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1.
Production of polymers by cyanobacteria grown in wastewater: Current status, challenges and future perspectives.
Arias, DM, García, J, Uggetti, E
New biotechnology. 2020;:46-57
Abstract
Cyanobacteria are prokaryotic oxygenic phototrophs receiving attention in a wide variety of technological applications such as food and feed supplements and production of valuable polymers. Among these, carbohydrates (e.g. glycogen) and polyhydroxyalkanoates (PHAs) are of increasing interest due to their potential as a biofuel substrate and bioplastics, respectively. However, biofuels and bioplastics from cyanobacteria have seen many years of effort towards commercialization with only limited success. Their main limitation for polymer production is the high cost of the nutrient source; wastewater, as an inexpensive and widely available alternative, may overcome this bottleneck. Though cyanobacteria have demonstrated a capacity to treat wastewater effluents, their cultivation in such a variable environment involves certain challenges of which the chief one is linked to contamination by other species, especially green algae. This would represent a serious drawback during cyanobacterial biomass production and affect further PHA and carbohydrate production. The present study reviews the potential of cyanobacteria to grow in wastewater effluents from different sources. Conditions favoring them in mixed-culture reactors are described, focusing on nutritional and operational aspects. Current advances and future prospects in PHA and carbohydrate production are explored and discussed.
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2.
Disinfection technology of hospital wastes and wastewater: Suggestions for disinfection strategy during coronavirus Disease 2019 (COVID-19) pandemic in China.
Wang, J, Shen, J, Ye, D, Yan, X, Zhang, Y, Yang, W, Li, X, Wang, J, Zhang, L, Pan, L
Environmental pollution (Barking, Essex : 1987). 2020;:114665
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Abstract
Hospitals are important sources of pollutants resulted from diagnostic, laboratory and research activities as well as medicine excretion by patients, which include active component of drugs and metabolite, chemicals, residues of pharmaceuticals, radioactive markers, iodinated contrast media, etc. The discharge of hospital wastes and wastewater, especially those without appropriate treatment would expose the public in danger of infection. In particular, under the Coronavirus Disease 2019 (COVID-19) pandemic context in China, it is of great significance to reduce the health risks to the public and environment. In this study, technologies of different types of hospital wastes and wastewater disinfection have been summarized. Liquid chlorine, sodium hypochlorite, chlorine dioxide, ozone, and ultraviolet irradiation disinfection are commonly used for hospital wastewater disinfection. While incineration, chemical disinfection, and physical disinfection are commonly used for hospital wastes disinfection. In addition, considering the characteristics of various hospital wastes, the classification and selection of corresponding disinfection technologies are discussed. On this basis, this study provides scientific suggestions for management, technology selection, and operation of hospital wastes and wastewater disinfection in China, which is of great significance for development of national disinfection strategy for hospital wastes and wastewater during COVID-19 pandemic.
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3.
Multiple strategies for maintaining stable partial nitritation of low-strength ammonia wastewater.
Sui, Q, Jiang, L, Di, F, Yue, W, Chen, Y, Wang, H, Chen, M, Wei, Y
The Science of the total environment. 2020;:140542
Abstract
Stable production of nitrite is an essential technical challenge for mainstream anaerobic ammonia oxidation (Anammox). Due to difficulties in the stable inhibition of nitrite oxidizing bacteria (NOB) and maintenance of long-term partial nitritation (PN), integrated multiple, rather than a single, controlling strategies were preferred especially in a continuous-flow treatment system. A mathematically model was developed to evaluate effects of integrated multiple-strategies on ammonia oxidizing bacteria (AOB) and NOB. Through experimental study and model simulation, intermittent aeration and low SRT (3.5 d) resulted in unstable nitrite accumulation. Integrated multiple-strategies of intermittent aeration, low SRT (3.5 d) and bioaugmentation achieved nitrite accumulation rate of 81% and NO2--N/NH4+-N ratio in effluent of 1.29, which was preferable for further anammox process. Meanwhile, the richness and diversity of microbial community increased due to the bioaugmentation. The AOB/NOB ratio increased from 13.8 to 34.1 which facilitated nitrite accumulation. In combination with bioaugmentation, the observed growth rates of AOB and NOB increased from -0.0835 and -0.0282 to 0.0434 and 0.0127 d-1, respectively, which promoted AOB outcompeting NOB in the mixed liquid.
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4.
Genome sequencing as a new window into the microbial community of membrane bioreactors - A critical review.
