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1.
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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2.
Current status and future prospects of sewer biofilms: Their structure, influencing factors, and substance transformations.
Li, W, Zheng, T, Ma, Y, Liu, J
The Science of the total environment. 2019;:133815
Abstract
With rapid urbanization, sewer systems are extensively being constructed for the collection and transportation of sewage to minimize the severe environmental and health issues, especially relating to the spread diseases. The existence of abundant biofilms on the inner walls of sewers could lead to potential risks such as sewer explosions, poisonous gas leaks, and pipe corrosions with the transformations of various kinds of pollutants. Therefore, it is urgent to clarify their inner mechanisms to safely govern sewer systems. In this study, the characteristics of sewer biofilms including their structure, influencing factors, and substance transformations were analyzed in-depth. The results reveal that sewer biofilms (1.0 mm depth approximately) consist of large quantities of inorganic and some organic substances, while the abundant functional genus of the bacteria and archaea are summarized. Sewer biofilms influencing factors were determined to be sewer operation mode, sewage characteristics, and shear stress. Further, the transformation of organics, sulfur, and nitrogen as well as emerging micropollutants (such as, biomarkers, antibiotic resistance genes, and engineered nanoparticles) was investigated to guarantee sewer security and public health. Therefore, the current review could be considered as guidance for researchers and decision-makers.
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3.
Research progress and application prospect of anaerobic biological phosphorus removal.
Yang, F, Zhang, C, Rong, H, Cao, Y
Applied microbiology and biotechnology. 2019;(5):2133-2139
Abstract
Anaerobic biological phosphorus removal has proposed a new direction for the removal of phosphorus from wastewater, and the discovery of phosphate reduction makes people have a more comprehensive understanding of microbial phosphorus cycling. Here, from the perspective of thermodynamics, the bioreduction reaction of phosphate was analyzed and its mechanism was discussed. The research progress of phosphate reduction and the application prospects of anaerobic biological phosphorus removal from wastewater were introduced, pointing out the situation and guiding the further research in this field.
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4.
Finding Knowledge Gaps in Aerobic Granulation Technology.
Sarma, SJ, Tay, JH, Chu, A
Trends in biotechnology. 2017;(1):66-78
Abstract
This review identifies the knowledge gaps in aerobic granulation technology and defines some problems for future studies. In particular, extracellular polymeric substances (EPSs) should be further characterized to understand the intermolecular interactions among these polymers, the role of chelating agents in destabilizing EPS ionic bridges needs further elucidation, and early detection of the quorum-quenching enzymes should be considered to avoid granule segregation and process failure. Furthermore, the process should be supplemented with volatile fatty acids as electron donors/carbon sources, and appropriate anoxic/anaerobic conditions should be provided for enhanced nitrogen and phosphorus removal. Finally, the biodegradation, bioaccumulation, biosorption, and mass transfer behaviors of the emerging contaminants within the granules need further investigation.
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5.
Recovery and reuse of sludge from active and passive treatment of mine drainage-impacted waters: a review.
Rakotonimaro, TV, Neculita, CM, Bussière, B, Benzaazoua, M, Zagury, GJ
Environmental science and pollution research international. 2017;(1):73-91
Abstract
The treatment of mine drainage-impacted waters generates considerable amounts of sludge, which raises several concerns, such as storage and disposal, stability, and potential social and environmental impacts. To alleviate the storage and management costs, as well as to give the mine sludge a second life, recovery and reuse have recently become interesting options. In this review, different recovery and reuse options of sludge originating from active and passive treatment of mine drainage are identified and thoroughly discussed, based on available laboratory and field studies. The most valuable products presently recovered from the mine sludge are the iron oxy-hydroxides (ochre). Other by-products include metals, elemental sulfur, and calcium carbonate. Mine sludge reuse includes the removal of contaminants, such as As, P, dye, and rare earth elements. Mine sludge can also be reused as stabilizer for contaminated soil, as fertilizer in agriculture/horticulture, as substitute material in construction, as cover over tailings for acid mine drainage prevention and control, as material to sequester carbon dioxide, and in cement and pigment industries. The review also stresses out some of the current challenges and research needs. Finally, in order to move forward, studies are needed to better estimate the contribution of sludge recovery/reuse to the overall costs of mine water treatment.
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6.
Efficiency and bacterial populations related to pollutant removal in an upflow microaerobic sludge reactor treating manure-free piggery wastewater with low COD/TN ratio.
