A simplified approach for activity monitoring in complex wastewater treatment processes

ICA 2017, 12th IWA Specialized Conference on Instrumentation, Control and Automation,11-14 June 2017, in Québec City, Québec, CanadaThe stoichiometric relations between substrate and product are the first parameter obtained for novel processes. We propose here a method for process monitoring that uses the stoichiometry matrix and a linear least square optimisation as a simple approach for process monitoring. The new method is benchmarked versus a well-established method: the continuous-discrete extended Kalman filter (CD-EKF) and both are compared estimating biological rates of a novel technology. It is seen that, although inferior to the CD-EKF, the new method can be an alternative for process monitoring in wastewater treatmen

Cometabolic enzymatic transformation of organic micropollutants under methanogenic conditions

This is a post-print version of the published article: Gonzalez-Gil, L., Carballa, M., & Lema, J. M. (2017). Cometabolic Enzymatic Transformation of Organic Micropollutants under Methanogenic Conditions. Environmental Science & Technology, 51(5), 2963-2971. https://doi.org/10.1021/acs.est.6b05549Anaerobic digestion (AD) has been shown to have the biological potential to decrease concentrations of several organic micropollutants (OMPs) in sewage sludge. However, the mechanisms and factors behind these biotransformations, which are essential for elucidating the possible transformation products and to foster the complete removal of OMPs via operational strategies, remain unclear. Therefore, this study investigated the transformation mechanisms of 20 OMPs during the methanogenic step of AD with a focus on the role of acetate kinase (AK), which is a key enzyme in methane production. The results from lab-scale methanogenic reactors showed that this step accounts for much of the reported OMP biotransformation in AD. Furthermore, enzymatic assays confirmed that AK transforms galaxolide, naproxen, nonylphenol, octylphenol, ibuprofen, diclofenac, bisphenol A, and triclosan. Except for galaxolide, for which further studies are required to refine conclusions, the OMP’s chemical structure was a determinant for AK action because only compounds that contain a carboxyl or hydroxyl group and have moderate steric hindrance were enzymatically transformed, likely by phosphorylation. For these seven compounds, this enzymatic mechanism accounts for 10–90% of the measured methanogenic biotransformation, suggesting that other active enzymes of the AD process are also involved in OMP biotransformationThis work was funded by Xunta de Galicia through the MicroDAN project (EM 2012/087) and by the Spanish government through the HOLSIA project (CTM2013-46750-R), a Ramón y Cajal contract (RYC-2012-10397) and an FPU Grant (FPU13/01255). The authors belong to CRETUS (AGRUP2015/02) and to the Galician Competitive Research Group (GRC 2013-032)S

Energetic and economic assessment of sludge thermal hydrolysis in novel wastewater treatment plant configurations

Novel wastewater treatment plants (WWTPs) are aimed to be more energetically efficient than conventional ones. Their first step is a chemical oxygen demand (COD) preconcentration stage with different alternatives, such as rotating belt filters (RBF), chemically enhanced primary treatment (CEPT), high-rate activated sludge (HRAS), or combinations thereof, in which energy requirements are substantially reduced. The COD recovered as sludge allows a noticeable increase of biogas production in anaerobic digestion (AD). In conventional WWTPs, sludge anaerobic biodegradability can be significantly enhanced by applying sludge pretreatment methods, such as thermal hydrolysis (TH), before AD. However, considering that novel-sludges are more anaerobically biodegradable than conventional ones, the impact of TH on their methane production is expected to result significantly lower. In this study, an energetic and economic assessment of applying TH in novel WWTPs was performed. We found that TH is only justified to reduce operational costs as long as sludge TS concentration in the feeding to the TH unit is higher than 1-2%. The HRAS is the scenario that leads to the lowest treatment costs (below 1 c€/m3 wastewater if sludge is thickened over 10% of TS). However, the WWTP based on CEPT for COD preconcentration leads to the lowest electricity consumption (below 0.01 kWh/m3 of wastewater), but even in the most favourable conditions the energy autarky was not achievable. Results show that the main impact of TH is mainly due to sludge disposal savings (270,000-430,000 €/year for a 500,000 inhabitants WWTP) rather than the increase of energy production (achieves maximum savings of 35,000-60,000 €/year). Payback time is very dependent on the WWTP size, ranging from 15 to 30 years for a 100,000 inhabitants WWTP and from 2 to 4 years for a 1,000,000 inhabitants WWTPThe authors would like to thank the EU (ID199) and AEI (PCIN-2015-22) for funding, in the frame of the collaborative international Consortium Pioneer_STP financed under Water Joint Programming Initiative. The authors belong to the Gali- cian Competitive Research Group ED431C 2017/029 and the CRETUS Strategic Partnership (ED431E 2018/01). These programmers are co-funded by FEDER (EU)S

