Sewer-mining: A water reuse option supporting circular economy, public service provision and entrepreneurship.

Water scarcity, either due to increased urbanisation or climatic variability, has motivated societies to reduce pressure on water resources mainly by reducing water demand. However, this practice alone is not sufficient to guarantee the quality of life that high quality water services underpin, especially within a context of increased urbanisation. As such, the idea of water reuse has been gaining momentum for some time and has recently found a more general context within the idea of the Circular Economy. This paper is set within the context of an ongoing discussion between centralized and decentralized water reuse techniques and the investigation of trade-offs between efficiency and economic viability of reuse at different scales. Specifically, we argue for an intermediate scale of a water reuse option termed 'sewer-mining', which could be considered a reuse scheme at the neighbourhood scale. We suggest that sewer mining (a) provides a feasible alternative reuse option when the geography of the wastewater treatment plant is problematic, (b) relies on mature treatment technologies and (c) presents an opportunity for Small Medium Enterprises (SME) to be involved in the water market, securing environmental, social and economic benefits. To support this argument, we report on a pilot sewer-mining application in Athens, Greece. The pilot, integrates two subsystems: a packaged treatment unit and an information and communications technology (ICT) infrastructure. The paper reports on the pilot's overall performance and critically evaluates the potential of the sewer-mining idea to become a significant piece of the circular economy puzzle for water.

Identification of potential sewer mining locations: a Monte-Carlo based approach.

Rapid urbanization affecting demand patterns, coupled with potential water shortages due to supply side impacts of climatic changes, has led to the emergence of new technologies for water and wastewater reuse. Sewer mining (SM) is a novel decentralized option that could potentially provide non-potable water for urban uses, including for example the irrigation of urban green spaces, providing a mid-scale solution to effective wastewater reuse. SM is based on extracting wastewater from local sewers and treatment at the point of demand and entails in some cases the return of treatment residuals back to the sewer system. Several challenges are currently in the way of such applications in Europe, including public perception, inadequate regulatory frameworks and engineering issues. In this paper we consider some of these engineering challenges, looking at the sewer network as a system where multiple physical, biological and chemical processes take place. We argue that prior to implementing SM, the dynamics of the sewer system should be investigated in order to identify optimum ways of deploying SM without endangering the reliability of the system. Specifically, both wastewater extraction and sludge return could result in altering the biochemical process of the network, thus unintentionally leading to degradation of the sewer infrastructure. We propose a novel Monte-Carlo based method that takes into account both spatial properties and water demand characteristics of a given area of SM deployment while simultaneously accounting for the variability of sewer network dynamics in order to identify potential locations for SM implementation. The outcomes of this study suggest that the method can provide rational results and useful guidelines for upscale SM technologies at a city level.

Reducing surface water pollution through the assessment of the cost-effectiveness of BMPs at different spatial scales.

Two kinds of agricultural Best Management Practices (BMPs) were examined with respect to cost-effectiveness (CE) in reducing sediment, nitrates-nitrogen (NO(3)-N) and total phosphorus (TP) losses to surface waters of the Arachtos catchment in Western Greece. The establishment of filter strips at the edge of fields and a non-structural measure, namely fertilization reduction in alfalfa, combined with contour farming and zero-tillage in corn and reduction of animal numbers in pastureland, were evaluated. The Soil and Water Assessment Tool (SWAT) model was used as the non-point-source (NPS) estimator, while a simple economic component was developed estimating BMP implementation cost as the mean annual expenses needed to undertake and operate the practice for a 5-year period. After each BMP implementation, the ratio of their CE in reducing pollution was calculated for each Hydrologic Response Unit (HRU) separately, for each agricultural land use type entirely and for the whole catchment. The results at the HRU scale are presented comprehensively on a map, demonstrating the spatial differentiation of CE ratios across the catchment that enhances the identification of locations where each BMP is most advisable for implementation. Based on the analysis, a catchment management solution of affordable total cost would include the expensive measure of filter strips in corn and only in a small number of pastureland fields, in combination with the profitable measure of reducing fertilization to alfalfa fields. When examined for its impact on river loads at the outlet, the latter measure led to a 20 tn or 8% annual decrease of TP from the baseline with savings of 15€/kg of pollutant reduction. Filter strips in corn fields reduced annual sediments by 66 Ktn or 5%, NO(3)-N by 71 tn or 9.5% and TP by 27 tn or 10%, with an additional cost of 3.1 €/tn, 3.3 €/kg and 8.1 €/kg of each pollutant respectively. The study concludes that considerable reductions of several pollutant types at the same time can be achieved, even at low total cost, by combining targeted BMP implementation strategies only in small parts of the catchment, also enabling policy makers to take local socio-economic constraints into consideration. The methodology and the results presented aim to facilitate decision making for a cost-effective management of diffuse pollution by enabling modelers and researchers to make rapid and reliable BMP cost estimations and thus being able to calculate their CE at the local level in order to identify the most suitable areas for their implementation.

Impacts of residence time during storage on potential of water saving for grey water recycling system.

