Evaluating the Performance of Spouted Bed Bio- Reactor (SBBR) during Aerobic Biodegradation of 2, 4 Dichlorophenol (DCP)

Transcription

1 Engineering Conferences International ECI Digital Archives : Bridging Modeling and Experimental Studies Proceedings Spring Evaluating the Performance of Spouted Bed Bio- Reactor (SBBR) during Aerobic Biodegradation of 2, 4 Dichlorophenol (DCP) Taghreed Al Khalid United Arab Emirates University Muftah El-Naas United Arab Emirates University Follow this and additional works at: Part of the Environmental Engineering Commons Recommended Citation Taghreed Al Khalid and Muftah El-Naas, "Evaluating the Performance of Spouted Bed Bio-Reactor (SBBR) during Aerobic Biodegradation of 2, 4 Dichlorophenol (DCP)" in ": Bridging Modeling and Experimental Studies", Dr. Domenico Santoro, Trojan Technologies and Western University Eds, ECI Symposium Series, (2014). This Conference Proceeding is brought to you for free and open access by the Proceedings at ECI Digital Archives. It has been accepted for inclusion in : Bridging Modeling and Experimental Studies by an authorized administrator of ECI Digital Archives. For more information, please contact franco@bepress.com.

2 Evaluating the Performance of Spouted Bed Bio-Reactor (SBBR) during Aerobic Biodegradation of 2, 4 Dichlorophenol (DCP) Taghreed Al Khalid, Muftah El-Naas Chemical and Petroleum Engineering Department, UAE University

3 Outline Introduction Properties of Chlorophenols Immobilization and Biofilm Reactors Goals and Objectives Method and Experimental Set-up Batch Biodegradation of 2, 4 DCP Continuous Biodegradation of 2, 4 DCP Assessment of Internal Mass Transfer Limitations Conclusions Acknowledgements 2

4 Introduction Pollution Problem Phenols are a major class of contaminants, carcinogens, highly toxic even at low ppm. Phenols + chlorine Chlorophenols more resistance to degradation Many chlorophenols (CPs) are included in the EPA (USA) list of priority pollutants. The UAE legislations: 0.1 mg/l total phenols in industrial water. 3

5 Introduction Sources of Contamination Petroleum refineries are the main sources of phenolic compounds in wastewaters. Mono-chlorophenols in particular, can be formed during the chlorination of wastewaters. 4

6 Introduction Why Biodegradation? Biodegradation is a more environmental friendly and cost effective alternative. No by-products (secondary pollution) Possibility of complete mineralization, which results in complete conversion to CO 2 and H 2 O 5

7 Chlorine Solubility Volatility Biodegradability Toxicity Properties of CP s Benzene ring cleavage Highly stable due to very strong carbon chlorine bond Relatively high solubility Degree of chlorination: Biodegradation Cl Cl 6

8 Immobilization and Biofilm Reactors High chlorophenol conc. Growth inhibition of cells Recent investigations focused on the use of immobilized cells rather than suspended or free cells: Biofilm reactors: Fluidized bioreactors (FBBR), fixedbed biofilm reactor, spouted bed bioreactor (SBBR), microporous membranes; packed bed reactor (PBR) 7

9 Immobilization and Biofilm Reactors Advantages of Immobilization Cell protection from toxicity of CP at high conc. Ease of separation and reutilization of the biomass Shorter hydraulic retention times and no biomass washout in continuous operation Flexibility of reactor design and the improved thermal and operational stability Higher tolerance to toxic and organic shock loads Drawback: Diffusion limitation 8

10 Goals and Objectives Task 1: Investigating biodegradation of 2, 4 DCP in batch operation Task 2: Evaluating the performance of SBBR in terms of hydrodynamics and tolerance to shock loads Task 3: Comparing the performance of the SBBR to that of the PBR Task 4: Assessing mass transfer limitations in PVA particles 9

11 Method: Preparation of Microbial Culture Commercial bacterial consortium: Pseudomonas putida Non-pathogenic Acclimatized up to 2, 4 DCP up to 200 mg/l (synthetic solutions) 10

