Evaluation of water stress of selected cases from water re-use or saving scenario s tested in SP5

Transcription

1 The project for sustainable water use in chemical, paper, textile and food industries Evaluation of water stress of selected cases from water re-use or saving Jean-Baptist Bayart - Veolia April 2012 AquaFit4Use is caquafit4use is co-financed by the European Union s 7 th Framework Programme

2 Executive summary This report is a result of the project AquaFit4Use, a large-scale European research project co-financed by the 7 th framework programme of the European Union on water treatment technologies and processes. Aquafit4Use project aims at developing and implementing new, reliable, cost-effective technologies, tools and methods for water supply, use and discharge in the main water consuming industries in order to significantly reduce water use. One of the objectives of these developments is the mitigation of environmental impacts. To achieve the sustainability objective of this project, it is essential to check whether new technologies and reuse options allows reducing environmental impacts of industrial water treatment. This study aims at assessing environmental impacts of water treatment solutions. Two levels of scales are investigated. First, the effect of water treatment processes on the actual toxicity of effluent is evaluated with the Whole Effluent Assessment (WEA) methodology. Then, a more holistic and macro scale assessment is performed in order to compare the water treatment options planned in different factories (considering different environmental impacts: water pollution but also carbon footprint or impact on human health, considering the whole life cycle of water treatment processes). Methodologies used for this macro-scale assessment are Life Cycle Assessment (LCA) and water footprint. Regarding effluents toxicity assessment, the substance-by-substance approach presents shortcomings (limited number of substances analyzed, combined effects of substances not considered, etc.). For this reason, WEA is recognized as the most accurate approach for effluent toxicity assessment. WEA is applied to three case studies: chemistry (Pertsorp), textile (Tekstina) and paper (Hamburger Rieger). In all three sectors, WEA shows that the evaluated treatment sequences typically resulted in a reduction in overall toxicity. In the chemical sector, the total toxicity of the conventional activated sludge effluent sample is already quite low and it is thus difficult to quantify toxicity reduction in comparison with other tested technologies in the treatment train. In the textile sector, particularly the MBR treatment results in a strong toxicity reduction, while AOP treatment has an opposite effect. Contrary to the results for the textile sector, anaerobic treatment has a major positive effect on wastewater toxicity in the paper sector. LCA and water footprint are applied to three case studies: food (CHS), textile (Tekstina) and paper (Hamburger Rieger). Results show that implementation of reuse generally leads to a reduction of the water footprint, but on the other hand to an increase of other environmental impacts (carbon footprint, impacts on human health, etc.) because of additional energy and chemicals consumption and sludge production. In order to mitigate environmental impacts of water treatment processes, it would be more efficient to reduce energy and chemical consumptions of processes, or to valorize sludge. Ensuring that the water finally discharged into the environment reaches an acceptable quality, is also essential regarding environmental footprint. Results also allow reminding that reducing the volume of water abstracted makes sense in areas under water stress. Generally, water reuse increases indirect water consumption due to additional energy and chemicals production. These indirect water consumptions might be located in areas facing higher water stress than the place where reuse is implemented. Finally, this study demonstrates the applicability and the usefulness of these recent environmental assessment methodologies. Both could help decision makers to better Page 2

3 understand implication of water treatment system improvements in term of environmental impacts mitigation, at a local level (through WEA) and global level (LCA and water footprint). Particularly, WEA and LCA / water footprint should be considered as complementary tools. Although WEA demonstrates the usefulness of water treatment solutions for toxicity reduction, it is essential to consider these water treatment solutions improvements in a broader context of environmental impacts through LCA. On the other hand, LCA and water footprint present clear limitations for effluent toxicity assessment that could be addressed through WEA. Links between these tools should be investigated in the future. Page 3

