Minglu Zhang

Bio: Minglu Zhang is an academic researcher from Nankai University. The author has contributed to research in topics: Chemistry & Fermentation. The author has an hindex of 2, co-authored 3 publications receiving 82 citations. Previous affiliations of Minglu Zhang include University of California, Irvine & Tsinghua University.

Composition and Variability of Biofouling Organisms in Seawater Reverse Osmosis Desalination Plants

Abstract: Seawater reverse osmosis (SWRO) membrane biofouling remains a common challenge in the desalination industry, but the marine bacterial community that causes membrane fouling is poorly understood. Microbial communities at different stages of treatment processes (intake, cartridge filtration, and SWRO) of a desalination pilot plant were examined by both culture-based and culture-independent approaches. Bacterial isolates were identified to match the genera Shewanella, Alteromonas, Vibrio, and Cellulophaga based on 16S rRNA gene sequencing analysis. The 16S rRNA gene clone library of the SWRO membrane biofilm showed that a filamentous bacterium, Leucothrix mucor, which belongs to the gammaproteobacteria, accounted for nearly 30% of the clone library, while the rest of the microorganisms (61.2% of the total clones) were related to the alphaproteobacteria. 16S rRNA gene terminal restriction fragment length polymorphism (T-RFLP) analysis indicated that bacteria colonizing the SWRO membrane represented a subportion of microbes in the source seawater; however, they were quite different from those colonizing the cartridge filter. The examination of five SWRO membranes from desalination plants located in different parts of the world showed that although the bacterial communities from the membranes were not identical to each other, some dominant bacteria were commonly observed. In contrast, bacterial communities in source seawater were significantly different based on location and season. Microbial profiles from 14 cartridge filters collected from different plants also revealed spatial trends.

Detection and quantification of enteroviruses in coastal seawaters from Bohai Bay, Tianjin, China.

Abstract: An 8-month survey was conducted to detect and quantify enteroviruses in Tianjin coastal seawaters of Bohai Bay to assess coastal water quality. Ten water samples were collected from Bohai Bay for the detection and quantification of enteroviruses by conventional reverse transcription polymerase chain reaction (RT-PCR) and SYBR Green real-time quantitative RT-PCR (qRT-PCR). Total viral nucleic acid was extracted from 500 mL of seawater samples concentrated by Centricon plus-70 centrifugal filter devices. The viral recovery rate was 29.1% based on viral seeding study. The centrifugal ultrafiltration method applied is e ective for viral recovery from small volume of polluted water, which may have broader applications to monitoring human virus in aquatic environment. Our results indicated that there was a severe viral contamination in seawater of Bohai Bay. Enteroviruses were detected at concentrations ranging from 1.7 10 6 to 6.3 10 7 copies/L by qRT-PCR. Sequencing analyses identified that all of the twenty clones as poliovirus type 2. This is the first quantitative report of human viruses in coastal waters of a metropolitan city in China. This study emphasized the importance for the local and central governments to monitor and assess the water quality.

Enhancing biomethane yield of coal in anaerobic digestion using iron/copper nanoparticles synthesized from corn straw extract

Abstract: • Nanoparticles (NPs) synthesized from corn straw extract promote methane production. • Iron NPs encourages the emergence of new liquid products. • Iron NPs promote nutrient exchange between bacteria. • Copper NPs inhibits the activity of acid-producing and CO 2 /H 2 -producing bacteria. • Iron NPs increase the abundance of functional gene for producing more methane. To investigate the influence of nanoparticles (NPs) as additives on methane production from coal, bituminous coal was selected for the biogas production experiment, and iron and copper NPs were synthesized by hydrothermal treatment of corn straw. Biomethane production, gas chromatography-mass spectrometry, microbial community structure, and functional gene expression were analyzed to determine the effect of NPs on coal conversion to biomethane. The optimal amount of iron NPs (Fe 3 O 4 ), composite NPs (Fe 3 O 4 /CuO), and copper NPs (CuO) for the biogas production experiment were 1.5 g/L, 1.0 g/L, and 1.5 g/L, respectively, and the corresponding methane production increased by 701.22%, 337.81%, and 12.20% compared to the biogas production experiment without NPs. After the addition of iron NPs, a new product (butylated hydroxytoluene) was produced, promoting fatty acid biosynthesis and decreasing the CO 2 accumulation. The abundance of liquid products in the biogas production with composite NPs was not significantly different from the experimental group without NPs. The microbial community structure analysis results showed that adding NPs eliminated Lysinibacillus in the bacterial community, while Pseudomonas prevailed as the dominant bacteria. Copper NPs inhibited acid-producing and CO 2 /H 2 -producing bacteria ( Sphaerochaeta ). The abundance of functional genes involved in glycolysis and methane metabolism in the biogas production experiment with iron NPs was the largest, promoting biomethane production. Gene abundance related to nitrate reduction was the highest in experiments with copper NPs, while the gene abundance related to sulfate reduction was the same between copper and iron NPs groups.