Grey water recycling has been generally accepted and is about to move into practice in terms of sustainable development. Previous research has revealed the bacteria re-growth in grey water and reclaimed municipal water during storage. However, in most present grey water recycling practices, impacts of water quality changes during storage on the system's performance and design regulation have not been addressed. In this paper, performance of a constructed wetland based grey water recycling system was analysed by taking the constraint of residence time during storage into account using an object based household water cycle model. Two indicators, water saving efficiency (WSE) and residence time index (RTI), are employed to reflect the system's performance and residence time during storage respectively. Results show that WSE and RTI change with storage tank volumes oppositely. As both high WSE and RTI cannot be achieved simultaneously, it is concluded that in order to achieve the most cost-effective and safe solution, systems with both small grey and green tanks are needed, whilst accepting that only relatively modest water saving efficiency targets can be achieved. Higher efficiencies will only be practicable if water quality deterioration in the green water tank can be prevented by some means (e.g. disinfection).

Portable biomedical devices: a critical issue during telecare services design.

OBJECTIVES: The selection of a portable biomedical device (PBD) is a key issue regarding telecare service design. The objective of this study is to investigate the accuracy parameters of a PBD under different settings and levels. METHODS AND MATERIALS: By using a commercial PBD, trials were performed in a referral cardiology center and on the Olympia Explorer of the Royal Olympia Cruises, and the Superfast XII of Superfast Ferries. Data were collected (February 2004 - June 2006) by performing: (1) 'in hospital' standalone trials; (2) 'in hospital' comparative trials; and (3) 'on board' trials. Semistructured interviews were also conducted with several subjects, their cardiologists and crewmembers. RESULTS: We investigated the accuracy parameters, namely the data precision (DP), the peripheral modules reliability (PMR) and the data transmission quality (DTQ). Although the outcomes of the comparative trials, via a statistical method verifying the DP (more than 95%), the trials 'on board' and 'in hospital' revealed a number of critical variables for the PMR and DTQ parameters. CONCLUSION: Telecare services design has accuracy parameter investigation needs. These parameters should be investigated simultaneously, while a compromise between them can act as a driving force to the telecare services success. The compromise is achieved by a smooth fit between DP and PMR with this fit varying within settings and levels.

A performance investigation of small-bore sewers.

This paper describes a full-scale physical model and its application to investigate the effectiveness/performance of small-bore sewers for a range of operational and design parameters. The implementation methodology involves observing the movement of synthetic gross solids in three small bore sewers (150, 100 and 75 mm diameter) for different volumes of simulated flush waves and gradients. The simulated flush waves were generated, using an automated wave sequencer, for three different flush volumes (3, 4.5 and 6 litres). To investigate the impact of solid shape factor, a number of tests were carried out using synthetic solids in combination with toilet tissue paper. In total, more than 1,000 tests were performed for different operational and design parameter combinations. Results obtained to date have confirmed earlier studies, particularly with respect to the role of flush volume in solids transport, and identified the impact of gradient variation and its significance particularly in small-bore sewers receiving low flush volume. Results from the physical model application exercise will be used to propose new design guidelines for wastewater collection systems with specific consideration to new developments and inform the decision support system, currently being developed as part of a research project on water cycle management for new developments (WaND).

Life cycle impact assessment of greywater recycling technologies for new developments.

This paper presents the life cycle impact assessment (LCIA) of four treatment technologies currently under investigation for recycling the greywater generated from households and describes the development of a new LCIA tool set produced in this study. The technologies investigated include reed beds, membrane bioreactors (MBR); membrane chemical reactors (MCR) and an innovative green roof water recycling system (GROW). The materials and energy required for the construction and operation phases of these technologies have been quantified for 20 development scales. All of the information gathered is used to prepare life cycle inventories for each technology. The inventories have been used as an input to Simapro Software for performing LCIA. Two assessment methods (CML-2 and Eco-indc-99) have been employed. For the CML method, the results were processed to express the environmental performance in ten impact categories including climate change/global warming, depletion of abiotic resources, acidification, eutrophication, and human toxicity. For the Eco-indc-99 method, results are shown in three generic environmental indicators: human health, eco system and natural resources. LCIA results obtained for 20 development scales have been used to develop a tool set using adaptive neuro-fuzzy inference system technique. The study results indicate that the technologies based on natural treatment processes (GROW and reed beds) have low environmental impact.

A decision support framework for sustainable urban water planning and management in new urban areas.

The paper discusses issues of decision support within the context of sustainable development and more specifically sustainable water cycle management to provide a context and a rationale for the decision support approach adopted within an on-going U.K. EPSRC-funded project, WaND. The paper proposes a set-up for a flexible, upgradeable, efficient and modular decision support framework and associated tools. Furthermore, the paper presents early prototypes of three decision support tools developed within the proposed framework including initial results for one of them.

Diffuse sources of heavy metals entering an urban wastewater catchment.

