Port Macquarie, Australia
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Johnston S.G.,Southern Cross University of Australia | Burton E.D.,Southern Cross University of Australia | Aaso T.,Port Macquarie Hastings Council | Tuckerman G.,Great Lakes Council
Chemical Geology | Year: 2014

Freshwater re-flooding is a relatively novel approach to remediate drained acid sulfate soil (ASS) wetlands. This study documents the geochemical consequences of restoring freshwater re-flooding for contemporary reduced inorganic sulfur (RIS) and iron species in two coastal floodplain ASS wetlands. Re-flooding has established predominantly reducing/suboxic conditions and encouraged organic carbon accumulation in surface sediments (~20-30%). The pH of former sulfuric horizons has increased by ~2-3 units, partly in response to alkalinity generation from anaerobic metabolism of organic carbon coupled with Fe(III) and SO4 2- reduction. Despite considerable sulfidisation, reactive Fe (FeR; sum of 1M HCl and citrate-dithionite extracts) and non-sulfidic Fe(II) remain abundant in both wetlands. High concentrations of Fe2+ (up to ~5mM) in wetland porewaters represent a considerable pool of labile net acidity and is partly a result of insufficient S(-II) to sequester excess Fe2+. Accumulation of iron sulfides appears to be constrained more by SO4 2- and carbon availability rather than FeR. Reformation and accumulation of RIS species is greatest in organic-rich surface horizons (~40-500μmolg-1), where time integrated RIS accumulation rates approximate 10-100nmolg-1 d-1. While pyrite is the dominant RIS species to have formed since re-flooding, there is anomalous accumulation of S(0) (up to 80μmolg-1), accounting for ~50% of the RIS pool in some samples. Greigite (Fe3S4) has formed in near-surface sediments and while AVS-S is a minor component of the RIS pool overall, at some locations maximum concentrations exceed 300μmolg-1. Contemporary near-surface pyrite is characterised by abundant small (200-300nm) crystals, in contrast to relic sedimentary pyrite of estuarine origin that is dominated by larger crystals with diverse habit. Although Fe and SO4 2- reduction are partly responsible for wetland-scale recovery from acute acidification, the resultant accumulation of diverse RIS species in surficial sediments indicates an oxidative component to the S-cycle and represents a hysteresis in S-cycling that contrasts markedly with the drained conditions existing before remediation. Analysis of seasonal climate fluctuations suggests that near-surface sediments containing contemporary RIS are vulnerable to oxidation and possible temporary re-acidification during future drought episodes. This study underscores the long-term legacy of ASS wetland drainage and highlights the need for both considered hydrological management of re-flooded wetlands and further study to quantify possible re-acidification risks associated with seasonal drought. © 2014 Elsevier B.V.


Johnston S.G.,Southern Cross University of Australia | Burton E.D.,Southern Cross University of Australia | Hagan R.,Southern Cross University of Australia | Aaso T.,Port Macquarie Hastings Council | Tuckerman G.,Great Lakes Council
Applied Geochemistry | Year: 2015

Titratable actual acidity (TAA) is a technique commonly used to estimate the existing pool of exchangeable H+ in acid sulfate soils (ASS). A widely adopted version of the TAA method involves titrating a 1M KCl suspension of oven-dry soil (1:40) with NaOH to a known pH endpoint. However, when ASS are subject to long term re-flooding during wetland remediation, former sulfuric horizons can develop substantial quantities of porewater Fe2+, non-sulfidic solid-phase Fe(II) and a variety of reduced inorganic sulfur (RIS) species (e.g. pyrite, mackinawite, greigite and elemental sulfur). For these sediments, an oven-drying approach may induce oxidation of the abundant Fe(II) and/or reactive RIS species, thereby generating H+ and leading to overestimation of existing in situ exchangeable H+. In this study, we compare TAA via the standard approach (1M KCl; 1:40; oven-dry soil, 4 hr extract; TAAD) with an identical O2-free extraction approach using wet-sediment (TAAW). We apply both methods to former sulfuric horizon sediments from freshwater re-flooded ASS wetlands. There are significant (α=0.01) differences (up to 12×) between TAA measured by the two methods, with the oven-dried standard approach overestimating TAA relative to the wet, O2-free approach in 85% of cases. Despite the fact that all AVS-S and some S(0) was oxidised during the oven-drying process, the increases in TAA (TAAD-TAAW) show very weak correlation(s) with corresponding losses in RIS species or increases in water soluble sulfate and KCl extractable sulfate. However, oven-drying caused substantial loss of 1M KCl exchangeable Fe(II) and 1M HCl-extractable Fe(II) and led to large increases in 1M HCl-extractable Fe(III). These changes in Fe fractions displayed strong positive linear correlation (α=0.01) with increases in TAA. Although this is not evidence of causality, it suggests that oxidation of Fe(II) species are playing an important role in the development of additional exchangeable H+ and may be largely responsible for the contrasting TAA derived by the two methods. The differences in TAA between the two methods are greatest in organic-rich surface sediments and are significantly positively correlated with total organic carbon content. These findings have major implications for accurately assessing TAA in re-flooded ASS wetlands. © 2014 Elsevier Ltd.