4 Content EXECUTIVE SUMMARY INTRODUCTION METHODS ACTUAL TOXICITY EVALUATION: WHOLE EFFLUENT ASSESSMENT MACRO SCALE: LIFE CYCLE ASSESSMENT AND WATER FOOTPRINT RESULTS AND ACHIEVEMENTS: WHOLE EFFLUENT ASSESSMENT CHEMICAL SECTOR: PERSTORP CASE STUDY TEXTILE SECTOR: TEKSTINA CASE STUDY PAPER SECTOR: HAMBURGER RIEGER CASE STUDY LIMITATIONS RESULTS AND ACHIEVEMENTS: LIFE CYCLE ASSESSMENT AND WATER FOOTPRINT FOOD SECTOR: CHS CASE STUDY TEXTILE SECTOR: TEKSTINA CASE STUDY PAPER SECTOR: HAMBURGER RIEGER CASE STUDY LIMITATIONS GENERAL RECOMMENDATION AND OUTLOOK GENERAL RECOMMENDATIONS FOR WHOLE EFFLUENT ASSESSMENT GENERAL RECOMMENDATIONS FOR LIFE CYCLE ASSESSMENT / WATER FOOTPRINT GENERAL RECOMMENDATIONS FOR LINKING WHOLE EFFLUENT ASSESSMENT AND LCA / WATER FOOTPRINT Page 4

5 1 Introduction Aquafit4Use project aims at developing and implementing new, reliable, cost-effective technologies, tools and methods for water supply, use and discharge in the main water consuming industries to significantly reduce water use. One of the objectives of these developments is the mitigation of environmental impacts. It is therefore essential to check whether new technologies and reuse options allows reducing environmental impacts of industrial water treatment. Environmental impacts of water treatment solutions are assessed at two level of scale. First, the actual toxicity of effluents and effect of water treatment processes on this toxicity is evaluated through sampling pilot s effluent. The methodology used for toxicity assessment is Whole Effluent Assessment (WEA). WEA is applied to three case studies: chemistry (Pertsorp), textile (Tekstina) and paper (Hamburger Rieger). These assessments provide some detail results on environmental impacts of actual effluents and on effects of treatment processes on water quality. In addition, an environmental assessment is performed at macro-scale in order to compare the different water treatment options planned in different factories with a more holistic approach (considering different environmental impacts: water pollution but also carbon footprint or impact on human health ; and considering the whole life cycle of water treatment processes). Methodologies used for this macro-scale assessment are Life Cycle Assessment (LCA) and water footprint. LCA and water footprint are applied to three case studies: food (CHS), textile (Tekstina) and paper (Hamburger Rieger). 2 Methods 2.1 Actual toxicity evaluation: Whole Effluent Assessment With regard to environmental impact assessment the substance-by-substance (SbS) approach has been, and still is, a successful policy instrument. Nevertheless it is recognized in the past decade that this approach has a number of shortcomings. Results from chemicals analysis of samples of wastewater, surface water or sediments, have indicated that only a limited number of the substances that may be present in those samples can be analyzed, identified and quantified. Moreover measured concentrations of compounds in environmental samples can poorly be related to the toxic levels for organisms present in the ecosystem, which should be protected. Finally, the substance approach does not take into account the combined effects of different substances that may be present together in environmental samples, and thus integrated approaches to assess effects of mixtures are needed. An approach for WEA as applied in this project can be defined as the assessment of effluents or treated effluents by using a range of biological methods to reveal (potential) effects, based on an assessment of potential hazards (acute toxicity, chronic toxicity, genotoxicity, endocrine disruption,..). Many different tests and protocols exist within the international context of application of WEA. One could better speak about a toolbox of tests to measure these parameters: persistence, bioaccumulation and toxicity. Since the entire sample is tested, the understanding of the combined effects of all known and unknown Page 5