Nguyen, LN, Commault, AS, Kahlke, T, Ralph, PJ, Semblante, GU, Johir, MAH, Nghiem, LD
The Science of the total environment. 2020;:135279
Abstract
Recent developed sequencing techniques have resulted in a new and unprecedented way to study biological wastewater treatment, in which most organisms are uncultivable. This review provides (i) an insight on state-of-the-art sequencing techniques and their limitations; (ii) a critical assessment of the microbial community in biological reactor and biofouling layer in a membrane bioreactor (MBR). The data from high-throughput sequencing has been used to infer microbial growth conditions and metabolisms of microorganisms present in MBRs at the time of sampling. These data shed new insight to two fundamental questions about a microbial community in the MBR process namely the microbial composition (who are they?) and the functions of each specific microbial assemblage (what are their function?). The results to date also highlight the complexity of the microbial community growing on MBRs. Environmental conditions are dynamic and diverse, and can influence the diversity and structural dynamics of any given microbial community for wastewater treatment. The benefits of understanding the structure of microbial communities on three major aspects of the MBR process (i.e. nutrient removal, biofouling control, and micropollutant removal) were symmetrically delineated. This review also indicates that the deployment of microbial community analysis for a practical engineering context, in terms of process design and system optimization, can be further realized.
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5.
Use of microalgae based technology for the removal of antibiotics from wastewater: A review.
Leng, L, Wei, L, Xiong, Q, Xu, S, Li, W, Lv, S, Lu, Q, Wan, L, Wen, Z, Zhou, W
Chemosphere. 2020;:124680
Abstract
The antibiotic resistance induced by the release of antibiotics to the environment has urged research towards developing effective technologies for antibiotic removal from wastewater. Traditional technologies such as activated sludge processes are not effective for antibiotic removal. Recently, microalgae-based technology has been explored as a potential alternative for the treatment of wastewater containing antibiotics by adsorption, accumulation, biodegradation, photodegradation, and hydrolysis. In this review, the toxicities of antibiotics on microalgae, the mechanisms of antibiotic removal by microalgae, and the integration of microalgae with other technologies such as ultraviolet irradiation (photocatalysis), advanced oxidation, and complementary microorganism degradation for antibiotic removal were discussed. The limitations of current microalgae-based technology and future research needs were also discussed.
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6.
Successive use of microorganisms to remove chromium from wastewater.
Elahi, A, Arooj, I, Bukhari, DA, Rehman, A
Applied microbiology and biotechnology. 2020;(9):3729-3743
Abstract
Heavy metal pollution is a direct consequence of the extensive utilization of heavy metals in various industrial processes. The persistence and nondegradability of heavy metals cause them to bioaccumulate in nature, and when they come in direct contact with the pristine environment, they not only contaminate it severely but also pose dire consequences to the health of all living forms on earth, including humans. Chromium (Cr) is one of the heavy metals which has been extensively used in various industrial processes such as mining, alloy manufacturing, tanning of hides and skins, pigment production, etc. However, it is regarded as a priority pollutant due to its highly toxic, teratogenic, mutagenic, and carcinogenic nature, and the U.S. Environmental Protection Agency (EPA) also categorized it into group "A" human carcinogen. In contrast to water-soluble hexavalent chromium (Cr6+), its reduced form, trivalent chromium (Cr3+), is relatively benign and readily precipitated at environmental pH. Thus, bioremediation of Cr6+ through microorganisms including bacteria, yeast, and algae provides a promising approach to decontaminate a metal-polluted environment. This review describes an overview of the microbial reduction of Cr6+, resistance mechanism, and the antioxidant profiling exhibited by these microorganisms when exposed to Cr6+. It also describes the pilot-scale study of the successive use of bacterial, fungal, and algal strains and the subsequent use of microbially purified water for the cultivation of plant growth. Multiple metal-resistant microorganisms are a good bioresource for green chemistry to eradicate environmental Cr6+. KEY POINTS • Hexavalent chromium (Cr6+) is highly toxic for living organisms including humans. • Microbial Cr resistance is mediated at the genetic, proteomic, and molecular levels. • Successive use of microorganisms is the best strategy to exterminate Cr6+from the environment.
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7.
Effects of copper on biological treatment of NMF- and MDG-containing wastewater from TFT-LCD industry.
