NITRIFICATION‐DENITRIFICATION OF RAW MUNICIPAL WASTEWATER WITHOUT 

RECIRCULATION, USING ENCAPSULATED MICROBIAL SYSTEMS

School of Environmental EngineeringTechnical University of Crete 

M. Farazaki, H. Marakas and P. Gikas

ΕΕΛ2

Typical wastewater treatment plant

School of Environmental EngineeringTechnical University of Crete

Primary clarifier

Inlet

Barscreen

Secondary clarifier

Tertiaryfilter

OutletAeration Disinfection

Air

Biosolids

BackWash flow

Denitrification

R

R

Conventional activated sludge process with nitrfication/denitrification

School of Environmental EngineeringTechnical University of Crete

Energy distribution in conventional municipal wastewater treatment plant

School of Environmental EngineeringTechnical University of Crete

Aprox. 12% of the energy consumption is used for primary sludge management

Energy requirements in an issue of increased concern, as about 0.5-0.7 kWh/m3 are required for treatment

Aprox. 60% of the energy consumption is used for aeration

How It WorksMicroscreen ‐ Operating principle

School of Environmental EngineeringTechnical University of Crete

Microscreen

a. Microscreen with open housing

b. Sludge removal (~45% TS)

c. Microscreen cloth (100-350μm openings)a

b c

Microscreen (Patra, Greece)

School of Environmental EngineeringTechnical University of Crete

How It Works Footprint requirements

1 ÷ 20

Wastewater flow: 4000m3/d:Microscreen footprint: 4 m2

Clarifier footprint: 82 m2

School of Environmental EngineeringTechnical University of Crete

Upflow sand filters, Adelanto, California(15000 m3/d)

School of Environmental EngineeringTechnical University of Crete

Inlet

Barscreen

Microscreen

BackWash flow

R

Trickling filter

B/WB/W

Outlet

Denitrification

Primaryfilter

Tertiaryfilter Disinfection

Biosolids

Solids removal Removal of dBOD & N

Polishing

Upfront solids removal (USR) process with biosolids gasification

DryerSyngas

co-generation engine

Heat

Solid residue

Gasifier

Electric energy

School of Environmental EngineeringTechnical University of Crete

Inlet

Barscreen

MicroscreenPrimary

filter

Upfront solids removal (USR) process with biosolids gasification

School of Environmental EngineeringTechnical University of Crete

BOD=240-320mg/LdBOD=90-130mg/LN-NH4+=25-50mg/LN-NO3

-=0-2mg/L

BOD=130-160mg/LdBOD=90-130mg/LN-NH4+=25-50mg/LN-NO3

-=0-2mg/L

BOD=90-130mg/LdBOD=90-130mg/LN-NH4+=25-50mg/LN-NO3

-=0-2mg/L

BOD=90-130mg/LdBOD=90-130mg/LN-NH4+=0-2mg/LN-NO3

-=25-50mg/L

BOD=90-130mg/LdBOD=90-130mg/LN-NH4+=0-2mg/LN-NO3

-=2-5mg/L

Air

τ>μhtr&

retainedautotrophs

CH3OH

μheterotrophic >μautotrophic

Oxic Anoxic

dBOD≈3.75N-NH4+

Scope of work

Investigate the performance of encapsulated microbial systems for nitrification/denitrification

Examine the feasibility of “once through” nitrification/denitrification system, with no need for addition of external carbon source

Investigate the appropriate hydraulic retention time for selective nitrification without BOD oxidation

Calculate the required reactor volume

School of Environmental EngineeringTechnical University of Crete

Δρ. Πέτρος Γκίκας

Biomass encapsulation process

School of Environmental EngineeringTechnical University of Crete

Δρ. Πέτρος Γκίκας

Biomass encapsulation process

School of Environmental EngineeringTechnical University of Crete

Δρ. Πέτρος Γκίκας

Lens shape encapsulated biomass

School of Environmental EngineeringTechnical University of Crete

Δρ. Πέτρος Γκίκας

Encapsulated biomass

School of Environmental EngineeringTechnical University of Crete

Lentikats Biocatalyst – Nitrification bacteria Nitrosomonas europaea and Nitrobacter winogradskyi

Lentikats Biocatalyst – Denitrification bacteria Paracoccus denitrificans and Pseudomonas fluorescens

Nitrification/Denitrification dual CSTR system

School of Environmental EngineeringTechnical University of Crete

Examined bioreactors

Nitrification/Denitrification bioreactors system

Inlet Outlet

Stage 1 Stage 2 Stage 3

Nitrification Denitrification

School of Environmental EngineeringTechnical University of Crete

Nitrification/Denitrification CSTR system

Ammonium removal rates: 79% - 99%

School of Environmental EngineeringTechnical University of Crete

Nitrification/Denitrification CSTR system

Nitrate as nitrogen removal rates: 95% - 98%

School of Environmental EngineeringTechnical University of Crete

Nitrification/Denitrification CSTR system

BOD removal rates: 73% - 90%

School of Environmental EngineeringTechnical University of Crete

Nitrification/Denitrification CSTR system

COD removal rates: 70% - 89%

School of Environmental EngineeringTechnical University of Crete

Nitrification/Denitrification CSTR system

TOC removal rates: 70% - 89%

School of Environmental EngineeringTechnical University of Crete

Nitrification reaction rates: Activated sludge system:   0.21 gNH4

+‐Nremoved/(gnitrifiers∙d) Encapsulated biocatalyst:  0.23 gNH4

+‐Nremoved/(gnitrifiers∙d)

Denitrification reaction rates: Activated sludge system:  0.23 gNO3

‐‐Nremoved/(gdenitrifiers∙d) Encapsulated biocatalyst: 0.25 gNO3

‐‐Nremoved/(gdenitrifiers∙d)

Comparisson of encapsulated/free biocatalyst

School of Environmental EngineeringTechnical University of Crete

At about 16 times saving space from nitrification/denitrification tanks

Encapsulated system contained about 16 times more nitrification or denitrification microorganisms per volume, compared to activated sludge system

Conclusions

Once through nitrification/denitrification process canbe achieved using encapsulated biocatalysts

BOD5, NH4+-N and NO3

--N outlet concentrations arebelow the limits imposed Directive 98/15/EC,especially for the lower hydraulic retention times.

The reactor volume for nitrification/denitrificationmay be reduced by 16 times, if encapsulatedsystems are used

The system also saves pumping energy, while therein no need for the use of external organic carbon

School of Environmental EngineeringTechnical University of Crete

petros.gikas@enveng.tuc.gr