6 substances within effluents, especially in complex mixtures is increased. The overall assessment of toxicity in complex samples is translated into cumulative toxic units (TU), as a result of TU obtained from each of selected toxicity tests, and does allow prioritizing samples or ranking them based on overall toxic load. WEA is applied to samples taken from selected points of treatment trains, operated at pilotscale in the chemical (Perstorp), paper (Hamburger Rieger) and textile (Tekstina) sectors. The acute toxicity (short term exposure studies) is assessed for 4 organisms, representing different trophic levels in the aquatic food chain (bacteria, algae, water flea and zebrafish embryo). 2.2 Macro scale: Life Cycle Assessment and Water Footprint LCA is an ISO standardized methodology allowing assessing potential environmental impacts of products, processes or services within a holistic life-cycle approach: impacts are evaluated considering the whole life-cycle of products or processes, from raw material extraction to waste disposal. In addition, LCA is a multi-criteria analysis: a wide range of environmental impacts are investigated (e.g. carbon footprint, eutrophication, ecotoxicity, etc.). These two particularities make LCA a powerful tool to highlight (and therefore potentially avoid) the transfer of environmental impacts, from one life-cycle phase to another (e.g. transfer of water pollution from the factory to the chemicals supplier s factory) or from an impact category to another (e.g. increase of carbon footprint vs reduction of water pollution). In recent years, environmental issues pertaining to water are gaining more and more interest, on both aspects of water scarcity (or water depletion) and water quality (or water pollution).the evaluation of environmental impacts generated by human activities on water resources, or water footprint is a gaining momentum, and many methodologies have been developed or are currently under development. In addition, an ISO standard ISO Water Footprint - Principles, requirements and guidelines is in preparation. These methodologies are based on the life-cycle thinking. Since water use is the central topic of Aquafit4Use, it is relevant to pay a special attention to these impacts on water resources. A special focus on water footprint results is done in this study. LCA and water footprint have been applied to three case studies: Cons. Hijos de M. Sanchez Besarte (CHS), Tekstina (TXT) and Hamburger Rieger Trostberg (HRT). The current water treatment system is assessed as well as potential future solutions to check their relevance in term of environmental impact mitigation. Regarding water footprint, different methodologies recently developed, or currently under development have been applied. This includes the Water Impact Index methodology, a simplified water footprint metric developed by Veolia through this project. Regarding LCA, a conventionally used methodology has been applied. However, most recent developments related to impact pertaining to water have been integrated within LCA (impacts of dams, impact of groundwater use, etc.). Page 6

7 3 Results and achievements: Whole Effluent Assessment 3.1 Chemical sector: Perstorp case study For the chemical sector, an overall view of the total measured TU in the sequence of treated samples gives an indication of reduction of toxic units. Thus, treatment methods might contribute to less impact of discharges to the environment. The total toxicity in the conventional activated sludge effluent sample of the chemical plant was however not very high (6.5 TU). It was thus difficult to quantify and compare toxicity reduction. Due to interferences in some of the bioassays, it has not been possible to distinguish for differences between treatment methods, though indications of improvement of water quality appeared. Furthermore, an influent sample was not included in the analyses. 3.2 Textile sector: Tekstina case study The toxicity in the raw textile waste water was high. The treatment with the 1 st stage treatment with an anaerobic biofilter did not have a pronounced effect, while the second stage treatment with a membrane bioreactor did show for all 4 test organisms a significant reduction of toxicity. The final AOP treatment had different effects with an improvement for zebrafish embryos, no effect for bacteria, and a strong and similar increase of toxicity for algae and water flea. The cause of this increased toxicity, higher than the toxicity in the original raw waste water effluent could not be investigated in this project but resulting oxidation products, metabolites of chemicals originally present in the waste water could contribute to increased toxicity. 3.3 Paper sector: Hamburger Rieger case study Chemicals present in samples of the paper industry did cause most pronounced toxic effects to bacteria, followed by fish. The anaerobic treatment both at pilot scale and full scale resulted in the highest toxicity reduction for both species. There were few cases where exceeding boundary conditions could contribute to toxicity, but this was only for algae which anyhow showed low toxic units. The highest toxicity observed for bacteria could not be attributed to deviations of boundary conditions but likely was caused by toxic chemicals. An exception is the effluent of the softening treatment where the overall high ph could have minor toxic effects to all organisms tested. 3.4 Limitations In this project, only one sampling campaign has been performed per sector. It should thus be emphasized that the conclusions are preliminary and they should be confirmed through other and more extensive sampling campaigns. Furthermore, with respect to overall ecological impact, it should be mentioned that the methods used investigate acute toxicity. Even in these conditions, undiluted samples sometimes still contained minor amounts of toxic compounds. These low levels of chemicals released to the environment could potentially have long-term chronic effects on organisms and populations. Page 7

