Removal of carbon and nutrients from wastewater in a moving bed - - PowerPoint PPT Presentation

Università di Palermo Dipartimento di Ingegneria Civile, Ambientale, Aerospaziale, dei Materiali (DICAM)

Athens 14-16 September 2016

Removal of carbon and nutrients from wastewater in a moving bed membrane biofilm reactor: the influence of the sludge retention time

• G. Mannina, M. Capodici, A. Cosenza, D. Di Trapani

Nutrients in wastewater (nitrogen and phosphorus compounds) may have adverse environmental impacts (eutrophication, toxicity towards the aquatic organisms, etc…)

Nutrients removal from wastewater is an imperative requirement especially when discharging in sensitive areas

Introduction

Alternatives for nutrient removal

Biological nutrient removal (BNR) from domestic wastewater is the most cost-effective method Mostly based on the alternation of anaerobic, anoxic and aerobic conditions

Several biological and physic-chemical methods have been developed to remove nutrients from wastewater

Anaerobic Anoxic Aerobic + +

Introduction

Examples of plant schemes for nutrients removal A2O Modified UCT Modified Bardenpho University of Cape Town (UCT)

Introduction

Moving bed biofilm membrane bioreactors

Very recently, a combination of MBR and biofilm systems has been proposed (inter alia Leyva-Diaz et al., 2013)

MBBR MBR MB-MBR

In the last years the recurrence to new and innovative technologies has been explored to improve the performances of BNR processes (MBR, MBBR, AnAmmox, Granular sludge….)

Introduction

Introduction

BNR systems adopting hybrid MB-MBR processes are very recent and there still is a lack of knowledge about the influence of specific key parameters Sludge retention time (SRT) might have a key role on the performance of a such complex system

Gain insight about the behavior

• f

a UCT pilot plant, combining both MBR and MBBR technology (UCT-MBMBR), subjected to SRT variation, in terms of:  system performance (carbon and nutrient removal)  biokinetic behavior  membrane fouling  activated sludge features  monitoring of GHG emission  DNA extraction

Aim of the study

UF hollow fiber membrane: (surface = 1.4 m2 , porosity = 0.03 m) The UCT-MBMBR pilot plant lay-out

Anaerobic Tank Anoxic Tank Aerobic Tank MBR Tank Clean In Place Tank ODR Qin QR2 QR1 QRAS

Suspended plastic carriers filing ratio: 15 and 40% (net surface area of 75 and 200 m2 m-3) anoxic and aerobic

Materials

Panoramic view of the UCT-MBMBR pilot plant

Anaerobic Aerobic ODR Anoxic MBR Carriers

Materials

The pilot plant was operated for 115 days according to three phases (each characterized by different SRT value) It was fed with a mixture of real wastewater (deriving from the University buildings) and synthetic wastewater (50% of the overall COD)

Experimental campaign

Average wastewater characteristics and main operational features

Parameter Units Phase I Phase II Phase III Value COD [mg L-1] 602 583 543 Total nitrogen (TN) [mg L-1] 55.46 76.91 105.00 Total phosphorus (TP) [mg L-1] 7.08 8.8 9.86 Permeate Flux [L m-2 h-1] 21 21 21 Flow rate [L h-1] 20 20 20 SRT [d] ∞ 30 15 HRT [h] 20 20 20 Duration [d] 0-66 67-95 96-115

Materials

• TMP monitoring (membrane fouling study)
• Respirometry (evaluation of kinetic/stoichiometric parameters)
• Extracellular polymeric substances (EPSs) production
• COD, NH4-N, NO3-N, NO2-N, TN, PO4-P, TP
• CST and SRF measurements
• Physical/chemical parameters (DO, pH, Temperature…)
• Monitoring of activated sludge and biofilm growth

Analytical methods

Methods

Results and discussion

 very high total COD removal efficiency (Phase I = 97%; Phase II = 98%; Phase III = 99%)

Organic carbon removal

 high biological contribution with moderate influence of the SRT  typical robustness of MBR process

200 400 600 800 1000 20 40 60 80 100 120 Concentration [mg L-1] Time [d]

CODIN CODOUT CODMBR

CODIN CODOUT

(a)

CODSUP,MBR

Phase I Phase II Phase III

20 40 60 80 100 20 40 60 80 100 120 COD efficiency removal [%] Time [d] bio tot phys

BIO TOT PHYS

(b)

Phase I Phase II Phase III

Results and discussion

 excellent nitrification performance (average efficiency: 97%) not influenced significantly by the SRT variation

Nitrification and nitrogen removal

 biofilm in the aerobic reactor (mostly autotrophic) contributed to nitrification  fluctuations of nitrogen removal efficiencies (Phase I = 62.92%, Phase II = 61%, Phase III = 54.55%) which reflected the denitrification trend

20 40 60 80 100 120 140 160 20 40 60 80 100 120 Concentration [mg L-1] Time [d] NH4_IN NHout No3_out

