Download - 412.063-730-005-00 Nutrient Removal
TRAINING
Jan Bos Van Hemelrijck – July 2013
Nutrient Removal
CONTENTS
1. Why aerobic wastewater treatment?
2. Nutrients
3. Nutrient removal
1. Fundamental process steps
2. Extra process steps
4. Biological nitrogen removal
1. Conventional nitrogen removal
2. LUCAS® time controlled nitrogen removal
5. Biological phosphorus removal
6. Combined nutrient removal
7. Trouble shooting
1. WHY AEROBIC WASTEWATER TREATMENT?
1. WHY AEROBIC WASTEWATER TREATMENT?
Produces a clear effluent, harmless for the environnement:
Removes organic compounds from the wastewater
(low effluent COD)
Removes NUTRIENTS like N and P (partially) Eutrophication risk!
Economical most feasible way
2. NUTRIENTS
2. NUTRIENTS
Nitrogen & phosphorus
Assimilative Removal =
biomass incorporation
Biological removal possible
Minerals: Ca, Mg, Na, Fe, K,…
Trace elements: S, Co, Cu, Zn, Mn, Ni,
Mo, Se, W,..
Biological removal impossible
MACRO-NUTRIENTS MICRO-NUTRIENTS↔
2. NUTRIENTS
N Kjeldahl-N org. bound-N + NH4+-N
Nitrate-N NO3--N (mg N/l)
Nitrite-N NO2—N (mg N/l)
Ammonium-N NH4+-N (mg N/l)
+Total-N KjN-N + NO3-N + NO2-N
P Total P (mg P/l) = org. bound P + PO43--P
Orthophosphate (mg P/l)
2.1 NITROGEN AND PHOSPHORUS
2. NUTRIENTS
2.2 MACRONUTRIENTS
Macronutrients are essential nutrients for healthy growth of biomass. N & P required depends on loading of WWTP
Anaerobic pathway: COD/N/P-ratio: 400/5/1
Aerobic pathway: COD/N/P-ratio: 100/2,5/0,3 – 100/5/1
Too little nutrients nutrients added Too much nutrients nutrients removed
3. NUTRIENT REMOVAL
3. NUTRIENT REMOVAL
To prevent eutrophication (algae blooms) in surface water Excessive growth of algae can cause:
Oxygen shortages (fish mortality) Toxine production (fish mortality) Problems with drinking water facilities (quality and treatability) Aesthetical nuisance (tourists, inhabitants,..) Odour problems
Why nutrient removal?
3. NUTRIENT REMOVAL
Algea blooms occur in combined presence of: light energy CO2 macronutrients (Nitrogen and Phosphorus) micronutrients (Cobalt, Iron, Molybdene, Manganese)
The absence of one of the first 3 factors will limit growth For this reason european and world-wide discharge limits are
N < 10 mg N/l P < 1 or 2 mg P/l
Occurrence of eutrophication
Bering sea
3. NUTRIENT REMOVAL
3.1 FUNDAMENTAL PROCESS STEPS
Feeding + Aeration Accumulation-Regeneration Reduce Filaments Active Volume
Settling + Discharge Passive Volume
Effluent
Sludge wasting
wastewaterfeeding
aeration sedimentation discharge
Effluent
Sludge wasting
wastewaterfeeding
aeration sedimentation discharge
3. NUTRIENT REMOVAL
3.2 EXTRA PROCESS STEPS
NITROGEN REMOVAL
Nitrification (aerated)
Denitrification (mixed + fed of fresh COD) in anoxic step
Nitrate recycle from aerobic to anoxic compartment
PHOSPHORUS REMOVAL
Alternation between aerobic and anaerobic steps
4. BIOLOGICAL NITROGEN REMOVAL
4. BIOLOGICAL NITROGEN REMOVAL
Nitrogen removal due to sludge growth Removal ratio is low: BOD/N 100/5 Incorporation of N in cell mass
Nitrogen removal due to dissimilative metabolism Removal ratio up to: BOD/N 100/35 Nitrogen is biologically transferred via nitrification and denitrification to
inert N2 and released into the atmosphere
4. BIOLOGICAL NITROGEN REMOVAL
Nitrification NH4
+ + 2 O2 NO3— + H2O + 2 H+
Nitrosomonas & Nitrobacter: autotrophic bacteria
Aeration
Denitrification
NO3- + 5 e- + 6 H+ ½ N2 + 3 H2O
CH2O + H2O CO2 + 4 e- + 4 H+
No O2 = No Aeration!!!=> NO3- !!!