Cheng, HH, Pien, TT, Lee, YC, Lu, IC, Whang, LM
Chemosphere. 2020;:127125
Abstract
This study aimed to evaluate the effects of copper on N-methylformamide (NMF)- and methyl diglycol (MDG)-containing wastewater treatment using batch experiments and a lab-scale anoxic-oxic (A/O) sequencing batch reactor (SBR). Batch experimental results indicated that aerobic degradation of NMF followed Monod-type kinetics. Copper inhibition on nitrification also followed Monod-type inhibition kinetics with copper-to-biomass ratio instead of copper concentration. Specific degradation rates of NMF and MDG under both aerobic and anoxic conditions decreased in the matrix of full-scale wastewater, and high copper dosage would further reduce the degradation rates. In the long-term presence of 0.5 mg/L copper, the A/O SBR could maintain stable and complete degradations of NMF and MDG, 95% of COD removal, and more than 50% of total nitrogen (TN) removal. High concentrations of copper spikes, including 40 mg/L and 110 mg/L, slowed down degradation rates for both NMF and MDG, but did not affect COD and TN removal efficiencies in the full 24 h-cycle operation. The long-term A/O SBR operation revealed that daily dosage of 0.5 mg/L copper was not detrimental to NMF/MDG degradations due to regularly wasting sludge, but 110 mg/L of copper spike obviously reduced NMF/MDG degradation rate although it could be recovered later by regularly wasting sludge and maintaining SRT at 20 days.
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8.
Evaluation of different culture media for detection and quantification of H. pylori in environmental and clinical samples.
Hortelano, I, Moreno, Y, Vesga, FJ, Ferrús, MA
International microbiology : the official journal of the Spanish Society for Microbiology. 2020;(4):481-487
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Abstract
The objective of the present study was to establish the most suitable culture medium for the isolation of H. pylori from environmental and clinical samples. Ten different culture media were compared and evaluated. Four of them had been previously described and were modified in this study. The rest of the media were designed de novo. Three different matrices, tap water, wastewater, and feces, were inoculated with serial dilutions of H. pylori NCTC 11637 strain at a final concentration of 104 and 103 CFU/ml and the recovery rates were calculated. From inoculated tap water and wastewater samples, H. pylori colonies were recovered from four out of the analyzed culture media. When fecal samples were analyzed, the isolation of the pathogen under study was only possible from two culture media. Different optimal media were observed for each type of sample, even for wastewater and stool samples. Nevertheless, our results indicated that the combination of Dent Agar with polymyxin B sulfate did not inhibit the growth of H. pylori and was highly selective for its recovery, regardless of the sample origin. Thus, we propose the use of this medium as a diagnostic tool for the isolation of H. pylori from environmental and clinical samples, as well as for epidemiological studies.
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Unfolding microbial community intelligence in aerobic and anaerobic biodegradation processes using metagenomics.
Tikariha, H, Purohit, HJ
Archives of microbiology. 2020;(6):1269-1274
Abstract
Environmental factors and available nutrients influence microbial communities, and with that, there exists a dynamic shift in community structure and hierarchy in wastewater treatment systems. Of the various factors, the availability and gradient of oxygen selectively enrich a typical microbial community and also form the community stratification which could be established through metagenomics studies. In recent years, metagenomics with various sets of bioinformatics tools has assisted in exploration and better insight into the organization and relation of the taxonomical and functional composition and associate physiological intelligence of the microbial communities. The microbial communities, under defined conditions acquire a typical hierarchy with flexible but active network of the metabolic route, which ensures the survival needs of every member residing in that community and their abundance. This knowledge of community functional organization defines the rule in designing and improving biodegradation processes in case of both aerobic and anaerobic systems.
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10.
Electro-Fenton with peroxi-coagulation as a feasible pre-treatment for high-strength refractory coke plant wastewater: Parameters optimization, removal behavior and kinetics analysis.
Zhou, X, Hou, Z, Lv, L, Song, J, Yin, Z
Chemosphere. 2020;:124649
Abstract
Electro-Fenton (EF) with peroxi-coagulation (PC) as an emerging electro-chemical advanced oxidation method has been extensively applied to treat refractory wastewater. However, the studies on the pretreatment of the raw coke plant wastewater by EF process were still lacking. In this study, a lab-scale EF system (Fe as anode and graphite as cathode) achieved the highest COD removal of 69.2% based on the preliminary experiments. The process parameters and corresponding COD removal performance were further optimized using response surface methodology (RSM) combined with Box-Behnken experimental design (BBD). The optimal conditions were obtained as: 3.2 mA cm-2 of current density, 2 h of the reaction time and 2.6 of the initial pH value, with the COD removal reaching 70.0%. Fourier infrared (FTIR), fluorescence excitation-emmission matrix (EEM) and gas chromatography-mass spectrometry (GC-MS) also revealed the degradation behaviors of dissolved organic matters (DOMs) by characterizing their structures and compositions before and after EF pretreatment, thus greatly improving the biodegradability of the wastewater. Moreover, the EF process for COD removal well followed third-order kinetics model. These findings give helpful guidance to design, optimize and control the EF process as a favourable pretreatment for actual refractory coking wastewater in practice.