Sidestream Treatment Research Articles

Feasibility study of electrodialysis as an ammonium reuse process for covering the nitrogen demand of an industrial wastewater treatment plant

Electrodialysis (ED) is a cost-effective membrane technology used is a variety of fields for desalination and concentration. This feasibility study explores the potential of ED as an NH4-N recovery technology from anaerobic digestate liquor (ADL), and the use of the concentrate as a nitrogen source in an industrial wastewater treatment plant (WWTP). Three neighboring WWTPs were the focus of this study: Two municipal WWTPs A and B, operating anaerobic sludge stabilization, and a pulp & paper WWTP C, utilizing urea as a nitrogen source. Two-stage bench-scale experiments with the municipal ADL from WWTP A and WWTP B were conducted, and performance indicators were determined. A concentration of approximately 10 g NH4-N/L and 15 g NH4-N/L was obtained in stages 1 and 2, respectively. The NH4-N removal was above 85 % in all experiment, while recovery varied between 25 and 95 %. The specific energy consumption (SEC) was on average 12.9 kWh/kg NH4-N. Moreover, mass and energy balances in a model WWTP demonstrated that an ED side-stream treatment for NH4-N removal coupled with microfiltration (MF) pre-treatment results in a net energy gain, also without the added benefit of the ED concentrate as a nitrogen source.

Effect of cations on aerobic granulation for sidestream treatment

Aerobic granular sludge (AGS) represents an aggregate of sludge formed through the self-immobilization of microorganisms under aerobic conditions. It is currently under scrutiny for its potential as a technology to reduce carbon emissions and promote sustainability. The practicality of AGS stems from its ability to encourage granule formation and enhance structural stability. In this study, a total of five cations (K+, Ca2+, Mg2+, Al3+, Fe3+) were introduced to facilitate stable structuring and the formation of granules for treating high-strength wastewater, such as side-stream treatment. As a result of the experiment, the loosely bound extracellular polymeric substances (LB-EPS) content in the cation-enhanced sludge witnessed a significant increase, leading to elevated total EPS content under all experimental conditions. Furthermore, the protein (PN)/polysaccharide (PS) ratio, a pivotal component of EPS influencing AGS's hydrophobicity and structural stability, exhibited a collective increase, with Mg2+ reaching the highest value of 1.7. The relationship between relative hydrophobicity and the PN/PS ratio was found to strongly impact sludge adhesion, with noteworthy results observed particularly for Mg2+, Al3+, and Fe3+. The viability of attached cells reached 96.8 %, the highest recorded in the case of Mg2+. In the context of treating high-strength wastewater, Mg2+ emerged as the optimal cation for accelerating AGS formation and enhancing structural stability.

Achieving partial nitrification by sludge treatment using sulfide: Optimal conditions determination, long-term stability evaluation and microbial mechanism exploration

This study proposes an innovative strategy for achieving PN in synthetic domestic wastewater by side-stream sludge treatment using sulfide as the sole control factor. By conducting controllable batch experiments and response surface analysis, optimal sulfide treatment conditions were firstly determined as 90 mg/L of sulfide, 7.5 of pH, 100 rpm of rotation and 12 h of treatment time. After treatment, half of ammonia oxidizing bacteria (AOB) activity remained, but nitrite oxidizing bacteria (NOB) activity was barely detected. Nitrite accumulation rate of long-term running PN steadily reached 83.9 % with 99.1 % of ammonia removal efficiency. Sulfide treatment increased community diversity and facilitated stability of microbiota functioning with PN phenotype, which might be sustained by the positive correlation between ammonia oxidation gene (amoA) and sulfur oxidation gene (soxB). Correspondingly, the network analysis identified the keystone microbial taxa of persistent PN microbiota as Nitrosomonas, Thauera, Truepera, Defluviimonas and Sulitalea in the later stage of long-term reactor.

