Technologies for anaerobic
wastewater treatment
Jan Bartáček
ICT Prague
Department of Water Technology and
Environmental Engineering
Jan.bartacek@vscht.cz
Anaerobic reactors differenciations
Anaerobic reactors
Immobilized
biomass
Suspended biomass
Biofilm
(on support)
Moving carrier
Fixed carrier
Granular
biomass
Reactors for Sludge Digestion
• On the principle of CSTR (Completely Stirred
Tank Reactor)
• Either SBR (Semi-Batch Reactors) or continuous
• Currently used mostly for sludge digestion
Reactors for Sludge Digestion
• With moving or fixed top
Reactors for Sludge Digestion
Reactors for Sludge Digestion
Reactors for Sludge Digestion
• With moving or fixed top
Biogas
Biogas
Overflow
Overflow
Raw
sludge
Digested
sludge
Raw
sludge
Digested
sludge
Reactors for Sludge Digestion
• Mixing
▫ Mechanical (only fixed top)
 Fast or slow
Reactors for Sludge Digestion
• Mixing
▫ Mechanical (only fixed top)
 Fast or slow
▫ Biogas recirculation
▫ Sludge recirculation
Reactors for Sludge Digestion
• Heating
▫ External
▫ Internal
▫ It is advantageous to
have large reactors –
smaller heat losses
Reactors for Sludge Digestion
• Egg-shaped digesters
Reactors for Sludge Digestion
• Egg-shaped digesters
Reactors for Sludge Digestion
• Egg-shaped digesters
▫ Smaller surface/volume ratio  smaller heat
losses
▫ Improved mixing properties (mixing with biogas)
Reactors for Sludge Digestion
•
•
•
•
Temperature: 20 – 55 °C
Materials: steel, concrete, plastics (smaller)
Retention time: 10 – 30 days
Pumping cycles: usually several time a day
(SBR). Advantageous to get close to continuous
systems (e.g. pumping every hour)
Development of anaerobic
wastewater technologies over time
Anaerobic reactors for WWT build
in recent years
Anaerobic reactors for WWT build
in recent years
Anaerobic Contac (AC) process
• Main difficulty – sludge
separation
▫ Solution:
 less mixing
 Improved
degasification
(vacuum)
 membrane separation
Anaerobic Filters (AF)
• Usually up-flow
▫ Problems with
clogging
• Suitable carrier
material
▫ originally natural
(gravel, coke, bamboo
segments)
▫ Recently plastics,
ceramics etc.
Anaerobic Filters (AF)
• Down-flow systems
▫ Less clogging
(suspended biomass
leaves reactor via
bottom
▫ First systems –
tubular
 Relatively small
contact area
Anaerobic Filters (AF)
• Down-flow systems
▫ Less clogging
(suspended biomass
leaves reactor via
bottom
▫ First systems –
tubular
 Relatively small
contact area
▫ Normal carriers can
also be used
"High Rate"Anaerobic Treatment
• Bioreactors in which the sludge retention time is
separated from the hydraulic retention time.
• Anaerobes can be maintained in the reactor at high
concentrations, enabling high volumetric conversion
rates, while the wastewater rapidly passes through the
reactor.
• The main mechanism of retaining sludge in the reactor is
immobilization onto support material (microorganisms
sticking to surfaces, eg. filter material in the "anaerobic
filter") or self-aggregation into pellets (microorganisms
sticking to each other, eg. sludge granules).
Up-flow Anaerobic Sludge Blanket
(UASB) reactor
biogas
effluent
granular
sludge
influent
Anaerobic granular sludge
Sekiguchi et al. 1999 Applied And
Environmental Microbiology, 65(3), 1280-1288.
Fernández, et al 2008. Chemosphere, 70(3), 462-474.