Comparison of membrane fouling and cleaning in one-pass reverse osmosis and two-pass nanofiltration approaches to seawater desalination

Abstract: A recent innovation in seawater desalination is the use of multi-stage and multi-pass combinations of nanofiltration (NF) and reverse osmosis (RO) membranes. One example of this approach is the “Long Beach method,” in which seawater passes through two different types of NF membranes to produce potable water. After several years of pilot studies comparing the performance of two-pass NF and single-pass RO systems, a number of membrane elements were sacrificed for autopsy analyses. The selected membranes represent different stages of operation including (1) new, (2) fouled, and (3) cleaned membranes. Used NF and RO spiral wound elements were removed from the first and last positions of the demonstration plant. Although operating data suggested no outward signs of membrane fouling – inorganic, organic, and bacterial accumulation were identified on all membranes. First pass RO and NF membranes contained similar amounts of deposited solids, while significantly fewer solids were found on second pass NF membranes. Viable, culturable marine bacteria were observed on all fouled and cleaned membranes, indicating that bacterial colonization of seawater NF/RO membranes was not (a) detected by plant performance monitoring devices, (b) prevented by microfiltration and chlorination, or (c) removed by chemical cleaning. Chemical cleaning recovered the measurable performance of both first pass RO and second pass NF membranes, but was relatively ineffective at removing deposited solids from first-pass NF membranes. Therefore, chemical-cleaning methods may need to be tailored and optimized more specifically for NF membranes used in seawater desalination.

Biochemical Process and Microbial Evolution in the Conversion of Corn Straw Combined with Coal to Biogas

Abstract: The combined anaerobic fermentation of coal and straw can increase the production of biogas. To explore the mechanism of adding corn straw to increase methane production, coal with different metamorphic degrees and corn straw were collected for biogas production simulation experiments under different substrate ratios. The changes in liquid products, the structure of lignocellulose in corn straw, and microbial evolution were monitored. The results showed that the combined fermentation of bituminous coal A with corn straw and bituminous coal C with corn straw at a mass ratio of 2:1 each ((AC-2) and (CC-2)) and that of bituminous coal B and corn straw at a mass ratio of 3:1 (BC-3) had the best gas production, and methane yields reached 17.28, 12.51, and 14.88 mL/g, respectively. The fermentation liquid had organic matter with more types and higher contents during the early and peak stages of gas production, and fewer types of organic matter were detected in the terminal stage. The degradation of lignocelluloses in the corn straw of AC-2 was higher. With the increase in fermentation time, the carbohydrates in the fermentation system increased and the degradation rate of cellulose decreased gradually. The abundance of genes related to nitrate reduction gradually increased, while that of sulfate reduction was on the contrary. Bacteria in the cofermentation system mainly metabolized carbohydrates. During cofermentation with high metamorphic coal, corn straw would be preferentially degraded. The structure of the archaea community changed from Methanosarcina and Methanothrix to Methanobacterium.

Marine Biofilms: A Successful Microbial Strategy With Economic Implications

Abstract: Bacteria and other microorganisms have evolved an ingenious form of life, where they cooperate and improve their chances of survival when subjected to environmental stress, called biofilms. In these communities of adhered cells, bacteria are protected by a matrix of extracellular polymeric substances that provide protection against e.g. temperature and pH fluctuations, UV exposure, changes in salinity, depletion of nutrients, antimicrobial compounds and predation. Their success in marine environments and the number of bacterial cells in the sea, allow them to colonize nearly all man-made surfaces in contact with seawater. The costs to maritime transport, aquaculture, oil and gas industries, desalination plants and other industries are significant which has led to the development of various strategies to prevent biofilm formation and cleaning of infected surfaces. In this review, the benefits for bacterial cells to live in biofilms and the consequences to human activities are discussed.

Do biological-based strategies hold promise to biofouling control in MBRs?

Abstract: Biofouling in membrane bioreactors (MBRs) remains a primary challenge for their wider application, despite the growing acceptance of MBRs worldwide. Research studies on membrane fouling are extensive in the literature, with more than 200 publications on MBR fouling in the last 3 years; yet, improvements in practice on biofouling control and management have been remarkably slow. Commonly applied cleaning methods are only partially effective and membrane replacement often becomes frequent. The reason for the slow advancement in successful control of biofouling is largely attributed to the complex interactions of involved biological compounds and the lack of representative-for-practice experimental approaches to evaluate potential effective control strategies. Biofouling is driven by microorganisms and their associated extra-cellular polymeric substances (EPS) and microbial products. Microorganisms and their products convene together to form matrices that are commonly treated as a black box in conventional control approaches. Biological-based antifouling strategies seem to be a promising constituent of an effective integrated control approach since they target the essence of biofouling problems. However, biological-based strategies are in their developmental phase and several questions should be addressed to set a roadmap for translating existing and new information into sustainable and effective control techniques. This paper investigates membrane biofouling in MBRs from the microbiological perspective to evaluate the potential of biological-based strategies in offering viable control alternatives. Limitations of available control methods highlight the importance of an integrated anti-fouling approach including biological strategies. Successful development of these strategies requires detailed characterization of microorganisms and EPS through the proper selection of analytical tools and assembly of results. Existing microbiological/EPS studies reveal a number of implications as well as knowledge gaps, warranting future targeted research. Systematic and representative microbiological studies, complementary utilization of molecular and biofilm characterization tools, standardized experimental methods and validation of successful biological-based antifouling strategies for MBR applications are needed. Specifically, in addition, linking these studies to relevant operational conditions in MBRs is an essential step to ultimately develop a better understanding and more effective and directed control strategy for biofouling.