Bipolar membrane electrodialysis for nutrient recovery from anaerobic digestion dewatering sidestream

Anaerobic digestion (AD) offers an efficient means for treating sludge generated in wastewater treatment plants (WWTPs), but nutrient-rich AD dewatering sidestream contributes as much as 30 % of the overall nutrient loading of WWTPs. Several electrochemical approaches are being developed as a sidestream treatment strategy to prevent return of nutrients to WWTP headworks and recover them for fertilizer production. One such method is to produce acids and bases, essential chemicals necessary to facilitate nutrient recovery, using bipolar membrane electrodialysis (BMED). In this study we show simultaneous separation of nutrients and production of acid/base streams with an additional consideration for increasing the concentration of ammonium and phosphate in the final product stream by systematically altering compartment flow rates and hence the retention time of each stream. Using a three-compartment BMED system with a synthetic sidestream containing 50 mM NH3-N and 2 mM PO4-P, we achieved up to 80 % ammonia removal (via a cation exchange membrane) and up to 60 % phosphate removal (via an anion exchange membrane) at a productivity of 34.2 L m−2 h−1. Separated ammonia was recovered (>90 %) in a subsequent membrane contactor (MC) that was fed with acid and base streams produced by the BMED unit. A phosphate recovery > 80 % was achieved by chemical precipitation (CP). In a combined BMED-MC-CP process, the concentrated final product contained 333.9 mM NH3-N and 3.1 mM PO4-P with an energy consumption of 8.9 kWh kg−1 N recovered. These results illustrate that the BMED-based treatment train is a promising strategy for nutrient recovery from AD dewatering sidestream.

Thermal hydrolysis pretreatment of wastewater biosolids: Modelling the impact of the aerobic sludge age

This study investigates the impact of thermal hydrolysis pretreatment (THP) on the characteristics of wastewater biosolids, methane production, anaerobic biodegradability, and recycled sidestream nitrogen loads, as a function of the sludge age of the activated sludge (AS) system through a series of BioWin simulations of 3 different process configurations at sludge ages of 5, 10, 15, 20, 30, and 60 d, with and without thermal hydrolysis. BioWin's anaerobic digester and thermal hydrolysis units were calibrated by adopting and identifying various kinetic and operational parameters from the available literature and through series of full-scale plant simulations. Thermal hydrolysis improved the hydrolysis rates of the biosolids by 181%. Improvements in anaerobic biodegradability, mainly due to the conversion of endogenous products, ranged from 14% to 67% at sludge ages of 5–15 d. At sludge ages of 20–60 d, anaerobic biodegradability improved by 59% to 186% depending on the process configuration. At sludge ages of 15–60 d, methane production was relatively stable and insensitive to the biosolids composition. Despite the increase in the recycled nitrogen load by 42% to 127%, it only constituted 13% of the influent nitrogen load. Effluent ammonia concentrations remained unchanged and effluent nitrates concentrations only increased by 1.4 to 2 mg N/L, maintaining effluent standards without additional sidestream treatment.

How to Provide Nitrite Robustly for Anaerobic Ammonium Oxidation in Mainstream Nitrogen Removal.

Innovation in decarbonizing wastewater treatment is urgent in response to global climate change. The practical implementation of anaerobic ammonium oxidation (anammox) treating domestic wastewater is the key to reconciling carbon-neutral management of wastewater treatment with sustainable development. Nitrite availability is the prerequisite of the anammox reaction, but how to achieve robust nitrite supply and accumulation for mainstream systems remains elusive. This work presents a state-of-the-art review on the recent advances in nitrite supply for mainstream anammox, paying special attention to available pathways (forward-going (from ammonium to nitrite) and backward-going (from nitrate to nitrite)), key controlling strategies, and physiological and ecological characteristics of functional microorganisms involved in nitrite supply. First, we comprehensively assessed the mainstream nitrite-oxidizing bacteria control methods, outlining that these technologies are transitioning to technologies possessing multiple selective pressures (such as intermittent aeration and membrane-aerated biological reactor), integrating side stream treatment (such as free ammonia/free nitrous acid suppression in recirculated sludge treatment), and maintaining high activity of ammonia-oxidizing bacteria and anammox bacteria for competing oxygen and nitrite with nitrite-oxidizing bacteria. We then highlight emerging strategies of nitrite supply, including the nitrite production driven by novel ammonia-oxidizing microbes (ammonia-oxidizing archaea and complete ammonia oxidation bacteria) and nitrate reduction pathways (partial denitrification and nitrate-dependent anaerobic methane oxidation). The resources requirement of different mainstream nitrite supply pathways is analyzed, and a hybrid nitrite supply pathway by combining partial nitrification and nitrate reduction is encouraged. Moreover, data-driven modeling of a mainstream nitrite supply process as well as proactive microbiome management is proposed in the hope of achieving mainstream nitrite supply in practical application. Finally, the existing challenges and further perspectives are highlighted, i.e., investigation of nitrite-supplying bacteria, the scaling-up of hybrid nitrite supply technologies from laboratory to practical implementation under real conditions, and the data-driven management for the stable performance of mainstream nitrite supply. The fundamental insights in this review aim to inspire and advance our understanding about how to provide nitrite robustly for mainstream anammox and shed light on important obstacles warranting further settlement.

