This paper evaluates life cycle Greenhouse Gas (GHG) emissions of a Seawater Reverse Osmosis (SWRO) desalination plant and assesses its performance under three power supply scenarios. A Life Cycle ...Assessment (LCA) analysis is conducted for a plant located in Perth, Western Australia (WA). Input and output flows of SWRO plant are based on literature and Perth desalination plants. The Simapro Australian and Ecoinvent databases are used for operational phase Life Cycle Inventory (LCI). An LCI for the construction phase of the plant is developed using economic input-output analysis. Electricity supply scenarios are "100% WA grid", "100% wind energy" and "92% wind energy plus 8% Photovoltaic (PV) solar energy". Results indicate that renewable energy powered desalination plants achieve GHG emissions reduction of similar to 90% compared to the plant powered by WA grid scenario. For the plant powered by fossil based grid electricity, electricity use in the operational phase is found to be responsible for more than 92% of its GHG emissions. On the other hand, for the plants powered by renewable energy, the highest contribution belongs to chemical use in the operational phase (60%) followed by the construction phase (17%). Indirect emissions due to the electricity consumption in the chemical, wind turbine and PV solar panel manufacturing are found to contribute the lion's share (36-39%) of the life cycle emissions for the renewable energy powered desalination plants. Any improvement in fuel mixes in grid electricity towards cleaner energy sources can be beneficial by reducing impacts associated with upstream electricity use in manufacturing. This work provides the first reference to identify and quantify supply chain contributions to the overall environmental impact associated with renewable energy powered desalination plants.
Extracellular polysaccharides (EPS) have been recognized as significant contributors to membrane biofouling. This study compared membrane fouling by different commercially available polysaccharides ...(alginate, a commonly used model, as well as xanthan and pullulan) and polysaccharides isolated from naturally adherent marine bacteria (RSW 8, RSW 12, RSW 14 and FSW 6) in forward osmosis (FO) and reverse osmosis (RO). In FO experiments, a new approach was developed to maintain stable osmotic pressure by continuously saturating the sodium chloride draw solution, enabling a direct comparison of fouling in FO and RO. Under identical operating conditions and feed water chemistry, commercial polysaccharides and naturally produced polysaccharides fouled the membrane to different extents. For commercial polysaccharides, alginate and xanthan caused more severe fouling in RO than in FO; while pullulan caused minimal fouling in both processes. In FO, the extent of fouling by three polysaccharides followed the order of xanthan>alginate>pullulan. This could be explained by increased feed solution viscosity following the addition of selected commercial polysaccharides and thus varied accumulation of polysaccharide on the membrane. In RO, alginate caused the most severe fouling likely due to the formation of gels in the presence of calcium. By contrast, pullulan which lacks carboxyl functional groups was negligibly affected by calcium and caused minimal fouling. The polysaccharides naturally produced by marine bacteria (FSW 6, RSW 8 and RSW 14) improved permeate flux in FO rather than fouling. This indicated some polysaccharides could improve membrane performance. However, in RO the naturally produced polysaccharides only RSW 14 did not reduce permeate flux but RSW 12 and RSW 8 did cause significant flux decline or fouling. This study highlights the importance of selecting representative polysaccharide models for fouling research.
•This paper compared the fouling in FO and RO membranes by polysaccharide, both commercial and naturally produced ones from the RO plant.•All the tested naturally occurring polysaccharides improved permeate flux rather than fouling in FO.•It is important to select representative polysaccharide model for fouling research.