12 Methods: Immobilization The biomass is immobilized on PVA Gel PVA has better mechanical properties, and it is more durable. 11

13 Method: Experimental Set-up Spouted Bed Bioreactor (SBBR): Good mixing and temperature control (1) Refrigerated /Heating Circulator, (2) Flowmeter, (3) SBBR, (4) Valve, (5) Peristaltic Pump, (6) Effluent, (7) Feed Tank 12

14 Methods: Experimental Set-up SBBR PBR 13

15 Batch Biodegradation of 2, 4 DCP in SBBR 250 Concentration (mg/l) % Removal 28 ppm 55 ppm 100 ppm 150 ppm 200 ppm Time (min) 14

16 Continuous Biodegradation of 2, 4 DCP Reactor hydrodynamics: Effect of Liquid Flow Rate LFR will affect HRT Effect of LFR Effect of LFR Concentration (mg/l) Time (min) 3.3 ml/min 5.3 ml/min 10.4 ml/min 15 ml/min 49.3% 94.2% % Removal % Removal DCP concentration Liquid Flow Rate (ml/min) S. S. Effluent DCP Concentration (mg/l) 15

17 Continuous Biodegradation of 2, 4 DCP Reactor hydrodynamics: Effect of Initial DCP Concentration Concentration (mg/l) mg/l 50 mg/l 75 mg/l 100 mg/l 95.5% % Removal % Removal Rate Biodegradation Rate (mg/l.h) Time (min) , 4 DCP Initial Concentration (mg/l) 16

18 Continuous Biodegradation of 2, 4 DCP Assessment of SBBR Performance: Degradation Capacity DC = (S i S e ) / HRT Combined Effects of LFR and C o of DCP % 780 g/m 3 /d 45 % Removal % Removal Degradation Capacity Degradation Capacity (mg/l.h) Organic Loading Rate (mg/l.h) 17

19 Continuous Biodegradation of 2, 4 DCP Assessment of SBBR Performance: Response to Shock Loading Organic Load Shock Hydraulic Load Shock Concentration (mg/l) effluent influent Concentration (mg/l) effluent conc. HRT Hydraulic Residence Time (h) Time (min) Time (min) 18

20 Continuous Biodegradation of 2, 4 DCP Assessment of SBBR Performance: SBBR compared to PBR 100 Concentration (mg/l) % Packed Run 1 Packed Run 2 Packed Run 3 SBBR Run 1 SBBR Run 2 77% 1414 g/m 3 /d Time (min) 19

21 Assessment of Internal Mass Transfer Limitations Immobilization of microbial cells effectively increased the tolerance of P. putida to DCP concentrations beyond 100 mg/l. Biodegradation rate (mg/l.h) free cells immobilized cells Concentration (mg/l) 20

22 Assessment of Internal Mass Transfer Limitations Effectiveness factor (η) = r s is the rate at the outer surface For SBBR, external mass transfer resistance can be neglected, r s is the rate by free bacteria For η << 1, intraparticle diffusion r C A is significant (C A << C As ) For η 1, intraparticle diffusion is not significant (C A ~ C As ) R C As Diffusion of substrate 21

23 Assessment of Internal Mass Transfer Limitations For Runs 1: r free = 9.06 mg/l.h r immobilized = 7.8 mg/l.h 120 η = 7.8/9.06= 0.86 For Runs 2: r free = 10.7 mg/l.h r immobilized = 11.1 mg/l.h η = 1 Concentration (mg/l) Run 1 immobilized Run 2 immobilized Run 1 free Run 2 free Not diffusion limited Improvement in performance of used particles Time (h) 22

24 Conclusions Immobilization is an effective technique for reuse of biomass on a wide range of concentrations. Complete removal of the contaminant in the batch operation, up to 200 mg/l. Combined high degradation capacities and high percent removals ( g/m 3 /d & high % removal (77-90), were achieved in the continuous operation. Diffusion is a limiting factor in immobilized-cell bioprocesses. The SBBR and the porous structure of the PVA gel play a key role in overcoming this limitation. 23

25 Acknowledgements Financial support provided by the UAE University as part of the PhD Scholarship Program 24

26 25 T. Al Khalid May 26, 2014