Meng, J, Li, J, Li, J, Sun, K, Antwi, P, Deng, K, Wang, C, Buelna, G
Bioresource technology. 2016;:166-73
Abstract
A novel upflow microaerobic sludge reactor (UMSR) had proved excellent in nitrogen removal from manure-free piggery wastewater characterized by high concentration of ammonium (NH4(+)-N) and low chemical oxygen demand (COD) to total nitrogen (TN) ratio, but the biological mechanism in the UMSR was still indeterminate. With a constant nitrogen loading rate of 1.10kg/(m(3)d) at hydraulic retention time 8h, the UMSR was kept performing for 67days in the present research and the average load removal of COD, NH4(+)-N and TN was as high as 0.72, 0.76 and 0.94kg/(m(3)d), respectively. Compared with the inoculated sludge, the acclimated sludge was richer in genera responsible for the biological removal of carbon, nitrogen and phosphorus. Ammonium oxidation bacteria, heterotrophic denitrifiers, autotrophic denitrifiers and phosphate accumulating organisms coexisted perfectly in the microaerobic system, and their synergistic action made the UMSR perform well in COD, NH4(+)-N, TN and phosphate removal.
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7.
Dewatering in biological wastewater treatment: A review.
Christensen, ML, Keiding, K, Nielsen, PH, Jørgensen, MK
Water research. 2015;:14-24
Abstract
Biological wastewater treatment removes organic materials, nitrogen, and phosphorus from wastewater using microbial biomass (activated sludge, biofilm, granules) which is separated from the liquid in a clarifier or by a membrane. Part of this biomass (excess sludge) is transported to digesters for bioenergy production and then dewatered, it is dewatered directly, often by using belt filters or decanter centrifuges before further handling, or it is dewatered by sludge mineralization beds. Sludge is generally difficult to dewater, but great variations in dewaterability are observed for sludges from different wastewater treatment plants as a consequence of differences in plant design and physical-chemical factors. This review gives an overview of key parameters affecting sludge dewatering, i.e. filtration and consolidation. The best dewaterability is observed for activated sludge that contains strong, compact flocs without single cells and dissolved extracellular polymeric substances. Polyvalent ions such as calcium ions improve floc strength and dewaterability, whereas sodium ions (e.g. from road salt, sea water intrusion, and industry) reduce dewaterability because flocs disintegrate at high conductivity. Dewaterability dramatically decreases at high pH due to floc disintegration. Storage under anaerobic conditions lowers dewaterability. High shear levels destroy the flocs and reduce dewaterability. Thus, pumping and mixing should be gentle and in pipes without sharp bends.
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8.
Fate of estrogenic hormones in wastewater and sludge treatment: A review of properties and analytical detection techniques in sludge matrix.
Hamid, H, Eskicioglu, C
Water research. 2012;(18):5813-33
Abstract
Estrogenic hormones (estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethinylestradiol (EE2)) are the major contributor to the total estrogenicity in waterways. Presence of these compounds in biosolids is also causing concern in terms of their use as soil amendment. In comparison with wastewater treatment, removal of estrogenic compounds in sewage sludge has received less attention. This paper presents a literature review regarding the source and occurrence of these pollutants in our environment. The removal pathways of estrogenic compounds in engineered systems, such as full-scale wastewater treatment plants (WWTPs), are also discussed. Review of the fate studies revealed that activated sludge system with nutrient removal shows very high (>90%) removal of estrogenic hormones in most of the cases. Although, aerobic digestion showed better attenuation of estrogenic compounds, anaerobic digestion increased the overall estrogenicity of biosolids. Finally, this paper highlights the challenges involved in analytical determination of these compounds in sewage sludge matrix.
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9.
Microbiology of 'Candidatus Accumulibacter' in activated sludge.
He, S, McMahon, KD
Microbial biotechnology. 2011;(5):603-19
Abstract
'Candidatus Accumulibacter' is a biotechnologically important bacterial group that can accumulate large amounts of intracellular polyphosphate, contributing to biological phosphorus removal in wastewater treatment. Since its first molecular identification more than a decade ago, this bacterial group has drawn significant research attention due to its high abundance in many biological phosphorus removal systems. In the past 6 years, our understanding of Accumulibacter microbiology and ecophysiology has advanced rapidly, largely owing to genomic information obtained through shotgun metagenomic sequencing efforts. In this review, we focus on the metabolism, physiology, fine-scale population structure and ecological distribution of Accumulibacter, aiming to integrate the information learned so far and to present a more complete picture of the microbiology of this important bacterial group.
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10.
Bacterial phosphate metabolism and its application to phosphorus recovery and industrial bioprocesses.
Hirota, R, Kuroda, A, Kato, J, Ohtake, H
Journal of bioscience and bioengineering. 2010;(5):423-32
Abstract
Enhanced biological phosphorus removal (EBPR) has become a well-established process and is currently applied in many full-scale wastewater treatment processes. Phosphorus recovered from EBPR waste sludge can be used as a raw material for the fertilizer industry, if a sound recycling strategy is developed and applied. In this review, we summarize our current knowledge on phosphate metabolism in bacteria, focusing on molecular mechanisms of bacterial polyphosphate (polyP) accumulation. A simple method for releasing polyP from EBPR waste sludge and recovering phosphorus in a reusable form for the fertilizer industry is presented. We also describe a recent development of bioprocesses for the expanded use of polyP in the production of value-added chemicals.