Chen Z.,University of Technology, Sydney | Ngo H.H.,University of Technology, Sydney | Guo W.,University of Technology, Sydney | Pham T.T.N.,University of Technology, Sydney | And 6 more authors.
Science of the Total Environment | Year: 2014

With a constantly growing population, water scarcity becomes the limiting factor for further social and economic growth. To achieve a partial reduction in current freshwater demands and lessen the environmental loadings, an increasing trend in the water market tends to adopt recycled water for household laundries as a new recycled water application. The installation of a small pre-treatment unit for water purification can not only further improve the recycled water quality, but also be viable to enhance the public confidence and acceptance level on recycled water consumption. Specifically, this paper describes column experiments conducted using a 550. mm length bed of zeolite media as a one-dimensional flow reactor. The results show that the zeolite filter system could be a simple low-cost pre-treatment option which is able to significantly reduce the total hardness level of recycled water via effective ion exchange. Additionally, depending on the quality of recycled water required by end users, a new by-pass controller using a three-level operation switching mechanism is introduced. This approach provides householders sufficient flexibility to respond to different levels of desired recycled water quality and increase the reliability of long-term system operation. These findings could be beneficial to the smooth implementation of new end uses and expansion of the potential recycled water market. The information could also offer sound suggestions for future research on sustainable water management and governance. © 2014 Elsevier B.V.


Mainali B.,University of Technology, Sydney | Pham T.T.N.,University of Technology, Sydney | Ngo H.H.,University of Technology, Sydney | Guo W.,University of Technology, Sydney | And 4 more authors.
Science of the Total Environment | Year: 2013

This study investigates the community perception of household laundry as a new end use of recycled water in three different locations of Australia through a face to face questionnaire survey (n=478). The study areas were selected based on three categories of (1) non-user, (2) perspective user and (3) current user of recycled water. The survey results indicate that significantly higher number (70%) of the respondents supported the use of recycled water for washing machines (χ2=527.40, df=3; p=0.000). Significant positive correlation between the overall support for the new end use and the willingness of the respondents to use recycled water for washing machine was observed among all users groups (r=0.43, p=0.000). However, they had major concerns regarding the effects of recycled water on the aesthetic appearance of cloth, cloth durability, machine durability, odour of the recycled water and cost along with the health issues. The perspective user group had comparatively more reservations and concerns about the effects of recycled water on washing machines than the non-users and the current users (χ2=52.73, df=6; p=0.000). Overall, community from all three study areas are willing to welcome this new end use as long as all their major concerns are addressed and safety is assured. © 2013 Elsevier B.V.


