Model-based assessment of estrogen removal by nitrifying activated sludge.

Complete removal of estrogens such as estrone (E1), estradiol (E2), estriol (E3) and ethinylestradiol (EE2) in wastewater treatment is essential since their release and accumulation in natural water bodies are giving rise to environment and health issues. To improve our understanding towards the estrogen bioremediation process, a mathematical model was proposed for describing estrogen removal by nitrifying activated sludge. Four pathways were involved in the developed model: i) biosorption by activated sludge flocs; ii) cometabolic biodegradation linked to ammonia oxidizing bacteria (AOB) growth; iii) non-growth biodegradation by AOB; and iv) biodegradation by heterotrophic bacteria (HB).

Modeling electron competition among nitrogen oxides reduction and N O accumulation in hydrogenotrophic denitrification.

Hydrogenotrophic denitrification is a novel and sustainable process for nitrogen removal, which utilizes hydrogen as electron donor, and carbon dioxide as carbon source. Recent studies have shown that nitrous oxide (N O), a highly undesirable intermediate and potent greenhouse gas, can accumulate during this process. In this work, a new mathematical model is developed to describe nitrogen oxides dynamics, especially N O, during hydrogenotrophic denitrification for the first time.

Data on metagenomic profiles of activated sludge from a full-scale wastewater treatment plant.

The data in this article mainly present the sequences of activated sludge from a full-scale municipal wastewater treatment plant (WWTP) carrying out simultaneous nitrogen and phosphorous removal in Beijing, China. Data include the operational conditions and performance, dominant microbes and taxonomic analysis in this WWTP, and function annotation results based on SEED, Clusters of Orthologous Groups (COG), and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Sequencing data were generated by using Illumina HiSeq.

Modelling the long-term effect of wastewater compositions on maximum sulfide and methane production rates of sewer biofilm.

Reliable modelling of sulfide and methane production in sewer systems is required for efficient sewer emission management. Wastewater compositions affect sulfide and methane production kinetics through both its short-term variation influencing the substrate availability to sewer biofilms, and its long-term variation affecting the sewer biofilm structure. While the short-term effect is well considered in existing sewer models with the use of Monod or half-order equations, the long-term effect has not been explicitly considered in current sewer models suitable for network modelling.

Free nitrous acid-based nitrifying sludge treatment in a two-sludge system enhances nutrient removal from low-carbon wastewater.

A new method to enhance nutrient removal from low carbon-wastewater was developed. The method consists of a two-sludge system (i.e.

Achieving Stable Mainstream Nitrogen Removal via the Nitrite Pathway by Sludge Treatment Using Free Ammonia.

Biological nitrogen removal through the nitrite pathway (NH → NO → N) is favorable for wastewater treatment plants without sufficient carbon sources. This study demonstrates an innovative approach for attaining the nitrite pathway based on sludge treatment using free ammonia (FA, i.e.

Occurrence State and Molecular Structure Analysis of Extracellular Proteins with Implications on the Dewaterability of Waste-Activated Sludge.

The occurrence state and molecular structure of extracellular proteins were analyzed to reveal the influencing factors on the water-holding capacities of protein-like substances in waste-activated sludge (WAS). The gelation process of extracellular proteins verified that advanced oxidation processes (AOPs) for WAS dewaterability improvement eliminated the water affinity of extracellular proteins and prevented these macromolecules from forming stable colloidal aggregates. Isobaric tags for relative and absolute quantitation proteomics identified that most of the extracellular proteins were originally derived from the intracellular part and the proteins originally located in the extracellular part were mainly membrane-associated.

Aged refuse enhances anaerobic digestion of waste activated sludge.

In this work, a low-cost alternative approach (i.e., adding aged refuse (AR) into waste activated sludge) to significantly enhance anaerobic digestion of sludge was reported.

Quantifying nitrous oxide production pathways in wastewater treatment systems using isotope technology - A critical review.

Nitrous oxide (NO) is an important greenhouse gas and an ozone-depleting substance which can be emitted from wastewater treatment systems (WWTS) causing significant environmental impacts. Understanding the NO production pathways and their contribution to total emissions is the key to effective mitigation. Isotope technology is a promising method that has been applied to WWTS for quantifying the NO production pathways.

Unraveling microbial structure and diversity of activated sludge in a full-scale simultaneous nitrogen and phosphorus removal plant using metagenomic sequencing.