Anion exchange membrane (AEM)-equipped electrochemical cells can be used for removing the carbon dioxide (CO
2
) from biogas, thereby upgrading its energy content. The CO
2
absorbed in the catholyte ...can be transported across the AEM as (bi)carbonate and then recovered in the anodic chamber of the electrochemical cell. However, CO
2
regeneration in the anode chamber diminishes the oxygen (O
2
) content in the anodic gas stream. Given this electrochemically produced oxygen can have a high-industrial application value, such as for promoting more efficient biological wastewater treatment processes, we hereby proposed and validated a three-chamber electrochemical cell configuration capable of removing CO
2
and recovering it in an intermediate chamber, with a concomitant anodic generation of high-purity O
2
gas. Our prototype successfully facilitated CO
2
recovery in a separate chamber preventing CO
2
contamination of the anodic O
2
gas stream. Results also suggested that an approximately tenfold increase in CO
2
loading rate enhanced the relative CO
2
diffusion flux from 5 to 43% through the AEM, by lowering the catholyte pH as well as improving gas–liquid CO
2
transfer. A mathematical model was also developed to accurately predict the polarization performance of the electrochemical cell.
Graphical abstract
A novel membraneless bioelectrochemical system termed rotatable bioelectrochemical contactor (RBEC) was fabricated and evaluated for its ability to recover useful energy (here methane) from a low ...organic strength wastewater. We studied the operational characteristics of the RBEC by operating it as a three-electrode electrolysis cell. A stack of conductive disks (each subdivided into two half disks), similar to rotating biological contactors, were rotated with one-half disk immersed in the wastewater and the other into the gas headspace. By carrying out regular half rotations (180° rotation) the anode became the cathode and vice versa. This operation resulted in the build-up of a biofilm that could catalyze both an anodic acetate oxidation and a cathode-driven methanogenesis. Methane production rate was directly proportional to the applied electrical energy. Increase in current density (from 0.16 to 4.1 A m−2) resulted in a faster COD removal (from 0.2 to 1.38 kg COD m−3 day−1) and methane production (from 0.04 to 0.53 L L−1 day−1). Of the electrons flowing across the circuit, over 80% were recovered as methane. Such methane production was electrochemically driven by the headspace-exposed cathodic half disks, which released the methane directly to the gas-phase. Energy analysis shows that the new design requires less energy for COD removal than what is typically required for oxygen supply in activated sludge processes. Because the system could operate without wastewater recirculation against gravity; additional pH buffer chemicals; ion-exchange membranes or electrochemical catalysts, it has desirable characteristics for process up-scale. Further, the current report shows the first example of a BES with identical biofilm (due to intermittent polarity inversion) on both electrodes.
Water is economically cheap, which fails to consider its intrinsic environmental and social value. However, given the uncertain future around the availability of water resources to provide ...industrial, environmental and social services, water conservation is now of significant concern to industries across the globe. Recently, an extension of water conservation has emerged as zero liquid discharge, whereby no water at all is released from industrial processes, regardless of its quality.
Water auditing is a tool that can be used to identify water conservation strategies, ideally leading to zero liquid discharge. This article discusses a water audit conducted on a sodium cyanide plant, where flows were determined using historical data, proxy data, and known scientific relationships. Water quality throughout the process was defined as contaminated or uncontaminated. From this simple audit, two major water conservation measures were identified and modelled which could reduce inputs and outputs by ∼40%. These were the reuse of rain water falling throughout the plant's boundaries instead of demineralised scheme water, and the improvement of the efficiency of one of the cooling towers.
Such a methodology could be easily applied by other industries so as to improve their water conservation. The auditing method may lead to suggestions of conservation techniques for implementation either through retrofitting existing plants or contributing to the design of new ones.
•Multiple methods can be used to determine historical flows in water audits.•Water auditing indicates areas for conservation, such as alternative water sources.•Results of water audits can inform both plant retrofits and new infrastructure.•Water auditing contributes to achieving zero liquid discharge.
