Water Treatment Handbook

Abstract

EXECUTIVE SUMMARY Water is an essential need, a limited and scarce resource that must be protected. Water reuse and desalination are nowadays the most outstanding solutions to increase water resources availability. However, as long as desalination is not a sustainable option, wastewater treatment and reuse is the most sustainable solution for the used water. In this sense, the full implementation of the Urban Waste Water Treatment Directive (91/271/EEC) in Europe will contribute to obtain treated wastewaters of quite high quality that could be reused for certain uses or improved by polishing steps for applications with higher quality requirements. Moreover, Article 12 of this Directive mentions that treated water shall be re-used whenever appropriate. Nevertheless, regardless the extensive application of reclaimed water for irrigation, the potential for water re-use and recycling has not yet been exploited in many European areas. A decisive factor to achieve a higher percentage of water re-use is the establishment of effective incentives, which in many instances will be of either an economic or a regulatory nature. One fundamental advantage of water re-use is the fact that in many cases the resource employed is available in the vicinity of its prospective new use, i.e. urban agglomerations and industrial sites. The limiting factor for water re-use can in many circumstances be the quality of the water available linked to the treatment processes (technology) and potential hazards for secondary users. To examine the economic viability of water re-use a careful cost- benefit analysis for the various parties involved needs to be carried out. Even though water reuse is currently implemented in many countries, different water reuse projects did not succeed due to the absence of a Integrated Water Resources Management Plan. Likewise, feasibility studies can contribute to succeed in the implementation of a water reuse project. A feasibility study is defined as an evaluation or analysis of the potential impact of a proposed project or program, covering extensive data related to its financial and operational impact, including its advantages and disadvantages and its comparison with the existing situation and scheduling the proposed plan. Taking into account all these considerations, in the framework of the AQUAREC (Integrated Concepts for Reuse of Upgraded Wastewater) European Project these Guidelines on feasibility studies for water reuse systems have been prepared with the purpose of developing a useful methodology to assist the different stakeholders (administration, engineering companies, water management bodies, etc.) involved in the planning of a water reuse programme in a specific area. A thorough feasibility study should be tackled from a multidisciplinary approach considering many different aspects such as geological, technical, economical, environmental, sociological, and quality and risks issues. All of them can condition the final decision and success of a Handbook on feasibility studies for water reuse systems water reuse project. Consequently, the consideration of them all is recommended to reach a reliable decision when facing water reuse practices. Accordingly, within AQUAREC methodology the different aspects and their assessment tools are addressed. Considering the great number of issues to be addressed and the aim of this handbook of being a practical, easy to read and understand as well as brief document, only the key points and basic information considered in each section and some relevant links supporting the information supplied are described. This handbook strictly follows a pre-defined structure to perform a feasibility study on water reuse, as described in Chapter 2, and its subsequent chapters further develop its major features. As most publications, a feasibility study starts with an executive summary where the existing situation, scope of the project and major findings are described. Next, a full and extensive compilation and review of the background information and data related to the studied zone is needed. Accordingly, Chapter 3 summarises the methodology to achieve this, comprising data analysis on the main characteristics of the tackled zone such as geography and topography or climate, water balance of the region, characteristics of water supply and sanitation, planning and identification of reclaimed water potential users, etc. In parallel, according to the wastewater composition and reclaimed water quality for specific uses different technological alternatives are feasible. Therefore, in Chapter 4 the methodology for the proposed technology options evaluation is presented including a brief description of the system, its advantages and disadvantages, equipment and land requirements as well as costs, basic system layout and site possibilities. Regarding this topic, the risk analysis, foreseen treated water quality and technological considerations (main treatment trains, technological advances, etc.) should be analysed too. Moreover, the accomplishment of an environmental impact assessment of those proposed solutions compared to the situation at present is a compulsory requirement to fulfil when implementing any water reuse project. In view of that, in Chapter 5 an Environmental Impact Assessment Multiple-Level (EIAML) approach and its multidisciplinary application for water reuse feasibility studies is addressed. This systematic analysis, covering social, cultural, economic and ecological constraints, supports ecologically sustainable water management using the best practicable techniques of decision-making processes addressed to the environmental effects of a water reuse project. Basic strengths of the EIA procedures are proposed by reflecting both the application of the procedures laid down by the current legislation and the potential application of best practices by individual Member States that could be adopted in their own guidance on screening, scoping, reviewing and performing cumulative impact assessment. The main supportive procedures and tools for developing Decission Support Systems (DSS) and determination of all EIA components in the feasibility and operational phases of the water reuse project are analysed and include: 1. Hazard Analysis and Critical Control Points - HACCP system, with an analysis and definition of major requirements of a water reuse programme and environmental values to be protected; 2. Driving Force – Pressure – State – Impact –Response - DPSIR system, focusing on the formal optimisation of the relationships between various sectors of human activity and the environment as causal chains; 3. Strategic Environmental Appraisal - SEA supportive framework, aiming at making explicit the cause-effect relationships between interacting components of complex social, economic and environmental systems and at organising the effective information flow between its parts. Likewise, the impact of the implementation of the proposed solutions on population, industry, agriculture, etc. needs be analysed too. In this sense, Chapter 6 defines main social, environmental and economical key indicators to be considered in the formulation of water reuse feasibility studies and describes their assessment methodologies. Additionally, public acceptance to water reuse and a public participatory plan are two other important issues also covered in this chapter. The latter is needed to confirm the public acceptance of the considered water reuse project and, consequently, the approval of the final users and consumers of reclaimed water. In this sense, several water reuse projects have not succeeded due to the over-estimation of the potential users of the obtained water. According to this general feasibility study methodology structure, once the proposed systems evaluation is performed, covered by Chapters 4-6 in these guidelines, the proposals should be faced with the existing system for comparison. Hence, Chapter 7 briefs different assessment methodologies and computer network modelling analysis approaches. In fact, probable costs (cost of reclaimed water reuse, price of reclaimed water…) and cost-effectiveness analysis of the different proposed options must be conducted. Most of the existing methodologies for economical assessment only consider internal costs, but external impacts (environmental and social) and the opportunity cost derived from the proposed project have to be taken into consideration too. A financial analysis might also be conducted. Last but not least, the different funding sources in Europe for this type of projects are also summarised, as funding and management of a water reuse system are key elements for its feasible implementation. Without a workable funding and management component, any capital development program obviously remains only a plan. This thorough analysis will help to choose the most suitable alternative, so the last sections in a feasibility analysis performance refer to the main conclusions of the whole feasibility study, the proposed recommendations, the foreseen schedule for the implementation plan - including the possible demonstration projects - and other issues such as needed agreements, contracts and responsibilities of the different involved parts or even references. All these aspects are framed within Chapter 8 of this handbook. To finish, attached to the main report different annexes with useful data and supporting information are included. Annex I deals with general information on data collection, Annex II widens information on wastewater treatment technologies and Annex III presents and describes the key indicators (social, environmental and economical) developed for supporting water reuse feasibility studies. Beyond these guidelines, further interesting and complementary information on water reuse is available at the AQUAREC web site (www.aquarec.org) including different case studies on feasibility studies on water reuse, guidelines on stakeholder engagement, education and surveys, a manual on management of water reuse systems in the implementation /operation phase, a design support software for water reuse (WTRNet) and so on.