Demand response within the energy-for-water-nexus - A review. ESRI WP637, October 2019

A promising tool to achieve more flexibility within power systems is demand re-sponse (DR). End-users in many strands of industry have been subject to research up to now regarding the opportunities for implementing DR programmes. One sector that has received little attention from the literature so far, is wastewater treatment. However, case studies indicate that the potential for wastewater treatment plants to provide DR services might be significant. This review presents and categorises recent modelling approaches for industrial demand response as well as for the wastewater treatment plant operation. Furthermore, the main sources of flexibility from wastewater treatment plants are presented: a potential for variable electricity use in aeration, the time-shifting operation of pumps, the exploitation of built-in redundan-cy in the system and flexibility in the sludge processing. Although case studies con-note the potential for DR from individual WWTPs, no study acknowledges the en-dogeneity of energy prices which arises from a large-scale utilisation of DR. There-fore, an integrated energy systems approach is required to quantify system and market effects effectively

Fermentation strategies for PHB production in a novel membrane bioreactor : investigating batch and fed-batch operations

Gas-transfer membranes have been successfully deployed as efficient aeration devices in wastewater treatment. There is an increasing interest in using such membrane technology in industrial biotechnology. This study proposes membrane bioreactors as a novel bioreactor setup for polyhydroxybutyrate (PHB) production using Cupriavidus necator, whereby gas-transfer membranes are used for aeration. A proof-of-concept membrane bioreactor was built by combining a 50 ml centrifuge tube with hollow fiber membrane bundles. Different numbers and length of polydimethylsiloxane (PDMS) hollow fiber membranes were used to create membrane bundles with varying specific surface areas for oxygen transfer. In batch mode, a maximum biomass concentration of 10.3 g/L, which corresponds to a yield of 0.67 g biomass/g substrate, was achieved with 250 m2/m3 as the specific surface area of the membranes and 40 rpm as the liquid recirculation rate. Two different fed-batch modes were investigated to induce PHB production by applying nitrogen source limitation via fill-and-draw and two-step feeding strategies. A PHB level of 22% was obtained with fill-and-draw feeding by supplying 0.25 g/L NH4Cl after initial cultivation. Results indicate that membrane bioreactors are promising for C. necator cultivation, but further research is needed to enhance the PHB productivity

Models of demand response and an application for wastewater treatment plants1. ESRI Research Bulletin February 2020/04

Demand response can be defined as any change of the usual electricity demand pattern in response to a price signal from the electricity supplier. It is widely seen as a promising tool to increase energy system flexibility: electricity demand can increase when there is a surplus of electricity available, such as when wind levels are high, and can reduce when there is a shortage of electricity. In the industrial sector in particular, the potential for demand response can be significant. This is because electricity costs can be a big share of total costs and therefore there is a strong incentive to reduce electricity expenditures in order to be competitive. However, to date, the demand response from industrial electricity users has only been examined in a generic way, without taking account of their specific characteristics. Any results arising from these examinations are therefore of limited use for policy makers and industry participants

A Review of Nanomaterials and Technologies for Enhancing the Antibiofilm Activity of Natural Products and Phytochemicals

Biofilms are communities of microorganisms encased in a self-produced matrix constituted of extracellular polymeric substances (EPS). The recalcitrant and often harmful nature of biofilms, particularly in the biomedical field, motivates a search for antibiofilm compounds and materials. Within this context, nanoparticles (NPs) represent a promising platform for antibiofilm technologies due to their increased penetration into biofilms and facility of tailoring type, size, shape, and surface functionalization. The association of NPs with natural products and phytochemicals is even more appealing as an antibiofilm strategy, since the antimicrobial activity of essential oils, extracts, and isolated compounds can be improved when they are carried on the surface of NPs or encapsulated within them, as well as combined in formulations such as in nanoemulsions. This review article aims to provide an overview of recent methodologies for natural product delivery using nanomaterials and nanoformulations for the effective combat and eradication of bacterial and fungal biofilms. The nano-based technologies are categorized based on the type of antimicrobial delivery (NP coating, encapsulation, or nanoemulsions), and a selection of some widely reported natural substances (curcumin, propolis, and cinnamon components) is explored in more depth.Science Foundation Irelan

The effects of extrinsic factors on the structural and mechanical properties of Pseudomonas fluorescens biofilms: A combined study of nutrient concentrations and shear conditions

The growth of biofilms on surfaces is a complicated process influenced by several environmental factors such as nutrient availability and fluid shear. In this study, combinations of growth conditions were selected for the study of Pseudomonas fluorescens biofilms including as cultivation time (24- or 48 h), nutrient levels (1:1 or 1:10 King B medium), and shear conditions (75 RPM shaking, 0.4 mL min −1 or 0.7 mL min −1). The use of Confocal Laser Scanning Microscopy (CLSM) determined biofilm structure, while liquid-phase Atomic Force Microscopy (AFM) techniques resolved the mechanical properties of biofilms. Under semi-static conditions, high nutrient environments led to more abundant biofilms with three times higher EPS content compared to biofilms grown under low nutrient conditions. AFM results revealed that biofilms formed under these conditions were less stiff, as shown by their Young's modulus values of 2.35 ± 0.08 kPa, compared to 4.98 ± 0.02 kPa for that of biofilms formed under low nutrient conditions. Under dynamic conditions, however, biofilms exposed to low nutrient conditions and high shear rates led to more developed biofilms compared to other tested dynamic conditions. These biofilms were also found to be significantly more adhesive compared to their counterparts grown at higher nutrient conditions.European Research CouncilScience Foundation IrelandEC Framework (FP7