Deregulation of Ribosome Biogenesis in Nitrite-Oxidizing Bacteria Leads to Nitrite Accumulation.

Nitrite (NO2-) accumulation caused by nitrite-oxidizing bacteria (NOB) inhibition in nitrification is a double-edged sword, i.e., a disaster in aquatic environments but a hope for innovating nitrogen removal technology in wastewater treatment. However, little information is available regarding the molecular mechanism of NOB inhibition at the cellular level. Herein, we investigate the response of NOB inhibition on NO2- accumulation established by a side-stream free ammonia treatment unit in a nitrifying reactor using integrated metagenomics and metaproteomics. Results showed that compared with the baseline, the relative abundance and activity of NOB in the experimental stage decreased by 91.64 and 68.66%, respectively, directly resulting in a NO2- accumulation rate of 88%. Moreover, RNA polymerase, translation factors, and aa-tRNA ligase were significantly downregulated, indicating that protein synthesis in NOB was interfered during NO2- accumulation. Further investigations showed that ribosomal proteins and GTPases, responsible for bindings between either ribosomal proteins and rRNA or ribosome subunits, were remarkably downregulated. This suggests that ribosome biogenesis was severely disrupted, which might be the key reason for the inhibited protein synthesis. Our findings fill a knowledge gap regarding the underlying mechanisms of NO2- accumulation, which would be beneficial for regulating the accumulation of NO2- in aquatic environments and engineered systems.

Electrochemically Mediated Ammonia Removal and Recovery from Wastewater Using Functional Membranes

Wastewater treatment plants (WWTPs) typically use anaerobic digestion (AD) to treat sludge, but ammonia produced during AD process returns to the headworks of WWTPs. The amount of ammonia in the liquid stream produced after dewatering the stabilized sludge, commonly referred to as dewatering sidestream, could contribute as high as 20% of the overall ammonia loading to WWTPs. Several sidestream treatment technologies are being developed not only to prevent additional ammonia inputs to WWTPs, but also to valorize ammonia for fertilizer production. Electrochemically mediated processes can achieve this goal in two simultaneous steps: (1) ammonium separation from wastewater through a cation-exchange membrane and (2) ammonium-to-ammonia conversion for its recovery by membrane stripping. Although electrochemical reactions in electrodialysis or flow-electrode capacitive deionization have been shown to drive the separation and increase the solution pH, an acid solution must be externally fed in the subsequent stripping process. Here, we demonstrated the use of bipolar membrane electrodialysis (BMED) to separate ammonium while simultaneously producing acid and base streams. Using a three-compartment BMED cell (effective repeating unit area = 29.2 cm2) with a synthetic sidestream containing 50 mM total ammonia nitrogen (TAN), we achieved TAN removal up to 80% with energy consumption less than 10 kWh kg−1 N at a productivity of 34.2 L m−2-repeating unit membrane area h−1 (LMH). The separated ammonia was recovered (>90%) in a subsequent membrane contactor that was fed with acid and base streams produced from the BMED cell. We specifically focused on increasing TAN concentration in the final product stream by changing relative flow rate of acid/base streams, which allowed for concentrating TAN nearly 8 times greater than the feed. These results show the use of BMED coupled with membrane stripping enables ammonia recovery without the need for chemical inputs, representing a promising sidestream treatment technology.

Insights on biological phosphorus removal with partial nitrification in single sludge system via sidestream free ammonia and free nitrous acid dosing

