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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.
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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4.
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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5.
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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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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Potential of enzymatic process as an innovative technology to remove anticancer drugs in wastewater.
Pereira, CS, Kelbert, M, Daronch, NA, Michels, C, de Oliveira, D, Soares, HM
Applied microbiology and biotechnology. 2020;(1):23-31
Abstract
Anticancer drugs are a class of pharmaceutical compounds that have been found in hospital, domestic, and industrial wastewaters and also in surface waters. They have been showing recalcitrance to conventional wastewater treatment technologies and present a potential risk to environment and human health, since they exhibit cytotoxic, teratogenic, and carcinogenic among other effects in higher organisms, even at low concentrations. The presence of these compounds in the environment is a recent challenge for wastewater treatment and some alternative strategies to remove them were already studied, such as white-rot fungi (WRF) technologies. Despite promising results, processes involving fungi are complex, have high reaction times, and require nutrient addition for fungus growth and maintenance. Due to this potential, strategies to make the technology feasible were studied, such as the possibility for direct application of enzymes secreted by WRF. Enzymatic processes were studied in the removal of other pharmaceuticals such as antibiotics, anti-inflammatory, and steroid hormones; however, to the best of our knowledge, there is a gap on literature about their direct action on anticancer drugs.
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High-strength wastewater treatment using microbial biofilm reactor: a critical review.
Abdelfattah, A, Hossain, MI, Cheng, L
World journal of microbiology & biotechnology. 2020;(5):75
Abstract
Biofilm reactors retain microbial cells in the form of biofilm which is attached to free moving or fixed carrying materials, thus providing a high active biomass concentration and automatic liquid and solid separation. Nowadays, microbial biofilm reactors have been widely used in high-strength wastewater treatment where very high pollutant removal efficiency is required, which usually requires excessive space and aeration energy for conventional activated sludge-based treatment. This paper provides an overview of microbial biofilm reactors developed over the last half-century, including moving bed biofilm reactor (MBBR), trickling filter (TF) reactor, rotating biological contactor (RBC), membrane biofilm reactor (MBfR), passive aeration simultaneous nitrification and denitrification (PASND) biofilm reactor, for their applications in high-strength wastewater treatment of not only removing carbon, nitrogen, sulphur but also a variety of oxidized contaminants including perchlorate and bromate. Despite the advance of biofilm reactor that exhibits high resistance to excessive pollutants loading, its drawbacks both from engineering and microbiological point of view are reviewed. The future prospects of biofilm reactor are also discussed in this review paper.
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10.
Winery wastewater treatment: a critical overview of advanced biological processes.
Bolzonella, D, Papa, M, Da Ros, C, Anga Muthukumar, L, Rosso, D
Critical reviews in biotechnology. 2019;(4):489-507
Abstract
Wine production is one of the leading sectors of the food processing industry. The wine industry produces a large amount of wastewater characterized by a high strength in terms of organic pollution and large variability throughout the year. Most of the organic matter is soluble and easily biodegradable. On the other hand, nitrogen and phosphorous are lacking. The aerobic and anaerobic processes are largely applied for winery wastewater treatment because they can quickly react to changes in the organic loading. This review analyzes e applied biological systems, considering both aerobic and anaerobic processes, and different reactor configurations. The performances of different biological processes are evaluated in terms of operational conditions (organic loading rate and hydraulic retention time). Aerobic processes can guarantee chemical oxygen demand removal up to 98% for organic loading rates of some 1-2 kg of chemical oxygen demand m-3d-1 but requires good aeration systems to supply the required process oxygen. The management cost of these processes could be high considering the power density in the range 60-70 W m-3reactor and that nutrients should be added to support biomass growth. On the other hand, anaerobic processes are able to face high organic loads with low running costs, but COD removal is generally limited to 90%. Combination of the two treatment systems (anaerobic followed by aerobic) could reduce management costs and meet high discharge standards.