Driven by energy neutral/positive of wastewater treatment plants, significant efforts have been made on the research and development of mainstream partial nitritation and anaerobic ammonium oxidation ...(anammox) (PN/A) (deammonification) process since the early 2010s. To date, feasibility of mainstream PN/A process has been demonstrated and proven by experimental results at various scales although with the low loading rates and elevated nitrogen concentration in the effluent at low temperatures (15–10 °C). This review paper provides an overview of the current state of research and development of mainstream PN/A process and critically analyzes the bottlenecks for its full-scale application. The paper discusses the following: (i) the current status of research and development of mainstream PN/A process; (ii) the interactions among aerobic ammonium-oxidizing bacteria, aerobic nitrite-oxidizing bacteria, anammox bacteria, and heterotrophic bacteria; (iii) the suppression of aerobic nitrite-oxidizing bacteria; (iv) process and bioreactors; and (v) suggested further studies including efficient and robust carbon concentrating pretreatment, deepening of understanding competition between autotrophic nitrogen-converting organisms, intensification of biofilm anammox activity, reactor design, and final polishing.
The addition of iron is a convenient way for removing phosphorus from wastewater, but this is often considered to limit phosphorus recovery. Struvite precipitation is currently used to recover ...phosphorus, and this approach has attracted much interest. However, it requires the use of enhanced biological phosphorus removal (EBPR). EBPR is not yet widely applied and the recovery potential is low. Other phosphorus recovery methods, including sludge application to agricultural land or recovering phosphorus from sludge ash, also have limitations. Energy-producing wastewater treatment plants increasingly rely on phosphorus removal using iron, but the problem (as in current processes) is the subsequent recovery of phosphorus from the iron. In contrast, phosphorus is efficiently mobilized from iron by natural processes in sediments and soils. Iron-phosphorus chemistry is diverse, and many parameters influence the binding and release of phosphorus, including redox conditions, pH, presence of organic substances, and particle morphology. We suggest that the current poor understanding of iron and phosphorus chemistry in wastewater systems is preventing processes being developed to recover phosphorus from iron-phosphorus rich wastes like municipal wastewater sludge. Parameters that affect phosphorus recovery are reviewed here, and methods are suggested for manipulating iron-phosphorus chemistry in wastewater treatment processes to allow phosphorus to be recovered.
In a membrane bioreactor (MBR), fast growth of anammox bacteria was achieved with a sludge residence time (SRT) of 12 days. This relatively short SRT resulted in a--for anammox ...bacteria--unprecedented purity of the enrichment of 97.6%. The absence of a selective pressure for settling, and dedicated cultivation conditions led to growth in suspension as free cells and the complete absence of flocs or granules. Fast growth, low levels of calcium and magnesium, and possibly the presence of yeast extract and a low shear stress are critical for the obtainment of a completely suspended culture consisting of free anammox cells. During cultivation, a population shift was observed from Candidatus "Brocadia" to Candidatus "Kuenenia stuttgartiensis." It is hypothesized that the reason for this shift is the higher affinity for nitrite of "Kuenenia." The production of anammox bacteria in suspension with high purity and productivity makes the MBR a promising tool for the cultivation and study of anammox bacteria. Biotechnol. Bioeng. 2008;101: 286-294.
ANaerobic AMMonium OXidation (anammox) is an established process for efficient nitrogen removal from wastewater, relying on anammox bacteria to form stable biofilms or granules. To understand the ...formation, structure, and stability of anammox granules, it is important to determine the composition of the extracellular polymeric substances (EPS). The aim of this research was to elucidate the nature of the proteins, which are the major fraction of the EPS and were suspected to be glycosylated. EPS were extracted from full-scale anammox granular sludge, dominated by " Candidatus Brocadia", and subjected to denaturing polyacrylamide gel electrophoresis. By further analysis with mass spectrometry, a high abundant glycoprotein, carrying a heterogeneous O-glycan structure, was identified. The potential glycosylation sequence motif was identical to that proposed for the surface layer protein of " Candidatus Kuenenia stuttgartiensis". The heavily glycosylated protein forms a large fraction of the EPS and was also located by lectin staining. Therefore, we hypothesize an important role of glycoproteins in the structuring of anammox granules, comparable to the importance of glycans in the extracellular matrix of multicellular organisms. Furthermore, different glycoconjugates may have distinct roles in the matrix of granular sludge, which requires more in-depth characterization of different glycoconjugates in future EPS studies.