The sidestream sludge treatment by free ammonium (FA)/free nitrous acid (FNA) dosing was frequently demonstrated to maintain the nitrite pathway for the partial nitrification (PN) process. Nevertheless, the inhibitory effect of FA and FNA would severely influence polyphosphate accumulating organisms (PAOs), destroying the microbe-based phosphorus (P) removal. Therefore, a strategic evaluation was proposed to successfully achieve biological P removal with a partial nitrification process in a single sludge system by sidestream FA and FNA dosing. Through the long-term operation of 500 days, excellent phosphorus, ammonium and total nitrogen removal performance were achieved at 97.5 ± 2.6 %, 99.1 ± 1.0 % and 75.5 ± 0.4 %, respectively. Stable partial nitrification with a nitrite accumulation ratio (NAR) of 94.1 ± 3.4 was attained. The batch tests also reported the robust aerobic phosphorus uptake based on FA and FNA adapted sludge after exposure of FA and FNA, respectively, suggesting the FA and FNA treatment strategy could potentially offer the opportunity for the selection of PAOs, which synchronously have the tolerance to FA and FNA. Microbial community analysis suggested that Accumulibacter, Tetrasphaera, and Comamonadaceae collectively contributed to the phosphorus removal in this system. Summarily, the proposed work presents a novel and feasible strategy to integrate enhanced biological phosphorus removal (EBPR) and short-cut nitrogen cycling and bring the combined mainstream phosphorus removal and partial nitrification process closer to practical application.

Acceleration of Aerobic Granulation in Sidestream Treatment with Exogenous Autoinducer

Aerobic granular sludge (AGS) is a special type of biofilm formed by the self-aggregation of microorganisms and extracellular polymers and is considered a promising technology for wastewater treatment. However, new strategies are still being proposed as to how to improve the extracellular polymeric substances (EPS) production that influences the formation of AGS. Recently, the acceleration of aerobic granulation using autoinducers such as N-acyl-homoserine lactone (AHL)-mediated quorum sensing has been reported. However, it is not yet fully understood due to knowledge gaps on the correlations depending on the type of AHL used. In this study, to evaluate the effects of various AHL on the AGS formation of activated sludge, the secretion of extracellular polymeric substances, biofilm formation, and sludge characteristics were comprehensively investigated. Among the AHL types, tightly bound EPS (TB-EPS) and loosely bound EPS (LB-EPS) in the reactor with C8-HSL added were 18.49 and 74.07 mg/g VSS, respectively, which represented increases of 3.15% and 53.76% compared to the control group. Additionally, C8-HSL increased the relative hydrophobicity and biomass volume by 153% and 218%, respectively. As a result, AHL had a positive effect on biomass content, an increase in sludge size, and an improvement in sludge sedimentation in the early stage of granulation, and C8-HSL was found to be the most suitable for initial granulation among AHL types.

In-situ sulfite treatment enhanced the production of short-chain fatty acids from waste activated sludge in the side-stream anaerobic fermentation

Sulfite-based technology could enhance methane production from anaerobic sludge digestion. However, its potential for in-situ direct sludge treatment without anaerobic sludge addition in the side-stream remains unclear. This study investigated the feasibility of using in-situ sulfite treating sludge for short-chain fatty acids (SCFAs) production via anaerobic fermentation of waste activated sludge (WAS) as a side-stream treatment. In-situ sulfite direct sludge treatment enhanced SCFAs and acetic acid production by 2.03 and 4.89 times at 500 mg S/L compared to the control. With in-situ sulfite treatment, WAS hydrolysis and acidification were enhanced while methanogenesis was spontaneously hindered. The in-situ sulfite treatment inactivated pathogens and improved the sludge dewatering properties. The relative abundances of SCFAs-production microbial were stimulated, facilitating the sludge bioconversion. The produced SCFAs from in-situ sulfite side-stream treatment could be applied as an “internal carbon source” to enhance biological nutrient removal to improve economic and environmental value from sludge treatment.

Controlling anammox speciation and biofilm attachment strategy using N-biotransformation intermediates and organic carbon levels

Conventional nitrogen removal in wastewater treatment requires a high oxygen and energy input. Anaerobic ammonium oxidation (anammox), the single-step conversion of ammonium and nitrite to nitrogen gas, is a more energy and cost effective alternative applied extensively to sidestream wastewater treatment. It would also be a mainstream treatment option if species diversity and physiology were better understood. Anammox bacteria were enriched up to 80%, 90% and 50% relative abundance, from a single inoculum, under standard enrichment conditions with either stepwise-nitrite and ammonia concentration increases (R1), nitric oxide supplementation (R2), or complex organic carbon from mainstream wastewater (R3), respectively. Candidatus Brocadia caroliniensis predominated in all reactors, but a shift towards Ca. Brocadia sinica occurred at ammonium and nitrite concentrations > 270 mg NH4–N L−1 and 340 mg NO2–N L−1 respectively. With NO present, heterotrophic growth was inhibited, and Ca. Jettenia coexisted with Ca. B. caroliniensis before diminishing as nitrite increased to 160 mg NO2–N L−1. Organic carbon supplementation led to the emergence of heterotrophic communities that coevolved with Ca. B. caroliniensis. Ca. B. caroliniensis and Ca. Jettenia preferentially formed biofilms on surfaces, whereas Ca. Brocadia sinica formed granules in suspension. Our results indicate that multiple anammox bacteria species co-exist and occupy sub-niches in anammox reactors, and that the dominant population can be reversibly shifted by, for example, changing nitrogen load (i.e. high nitrite concentration favors Ca. Brocadia caroliniensis). Speciation has implications for wastewater process design, where the optimum cell immobilization strategy (i.e. carriers vs granules) depends on which species dominates.