Activated sludge contains highly complex microbial communities, which play crucial roles in pollutant removal performance in wastewater treatment plants (WWTPs). Metagenomic sequencing was applied to characterize microbial community and functional profiles within activated sludge from a full-scale municipal WWTP carrying out simultaneous nitrogen and phosphorous removal (SNPR). We applied the assembled contigs (N90 of 591bp) and predicted genes to conduct taxonomic and function annotations, respectively.

Approach of describing dynamic production of volatile fatty acids from sludge alkaline fermentation.

In this work, a mathematical model was developed to describe the dynamics of fermentation products in sludge alkaline fermentation systems for the first time. In this model, the impacts of alkaline fermentation on sludge disintegration, hydrolysis, acidogenesis, acetogenesis, and methanogenesis processes are specifically considered for describing the high-level formation of fermentation products. The model proposed successfully reproduced the experimental data obtained from five independent sludge alkaline fermentation studies.

Nitrous Oxide Production in a Granule-based Partial Nitritation Reactor: A Model-based Evaluation.

Sustainable wastewater treatment has been attracting increasing attentions over the past decades. However, the production of nitrous oxide (NO), a potent GHG, from the energy-efficient granule-based autotrophic nitrogen removal is largely unknown. This study applied a previously established NO model, which incorporated two NO production pathways by ammonia-oxidizing bacteria (AOB) (AOB denitrification and the hydroxylamine (NHOH) oxidation).

Modeling aerobic biotransformation of vinyl chloride by vinyl chloride-assimilating bacteria, methanotrophs and ethenotrophs.

Recent studies have investigated the potential of enhanced groundwater Vinyl Chloride (VC) remediation in the presence of methane and ethene through the interactions of VC-assimilating bacteria, methanotrophs and ethenotrophs. In this study, a mathematical model was developed to describe aerobic biotransformation of VC in the presence of methane and ethene for the first time. It examines the metabolism of VC by VC-assimilating bacteria as well as cometabolism of VC by both methanotrophs and ethenotrophs, using methane and ethene respectively, under aerobic conditions.

Quantitative evaluation on the characteristics of activated sludge granules and flocs using a fuzzy entropy-based approach.

Activated sludge granules and flocs have their inherent advantages and disadvantages for wastewater treatment due to their different characteristics. So far quantitative information on their evaluation is still lacking. This work provides a quantitative and comparative evaluation on the characteristics and pollutant removal capacity of granules and flocs by using a new methodology through integrating fuzzy analytic hierarchy process, accelerating genetic algorithm and entropy weight method.

Comparison of different two-pathway models for describing the combined effect of DO and nitrite on the nitrous oxide production by ammonia-oxidizing bacteria.

The aim of this work is to compare the capability of two recently proposed two-pathway models for predicting nitrous oxide (NO) production by ammonia-oxidizing bacteria (AOB) for varying ranges of dissolved oxygen (DO) and nitrite. The first model includes the electron carriers whereas the second model is based on direct coupling of electron donors and acceptors. Simulations are confronted to extensive sets of experiments (43 batches) from different studies with three different microbial systems.

Biotransformation of acyclovir by an enriched nitrifying culture.

This work evaluates the biodegradation of the antiviral drug acyclovir by an enriched nitrifying culture during ammonia oxidation and without the addition of ammonium. The study on kinetics was accompanied with the structural elucidation of biotransformation products through batch biodegradation experiments at two different initial levels of acyclovir (15 mg L and 15 μg L). The pseudo first order kinetic studies of acyclovir in the presence of ammonium indicated the higher degradation rates under higher ammonia oxidation rates than those constant degradation rates in the absence of ammonium.

A modeling approach to direct interspecies electron transfer process in anaerobic transformation of ethanol to methane.

Recent studies have shown that direct interspecies electron transfer (DIET) plays an important part in contributing to methane production from anaerobic digestion. However, so far anaerobic digestion models that have been proposed only consider two pathways for methane production, namely, acetoclastic methanogenesis and hydrogenotrophic methanogenesis, via indirect interspecies hydrogen transfer, which lacks an effective way for incorporating DIET into this paradigm. In this work, a new mathematical model is specifically developed to describe DIET process in anaerobic digestion through introducing extracellular electron transfer as a new pathway for methane production, taking anaerobic transformation of ethanol to methane as an example.

Modelling Methane Production and Sulfate Reduction in Anaerobic Granular Sludge Reactor with Ethanol as Electron Donor.

