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Utilisation of groundwater desalination and wastewater reuse in thewater supply of seasonally stressed regions


The methodology can be summarised as follows: a) Identification or development of suitable methods or models to describe each main process that affects the system or forms part of the proposed scheme, i.e. each element of the problem: hydrologic budget and natural recharge (infiltration) of the aquifer, groundwater dynamics including sea intrusion, water demand that must be satisfied by the aquifer, desalination, and recharge with reclaimed water following suitable treatment. b) Development of a Decision Aid Tool (DAT) that integrates, on-line or off-line, all of the above methods or models and uses this information and an optimisation procedure to evaluate alternative exploitation schemes (scenarios) on the basis of their economic performance and to identify the optimal scheme(s).Refinement and practical tuning of DAT, as well as demonstration applications, were accomplished in three pilot case studies. Their locations were chosen so as to include aquifers with different characteristics and water supply systems exposed to different conditions of stress. These aquifers are the Coastal Aquifer of Israel and two aquifers in the islands of Rhodes and Cyprus, which are currently exploited rather heavily, experiencing salinity problems of varied degrees; therefore, careful management of their resources is required. The WASSER concept opens up new options for the water supply of those locales, where desalination of seawater is being considered currently as a means of meeting the rising water demand. The result is a combination of applied research and software development. The work accomplished in the framework of this project relates to the following major solution elements: 1) Establishment of water demand, hydrologic budget and stochastic analysis of groundwater dynamics, in terms of quantity and quality, with explicit consideration of recharge augmentation by treated wastewater of specific quality characteristics, and model calibration and verification with field data from the three study sites. 2) Theoretical assessment of desalination technology, determination, at the pilot plant scale, of the effort and cost required to desalinate brackish ground-water, scaling up to industrial size installations, and mathematical encapsulation of primary techno-economic plant operation features. Similarly, compilation of the relevant database for the engineering and economics of wastewater treatment and reuse technology. 3) Incorporation of water demand data and information derived from the analyses of surface hydrology, groundwater dynamics, as well as of desalination and wastewater treatment and reuse in a Decision Aid Tool (DAT). DAT is a shell that consists of an optimisation package and a package for the detailed evaluation of alternative scenarios based on economic and environmental aspects.4) Application of the DAT (case studies), at the three locales chosen for model development, and comparison with traditional alternatives. The fields of science are: water resource management/engineering (666), waste management/recycling (665), water: hydrology (669), water: monitoring/quality/treatment (670), water: rational and efficient use (671); the numbers in parenthesis refer to subject description codes for TIPs under FTP5.The product relies on the use of decision support tools (152) and programming/information systems (510), and addressing of economic and environmental impacts (176).DAT consists of a number of subroutines developed in Visual Basic and associated forms. The forms constitute a user-friendly interface, where relevant information can be entered by the user or viewed in appropriate format (e.g., tables, graphs, etc.). DAT integrates other programmes developed using other computer languages (e.g., screening model in FORTRAN). DAT has been also linked to the GIS Mapinfo, so that, if this commercial software is installed on the user�s PC, some of the data can be entered or viewed on maps (as thematic layers). In addition to the obvious data input, data processing and data output �blocks�, DAT comprises the following main parts: i) A �screening model�, which uses simplified versions of the system components to identify, on the basis of an economic objective and environmental constraints, the best alternatives (solutions), thus reducing the number of possibilities to be studied further; dynamic Programming was chosen as the optimisation technique. A user-friendly interface has been developed to facilitate data input and model runs for the simulation of the aquifer (using the USGS SUTRA model). ii) Preliminary design of the desalination installations and estimation of the corresponding capital and Operation and Maintenance (O&M) cost for a 20-year planning horizon. iii) Estimation of all other costs involved in the scheme, i.e. wastewater treatment, pumping, recharge, etc. iv) Detailed economic analysis of a given scheme on the basis of its Net Present Value (NPV), including sensitivity analysis for various parameters such as the cost of electricity.