Anaerobic digestion without biogas? Kleerebezem, Robbert; Joosse, Bart; Rozendal, Rene ...
Reviews in Environmental Science and Biotechnology,
12/2015, Letnik:
14, Številka:
4
Journal Article, Book Review
Odprti dostop
Anaerobic digestion for the production of methane containing biogas is the classic example of a resource recovery process that combines stabilization of particulate organic matter or wastewater ...treatment with the production of a valuable end-product. Attractive features of the process include the production of a single end-product from a heterogeneous feedstock, and in-situ product separation of the gaseous end-product. Despite these intrinsic attractive properties of the process, the economic added value of the biogas produced is limited, enabling the development of alternative processes that yield higher-value end-products. Typically the production of higher value end-products from low value feedstock and industrial wastewater proceeds via intermediate production of organic acids (and carbon dioxide and molecular hydrogen). Optimization of organic acid production from particulate feedstocks and wastewater for development of the organic acid based resource recovery route receives significant research attention. The organic acid stream generated as such, has no economic value, but if organic acids can either be concentrated via membrane separation or (bio)converted to an end-product that can easily be separated from the liquid, an attractive biomass processing scheme can be developed. Attractive end-products of organic acid processing include polyhydroxyalkanoates, medium chain length fatty acids, or other organic molecules using bio-electrochemical systems. Overall we suggest that these novel bioprocessing routes for conversion of low value feedstock to higher added value products will contribute to a sustainable future and will change the economic status of organic waste.
Nitrous oxide (N
2O), a potent greenhouse gas, can be emitted during wastewater treatment, significantly contributing to the greenhouse gas footprint. Measurements at lab-scale and full-scale ...wastewater treatment plants (WWTPs) have demonstrated that N
2O can be emitted in substantial amounts during nitrogen removal in WWTPs, however, a large variation in reported emission values exists. Analysis of literature data enabled the identification of the most important operational parameters leading to N
2O emission in WWTPs: (i) low dissolved oxygen concentration in the nitrification and denitrification stages, (ii) increased nitrite concentrations in both nitrification and denitrification stages, and (iii) low COD/N ratio in the denitrification stage. From the literature it remains unclear whether nitrifying or denitrifying microorganisms are the main source of N
2O emissions. Operational strategies to prevent N
2O emission from WWTPs are discussed and areas in which further research is urgently required are identified.
Over the past twenty years, the knowledge and understanding of wastewater treatment has advanced extensively and moved away from empirically-based approaches to a fundamentally-based first-principles ...approach embracing chemistry, microbiology, and physical and bioprocess engineering, often involving experimental laboratory work and techniques. Many of these experimental methods and techniques have matured to the degree that they have been accepted as reliable tools in wastewater treatment research and practice.
For sector professionals, especially the new generation of young scientists and engineers entering the wastewater treatment profession, the quantity, complexity and diversity of these new developments can be overwhelming, particularly in developing countries where access to advanced level laboratory courses in wastewater treatment is not readily available. In addition, information on innovative experimental methods is scattered across scientific literature and only partially available in the form of textbooks or guidelines. This book seeks to address these deficiencies. It assembles and integrates the innovative experimental methods developed by research groups and practitioners around the world and broadly applied in wastewater treatment research and practice.
Experimental Methods in Wastewater Treatment book forms part of the internet-based curriculum in sanitary engineering at UNESCO-IHE and, as such, may also be used together with video recordings of methods and approaches performed and narrated by the authors, including guidelines on best experimental practices. The book is written for undergraduate and postgraduate students, researchers, laboratory staff, plant operators, consultants, and other sector professionals.