Benchmarking sidestream shortcut nitrogen removal processes against nitrous oxide recovery from a life cycle perspective

Anaerobic digestion effluent adds significantly to nutrient loading, energy consumption, and emissions of wastewater treatment plants. Sustainably treating this ammonia-rich sidestream requires systematic analysis on environmental impacts of shortcut nitrogen removal processes. Coupled Aerobic–Anoxic Nitrous Decomposition Operation (CANDO) is a novel biotechnology for sidestream nitrogen removal with energy recovery potential from N2O. Nevertheless, the environmental impacts of CANDO remain unknown after initial scale-up studies. In this study, three sidestream treatment processes, namely, nitritation-denitritation, nitritation-anammox, and CANDO, integrated with mainstream anaerobic-anoxic-oxic (A2O) treatment routes, are assessed by process simulation and life cycle assessment (LCA). The results show that the nitritation-anammox process has the smallest effect on human health, ecosystem quality, and resource availability among the three routes. Furthermore, the global warming potential generated from the CANDO-A2O process is 157 kg CO2 eq per cubic meter of anaerobic digestion liquid treated, which is slightly higher than nitritation-anammox-A2O (132 kg CO2 eq) but remarkably lower than nitritation-denitritation-A2O (248 kg CO2 eq). With low carbon emission and promising alternatives for carbon source, the CANDO-A2O route exhibits great potential in achieving carbon neutrality. This work is the first to quantitatively evaluate the potential environmental impacts of CANDO from a life cycle perspective, providing insights on the adoption and optimization of shortcut nitrogen removal processes in sidestream treatment.

Environmental and Economic Impacts of Managing Nutrients in Digestate Derived from Sewage Sludge and High-Strength Organic Waste.

Increasingly stringent limits on nutrient discharges are motivating water resource recovery facilities (WRRFs) to consider the implementation of sidestream nutrient removal or recovery technologies. To further increase biogas production and reduce landfilled waste, WRRFs with excess anaerobic digestion capacity can accept other high-strength organic waste (HSOW) streams. The goal of this study was to characterize and evaluate the life-cycle global warming potential (GWP), eutrophication potential, and economic costs and benefits of sidestream nutrient management and biosolid management strategies following digestion of sewage sludge augmented by HSOW. Five sidestream nutrient management strategies were analyzed using environmental life-cycle assessment (LCA) and life-cycle cost analysis (LCCA) for codigestion of municipal sewage sludge with and without HSOW. As expected, thermal stripping and ammonia stripping were characterized by a much lower eutrophication potential than no sidestream treatment; significantly higher fertilizer prices would be needed for this revenue stream to cover the capital and chemical costs. Composting all biosolids dramatically reduced the GWP relative to the baseline biosolid option but had slightly higher eutrophication potential. These complex environmental and economic tradeoffs require utilities to consider their social, environmental, and economic values in addition to present or upcoming nutrient discharge limits prior to making decisions in sidestream and biosolids management.

Efficiency of Sidestream Nitritation for Modern Two-Stage Activated Sludge Plants.

