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