas injection
lines
Gas header
Foam
Separator Scam Breaker
Screw-impeller sludge
mixing pump with
draft-tube assembly
Solids recirculation
header
Digested
biosolids
overflow
Raw sludge
influent
Heat
exchanger
Alternate biosolids
wasting to storage tank
Nozzle for mixing
Unconfined gas mixing Mechanical draft-tube mixing Pumped recirculation mixing
To gas utilization
Mixing Systems For Egg-Shaped Anaerobic Digesters
Figure by MIT OCW.
Adapted from: WEF. Wastewater Treatment Plant Design. Water Environment Federation, Alexandria,
Virginia, 2003.
Figure by MIT OCW.
Adapted from: Hammer, M. J., and M. J. Hammer, Jr. Water and Wastewater Technology.
5th ed. Upper Saddle River, NJ: Prentice-Hall, Inc., 2004. Figure 11-56.
Belt tension roller
Polymer
Sludge feed
Gravity drainage zone Alignment roller
Cake discharge belt conveyor
Belt wash
High pressure zone
Upper beltStatic Box
Wedge zone
Lower belt
A
Filtrate & wash-water collection