The operational costs of wastewater treatment plants (WWTPs) are mainly driven by electric power consumption, making the energy-efficient operation an all-time present target for engineers and operators. A well known approach to reduce the demand for purchased electricity is the operation of an anaerobic sludge stabilisation process. Although anaerobic digesters make it possible to recover large quantities of energy-rich methane gas, additional strategies are required to handle the increased internal return flow of nitrogen, which arises with the sludge dewatering effluent (SDE). SDE treatment increases the oxygen demand and in turn the energy required for aeration. In this study, different SDE treatment processes were compared with regard to the treatment in mainstream, sidestream nitritation, as well as nitritation combined with anammox for two-stage and single-stage WWTPs. Although SDE treatment in sidestream nitritation was found to have no effect on the energy demand of single-stage WWTPs, this concept allows the treatment capacity in the activated sludge tank to be raised, while contributing to a high nitrogen removal under carbon limitation. In contrast, SDE sidestream treatment showed great potential for saving energy at two-stage WWTPs, whereby sidestream nitritation and the further treatment in the first stage was found to be the most efficient concept, with a savings of approx. 11% of the aeration energy.

Achieving robust mainstream nitrite shunt at pilot-scale with integrated sidestream sludge treatment and step-feed

As a promising energy- and carbon efficient process for nitrogen removal from wastewater, mainstream nitrite shunt has been extensively researched. However, beyond the laboratory it is challenging to maintain stable performance by suppressing nitrite-oxidising bacteria (NOB). In this study, a pilot-scale reactor system receiving real sewage was operated in two stages for >850 days to evaluate two novel NOB suppression strategies for achieving nitrite shunt: i) sidestream sludge treatment based on alternating free nitrous acid (FNA) and free ammonia (FA) and ii) sidestream FNA/FA sludge treatment integrated with in-situ NOB suppression via step-feed. The results showed that, with sidestream sludge treatment alone, NOB developed resistance relatively quickly to the treatment, leading to unstable nitrite shunt. In contrast, robust nitrite shunt was achieved and stably maintained for more than a year when sidestream sludge treatment was integrated with a step-feed strategy. Kinetic analyses suggested that sludge treatment and step-feed worked in synergy, leading to stable NOB suppression. The integrated strategy demonstrated in this study removes a key barrier to the implementation of stable mainstream nitrite shunt.

Cultivation of Nitrifying and Nitrifying-Denitrifying Aerobic Granular Sludge for Sidestream Treatment of Anaerobically Digested Sludge Centrate

In this study, three 1.2-L aerobic granular sludge sequencing batch reactors (AGS-SBRs) were used to cultivate nitrifying and nitrifying-denitrifying granules (w/supplemental carbon) and investigate sidestream treatment of synthetic-centrate and real-centrate samples from Ashbridges Bay Treatment Plant (ABTP) in Toronto, Ontario, Canada. Results showed that although the cultivation of distinct granules was not observed in the nitrifying reactors, sludge volume index (SVI30) values achieved while treating real and synthetic centrate were 72 ± 12 mL/g and 59 ± 11 mL/g (after day 14), respectively. Ammonia-nitrogen (NH3-N) removal in the nitrifying SBRs were 93 ± 19% and 94 ± 16% for real and synthetic centrate, respectively. Granules with a distinct round structure were successfully formed in the nitrifying-denitrifying SBR, resulting in an SVI30 of 52 ± 23 mL/g. NH3-N, chemical oxygen demand (COD) and phosphorus (P) removal in the nitrifying-denitrifying SBR were 92 ± 9%, 94 ± 5%, and 81 ± 14% (7th to 114th day), respectively with a low nitrite (NO2-N) and nitrate (NO3-N) concentration in the effluent indicating simultaneous nitrification-denitrification (SND) activity. High nutrient removal efficiencies via the nitrification and SND pathways shows that AGS technology is a viable process for treating sidestreams generated in a WWTP.

Toward Mainstream Anammox by Integrating Sidestream Treatment.

ADVERTISEMENT RETURN TO ISSUEPREVViewpointNEXTToward Mainstream Anammox by Integrating Sidestream TreatmentShenbin Cao*Shenbin CaoChair of Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall 3, 85748 Garching, Germany*Phone: +49.89.289.13701; fax: +49.89.289.13718; email: [email protected]More by Shenbin Caohttps://orcid.org/0000-0002-8464-7287, Konrad KochKonrad KochChair of Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall 3, 85748 Garching, GermanyMore by Konrad Kochhttps://orcid.org/0000-0001-5425-0169, Rui DuRui DuNational Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Beijing University of Technology, Beijing 100124, ChinaWater Chemistry and Water Technology, Engler-Bunte-Institut, Karlsruhe Institute of Technology, Karlsruhe 85748, GermanyMore by Rui Duhttps://orcid.org/0000-0002-7306-4705, George F WellsGeorge F WellsDepartment of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois 60208, United StatesMore by George F Wellshttps://orcid.org/0000-0002-9100-1628, Liu YeLiu YeSchool of Chemical Engineering, the University of Queensland, St. Lucia, Queensland 4072, AustraliaMore by Liu Yehttps://orcid.org/0000-0001-5478-0864, and Jörg E. DrewesJörg E. DrewesChair of Urban Water Systems Engineering, Technical University of Munich, Am Coulombwall 3, 85748 Garching, GermanyMore by Jörg E. Dreweshttps://orcid.org/0000-0003-2520-7596Cite this: Environ. Sci. Technol. 2022, 56, 15, 10553–10556Publication Date (Web):July 18, 2022Publication History Received6 May 2022Published online18 July 2022Published inissue 2 August 2022https://doi.org/10.1021/acs.est.2c03256Copyright © 2022 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1226Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (3 MB) Get e-AlertsSUBJECTS:Anions,Bacteria,Cations,Nitrogen,Wastewater Get e-Alerts

