Biodegradation of bisphenol A (BPA) by Chlorella-activated sludge bacterial consortium

Transcription

1 Biodegradation of bisphenol A (BPA) by Chlorella-activated sludge bacterial consortium Erjin Eio, Kenji Tsuchiya, Minako Kawai, Chiaki Niwa, Tatsuki Toda Graduate School of Engineering, Soka University, Japan

2 BPA demand and supply Introduction 2 Automotive components Polycarbonate plastics Plastic bottles and containers CDs and DVDs Global Bisphenol A (BPA) market will exceed 6.3 million metric tons by 2015 (Global Industry Analysts, 2010) Wastewater containing BPA from manufacturing will increase Wastewater contaminated with BPA is treated by activated sludge, advance oxidation process etc. High energy and high cost are required

3 Landfill leachate 3 Plastics manufacturing plant effluent BPA concentration Landfill leachate: mg/l (Yamada et al., 1999 ; Yamamoto et al., 2001) Plastics manufacturing plant effluent : 46.9 mg/l (Staples et al., 1995)

4 Algal-bacterial System 4 Carbon BPA Application to chemicals: Bacterial Oxidation Bacteria O2 CO2 Algal Photosynthesis Algae Phenanthrene 100% removal of 200 mg/l (Muñoz et al., 2003) Salicylate 100% removal of 1000 mg/l (Muñoz et al., 2006a) Bacteria Bacteria isolated from activated sludge able to degrade BPA (Lobos et al., 1992) Algae Pollutant tolerant and fast growing species (Muñoz et al., 2006b) Chlorella sorokiniana Chlorella vulgaris

5 5 Objective To determine the biodegradation of bisphenol A (BPA) by Chlorella-activated sludge bacterial consortium Algal BPA inhibition and degradation test Bacterial BPA degradation test Algal-bacterial BPA degradation test

6 Study 1: Algal BPA Inhibition and Degradation Test 6 Headspace: CO 2 /N 2 : 30/70 Mineral Salt Medium (MSM) + BPA Algae: Initial Chl a concentration: 0.5 mg/l Chlorella sorokiniana (NIES- 2168) Chlorella vulgaris (NIES- 2170) 100 ml Septum + Aluminum cap Axenic algae Experimental design Biotic (with algae) BPA concentration in MSM: 0, 10, 20, 50 mg/l Abiotic (without algae) BPA concentration in MSM: 10, 20, 50 mg/l Experimental conditions Temperature: 25 ± 1 C Light intensity: 300 µmol photons/m 2 /s Light dark cycle: 12L : 12D Headspace: CO 2 /N 2 : 30/70 Analysis parameters Chlorophyll a (Chl a) BPA concentration

7 Chl a (mg/l) Chl a (mg/l) Algal BPA Inhibition Test: Algal Chl a concentration C. sorokiniana C. vulgaris C. vulgaris has higher tolerance to BPA Time (hours) * * ** Significant difference * (p < 0.05), ** (p < 0.01) 0 mg/l 10 mg/l 20 mg/l 50 mg/l 7

8 Residual BPA (%) Algal BPA Degradation Test: Residual BPA CS CV CS CV CS CV 10 mg/l 20 mg/l 50 mg/l Initial BPA concentration Biotic loss Abiotic loss Remained CS :C. sorokiniana CV :C. vulgaris

9 Study 2: Bacterial BPA Degradation Test 9 <Bacterial acclimatization > MSM + BPA 50 mg/l Aeration Activated sludge bacteria taken from Kitano sewage center 3 months acclimatization Stock culture Kept for further experiment use

10 Bacterial BPA Degradation Test 10 <Bacterial BPA degradation> Aeration Experimental design BPA concentration in MSM: 0, 10, 20, 50 mg/l Bacteria Bacteria: 100 ml MSM + BPA Experimental conditions Temperature: 25 ± 1 C Light intensity: 300 µmol photons/m 2 /s Light dark cycle: 12L :12D Initial cells: 2.0 x 10 5 cells/ml Acclimatized bacteria taken from activated sludge of Kitano Analysis parameters Bacterial cell density BPA concentration sewage center