8 4 Results and achievements: Life Cycle Assessment and water footprint 4.1 Food sector: CHS case study Water footprint, is mainly driven by the use of water by background processes, and especially by chemicals production (urea and phosphoric acids). The production of these chemicals requires high amounts of water, potentially in area facing high water stress. The production of these chemicals is also responsible for water pollution (eutrophication). The water footprint generated by direct water use by the factory seems to be low compared to the overall water footprint. Electricity and chemicals consumption are also the main contributors to other environmental impacts (carbon footprint, human health and ecosystem quality). Among water treatment processes, wastewater treatment already in place (MBBR, rotating sieves, equalization tanks) are the main contributors to environmental impacts because of urea, phosphoric acid and electricity consumption. The alternative scenario which consists in reusing part of the water used in washing processes for equipment cleaning seems to be the best environmental solution as it allows a reduction of electricity and chemicals consumption. This study highlights that for this specific case, reducing direct water use is not the main lever for reducing the water footprint but also other environmental impacts. Reducing the quantity of chemicals consumed, choosing chemicals suppliers located in area with lower water stress and/or that are using renewable sources of energy, and that ensure a good treatment of their effluents would be more efficient solutions to reduce the environmental footprint of water treatment processes. One should pay attention to additional sludge generated by membrane filtration. Sending this sludge to landfill could have an impact. Valorization of these sludge (agronomic or through energy production) would be a solution to decrease overall environmental impacts. 4.2 Textile sector: Tekstina case study For the textile case study, the water footprint is mainly generated by direct water use. In order to reduce the water footprint, there are two main improvement levers: the reduction of the quantity of water abstracted, and the improvement of the quality of the water discharged into the environment. The implementation of water reuse through new water treatment processes could potentially allow reducing the water footprint. However, it generates transfer of environmental impacts: From an impact category to others: the reduction of water abstraction is responsible for increase of carbon footprint but also potentially water pollution, impacts on human health and on ecosystem quality. These additional impacts are mainly due to increase of electricity consumption. From a life-cycle phase to another: impacts generated by direct water abstraction are transferred to impacts of water abstraction for electricity production. Page 8

9 Therefore, the potential implementation of these solutions should be made carefully if the goal is to reduce environmental impacts. Among new water treatment processes, evapoconcentration and AOP contribute significantly to increase indirect environmental impacts as these processes are energy intensive. If reducing the amount of water abstracted from the environment is essential, the scenario which consist in a flow separation between low-medium concentration effluents (treated with MBR) and high concentration effluents (treated with evapoconcetration) could be an acceptable compromise between the reduction of water footprint and the increase of other environmental impacts. However, considering the low level of water stress in Slovenia, water saving is questionable. In order to reduce the global environmental footprint of water treatment processes, it would be more useful to select water treatment processes that are not too energy intensive. Ensure a good quality of the water treated is also essential. 4.3 Paper sector: Hamburger Rieger case study The water footprint is mainly generated by direct water use, but indirect water use for chemicals and electricity production is not negligible. The difference of water stress level between Trostberg area and other German area where indirect water use could occur explain this contribution of background processes. In order to reduce the water footprint, there are two main improvement levers: the reduction of the quantity of water abstracted, and the improvement of the quality of the water discharged into the environment. The implementation of water reuse through new water treatment processes could potentially allow reducing the water footprint. However, it generates transfer of environmental impacts: From an impact category to others: the reduction of water abstraction is responsible for increase of carbon footprint but also potentially water pollution, impacts on human health and on ecosystem quality. These additional impacts are mainly due to increase of electricity consumption and sludge management. From a life-cycle phase to another: impacts generated by direct water abstraction are transferred to impacts of water abstraction for electricity production. Again, the potential implementation of these solutions should be made carefully if the goal is to reduce environmental impacts. Among new water treatment processes, evapoconcentration contributes significantly to increase indirect environmental impacts as this process is energy intensive. If reducing the amount of water abstracted from the environment is essential, the scenario which consists in re-using wastewater from the clarifier to paper processes without addition of new wastewater treatment processes would be the best solution in order to avoid impact transfer. Page 9