Partial nitritation/anammox (PN/A) has been one of the most innovative developments in biological wastewater treatment in recent years. With its discovery in the 1990s a completely new way of ...ammonium removal from wastewater became available. Over the past decade many technologies have been developed and studied for their applicability to the PN/A concept and several have made it into full-scale. With the perspective of reaching 100 full-scale installations in operation worldwide by 2014 this work presents a summary of PN/A technologies that have been successfully developed, implemented and optimized for high-strength ammonium wastewaters with low C:N ratios and elevated temperatures. The data revealed that more than 50% of all PN/A installations are sequencing batch reactors, 88% of all plants being operated as single-stage systems, and 75% for sidestream treatment of municipal wastewater. Additionally an in-depth survey of 14 full-scale installations was conducted to evaluate practical experiences and report on operational control and troubleshooting. Incoming solids, aeration control and nitrate built up were revealed as the main operational difficulties. The information provided gives a unique/new perspective throughout all the major technologies and discusses the remaining obstacles.
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•More than 100 full-scale partial nitritation/anammox installations worldwide by 2014.•In depth survey of 14 full-scale installations.•Discussion of practical experiences, process control and troubleshooting.
Aerobic granular sludge technology has been extensively studied over the past 20 years and is regarded as the upcoming new standard for biological treatment of domestic and industrial wastewaters. ...Aerobic granules (AG) are dense, compact, self-immobilized microbial aggregates that allow better sludge-water separation and thereby higher biomass concentrations in the bioreactor than conventional activated sludge aggregates. This brings potential practical advantages in terms of investment cost, energy consumption and footprint. Yet, despite the relevant advances regarding the process of AG formation, instability of AG during long-term operation is still seen as a major barrier for a broad practical application of this technology. This paper presents an up-to-date review of the literature focusing on AG stability, aiming to contribute to the identification of key factors for promoting long-term stability of AG and to a better understanding of the underlying mechanisms. Operational conditions leading to AG disintegration are described, including high organic loads, particulate substrates in the influent, toxic feed components, aerobic feeding and too short famine periods. These operational and influent wastewater composition conditions were shown to influence the micro-environment of AG, consequently affecting their stability. Granule stability is generally favored by the presence of a dense core, with microbial growth throughout the AG depth being a crucial intrinsic factor determining its structural integrity. Accordingly, possible practical solutions to improve granule long-term stability are described, namely through the promotion of minimal substrate concentration gradients and control of microbial growth rates within AG, including anaerobic, plug-flow feeding and specific sludge removal strategies.
•AGS technology is viewed as the future standard in wastewater biological treatment.•AGS stability during long-term operation is a main challenge for broad application.•Granule structure depends on the operational conditions and wastewater composition.•Controlling the microbial growth at low rates is a key factor for stabilizing AGS.•Advances in operational strategies to enhance AGS stability are herein reviewed.
Abstract
Antibiotic resistance genes (ARGs) are widespread among bacteria. However, not all ARGs pose serious threats to public health, highlighting the importance of identifying those that are ...high-risk. Here, we developed an ‘omics-based’ framework to evaluate ARG risk considering human-associated-enrichment, gene mobility, and host pathogenicity. Our framework classifies human-associated, mobile ARGs (3.6% of all ARGs) as the highest risk, which we further differentiate as ‘current threats’ (Rank I; 3%) - already present among pathogens - and ‘future threats’ (Rank II; 0.6%) - novel resistance emerging from non-pathogens. Our framework identified 73 ‘current threat’ ARG families. Of these, 35 were among the 37 high-risk ARGs proposed by the World Health Organization and other literature; the remaining 38 were significantly enriched in hospital plasmids. By evaluating all pathogen genomes released since framework construction, we confirmed that ARGs that recently transferred into pathogens were significantly enriched in Rank II (‘future threats’). Lastly, we applied the framework to gut microbiome genomes from fecal microbiota transplantation donors. We found that although ARGs were widespread (73% of genomes), only 8.9% of genomes contained high-risk ARGs. Our framework provides an easy-to-implement approach to identify current and future antimicrobial resistance threats, with potential clinical applications including reducing risk of microbiome-based interventions.
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