11 Bacterial cell density (cells/ ml) BPA concentration (mg/l) Bacterial BPA Degradation Test: BPA & bacterial cells mg/l 20 mg/l 50 mg/l Detection limits Increase of BPA concentration decrease of BPAdegrading activity (Zhang et al 2007) Complete BPA removal in this study might be due to the long period of acclimatization mg/l 10 mg/l 20 mg/l 50 mg/l Time (hours)

12 Schematic Diagram of Formation of Acclimatized Bacterial Consortium 12 High BPA concentration Assembly of bacteria with wide range of catabolic pathway Utilize BPA Utilize intermediate compounds Before acclimatization After acclimatization BPA intermediate compounds BPA Modified from Suthersan, 1999

13 Study 3: Algal-bacterial BPA Degradation Tests 13 Algae MSM + BPA 100 ml Bacteria Air Septum Algae: Initial Chl a concentration: 0.5 mg/l Chlorella sorokiniana (NIES- 2168) Chlorella vulgaris (NIES- 2170) Bacteria: Initial cells: 2.0 x 10 5 cells/ml Acclimatized bacteria taken from activated sludge of Kitano sewage center Experimental design BPA concentration in MSM: 0, 10, 20, 50 mg/l Experimental conditions Temperature: 25 ± 1 C Light intensity: 300 µmol photons/m 2 /s Light dark cycle: 12L :12D Analysis parameters Chl a Bacterial cell density BPA concentration

14 Bacterial cell density (cells/ ml) BPA concentration (mg/l) Bacteria l cell density (cells/ ml) Algal-bacterial BPA Degradation Tests: BPA & bacterial cells C. sorokiniana + Bacteria < 2mg/L C. vulgaris + Bacteria Time (hours) C. sorokiniana + Bacteria in BPA 10 mg/l C. sorokiniana + Bacteria in BPA 20 mg/l C. sorokiniana + Bacteria in BPA 50 mg/l C. vulgaris + Bacteria in BPA 10 mg/l C. vulgaris + Bacteria in BPA 20 mg/l C. vulgaris + Bacteria in BPA 50 mg/l mg/l 10 mg/l 20 mg/l 50 mg/l Time (hours)

15 Chl a (mg/l) Chl a (mg/l) Chl a (mg/l) Chl a (mg/l) Time (hours) Symbiotic relationship Algae Comparison of Algal-bacterial System and Algal System 15 C. sorokiniana + Bacteria Significant difference * (p < 0.05) ** (p < 0.01) * * C. vulgaris + Bacteria 0 mg/l 10 mg/l 20 mg/l 50 mg/l Bacteria C. sorokiniana (Study 1) C. vulgaris (Study 1) Time (hours) CO 2 (Bashan et al 2002) Growth-promoting substances (Croft et al 2002) Reduce the BPA inhibitory effect on algae (this study) * * **

16 BPA removal rate (mg/l/h) Comparison of Bacterial System and Algal-bacterial Systems Without mechanical aeration ** ** Significant difference ** (p < 0.01) 10 mg/l 20 mg/l 50 mg/l Symbiotic relationship Oxygen supplier Enhanced BPA removal Algae Bacteria

17 17 Conclusions Algal system was less efficient in treating high concentration of BPA algal inhibition low BPA degradation rate Acclimatized activated sludge bacteria removed BPA to a satisfactory level with mechanical aeration An algal-bacterial system showed promising BPA removal rate by photo-oxygenation Chlorella-activated sludge bacterial consortium demonstrated a cost-effective and efficient bioremediation technique for removing BPA

18 Acknowledgement This research was partially funded by a grant from the Center of Excellence for Private Universities from Japan s Ministry of Education, Culture, Science and Technology from 2009 to Thank you very much