New legislation such as the Water Framework Directive (WFD) will require Member States to better understand the concentrations and loads of contaminants entering surface waters. This will include inputs from wastewater treatment plants (WWTP) as well as from other urban, industrial and agricultural sources. A review of available literature revealed a shortage of data on the levels and sources of heavy metals entering WWTP from urban sources. As a consequence, the concentrations of heavy metals (cadmium, chromium, copper, mercury, nickel, lead and zinc) were determined in the wastewater from an urban catchment located in the UK, as part of a project undertaken for UK Water Industry Research (UKWIR). Both foul and surface water samples were taken. Metal concentrations varied considerably in the foul water samples, both between sources and over the course of the week. Concentrations of most metals were higher in the Monday town centre samples, attributed to leaching from stagnant water remaining in the pipework of office buildings over the weekend. Runoff concentrations were higher in the light industrial estate samples than in the domestic samples for all the metals, and exhibited highest levels in the 'first flush' samples, coincident with the initial flow of runoff containing the highest concentrations of suspended solids.

Sources of priority substances entering an urban wastewater catchment--trace organic chemicals.

The implementation of new legislation such as the Water Framework Directive (WFD) requires Member States to gain a better understanding of priority substances entering surface waters. This will include inputs from wastewater treatment works as well as from other urban, industrial and agricultural sources. There is currently a lack of available data regarding the magnitude and sources of organic priority substances entering treatment works. As a consequence the concentrations of organic priority substances including PAHs, surfactants, polybrominated diphenylethers (PBDEs), diethylhexyl phthalate (DEHP), pesticides and solvents were determined in the wastewater from an urban catchment located in the UK, as part of a project undertaken for UK Water Industry Research (UKWIR). Most organic priority substances were detected in the microg/l range. Significant variations in the concentration of linear alkylbenzene sulphonate (LAS), DEHP, PBDEs and nonylphenol ethoxylates (NPEOs), in particular, were observed for the different sources. The greatest differences were evident between new and older domestic discharges. Solvent levels varied considerably reflecting use and production within the catchment. Chloroform levels were highest in domestic effluent, while trichloroethene and tetrachloroethene were detected only in commercial samples.

Integrating river basin management and the coastal zone: the (blue) Danube and the (black) sea.

In order to effectively manage the wide variety of physical, chemical biological and ecological processes in a sensitive coastal environment such as the Black Sea, current environmental management objectives are no longer sufficient: a new management approach has to address the intimate functional linkage between the river basin and the costal environment. Current water quality legislation requires compliance to emission levels based on the chemical analysis of water samples taken at discharge points, such as treatment plants discharging into rivers. While such measures provide a relative indication of the water quality at the point of discharge, they fail to describe accurately and sufficiently the quality of the water received from the watershed or basin. As water flows through the catchment, rainfall run-off from urban and agricultural areas carries sediments, pesticides, and other chemicals into river systems, which lead to coastal waters. The impact of the Kosovo crisis on the Danube ecosystems provides a poignant example of the effects of such diffused pollution mechanisms and reveals a number of interesting pollution mechanisms. This paper discusses both the effects of diffused pollution on the Black Sea, drawing from state-of-the-art reports on the Danube, and proposes a framework for a decision support system based on distributed hydrological and pollution transport simulation models and GIS. The use of ecological health indicators and fuzzy inference supporting decisions on regional planning within this framework is also advocated. It is also argued that even the recently produced GEF document on Black Sea protection scenarios should benefit significantly if the concept of pollution reduction from both urban, industrial and rural areas should undergo a systematic conceptual update in the view of the recent recommendations of the UNEP IETC (2000) document.

Co-operative health information networks in Europe: experiences from Greece and Scotland.

BACKGROUND: Internet technology is transforming the general approach to communication and dissemination of information in the field of healthcare. However, it is also creating problems in terms of finding information, and knowing what credibility to place on the information found. The chaotic nature of the World Wide Web (WWW) and the simplistic approach adopted by search engines can make the task of finding relevant information difficult, and the user can waste considerable amounts of time on the process. Even when information is found, there is no general quality assurance process that can guarantee the credibility of the resulting information. OBJECTIVE: The aim of this research was to develop an approach for establishing co-operative health information networks (CHINs) with different focuses, which can be used in different parts of Europe. The resulting CHINs would provide organised healthcare information and support comprehensive and integrated sets of healthcare telematic services for a broad range of users. Such developments would reduce the difficulties of finding information and knowing what credibility to ascribe to it. METHODS: A common approach has been developed based on drawing together contributions from the major healthcare service providers in the region. Standard structures are recommended so that information is presented in a uniform way. Appropriate mechanisms ensure adequate security and a level of quality assurance for the end user. RESULTS: Since 1996, CHINs have been developed in six European countries as part of a European Union (EU) project. This paper presents the overall approach adopted, and the achievements in two different regions of Europe (Greece and Scotland). Although the circumstances in these two regions are very different, in both cases the resulting CHIN has proved successful. CONCLUSIONS: CHINs offer a solution to the difficulty of finding relevant health information on the Internet and guaranteeing its credibility. They can be used in different ways in different regions, and have major benefits for both information providers and end users.