10 However, considering the low level of water stress in Trostberg area, water saving is questionable. In order to reduce the global environmental footprint of water treatment processes, it would be more useful to select water treatment processes that are not too energy intensive. Ensure a good quality of the water treated is also essential. 4.4 Limitations LCA and water footprint are recent tools and methodologies and some limitations contributing to a high degree of uncertainties should be mentioned. Data obtained from the different partners might not reflect a realistic case. For CHS case study, data are obtained from process modeling and not from on-site measurements. For Tekstina and Hamburger Rieger, data come from pilot trials and might not reflect the industrial scale of processes. In addition, some data are missing as it was not possible to measure or model them. When it was possible, these data have been replaced through assumptions. For some processes, it was not possible to get data from the different partners (example: data on municipal water utilities, data on chemicals production, etc.). In that case, some assumptions have been made to model the different processes. Especially, the modeling of municipal WWTP could be enhanced. Uncertainties pertaining to LCA and water footprint methodologies are also high. It could be expressed as impact assessment in LCA aims at modeling very complex environmental mechanism in a generic way. Especially, impacts on aquatic ecotoxicity and more generally damages on Ecosystem Quality and Human Health should be interpreted carefully. Page 10

11 5 General Recommendation and outlook 5.1 General recommendations for Whole Effluent Assessment Within the budgetary constraints, only a limited number of samples could be taken and analyzed. For each sector, sampling was limited to one occasion. Broader and longer sampling campaigns would be necessary to provide conclusive results on the effectiveness of treatment steps to reduce the initial toxicity of the raw wastewater. Furthermore, WEA should ideally be supported by chemical analysis, to enable a correct explanation of observed toxicity decreases or increases. Particularly for AOP treatment, strong increases in toxicity were observed, which could not be explained. 5.2 General recommendations for Life Cycle Assessment / Water Footprint Following limitations have been pointed out regarding the application of LCA and Water Footprint to industrial water management and could be topic for further research: LCIA and Water Footprint methodologies are rather recent and should be enhanced to reduce results uncertainties. LCA databases are uncertain for the application of water footprint. These databases should be enhanced. Data obtained from pilot trials might not reflect the industrial scale of processes. Data extrapolation from pilot scale to full-scale should be investigated. The fate of industrial pollutants in municipal WWTP is not well addressed in this report and could be a topic for further research. Data obtained from models could be undertrain since models are not well calibrated. Therefore, validity of models should be checked and improved. 5.3 General recommendations for linking Whole Effluent Assessment and LCA / Water Footprint WEA and LCA/water footprint are two methodologies aiming at evaluating potential environmental impact of products or processes. However, they have different objectives. WEA aims at addressing local impacts of an effluent through its toxicity assessment whereas LCA is a more holistic approach aiming at comparing solutions through their overall environmental footprint. Nevertheless, a complementarity aspect could be identified between these two tools. Although WEA demonstrate the usefulness of water treatment solutions for toxicity reduction, it is essential to consider these water treatment solutions improvements in a broader context of environmental impacts through LCA. In addition, toxicity and ecotoxicity are environmental issues investigated in LCA and water footprint. It has been noticed that the consideration of these impacts in LCA is however week (substance by substance approach). Therefore, integrating WEA results in LCA / Water Footprint study could allow enhancing the reliability of results. Since LCA is partly based on generic data (databases) and WEA relies upon on-site experimentations, linking these methodologies is a challenge. Page 11