Mainali B.,University of Technology, Sydney | Pham T.T.N.,University of Technology, Sydney | Ngo H.H.,University of Technology, Sydney | Guo W.,University of Technology, Sydney | And 5 more authors.
Science of the Total Environment | Year: 2014

Laundry is a potential new end use of recycled water in dual reticulation systems. Generally, the community is willing to accept this new end use if it can meet the concerns on health issues, durability of washing machine, cloth quality and aesthetic appearance. This study addresses all these major concerns thereby assisting in the introduction and promotion of this new end use in the existing and proposed dual reticulation systems. Five representative cloth materials were selected for washing in tap water and in recycled water for up to 50 wash cycles for comparative studies. The tearing/tensile strength tests were used for the assessment of cloth durability. ANOVA one way test was applied for the significance analysis (Tukey's test p. <. 0.05) which indicated that there is no significant change in the tensile/tearing strengths of washed cloth samples. Scanning electron microscope (SEM) images of the washed cloth samples found no distinct change in surface morphology. Textile colour analysis (CIEDE2000) analysed the variation in colour of the washed cloth samples and showed that the change in colour {increment}E ranges from 0-1 revealing no visible difference in colour of cloth samples. Langelier Saturation Index (LSI) was used as the indicator for predicting corrosive/scaling potential of recycled water. The LSI values ranged from +. 0.5 to - 0.5, indicating no corrosive or scaling potential of recycled water. The microbiological study of the cloth samples washed in recycled water indicated that there was no contamination with representative bacteria. As the recycled water has similar effects like tap water on cloth and washing machine, it is safe to use for laundry. © 2013 Elsevier B.V.


Chen Z.,University of Technology, Sydney | Ngo H.H.,University of Technology, Sydney | Guo W.S.,University of Technology, Sydney | Listowski A.,Sydney Olympic Park Authority | And 3 more authors.
Science of the Total Environment | Year: 2012

This paper aims to put forward several management alternatives regarding the application of recycled water for household laundry in Sydney. Based on different recycled water treatment techniques such as microfiltration (MF), granular activated carbon (GAC) or reverse osmosis (RO), and types of washing machines (WMs), five alternatives were proposed as follows: (1) do nothing scenario; (2) MF. +. existing WMs; (3) MF. +. new WMs; (4) MF-GAC. +. existing WMs; and (5) MF-RO. +. existing WMs. Accordingly, a comprehensive quantitative assessment on the trade-off among a variety of issues (e.g., engineering feasibility, initial cost, energy consumption, supply flexibility and water savings) was performed over the alternatives. This was achieved by a computer-based multi-criteria analysis (MCA) using the rank order weight generation together with preference ranking organization method for enrichment evaluation (PROMETHEE) outranking techniques. Particularly, the generated 10,000 combinations of weights via Monte Carlo simulation were able to significantly reduce the man-made errors of single fixed set of weights because of its objectivity and high efficiency. To illustrate the methodology, a case study on Rouse Hill Development Area (RHDA), Sydney, Australia was carried out afterwards. The study was concluded by highlighting the feasibility of using highly treated recycled water for existing and new washing machines. This could provide a powerful guidance for sustainable water reuse management in the long term. However, more detailed field trials and investigations are still needed to effectively understand, predict and manage the impact of selected recycled water for new end use alternatives. © 2012 Elsevier B.V.


Chen Z.,University of Technology, Sydney | Ngo H.H.,University of Technology, Sydney | Guo W.,University of Technology, Sydney | Lim R.,University of Technology, Sydney | And 5 more authors.
Science of the Total Environment | Year: 2014

Nowadays, recycled water has provided sufficient flexibility to satisfy short-term freshwater needs and increase the reliability of long-term water supplies in many water scarce areas, which becomes an essential component of integrated water resources management. However, the current applications of recycled water are still quite limited that are mainly associated with non-potable purposes such as irrigation, industrial uses, toilet flushing and car washing. There is a large potential to exploit and develop new end uses of recycled water in both urban and rural areas. This can greatly contribute to freshwater savings, wastewater reduction and water sustainability. Consequently, the paper identified the potentials for the development of three recycled water new end uses, household laundry, livestock feeding and servicing, and swimming pool, in future water use market. To validate the strengths of these new applications, a conceptual decision analytic framework was proposed. This can be able to facilitate the optional management strategy selection process and thereafter provide guidance on the future end use studies within a larger context of the community, processes, and models in decision-making. Moreover, as complex evaluation criteria were selected and taken into account to narrow down the multiple management alternatives, the methodology can successfully add transparency, objectivity and comprehensiveness to the assessment. Meanwhile, the proposed approach could also allow flexibility to adapt to particular circumstances of each case under study. © 2013 Elsevier B.V.