Nanofiltration-induced cell death: An integral perspective of early stage biofouling under permeate flux conditions

The performance of pressure-driven membrane filtration processes for water treatment is hampered by biofouling. A relevant, but often overlooked aspect of this phenomenon concerns the localized microenvironment at the membrane interface. A key question is the level of stress on adhering cells and how this impacts on the developing biofilm. In this study, Pseudomonas fluorescens biofilms were monitored after 1, 2 and 7-day cross-flow nanofiltration experiments using confocal microscopy with live/dead staining which enabled analysis of both biofilm structure and the spatial localization of dead versus live cells. A significant increased level of biomass at low- compared to high-flux conditions (2-day experiments) suggested hindrance of bacterial proliferation at higher fluxes. An increase in live cell fractions was generally observed between 24- and 48-h at low flux conditions (3 bar), while the fraction of dead/injured cells remained constant during that same period. At higher flux conditions (15 bar), the volume of live cell fractions remained constant over 24- and 48-h experiments. The implications of these findings point to the need to reevaluate classical contact-killing strategy for controlling membrane fouling; initial membrane fouling events are characterized by an initially-induced cell death stage followed by an adaptation period through which surviving cells are able to acclimatize in their respective environments. This study emphasizes the need to better understand the role of operating parameters and its resulting cell death during early stage fouling. It is in this context that fouling management strategies can be further developed.European Research CouncilScience Foundation IrelandEuropean Commission - Seventh Framework Programme (FP7

Bacterial adhesion onto nanofiltration and reverse osmosis membranes: Effect of permeate flux

The influence of permeate flux on bacterial adhesion to NF and RO membranes was examined using two model Pseudomonas species, namely Pseudomonas fluorescens and Pseudomonas putida. To better understand the initial biofouling profile during NF/RO processes, deposition experiments were conducted in cross flow under permeate flux varying from 0.5 up to 120 L/(h m2), using six NF and RO membranes each having different surface properties. All experiments were performed at a Reynolds number of 579. Complementary adhesion experiments were performed using Pseudomonas cells grown to early-, mid- and late-exponential growth phases to evaluate the effect of bacterial cell surface properties during cell adhesion under permeate flux conditions. Results from this study show that initial bacterial adhesion is strongly dependent on the permeate flux conditions, where increased adhesion was obtained with increased permeate flux, until a maximum of 40% coverage was reached. Membrane surface properties or bacterial growth stages was further found to have little impact on bacterial adhesion to NF and RO membrane surfaces under the conditions tested. These results emphasise the importance of conducting adhesion and biofouling experiments under realistic permeate flux conditions, and raises questions about the efficacy of the methods for the evaluation of antifouling membranes in which bacterial adhesion is commonly assessed under zero-flux or low flux conditions, unrepresentative of full-scale NF/RO processes.European Research Council (ERC

Nanoparticle–Biofilm Interactions: The Role of the EPS Matrix

The negative consequences of biofilms are widely reported. A defining feature of biofilms is the extracellular matrix, a complex mixture of biomacromolecules, termed EPS, which contributes to reduced antimicrobial susceptibility. EPS targeting is a promising, but underexploited, approach to biofilm control allowing disruption of the matrix and thereby increasing the susceptibility to antimicrobials. Nanoparticles (NPs) can play a very important role as ’carriers’ of EPS matrix disruptors, and several approaches have recently been proposed. In this review, we discuss the application of nanoparticles as antibiofilm technologies with a special emphasis on the role of the EPS matrix in the physicochemical regulation of the nanoparticle–biofilm interaction. We highlight the use of nanoparticles as a platform for a new generation of antibiofilm approaches.Science Foundation Irelan

Modelling demand response with process models and energy systems models: Potential applications for wastewater treatment within the energy-water nexus

A promising tool to achieve more flexibility within power systems is demand response (DR). End users in many strands of industry have been subject to research regarding the opportunities for implementing DR programmes. We review recent DR modelling approaches in the realm of energy systems models and industrial process models. We find that existing models over- or underestimate the available DR potential from an industrial end user for two main reasons. First, the interaction between power system operation and industrial process operation caused by DR is not taken into account. Second, models abstract from critical physical process constraints affecting the DR potential. To illustrate this, we discuss the wastewater treatment process as one industrial end user within the energy-water nexus, for which the lack of suitable modelling tools is affecting the accurate assessment of the DR potential. Case studies indicate the potential for wastewater treatment plants to provide DR, but no study acknowledges the endogeneity of energy prices which arises from a large-scale utilisation of DR. Therefore, we propose an integrated modelling approach, combining energy system optimisation with the level of operational detail in process simulation models. This will yield a higher level of accuracy regarding the assessment of DR potential from a specific process, such as wastewater treatment.Science Foundation IrelandESIPP UC