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DEMON: stable and sustainable N-removal
Developed at Innsbruck University, Austria
Full scale experience since 2003 at Strass WWTP
Nine full scale installations in operation in Europe, six under construction (mostly references on liquors from municipal sewage sludge)
Technology under license from University of Innsbruck (Dr. Bernhard Wett)
3
Side stream treatment implemented
effluentinfluent
Digester
Primary sedimentati
on
Activated sludge
Final clarifier
Dewatering
Sludge
Liquor Treatment
Return Liquors
4
Nitrogen CycleReduced Organic
N-components
N-Assimilation(plants, micro-
organisms
NO3-
NO2-
N2 NH3
N-fixation
N2O
Nitrification(Nitrobacter)
Nitritation(Nitrosomonas)
N-Assimilation(plants, micro-
organisms
Microbial degradation
NO2-
SHARON
DEMON
Denitrification
0.5 mol N2
1 mol NO3-
1 mol NO2-
C-source → sludge
1 mol NH4+
1 mol NO2-
CO2 → sludge
O2
O2
CO2 → sludge
C-source → sludge
Traditional biological nitrogen removal
DEMON nitrogen removal: deammonification
0.5 mol N2 + 0.1 mol NO3
1 mol NO3-
1 mol NO2-
C-source → sludge
1 mol NH4+
0,5 mol NO2-
0,5 O2
O2
C-source → sludgeCO2 → sludge
CO2 → sludge
CO2 → sludge
1.25 NH4+ + 1.25 O2 1.25 NO2
-
NH4+ + 1.25 NO2
- N2 + 0.25 NO3- + 2 H2O
2.25 NH4+
Aerated period
Anoxic period
DEMON characteristics
Standard SBR configuration Low energy requirement, as only 55% of ammonia is oxidised
to nitrite; No requirement for an external source of carbon (such as
methanol); Low sludge production; Stable process due to pH control, process adjusts to changes
in flow and load automatically; No sensitivity to phosphate in sludge liquors, no pre-treatment
required.
DEMON Control
Control aeration Sufficient oxygen for nitrification Oxygen level limiting for Nitrite oxidizing bact.
Control nitrification process Produce nitrite for deammonification process Avoid inhibition due to excess nitrite
Control sludge age Sufficiently long for
anammox to grow (>20 days) Too short for NOB to grow
0.3 mg/l O2
pH control
Cyclone
Cyclone for sludge age control
Surplus sludge
Surplus sludge discharge (NOB)
Sludge returnto reactor(anammox bacteria)
DEMON references (operational)
Location Year Capacity Liquor source
Heidelberg, D 2008 480 m³/d, 600 kg/day NH4-N Mesophilic digested sludge
Thun, CH 2008 300 m³/d, 400 kg/day NH4-N Mesophilic digested sludge
Glanerland, CH 2007 250 m³/d, 250 kg/day NH4-N Mesophilic digested sludge
Strass, A 2004 250 m³/d, 500 kg/day NH4-N Mesophilic digested sludge
Plettenberg, D 2007 100 m³/d, 80 kg/day NH4-N Mesophilic digested sludge
Limmattal, CH 2010 250 m³/d, 250 kg/day NH4-N Mesophilic digested sludge
Etappi Oy, Fi 2009 330 m³/d, 990 kg/day NH4-N Biogas production
Balingen, D 2009 400 m³/d, 192 kg/day NH4-N Mesophilic digested sludge
Zalaegerszeg, Hu 2010 160 m³/d, 160 kg/day NH4-N Mesophilic digested sludge
Gengenbach, D 2008 50 m³/d, 50 kg/day NH4-N Mesophilic digested sludge
Apeldoorn, NL 2009 1270 m³/d, 1690 kg/day NH4-N Mesophilic digested sludge
DEMON references (under construction)
Location Year Capacity Liquor source
Kecskemet, Tu 1300 kg/day NH4-N Mesophilic digested sludge
Kokkola, Fi 600 kg/day NH4-N Mesophilic digested sludge
Lahr, D 235 kg/day NH4-N Mesophilic digested sludge
Erpfendorf, D 120 kg/day NH4-N Mesophilic digested sludge
Alltech, D 2400 kg/day NH4-N Biogas/yeast
Rickenbach, D 50 kg/day NH4-N Dairy
Nieuwegein, NL 450 kg/day NH4-N Mesophilic digested sludge
Amersfoort, NL 600 kg/day NH4-N Mesophilic digested sludge
Design Basis DEMON Nieuwegein
Parameter Unit Average Max Peak
Flow m3/d 258 420 480
NH4-N mg/l 1.059 1.012 1.012
kg/d 273 425 486
Batch proces DEMON
No. of cycles per day : 4
Cycle volume : 120 m³/cycle (peak)
Cycle time : 6 h
1. Fill + Aerate phase : 4,5 h
1. Settlement phase : 0,75 h
1. Discharge phase : 0,75 h
DEMON reactorProcess Flow Diagram
Filtrate Buffer Tank
DEMON Reactor
Cyclone
Filtrate Break Tank
Surplussludge
DEMON effluent
G.A. Drawing