Microbial inefficient substrate use through the perspective of resource allocation models

Microorganisms extract energy from substrates following strategies that may seem suboptimal at first glance. Beyond the so-called yield-rate trade-off, resource allocation models, which focus on assigning different functional roles to the limited number of enzymes that a cell can support, offer a framework to interpret the inefficient substrate use by microorganisms. We review here relevant examples of substrate conversions where a significant part of the available energy is not utilised and how resource allocation models offer a mechanistic interpretation thereof, notably for open mixed cultures. Future developments are identified, in particular, the challenge of considering metabolic flexibility towards uncertain environmental changes instead of strict fixed optimality objectives, with the final goal of increasing the prediction capabilities of resource allocation models. Finally, we highlight the relevance of resource allocation to understand and enable a promising biorefinery platform revolving around lactate, which would increase the flexibility of waste-to-chemical biorefinery schemese authors would like to acknowledge the support of the Spanish Ministry of Education (FPU14/05457) and project CONSERVAL (INTERREG V-A Spain-Portugal, POCTEP), co-financed by the ERDF (Ref: 2352). The authors belong to the Galician Competitive Research Group (ED431C2017/029) and to the CRETUS Strategic Partnership (ED431E 2018/01), both programmes are co-funded by Xunta de Galicia and ERDF (EU)S

Measuring energy demand and efficiency at WWTPs: an econometric approach

Frontiers International Conference on Wastewater TreatMent. 21-24 may 2017. Palermo-Ital

A systematic methodology for the robust quantification of energy efficiency at wastewater treatment plants featuring Data Envelopment Analysis

© 2018. This is the accepted manuscript of the following article: Longo, S., Hospido, A., Lema, J., & Mauricio-Iglesias, M. (2018). A systematic methodology for the robust quantification of energy efficiency at wastewater treatment plants featuring Data Envelopment Analysis. Water Research, 141, 317-328. doi: 10.1016/j.watres.2018.04.067This article examines the potential benefits of using Data Envelopment Analysis (DEA) for conducting energy-efficiency assessment of wastewater treatment plants (WWTPs). WWTPs are characteristically heterogeneous (in size, technology, climate, function ...) which limits the correct application of DEA. This paper proposes and describes the Robust Energy Efficiency DEA (REED) in its various stages, a systematic state-of-the-art methodology aimed at including exogenous variables in nonparametric frontier models and especially designed for WWTP operation. In particular, the methodology systematizes the modelling process by presenting an integrated framework for selecting the correct variables and appropriate models, possibly tackling the effect of exogenous factors. As a result, the application of REED improves the quality of the efficiency estimates and hence the significance of benchmarking. For the reader's convenience, this article is presented as a step-by-step guideline to guide the user in the determination of WWTPs energy efficiency from beginning to end. The application and benefits of the developed methodology are demonstrated by a case study related to the comparison of the energy efficiency of a set of 399 WWTPs operating in different countries and under heterogeneous environmental conditionsThe authors belong to the Galician Competitive Research GroupGRC2013-032 and the CRETUS strategic partnership (AGRUP2015/02), co-funded by FEDER (EU). Besides, they are supported by ‘ENERWATER’ Coordination Support Action that has received founding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 649819S