Poor cathodic oxygen reduction and the detrimental buildup of a pH gradient between anode and cathode are the major hurdles in the development of sustainable microbial fuel cells (MFCs). This article ...describes and tests a concept that can help overcoming both of these limitations, by inverting the polarity of the MFC repeatedly, allowing anodic and cathodic reactions to occur alternately in the same half-cell and hence neutralizing its respective pH effects. For simplicity, we studied polarity inversion exclusively in one half-cell, maintaining its potential at −300 mV (vs Ag/AgCl) by a potentiostat. An alternating supply of acetate and dissolved oxygen to the biofilm resulted in the tested half-cell repeatedly changing from an anode to a cathode and vice versa. This repeated inversion of current direction avoided the detrimental drifting of the electrolyte pH. Control runs without current inversion ceased to produce current, as a result of anode acidification. The presence of the anodophilic biofilm survived the intermittent oxygen exposure and could measurably facilitate the cathodic reaction by reducing the apparent oxygen overpotential. It enabled cathodic oxygen reduction at about −150 mV (vs Ag/AgCl) compared to −300 mV (vs Ag/AgCl) for the same electrode material (granular graphite) without biofilm. Provided that a suitable cathodic potential was chosen, the presence of “anodophilic bacteria” at the cathode could enable a 5-fold increase in power output. Overall, the ability of an electrochemically active biofilm to catalyze both substrate oxidation and cathodic oxygen reduction in a single bioelectrochemical system has been documented. This property could be useful to alleviate both the cathodic oxygen reduction and the detrimental drifting of electrolyte pH in an MFC system. Further research is warranted to explore the application of such bidirectional microbial catalytic properties for sustainable MFC processes.
Microbiomes of full-scale seawater reverse osmosis membranes are complex and subject to variation within and between membrane units. The pre-existing bacterial communities of unused membranes before ...operation have been largely ignored in biofouling studies. This study is novel as unused membranes were used as a critical benchmark for comparison. Fouled seawater reverse osmosis membrane biofilm communities from an array of autopsied membrane samples, following a 7-year operational life-span in a full-scale desalination plant in Western Australia, were characterised by 16S rRNA gene metabarcoding using the bacterial primers 515F and 806R. Communities were then compared based on fouling severity and sampling location. Microbiomes of proteobacterial predominance were detected on control unused membranes. However, fouled membrane communities differed significantly from those on unused membranes, reflecting that operational conditions select specific bacteria on the membrane surface. On fouled membranes,
were also predominant but families differed from those on unused membranes, followed by
and
.
correlated with stable, mature and thick biofilms such as those in severely fouled membranes or samples from the feed end of the membrane unit, while
and
were predominantly found in biofilms on fouled but visually clean, and moderately fouled samples or those from reject ends of membrane units.
predominated the thin, compact biofilms at the mid-feed end of membrane units. The study also supported the importance of
and glycosphingolipid-producing bacteria, namely
and
, in primary attachment and biofilm recalcitrance. Nitrate-and-nitrite-reducing bacteria such as
,
and some
were also prevalent across all fouled membranes and appeared to be critical for ecological balance and biofilm maturation.
Industrial enterprises around the world are grappling with greenhouse gas emission reduction expectations, whether being driven by respective government policy for climate change or by shareholders ...to drive corporate sustainability through maintaining access to their ‘net zero’-demanding markets. In some instances, the enterprises co-located within complex industrial areas are coming together to face the common carbon reduction challenge as a collective. The Kwinana Industrial Area in Perth, Western Australia is well regarded on the world's stage as a successful integrated heavy industrial precinct, presenting as an extensive, complex, and broad-based example of Industrial Symbiosis. In earlier papers, the authors have posited a novel four-dimensional framework to expand the definition of Industrial Symbiosis to be used to understand why one industrial precinct may be more successful for its resident industries to operate within than another, and for application in the design of new industrial areas. The four dimensions are described as Materials Exchange, Skilled Workforce, Support Industry, and Governance. Through the lens of climate change literature and policy frameworks, we investigate the governance dimension and industry's response to the contemporary climate challenge. The outputs of the paper include a literature review of the governance dimension, and a description of the cascading nature of climate change policy from global through to the enterprise level. We illustrate how climate change governance is enhanced in practice by detailing how the enterprises in Kwinana collectively responded to the global requirement for carbon reduction, achieved through the facilitative governance-based intervention of their industry association, the Kwinana Industries Council. Exploring this in-practice example helped to consolidate the hypothesis that successful industrial symbiosis is about positive relationships across several dimensions building towards improved Circular Economy outcomes.
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