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 Università di Palermo Dipartimento di Ingegneria Civile, Ambientale, Aerospaziale, dei Materiali (DICAM)
Introduction 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 Several biological and physic-chemical methods have been developed to remove nutrients from wastewater Biological nutrient removal (BNR) from domestic wastewater is the most cost-effective method Mostly based on the alternation of anaerobic, anoxic and aerobic conditions + + Anaerobic Anoxic Aerobic
Introduction Examples of plant schemes for nutrients removal A 2 O Modified Bardenpho University of Cape Modified UCT Town (UCT)
Introduction Moving bed biofilm membrane bioreactors 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….) Very recently, a combination of MBR and biofilm systems has been proposed (inter alia Leyva-Diaz et al., 2013) MBR MBBR MB-MBR
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
Aim of the study Gain insight about the behavior of 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
Materials The UCT-MBMBR pilot plant lay-out Q RAS Clean In Place Tank Q in MBR Tank ODR Q R2 Anaerobic Tank Anoxic Tank Aerobic Tank Q R1 UF hollow fiber membrane: (surface = 1.4 m 2 , porosity = 0.03 m) Suspended plastic carriers filing ratio: 15 and 40% (net surface area of 75 and 200 m 2 m -3 ) anoxic and aerobic
Materials Panoramic view of the UCT-MBMBR pilot plant Anaerobic ODR MBR Aerobic Carriers Anoxic
Materials Experimental campaign 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) Average wastewater characteristics and main operational features Phase I Phase II Phase III Parameter Units 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 [L h -1 ] Flow rate 20 20 20 SRT [d] ∞ 30 15 HRT [h] 20 20 20 Duration [d] 0-66 67-95 96-115
Methods Analytical methods TMP monitoring (membrane fouling study) Respirometry (evaluation of kinetic/stoichiometric parameters) Extracellular polymeric substances (EPSs) production COD, NH 4 -N, NO 3 -N, NO 2 -N, TN, PO 4 -P, TP CST and SRF measurements Physical/chemical parameters (DO, pH, Temperature…) Monitoring of activated sludge and biofilm growth
Results and discussion
Results and discussion Organic carbon removal 1000 Phase I Phase II Phase 100 III (b) (a) Concentration [mg L -1 ] COD efficiency removal [%] 800 80 600 60 bio BIO Phase Phase II Phase I tot TOT III 400 40 phys PHYS COD IN COD OUT COD SUP,MBR CODIN CODOUT CODMBR 20 200 0 0 0 20 40 60 80 100 120 0 20 40 60 80 100 120 Time [d] Time [d] very high total COD removal efficiency (Phase I = 97%; Phase II = 98%; Phase III = 99%) high biological contribution with moderate influence of the SRT typical robustness of MBR process
Results and discussion Nitrification and nitrogen removal Phase I Phase II Phase Phase 160 Phase II Phase I 100 (a) III III 140 N removal efficiency [%] (b) NH4_IN NH 4 -N IN 80 Concentration [mg L -1 ] 120 NHout NH 4 -N OUT No3_out 100 NO 3 -N OUT 60 80 40 60 40 20 20 denit N total hdenitr [%] htotale[%] hnitr [%] nit 0 0 0 20 40 60 80 100 120 0 20 40 60 80 100 120 Time [d] Time [d] excellent nitrification performance (average efficiency: 97%) not influenced significantly by the SRT variation 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
Results and discussion Phosphorus removal Phase tot Phase I 100 Phase II Phase 30 Phase I Phase II III (b) III (a) P removal efficiency [%] Concentration [mg L -1 ] 25 80 PO 4 -P IN PO4_IN 20 PO 4 -P OUT PO4_out 60 15 40 10 20 5 0 0 0 20 40 60 80 100 120 0 20 40 60 80 100 120 Time [d] Time [d] slight increase of bio-P removal with the SRT decrease. At high SRT the PAO activity is hampered by competition with ordinary heterotrophs
Results and discussion Biomass respiratory activity 1/2 Phase I Phase II Phase III 25 SOUR [mgO 2 g -1 VSSh -1 ] 20 15 10 Suspended Biomass 5 Biofilm 0 0 20 40 60 80 100 120 140 Time [d] higher heterotrophic activity in the suspended biomass compared to biofilm (more affine to organic carbon removal) 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”)
Results and discussion Biomass respiratory activity 2/2 Phase I Phase II Phase III 0.6 0.45 max,A [d -1 ] 0.3 0.15 Suspended Biomass Biofilm 0 0 20 40 60 80 100 120 140 Time [d] autotrophic activity more pronounced in the biofilm (specialization of biofilm towards nitrification) surprisingly, the suspended biomass showed an increasing autotrophic activity when reducing the SRT (“seeding” effect of nitrifiers from biofilm)
Results and discussion EPS production Phase II Phase III Phase I SRT = 30 d SRT = 15 d SRT = ∞ high EPS bound , likely 600 (a1) (a2) (a3) 500 EPS [mg gTSS -1 ] Anaerobic EPS P SMP P due to biofilm 400 EPS C SMP C 300 200 detachment 100 0 350 (b1) (b2) (b3) 300 Anoxic EPS [mg gTSS -1 ] the SRT decrease 250 200 150 could enhance the 100 50 biofilm detachment 0 350 (c1) (c3) (c2) 300 EPS [mg gTSS -1 ] thus increasing the Aerobic 250 200 150 EPS bound (worsening 100 50 the filtration 0 400 (d1) (d2) (d3) properties of the MBR EPS [mg gTSS -1 ] 300 200 physical membrane) 100 0 Phase II Phase III Phase I SRT = 30 d SRT = 15 d SRT = ∞
Results and discussion Membrane fouling Phase I Phase Phase II 50 Phase I ‐ 58th day Phase II ‐ 92nd day Phase III ‐ 114th day III (b2) (b3) (a) (b1) 4.38 2.57 2.71 0.91 0.56 7.91 1.96 14.00 Physical cleaning 8.24 40 R T [10 12 m -1 ] 30 92.75 94.16 69.85 20 Rm RPB RC,irr RC,rev Rm RPB RC,irr RC,rev Rm RPB RC,irr RC,rev 10 0 0 15 30 45 60 75 90 105 120 Time [d] 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
Conclusions 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
Message to take home! 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
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 Università di Palermo Research project of national interest PRIN2012 (D.M. 28 dicembre 2012 n. 957/Ric − Prot. 2012PTZAMC) Dipartimento di Ingegneria Civile, entitled “Energy consumption and GreenHouse Gas (GHG) emissions in the wastewater treatment Ambientale, Aerospaziale, dei plants: a decision support system for planning and management − http://ghgfromwwtp.unipa.it” Materiali (DICAM)
Athens 14-16 September 2016 1 st International Conference www.ficwtmod2017.it FICWTMOD2017 - Frontiers International Conference on wastewater treatment and modelling 21 – 24 May 2017, Palermo, Italy Supported by Università di Palermo Dipartimento di Ingegneria Civile, Ambientale, Aerospaziale, dei Materiali (DICAM)
Recommend
More recommend