Vacuum-enhanced anaerobic fermentation: Achieving process intensification, thickening and improved hydrolysis and VFA yields in a single treatment step

This study assessed the feasibility of a novel vacuum-enhanced anaerobic digestion technology, referred to as IntensiCarbTM (IC), under mild vacuum pressure (110 mbar), compared to a control (conventional fermenter), and evaluated the impact of the vacuum on the activities of various microbial groups. Both fermenters (test and control) were operated with mixed (50% v/v) municipal sludge at solids concentrations of 2–2.5%, pH of 7.8–8.1, 40–45 °C, a theoretical solids retention time (SRT) of 3 days with different hydraulic retention times (HRT). The intensification factor (IF) of the IC, defined as SRT/HRT, was controlled at 1.3 and 2.0. Simultaneous thickening and fermentation intensification were achieved. Compared with the control, the IC, despite the shorter HRTs, achieved 29.5 to 90.2% increase in the VFA yield (79 to 116 mg ΔVFA/ g VSS vs 61 mg ΔVFA/ g VSS), and 16.2% to 56.4% increase (280 to 377 mg ΔsCOD/ g VSS vs 241 mg ΔsCOD/ g VSS), in the hydrolysis yield. Fermentate from the IC exhibited comparable specific denitrification rates to acetate. Further, the solids-free condensate contained low nutrient concentrations, and thus was far superior to a typical centrates from dewatering as a carbon source. No adverse effects of vacuum on the activity of fermentative bacteria and methanogens were observed. This study demonstrated that the IC can be deployed as an intensification technology for both fermentation and anaerobic digestion of biosolids with the additional significant advantage, i.e. elimination of sidestream ammonia treatment requirements.

Expanding ASM models towards integrated processes for short-cut nitrogen removal and bioplastic recovery

In next-generation water resource recovery facilities (WRRFs), it is becoming increasingly important to save energy costs and promote resource recovery of valuable products. One way of reducing the substantial aeration energy costs at WRRFs is to employ shortcut N removal, while polyhydroxyalkanoate (PHA) production and recovery as bioplastic is a promising means of recovering a valuable product from biosolids. Both objectives can be achieved simultaneously through the Short-Cut Enhanced Phosphorus and PHA Recovery (SCEPPHAR) process. However, current mathematical models have not previously been employed to describe the behavior of such a process, which limits engineering design and optimisation of process operation. This work focusses on extending the ASM3 model towards the description of short-cut nitrogen removal and simultaneous PHA recovery in a sidestream treatment process. The calibrated and validated model described very well the nitritation process coupled with the aerobic feast/anoxic famine process for the selection of PHA producing organisms at a pilot-scale facility operated in Carbonera, Italy, where the normalised root mean squared error (NRMSE) was consistently <20%. Furthermore, the model applied to the PHA selection stage could effectively describe the PHA accumulation stage without recalibration. A simulation study was performed using the modified ASM3 model to assess the relative benefits of the SCEPPHAR process strategy as compared to the fully aerobic selection process for mixed culture PHA production. While the level of PHA production was found to be 34% lower with SCEPPHAR, a 43% savings in volatile fatty acids (VFAs) demand, a 15% decrease in Total suspended solids (TSS) production and a 28% decrease in oxygen demand were also achievable, which could lead to savings in operational costs. This study facilitates the design and optimisation of WRRFs that integrate short-cut N removal with PHA production, saving aeration energy costs while achieving resource recovery.