• Spherical biofilm
• Grown without
carrier material
• Heterogeneous,
densely packed
biomass
• Often stratified
(depends on
substrate
complexicity)
• Well settling
Up-flow Anaerobic Sludge Blanket
(UASB) reactor
biogas
g-l-s (3-phase)
separator
effluent
deflector
granular
sludge
influent
blanket
Up-flow Anaerobic Sludge Blanket
(UASB) reactor
biogas
g-l-s (3-phase)
separator
effluent
deflector
granular
sludge
influent
blanket
www.uasb.org
Up-flow Anaerobic Sludge Blanket
(UASB) reactor
biogas
g-l-s (3-phase)
separator
effluent
deflector
granular
sludge
influent
blanket
Up-flow Anaerobic Sludge Blanket
(UASB) reactor
Up-flow Anaerobic Sludge Bed
(UASB) reactor
Expanded and Fluidized bed
reactors
• Internal Circulation (IC)
reactor (Paques B.V.)
• Excellent mixing and
contact between ww and
biofilm
Expanded and Fluidized bed
reactors
• Internal Circulation (IC)
reactor (Paques B.V.)
• Excellent mixing and
contact between ww and
biofilm
Expanded and Fluidized bed
reactors
• Internal Circulation (IC)
reactor (Paques B.V.)
• Excellent mixing and
contact between ww and
biofilm
Expanded and Fluidized bed
reactors
• Expanded Granular
Sludge Bed (EGSB) reactor
(Biothane B.V)
EGSB vs. UASB
• Better mixing
• No problems with small inert particles
• Treatable wastewater (not in UASB):
▫ Low strength (<<1g/L) and cold (<10°C)
wastewater
▫ Long-chain fatty acids (even distribution, no
clumps formation)
▫ Wastewater with foaming problems
Moving bed reactors
• Biofilm on carrier material
Expanded and Fluidized bed
reactors
• Fluidized Bed (FB) reactor
• Needs carrier material as
biofilm support (can be
expensive)
• Regeneration of carrier
(eliminating overgrown
biofilm)
Anaerobic effluents
•
•
•
•
Relatively polluted in COD (~150 – 200 mg/L)
Unchanged or even increased Nammon and P-PO4
May contain biomass
…post-treatment is needed
• Usually “classical” DN systems. Often extensive
(ponds or wetlands).
• Problem – COD is not well degradable 
beneficial to mix with other, less polluted
wastewater
Liquid effluents - P
• Most often precipitation
▫ Iron (FeCl2, FeCl3, Fe2(SO4)3)
 Fe3++ PO43-  FePO4
▫ Struvite
 NH4+ + Mg2+ + PO43- + 6H2O  NH4MgPO4·6H2O
 Advantages:
Constrains:
Liquid effluents - N
• Nitrification/denitrification
• Nitritation/denitritation
• Deammonification
▫ SHARON-ANAMMOX
Liquid effluents - N
• Nitritation/denitritation
Liquid effluents - N
• Nitritation
▫ How to achieve inhibition of NOB?
 Low dissolved oxygen concentration (DO) ~ 0.7
mg/L
 High temperature (25-40 °C) + low retention
(SHARON process)
 High loading rate (NH2OH accumulation)
 SBR regime (pH changes)
Liquid effluents - N
• SHARON-ANAMMOX
Liquid effluents - N
• SHARON-ANAMMOX
Liquid effluents - N
• SHARON-ANAMMOX
Anammox bacteria
Liquid effluents - N
• SHARON-ANAMMOX
▫ Advantages
 Low energy demand
 Low substrate demand
▫ Constrains
 High temperature needed
 Slow growth
Biogas quality upgrading
• Mostly H2S removal
• CO2 removal
• Drying
Biogas upgrading - H2S removal
• S2- oxidation to sulphur
Thiothrix
Thiobacillus
Biogas upgrading
• THIOPAQ®
Biogas upgrading
• Microaeration
▫ Controlled air dosing into anaerobic reactors
▫ Dosing:
 Gas space
 Inlet/recycle
Technologies for anaerobic
wastewater treatment
Jan Bartáček
ICT Prague
Department of Water Technology and
Environmental Engineering
Jan.bartacek@vscht.cz