Enzymatic cometabolic biotransformation of organic micropollutants in wastewater treatment plants: a review

Biotransformation of trace-level organic micropollutants (OMPs) by complex microbial communities in wastewater treatment facilities is a key process for their detoxification and environmental impact reduction. Therefore, understanding the metabolic activities and mechanisms that contribute to their biotransformation is essential when developing approaches aiming to minimize their discharge. This review addresses the relevance of cometabolic processes and discusses the main enzymatic activities currently known to take part in OMPs removal under different redox environments in the compartments of wastewater treatment plants. Furthermore, the most common methodologies to decipher such enzymes are discussed, including the use of in vitro enzyme assays, enzymatic inhibitors, the analysis of transformation products and the application of several -omic techniques. Finally, perspectives on major challenges and future research requirements to improve OMPs biotransformation are proposedThis research was funded by the Spanish Government (Agencia Estatal de Investigación) through the ANTARES project (PID2019-110346RB-C21) and a PhD Xunta de Galicia Grant (ED481A-2018/113, David Kennes). Authors from Universidade de Santiago de Compostela belong to Galician Competitive Research Group (GRC ED431C 2017/29), which is co-funded by FEDER (EU)S

Air-side ammonia stripping coupled to anaerobic digestion indirectly impacts anaerobic microbiome

Air‐side stripping without a prior solid–liquid phase separation step is a feasible and promising process to control ammonia concentration in thermophilic digesters. During the process, part of the anaerobic biomass is exposed to high temperature, high pH and aerobic conditions. However, there are no studies assessing the effects of those harsh conditions on the microbial communities of thermophilic digesters. To fill this knowledge gap, the microbiomes of two thermophilic digesters (55°C), fed with a mixture of pig manure and nitrogen‐rich co‐substrates, were investigated under different organic loading rates (OLR: 1.1–5.2 g COD l−1 day−1), ammonia concentrations (0.2–1.5 g free ammonia nitrogen l−1) and stripping frequencies (3–5 times per week). The bacterial communities were dominated by Firmicutes and Bacteroidetes phyla, while the predominant methanogens were Methanosarcina sp archaea. Increasing co‐substrate fraction, OLR and free ammonia nitrogen (FAN) favoured the presence of genera Ruminiclostridium, Clostridium and Tepidimicrobium and of hydrogenotrophic methanogens, mainly Methanoculleus archaea. The data indicated that the use of air‐side stripping did not adversely affect thermophilic microbial communities, but indirectly modulated them by controlling FAN concentrations in the digester. These results demonstrate the viability at microbial community level of air side‐stream stripping process as an adequate technology for the ammonia control during anaerobic co‐digestion of nitrogen‐rich substratesThis research was supported by the European Community Seventh Framework Programme (ManureEcoMine project – 603744); and by the Spanish Government (AEI) through CDTI (SmartGreenGas project – 2014-CE224). The authors belong to the Galician Competitive Research Group ED431C 2017/029 and to the CRETUS Strategic Partnership (ED431E 2018/01), co-funded by FEDER (UE). Computational resources were kindly provided and supported by Fundacion Publica Galega Centro Tecnolóxico de Supercomputación de Galicia (CESGA)S

An exploratory data analysis of energy consumption of WWTP. Influencing factors and possible methods for benchmarking

Wastewater treatment plants are relevant energy consumers. As they carry out complex operations submitted to large variability caused by, among others, the influent and loading variations, the assessment of the performance is challenging. In this study we perform a regression analysis over a sample of 185 WWTP data in order to establish a regression model that predicts the average energy consumption of the plant given plant design and operation predictors such as the average influent flowrate, the COD loading and the plant loading factor. The regression model is also used to ascertain whether the location of the WWTP in France, Spain and Germany has an impact over the energy consumptio

Can nitrogen removal be a win-win situation?

10th World Congress of Chemical Engineering Barcelona, 3 October 201