In this work, a mathematical model based on growth kinetics of microorganisms and substrates transportation through biofilms was developed to describe methane production and sulfate reduction with ethanol being a key electron donor. The model was calibrated and validated using experimental data from two case studies conducted in granule-based Upflow Anaerobic Sludge Blanket reactors. The results suggest that the developed model could satisfactorily describe methane and sulfide productions as well as ethanol and sulfate removals in both systems.

Mathematical modeling of simultaneous carbon-nitrogen-sulfur removal from industrial wastewater.

A mathematical model of carbon, nitrogen and sulfur removal (C-N-S) from industrial wastewater was constructed considering the interactions of sulfate-reducing bacteria (SRB), sulfide-oxidizing bacteria (SOB), nitrate-reducing bacteria (NRB), facultative bacteria (FB), and methane producing archaea (MPA). For the kinetic network, the bioconversion of C-N by heterotrophic denitrifiers (NO→NO→N), and that of C-S by SRB (SO→S) and SOB (S→S) was proposed and calibrated based on batch experimental data. The model closely predicted the profiles of nitrate, nitrite, sulfate, sulfide, lactate, acetate, methane and oxygen under both anaerobic and micro-aerobic conditions.

Evaluation of Nitrous Oxide Emission from Sulfide- and Sulfur-Based Autotrophic Denitrification Processes.

Recent studies have shown that sulfide- and sulfur-based autotrophic denitrification (AD) processes play an important role in contributing to nitrous oxide (N2O) production and emissions. However, N2O production is not recognized in the current AD models, limiting their ability to predict N2O accumulation during AD. In this work, a mathematical model is developed to describe N2O dynamics during sulfide- and sulfur-based AD processes for the first time.

Insight into biological phosphate recovery from sewage.

The world's increasing population means that more food production is required. A more sustainable supply of fertilizers mainly consisting of phosphate is needed. Due to the rising consumption of scarce resources and limited natural supply of phosphate, the recovery of phosphate and their re-use has potentially high market value.

Nitrous Oxide Production in Co- Versus Counter-Diffusion Nitrifying Biofilms.

For the application of biofilm processes, a better understanding of nitrous oxide (N2O) formation within the biofilm is essential for design and operation of biofilm reactors with minimized N2O emissions. In this work, a previously established N2O model incorporating both ammonia oxidizing bacteria (AOB) denitrification and hydroxylamine (NH2OH) oxidation pathways is applied in two structurally different biofilm systems to assess the effects of co- and counter-diffusion on N2O production. It is demonstrated that the diffusion of NH2OH and oxygen within both types of biofilms would form an anoxic layer with the presence of NH2OH and nitrite ( ), which would result in a high N2O production via AOB denitrification pathway.

Assessment of Heterotrophic Growth Supported by Soluble Microbial Products in Anammox Biofilm using Multidimensional Modeling.

Anaerobic ammonium oxidation (anammox) is known to autotrophically convert ammonium to dinitrogen gas with nitrite as the electron acceptor, but little is known about their released microbial products and how these are relative to heterotrophic growth in anammox system. In this work, we applied a mathematical model to assess the heterotrophic growth supported by three key microbial products produced by bacteria in anammox biofilm (utilization associated products (UAP), biomass associated products (BAP), and decay released substrate). Both One-dimensional and two-dimensional numerical biofilm models were developed to describe the development of anammox biofilm as a function of the multiple bacteria-substrate interactions.

Biotransformation of pharmaceuticals by ammonia oxidizing bacteria in wastewater treatment processes.

Pharmaceutical residues could potentially pose detrimental effects on aquatic ecosystems and human health, with wastewater treatment being one of the major pathways for pharmaceuticals to enter into the environment. Enhanced removal of pharmaceuticals by ammonia oxidizing bacteria (AOB) has been widely observed in wastewater treatment processes. This article reviews the current knowledge on the biotransformation of pharmaceuticals by AOB.

Modeling of Nitrous Oxide Production from Nitritation Reactors Treating Real Anaerobic Digestion Liquor.

In this work, a mathematical model including both ammonium oxidizing bacteria (AOB) and heterotrophic bacteria (HB) is constructed to predict N2O production from the nitritation systems receiving the real anaerobic digestion liquor. This is for the first time that N2O production from such systems was modeled considering both AOB and HB. The model was calibrated and validated using experimental data from both lab- and pilot-scale nitritation reactors.