NH4-NIN NH4-NOUT NO3-NOUT

(a)

Phase I Phase II Phase III

20 40 60 80 100 20 40 60 80 100 120 N removal efficiency [%] Time [d]

hdenitr [%] htotale[%] hnitr [%]

denit Ntotal nit

(b)

Phase I Phase II Phase III

Results and discussion

Phosphorus removal

 slight increase of bio-P removal with the SRT decrease. At high SRT the PAO activity is hampered by competition with

• rdinary

heterotrophs

5 10 15 20 25 30 20 40 60 80 100 120 Concentration [mg L-1] Time [d]

PO4_IN PO4_out

PO4-PIN PO4-POUT

(a)

Phase I Phase II Phase III

20 40 60 80 100 20 40 60 80 100 120 P removal efficiency [%] Time [d]

tot

(b)

Phase I Phase II Phase III

Results and discussion

Biomass respiratory activity 1/2

 higher heterotrophic activity in the suspended biomass compared to biofilm (more affine to organic carbon removal)

5 10 15 20 25 20 40 60 80 100 120 140 SOUR [mgO2 g-1VSSh-1] Time [d] Suspended Biomass Biofilm

Phase I Phase II Phase III

Results and discussion

 significant influence of SRT on heterotrophic activity: decrease in Phase I (no sludge withdrawals, biomass “ageing”), increase when reducing the SRT (Phase II and III, biomass “renewal”)

0.15 0.3 0.45 0.6 20 40 60 80 100 120 140 max,A [d-1] Time [d] Suspended Biomass Biofilm

Phase I Phase II Phase III

Biomass respiratory activity 2/2

 autotrophic activity more pronounced in the biofilm (specialization of biofilm towards nitrification)

Results and discussion

 surprisingly, the suspended biomass showed an increasing autotrophic activity when reducing the SRT (“seeding” effect of nitrifiers from biofilm)

EPS production

 high EPSbound, likely due to biofilm detachment

Results and discussion

100 200 300 400 EPS [mg gTSS-1] 50 100 150 200 250 300 350 EPS [mg gTSS-1] 50 100 150 200 250 300 350 EPS [mg gTSS-1] 100 200 300 400 500 600 EPS [mg gTSS-1] Phase I SRT = ∞ Phase II SRT = 30 d Phase III SRT = 15 d (a1) (a2) (a3) (b1) (b2) (b3) (c1) (c2) (c3) (d1) (d2) (d3)

EPSP EPSC SMPP SMPC

Phase II SRT = 30 d Phase III SRT = 15 d Phase I SRT = ∞

Anaerobic Anoxic Aerobic MBR

 the SRT decrease could enhance the biofilm detachment thus increasing the EPSbound (worsening the filtration properties

• f

the physical membrane)

Membrane fouling

 fouling tendency mostly related to irreversible cake deposition  increase of pore blocking (biofilm detachment, more “hydrophobic”)  worsening of the filtration properties mainly due to EPS increase

Results and discussion

10 20 30 40 50 15 30 45 60 75 90 105 120 RT [1012m-1] Time [d]

Physical cleaning

(a)

Phase I Phase II Phase III

4.38 1.96 92.75 0.91

Phase I ‐ 58th day

Rm RPB RC,irr RC,rev

(b1) 2.57 2.71 94.16 0.56

Phase II ‐ 92nd day

Rm RPB RC,irr RC,rev

(b2) 7.91 8.24 69.85 14.00

Phase III ‐ 114th day

Rm RPB RC,irr RC,rev

(b3)

 Very high COD removal efficiency, no significant influence of SRT  Excellent nitrification even at the lowest SRT value  Presence of biofilm supported complete nitrification  SRT decrease enhanced bio-phosphorus removal  Specialization of the suspended and the attached biomass

Conclusions

To successfully apply a UCT-MBMBR system it is suggested to reduce the sludge age of the suspended biomass, in order to improve phosphorus removal, while the high residence time of the biofilm would sustain the complete nitrification. Possible to operate the system at lower MLSS concentration, thus reducing the energy demand

Message to take home!

Università di Palermo Dipartimento di Ingegneria Civile, Ambientale, Aerospaziale, dei Materiali (DICAM)

Athens 14-16 September 2016

Thank you for your attention

Giorgio Mannina

giorgio.mannina@unipa.it

Acknowledgements

This research was funded by Italian Ministry of Education, University and Research (MIUR) through the Research project of national interest PRIN2012 (D.M. 28 dicembre 2012 n. 957/Ric − Prot. 2012PTZAMC) entitled “Energy consumption and GreenHouse Gas (GHG) emissions in the wastewater treatment plants: a decision support system for planning and management − http://ghgfromwwtp.unipa.it”

Università di Palermo Dipartimento di Ingegneria Civile, Ambientale, Aerospaziale, dei Materiali (DICAM)

Athens 14-16 September 2016

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