Groundwater Quality: Processes, Contamination, Prevention, Remediation

• Measurement and monitoring
• Pollution resulting from irrigation with reclaimed sewage
• Contamination of soils and groundwater by non-aqueous phase liquids (NAPLs, which are mostly fuels)
• Control and management of aquifers subject to salination by encroachment from adjacent saline water bodies or from percolation of waters of higher salinity

About 60 % of Israel's water supply comes from groundwater, mainly the Coastal Aquifer and the Yarkon-Taninim Aquifer. The Coastal Aquifer, extending some 130 kilometers from Mount Carmel down to the Sinai, between 10 and 30 kilometers wide, with an area of 1900 square kilometers, is Israel's largest reservoir. It is the only reservoir which has a capacity large enough to carry over from one year to the next, in other words, the only reservoir which can help regulate the supply between wet and dry years. This aquifer lies directly underneath the surface, with no overlying protective layer, so that pollution from the land surface can reach it with little or no hindrance. The time of travel from the surface to the groundwater is long, but eventually pollution from domestic, agricultural and industrial activities, as well as accidental spills of polluting chemicals and fuels, will reach the groundwater. Similarly, the Yarkon- Taninim Aquifer, which is recharged from the Judean Mountains and then flows westward underneath the Coastal Aquifer, is also subject to the same dangers.

It is therefore of supreme importance to protect these aquifers from deterioration of the water quality, to prevent pollution, and remediate the quality in areas where it has been degraded. The objective of research in this area is to understand fully the physical, chemical and biological processes which occur at the surface and as the water percolates, flows through the unsaturated zone and then in the saturated zone, so as to be able to prevent pollution and take appropriate action where pollution has occurred. For example, pollution by fuels at gas stations and airfields are common occurrences; containing the affected area, removing the polluted water, treating and re-injecting the treated water, are strategies and techniques which need to be studied and perfected. In-situ monitoring methods are still lacking, and much more research is required before we can safely state that we know how to prevent pollution and counteract it when it does occur.

Salination of the aquifers, caused by encroachment of adjacent saline water bodies (including the sea) when water levels are lowered, is a major concern. Percolation of surface applied water having a higher salinity is another source of salination.

The same problems face many places in the world. Approaches and techniques have to be developed for protecting the aquifers against salination, and for optimal management of aquifers with saline water bodies.

Water Quality and Water Treatment

• Improvement of the quality of water available in water supply systems and classification of water resources qualities to different consumers.
• Preservation of groundwater quality
• Preservation and improvement of the quality of surface runoff.
• Preservation of the quality of surface water in natural streams and drainage systems.
• Management of water resources quality
• Wastewater recycling
• Integrated systems aiming at the preservation of water resources quality
• Disinfection methods which are effective in eliminating microorganisms and minimize the production of harmful disinfection by-products (DBPs)
• Incorporation of micro-filtration, nano-filtration and membrane processes as stages in advanced water treatment

Wastewater Treatment and Reuse

• Intensive processes for wastewater treatment: techniques which will advance the planning and operation of wastewater treatment plants
• Effluent quality standards for disposal and reuse, and methods for attaining improved quality
• Reuse of treated effluents
• Treatment and reuse of wastewater in rural communities. A Palestinian-Jordanian-Israeli cooperative project, supported presently by the Beracha Foundation.

Israel, its neighbors, and many other arid or semi-arid regions of the world, are turning toreclaimed wastewater as the next source of water for agriculture. As the population multiplies, and domestic water demands increase, countries face the imperative of shifting fresh water from agriculture to the cities. Because nations deem it necessary and desirable to maintain a certain level of agriculture as a means for self-sufficiency in food production and as a way of life for the farming ccommunity, an alternative source of water must be found.

Agriculture cannot pay the high price for desalinated water. But since it can tolerate waters of lower quality, an obvious source is reclaimed wastewater. Reuse of the treated wastewater also alleviates some of the environmental problems associated with discharging the wastewater into rivers or wadis.

Further research is needed to refine the methods for collecting, treating, storing and reusing wastewater, or of discharging it safely into the environment when there are no recipients of the reclaimed wastewater.Human health aspects, and environmental quality are closely connected with this area.

Desalination and Related Advanced Membrane Processes

• Thermal processes
  • Heat transfer in falling films
  • Zero-discharge Evaporator
  • Effect of non-condensables
  • Pretreatment of seawater
• Membrane processes
  • Uses of membranes for water problems
  • Pretreatment for RO processes
  • Fouling prevention on membranes
  • Dynamic membranes
• Alternative energy sources
  

While shifting fresh water from agriculture to the cities can meet the urban need for some years, it is agreed that desalination is the only long term solution for water scarcity. Since this is an expensive source of water, and the technology takes years to perfect and implement in an economic fashion, Israel and its neighbors must execute an intensive program of research, development, demonstration and implementation of desalination technologies. Desalination technologies are divided in two: (a) by membranes, and (b) by thermal processes. For desalination of brackish groundwater, membrane processes are the more economical. Much remains to be done to tailor the plant design to the specific quality of the feed water and the required quality of the product, and, in particular, to extend the useful life of the membranes, which constitute a major part of the cost. For desalination of sea-water, thermal processes may prove superior in some cases, but innovative designs must be developed.Large water factories based on dedicated power plants, implemented with Reverse Osmosis membranes that use electricity as energy source and Multi Effect Distillation units, that utilizes waste heat are the solution for large scale low cost water production.

The GWRI conducts basic and applied research in both types of technologies. More details may be fount at the web-site of The Rabin Desalination Laboratory.

Policy and Management

• Incorporating water quality considerations in management of water resources and systems (including reclaimed sewage); the economic value of water and environmental quality
• Incorporating reliability considerations in management of water resources and systems; the economic value of reliability
• Management of aquifers with waters of different qualities
• Privatization in the water sector
• A Negotiation Support System (NSS) to aid in negotiations over international waters
• Water Sensitive Urban Planning

Consideration of water quality is aimed at developing approaches and techniques for operation of water supply systems, where waters of different qualities are taken from sources, possibly treated, then blended in the system to supply water to a range of consumers. Reliability of supply has emerged in recent years as an important issue, as the demands rise and the existing capacity of the system is stretched beyond the original plan.

Models aid management of complex water resources that contain sources and a conveyance and distribution system that feed to the consumers. A model describes the physical system, all the constraints under which it is to be constructed and operated, and a set of objective functions. The best solution is determined through multi-objective analysis. Some of the objective functions are non-convex, sometimes non-smooth, calling for the development and use of special optimization methods. Such models are applied to a variety of water resources systems.

Water Sensitive Urban Planning (WaSUP)aims to develop policies and practices that minimize the negative effects of urban development on the quantity and quality of water resources. On the hydrologic side, it refers to the effect of impervious areas and urban activities on the quantity and quality of water infiltrating into the underlying aquifer and flowing into the waterways. On the hydraulic side, it relates to efficient use of water in the urban sector, and to options for recycling and using waters of different qualities for different purposes.