PubMed | City West Water, University of Technology, Sydney, Sydney Olympic Park Authority, Port Macquarie Hastings Council and 2 more.
Type: | Journal: The Science of the total environment | Year: 2014

With a constantly growing population, water scarcity becomes the limiting factor for further social and economic growth. To achieve a partial reduction in current freshwater demands and lessen the environmental loadings, an increasing trend in the water market tends to adopt recycled water for household laundries as a new recycled water application. The installation of a small pre-treatment unit for water purification can not only further improve the recycled water quality, but also be viable to enhance the public confidence and acceptance level on recycled water consumption. Specifically, this paper describes column experiments conducted using a 550 mm length bed of zeolite media as a one-dimensional flow reactor. The results show that the zeolite filter system could be a simple low-cost pre-treatment option which is able to significantly reduce the total hardness level of recycled water via effective ion exchange. Additionally, depending on the quality of recycled water required by end users, a new by-pass controller using a three-level operation switching mechanism is introduced. This approach provides householders sufficient flexibility to respond to different levels of desired recycled water quality and increase the reliability of long-term system operation. These findings could be beneficial to the smooth implementation of new end uses and expansion of the potential recycled water market. The information could also offer sound suggestions for future research on sustainable water management and governance.


PubMed | City West Water, University of Technology, Sydney, Sydney Olympic Park Authority, Port Macquarie Hastings Council and 2 more.
Type: | Journal: The Science of the total environment | Year: 2014

Nowadays, recycled water has provided sufficient flexibility to satisfy short-term freshwater needs and increase the reliability of long-term water supplies in many water scarce areas, which becomes an essential component of integrated water resources management. However, the current applications of recycled water are still quite limited that are mainly associated with non-potable purposes such as irrigation, industrial uses, toilet flushing and car washing. There is a large potential to exploit and develop new end uses of recycled water in both urban and rural areas. This can greatly contribute to freshwater savings, wastewater reduction and water sustainability. Consequently, the paper identified the potentials for the development of three recycled water new end uses, household laundry, livestock feeding and servicing, and swimming pool, in future water use market. To validate the strengths of these new applications, a conceptual decision analytic framework was proposed. This can be able to facilitate the optional management strategy selection process and thereafter provide guidance on the future end use studies within a larger context of the community, processes, and models in decision-making. Moreover, as complex evaluation criteria were selected and taken into account to narrow down the multiple management alternatives, the methodology can successfully add transparency, objectivity and comprehensiveness to the assessment. Meanwhile, the proposed approach could also allow flexibility to adapt to particular circumstances of each case under study.


PubMed | City West Water, Gold Coast Mail Center, University of Technology, Sydney, Sydney Olympic Park Authority and Port Macquarie Hastings Council
Type: | Journal: The Science of the total environment | Year: 2014

Laundry is a potential new end use of recycled water in dual reticulation systems. Generally, the community is willing to accept this new end use if it can meet the concerns on health issues, durability of washing machine, cloth quality and aesthetic appearance. This study addresses all these major concerns thereby assisting in the introduction and promotion of this new end use in the existing and proposed dual reticulation systems. Five representative cloth materials were selected for washing in tap water and in recycled water for up to 50 wash cycles for comparative studies. The tearing/tensile strength tests were used for the assessment of cloth durability. ANOVA one way test was applied for the significance analysis (Tukeys test p<0.05) which indicated that there is no significant change in the tensile/tearing strengths of washed cloth samples. Scanning electron microscope (SEM) images of the washed cloth samples found no distinct change in surface morphology. Textile colour analysis (CIEDE2000) analysed the variation in colour of the washed cloth samples and showed that the change in colour E ranges from 0-1 revealing no visible difference in colour of cloth samples. Langelier Saturation Index (LSI) was used as the indicator for predicting corrosive/scaling potential of recycled water. The LSI values ranged from +0.5 to -0.5, indicating no corrosive or scaling potential of recycled water. The microbiological study of the cloth samples washed in recycled water indicated that there was no contamination with representative bacteria. As the recycled water has similar effects like tap water on cloth and washing machine, it is safe to use for laundry.

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