Wang Ying

Dr. Meyer L. Rosoff and Rev. Benzion Bauer Prize for Excellence in Water Research, 2007

My name is Wang Ying, an M.Sc. student in Zuckerberg Institute for Water Research, J. Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev. I was born in Sichuan province, southwest China, where is famous for its beautiful landscape with a lot of mountains and rivers, as well as its delicious food.   In my childhood, I was very interested in arts and science. I participated in some dance trainings of Chinese traditional dance and Ballet. I completed my Bachelor’s degree in Bioengineering, Sichuan University. After that, I worked as a research assistant in Triticease Crops Research Institute, Guizhou University.

With a desire of advanced study, I join the M.Sc. program of Albert Katz International School for Desert Studies. Under the supervision of Prof. Gideon Oron and Dr. Moshe Herzberg, I am involving the research project of characteristics of Extracellular Polymeric Substances (EPS) and their correlation with membrane biofouling in a Hybrid Growth Membrane Bioreactor (HG-MBR).

Description of research:

Extracellular Polymeric Substances (EPS) Characteristics and their Relation to Membrane Fouling in a Hybrid Growth Membrane Bioreactor (HG-MBR)

Supervisors: Prof. Gideon Oron, Dr. Moshe Herzberg

Membrane fouling is the most restricted and challenging factor for the widespread applications of membrane technology, including membrane bioreactor (MBR) systems. EPS, which are metabolic products accumulating on bacterial cell surface, are recognized as the most significant factor affecting biofouling in membrane bioreactors (MBRs). In this research study, quantitative, qualitative and spatial distribution analyses of EPS, which were obtained from an HG-MBR, were investigated under different operating conditions, in order to get a better insight and offer a possible approach of controlling biofouling process.

Abstract:

Membrane fouling in a hybrid-growth membrane bioreactor (HG-MBR) is a complex process affected by many factors. EPS, the metabolic products accumulating on bacterial cell’s surface, are recognized as the most significant factor regarding membrane biofouling. In this research study, we elucidated the role of sludge retention time (SRT) in fouling of ultrafiltration (UF) membrane in a HG-MBR system. Under constant organic loading rate, decrease in SRT caused a reduction in both mixed liquor suspended solids and sessile biomass. Even though biomass concentration in the reactor was lower, fouling rate was accelerated.

A highest EPS concentration adsorbed to the membrane was analyzed with significantly higher fraction of polysaccharides than proteins at the lowest SRT of 2.2 days, suggesting the direct inducement of fouling is due to the increase of production of either EPS or soluble microbial products (SMP) at higher organic loading rate per biomass unit.

To study the effect of water chemistry on EPS fouling potential, EPS adherence kinetics and viscoelastic properties were analyzed during adsorption to silica coated crystals in a quartz crystal microbalance with dissipation (QCM-D). Higher rate of EPS deposition was observed under higher ionic strength due to charge shielding of both negatively charged substances and the substratum suggesting that electrostatic interactions control EPS adsorption. Further study on the adsorption and structural changes of a relatively uncharacterized EPS layers is undertaken at various solution chemistries (pH and concentration of divalent cations).

Fig. 1. Diagram of the Hybrid Growth Membrane Bioreactor (HG-MBR) system	Fig 2. Quartz Crystal Microbalance (QCM) with Dissipation
Fig 3. Frequency (Hz) and dissipation (unitless) shifts upon adsorption of EPS on silica coated QCM-D crystals. The flow through experiment was conducted by injecting the following solutions: (i) background NaCl solution; (ii) EPS in NaCl solution; (iii) unbound EPS were washed with NaCl background solution; (iv) DI water.