Solar disinfection is an augmentable, in situ-generated photo-Fenton reaction—Part 2: A review of the applications for drinking water and wastewater disinfection

Abstract: This is the second part of a comprehensive review article about photo-Fenton reaction at near-neutral pH used for water and wastewater disinfection. In this part, a critical revision of the fundamental physical, chemical and biological parameters affecting the photo-catalytic process efficiency are discussed. The effects of the chemical aspects, considered either as facilitators or competitors of photo-Fenton are deeply analyzed, with special focus on organic matter and its effect over bacterial inactivation. The role of solubilized iron and the biological nature of different pathogens are deeply assessed according to reported experimental data. Water temperature, turbidity, and radiation parameters like solar UV energy, ligh scattering and absorption during photo-Fenton are pictured in terms of treatment efficiency and suitable reactor design. Recent unconventional photo-Fenton strategies using iron chelates, iron oxides (including zero valent iron) and iron-based materials are also highlighted as new approaches to this process. Finally, the existing pilot scale studies in real conditions using photo-Fenton at near-neutral pH are revised, while alternative options and further research for real implementation are proposed.

How different is the composition of the fouling layer of wastewater reuse and seawater desalination RO membranes

Abstract: To study the effect of water quality and operating parameters on membrane fouling, a comparative analysis of wastewater (WW) and seawater (SW) fouled reverse osmosis (RO) membranes was conducted. Membranes were harvested from SWRO and WWRO pilot plants located in Vilaseca (East Spain), both using ultrafiltration as pretreatment. The SWRO unit was fed with Mediterranean seawater and the WWRO unit was operated using secondary effluent collected from the municipal wastewater treatment plant. Lead and terminal SWRO and WWRO modules were autopsied after five months and three months of operation, respectively. Ultrastructural, chemical, and microbiological analyses of the fouling layers were performed. Results showed that the WWRO train had mainly bio/organic fouling at the lead position element and inorganic fouling at terminal position element, whereas SWRO train had bio/organic fouling at both end position elements. In the case of WWRO membranes, Betaproteobacteria was the major colonizing species; while Ca, S, and P were the major present inorganic elements. The microbial population of SWRO membranes was mainly represented by Alpha and Gammaproteobacteria. Ca, Fe, and S were the main identified inorganic elements of the fouling layer of SWRO membranes. These results confirmed that the RO fouling layer composition is strongly impacted by the source water quality.

Bacterial community structure and variation in a full-scale seawater desalination plant for drinking water production

Abstract: Microbial processes inevitably play a role in membrane-based desalination plants, mainly recognized as membrane biofouling. We assessed the bacterial community structure and diversity during different treatment steps in a full-scale seawater desalination plant producing 40,000 m(3)/d of drinking water. Water samples were taken over the full treatment train consisting of chlorination, spruce media and cartridge filters, de-chlorination, first and second pass reverse osmosis (RO) membranes and final chlorine dosage for drinking water distribution. The water samples were analyzed for water quality parameters (total bacterial cell number, total organic carbon, conductivity, pH, etc.) and microbial community composition by 16S rRNA gene pyrosequencing. The planktonic microbial community was dominated by Proteobacteria (48.6%) followed by Bacteroidetes (15%), Firmicutes (9.3%) and Cyanobacteria (4.9%). During the pretreatment step, the spruce media filter did not impact the bacterial community composition dominated by Proteobacteria. In contrast, the RO and final chlorination treatment steps reduced the Proteobacterial relative abundance in the produced water where Firmicutes constituted the most dominant bacterial group. Shannon and Chao1 diversity indices showed that bacterial species richness and diversity decreased during the seawater desalination process. The two-stage RO filtration strongly reduced the water conductivity (>99%), TOC concentration (98.5%) and total bacterial cell number (>99%), albeit some bacterial DNA was found in the water after RO filtration. About 0.25% of the total bacterial operational taxonomic units (OTUs) were present in all stages of the desalination plant: the seawater, the RO permeates and the chlorinated drinking water, suggesting that these bacterial strains can survive in different environments such as high/low salt concentration and with/without residual disinfectant. These bacterial strains were not caused by contamination during water sample filtration or from DNA extraction protocols. Control measurements for sample contamination are important for clean water studies.