Easy biodegradable COD: Feeding + Mixing
atmosphere
4. BIOLOGICAL NITROGEN REMOVAL
Activated sludge can be adapted for biologic nitrogen removal by continuous alternation between aerobic and anoxic conditions
Conventional systems: sludge recycle from the aerated tank to the anoxic (mixed) tank
Cyclic operating systems: alternation in time between aeration and mixing in the same tank
Or combinations
4. BIOLOGICAL NITROGEN REMOVAL
4.1 CONVENTIONAL BIOLOGICAL N-REMOVAL
Effluent
denitrification
Influent
nitrification +
carbon oxidation
sludge recirculation waste sludge
Recycle of nitrate rich sludge
A B C
4. BIOLOGICAL NITROGEN REMOVAL
4.1 CONVENTIONAL BIOLOGICAL N-REMOVAL
Effluent
Anoxische faze
faze 1 – denitrificatie (anoxie)
Inf luent
supernatant
bezonken slib
Effluent
Anoxische faze
faze 1 – denitrificatie (anoxie)
Inf luent
supernatant
bezonken slib
Effluent
supernatantAerobe faze
Influent
faze 2 – nitrificatie + koolstofoxidatieSpuislib
bezonken slibEffluent
supernatantAerobe faze
Influent
faze 2 – nitrifica tie + koolstofoxidatieSpuislib
bezonken slib
4. BIOLOGICAL NITROGEN REMOVAL
4.2 LUCAS® TIME-CONTROLLED N-REMOVAL
LUCAS®-3:intermediate phase 1
LUCAS®-3:Main phase 1
Accumulation Regeneration Discharge
1 2 3
Influent
Final effluent
InfluentDischargeAccumulationSettling
1 2 3
Effluent
4. BIOLOGICAL NITROGEN REMOVAL
4.2 LUCAS® TIME-CONTROLLED N-REMOVAL
LUCAS®-3:intermediate phase 2
LUCAS®-3:Main phase 2
Discharge Regeneration Accumulation
1 2 3
EffluentInfluent
Influent DischargeAccumulationSettling
1 2 3
Effluent
5. BIOLOGICAL PHOSPHORUS REMOVAL
5. BIOLOGICAL PHOSPHORUS REMOVAL
Biological: Alternation anaerobic phases/zones aerobic phases/zones
Anaerobic: P release, VFA-uptake Aerobic: P surplus uptake
Physical-chemical by addition of FeCl3, Ca(OH)2, Al3+, ... Pre-precipitation: before aeration tank Simultaneous: in aeration tank Post-treatment: after aeration tank
5. BIOLOGICAL PHOSPHORUS REMOVAL
P-removal due to sludge growth (assimilation): Removal ratio is low : BOD/P = 100/1 Incorporation of P in cell mass
P-removal due to bioP metabolism: Removal ratio is still rather low : BOD/P = 100/5 Incorporation of P in internally stored
polyphosphate granules (up to 25% of cell mass)
Often combined with physico chemical P-removal
5. BIOLOGICAL PHOSPHORUS REMOVAL
Anaerobic phase (mixed/stirred phase):
Poly-P (internal) PO4-P (external) + energy
VFA (external) + energy PHB-polyhydroxybutyric acid (internal) + aerobic bioP mo
Aerobic phase (aerated phase):
PHB (stored) + O2 CO2 + H2O + Energy
PO4-P (external) + Energy Poly-P (internally stored) + aerobic bioP mo
5. BIOLOGICAL PHOSPHORUS REMOVAL
Bio-P removal by continuous anaerobic-aerobic alternation:
Anaerobic conditions: polyphosphate is hydrolysed (energy production) ortho-phosphates are released from cells acetate and VFA are taken-up, stored as C-source
Aerobic conditions: stored C-source is rapidly
used (growth advantage) large PO4-P uptake large Poly-P storage net PO4-P uptake
P-granules inside
Sludge flock
Acinetobacter species
Advantage:
Acinetobacter in aerobic phase/zone
5. BIOLOGICAL PHOSPHORUS REMOVAL
Biological P-removal by Acinetobacter species
Phosphate release
+ C-uptake
Phosphate uptake +
C-metabolism
Net P-uptake
5. BIOLOGICAL PHOSPHORUS REMOVAL
Effluent
phosphorus release,
anaerobic state
Influent
supernatant
sedimentated-sludge
phosphorus uptake and carbon oxidation,
aerobic state
sludge recycle 1
waste sludge
Recycle of polyphosphate rich sludge
A B C
Sludge recycle from the aerated tank to the anaerobic tank
Acidification: BODVFAVFA-uptake
5. BIOLOGICAL PHOSPHORUS REMOVAL
LUCAS® : TIME CONTROLLED BIO-P REMOVAL
Effluent
ExcessBio solids
A B C
aerobicanaerobic
Influent
Influent
Effluent
ExcessBio solids
A B C
aerobic anaerobicEffluent
ExcessBio solids
A B C
anaerobic aerobic
Inf luent
PHASE 2
PHASE 1
PHASE 3
6. COMBINED NUTRIENT REMOVAL
6. COMBINED NUTRIENT REMOVAL
Effluent
phosphorus release,
anaerobic state
Influent
supernatant
sedimentated-sludge
phosphorus uptake and carbon oxidation,
aerobic state
sludge recycle waste sludge
A C Ddenitrification
B
sludge recycle sludge recycle
Sludge recycle from aerated tank to anoxic tankSludge recycle from anoxic tank to anaerobic tank
6. COMBINED NUTRIENT REMOVAL
SBR: A: Anoxic/anaerobic/aerobic
Influent
Effluent
A
A A
Anoxic phaseMLSS is mixed
A
Anaerobic phaseMLSS is mixed
Decantation phase Aerobic phase
MLSS is aerated
Waste sludge
Influent
6. COMBINED NUTRIENT REMOVAL
NOTE: For better N-removal efficiencies the aerated main phase can be subdivised into several Aerobic-Anoxic subphases
7. TROUBLESHOOTING
7. TROUBLESHOOTING
N-removal Recirculation Aerobic-Anoxic comp. big enough? Aeration: NO3
- in effluent? DO: 1-3 mg O2/l pH: Optimum 7-8 Temperature:
Optimum 30-35°C Minimum 10-15°C
Toxic compounds? Sludge age (nitrifyers: slow growing!): 6 days if >20°C (more
at lower temperature) Sb (sludge load): < 0,2 – 0,4 kgCOD/kg MLSS.day Nitrite concentration? Aerobic-Anoxic subphases
7. TROUBLESHOOTING
P-removal pH: Optimum 6,5-8 Temperature: > 10-15°C Availability of VFA in anaerobic phase/zone DO in aerobic phase + alternation between
aerobic-anaerobic Sludge loading hich enough: higher Sb more
sludge production more P accumulated! Length aerobic phase: > 0,5 – 1 hour