Mekorot constantly searches for solutions to increase Israel’s water supply. One of these solutions is wastewater treatment and effluent reuse for agriculture.
The company aims at improving reclaimed water quality, thereby broadening the applications for which it can be used.
Mekorot’s treatment and reuse of wastewater improves Israel’s water balance by allowing the replacement of fresh water with treated wastewater for the irrigation of crops, thereby saving limited fresh water sources for domestic use.
The treated wastewater supplied by the company for agricultural use complies with strict health standards and contributes to preserving the environment by reducing ecological damage caused by untreated wastewater.
Mekorot is responsible for approximately 40% of the wastewater treated in Israel (approximately 200 million cubic meters a year), and for the reuse of 60% of the country’s treated wastewater for agriculture.
350 million cubic meters of effluents were reused in Israel for agriculture in 2005 – 75% of total treated raw sewage. Despite its small size and limited resources, Israel has achieved the highest rate of water reclamation in the world.
Wastewater treatment typically comprises four stages: pre-treatment, followed by primary, secondary and tertiary treatments. The treatment methods include oxidation ponds, activated sludge and MBR (mechanical bio reactor).
|Table of water reuse rates:
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Mekorot operates six wastewater treatment plants (WWTP) with a daily flow of 460,000 cubic meters and an annual capacity of around 180 million cubic meters. Following biological treatment, the effluents are routed to one of nine effluent reclamation plants. These plants filter and disinfect the effluent before it is supplied for irrigation.
The Shafdan effluents are inserted into the soil for tertiary treatment and to recharge the aquifer. Later, the water is pumped out and transported to the Negev. The total effluent supplied for agricultural purposes is 216 million cubic meters per year. Comprehensive water quality monitoring is carried out at all stages of the recharging process
Use of Innovative Technologies
One of Mekorot’s goals for the next decade is to increase its usage of all effluent water in order to prevent seepage into the environment of around 110 million cubic meters per year. To this end, Mekorot invests significantly in the development of cutting-edge technologies designed to increase the yield and reduce the cost of its treatment and reclamation processes. The technologies that Mekorot has deployed so far include
- AS – Activated Sludge
- SBT – Sequential Batch Treatment
- Aerobic and Anaerobic Sludge Treatment
- Gas Bio-generation SAT – Soil Aquifer Treatment
- Sand Filtration
- UF - Ultra Filtration
- Net Filtration
- Long Storage Reservoirs
Further, Mekorot continuously invests in new R&D in the areas of
- effluent desalination
- membrane treatment
- alternative methods for chlorine disinfection
Mekorot’s Major Wastewater Treatment Plants
Shafdan Wastewater Treatment Plants: Mekorot’s largest wastewater treatment plant is the Shafdan, a facility located in Israel’s heavily populated Dan Region. It is one of the most complex wastewater treatment plants in Israel and the most advanced in the Middle East.
Serving a population of two million persons in the Dan region, the plant treats 130 million cubic meters of wastewater annually. Mekorot operates both the facility and its pumping stations.
Secondary effluent from the Shafdan plant is used to infiltrate fields in Rishon Letzion and Yavne. From these fields, the effluent is recharged into groundwater reservoirs (aquifers) where it undergoes natural physical, biological and chemical processes that improve its quality and storage ability.
The quality of the reclaimed water is very high, making it suitable for all forms of irrigation. Israeli produce grown using reclaimed water includes oranges, carrots, potatoes, lettuce, wheat and flowers.
Note: the most common problem associated with recharging using a spreading basin is clogging of the surface by fine-grain sediment suspended in the recharged water and/or by microbial growth. In Mekorot’s Menashe and Shikma plants, this problem has been addressed by initially introducing the water into sedimentation basins to allow the suspended sediment to deposit, and afterwards transferring the improved water to recharge ponds.
Third Line to the Negev: From aquifers, backed by seasonal and operational reservoirs, water is pumped to the Negev for agricultural use through the “Third Line to the Negev,” a series of pipes 90 kilometers in length. This pipeline is separated from the two pipelines used to supply drinking water to the Negev.
Mekorot’s Artificial Recharge Activities
Artificial recharge of groundwater forms an integral part of Mekorot’s national water resources management scheme. It carries out extensive artificial recharge activities across all of Israel’s geographical, geological and hydrologic regions, using all three relevant types of water: flood water, potable water from the National Water Carrier and effluent water.
The goals of Mekorot’s artificial recharge program are to:
- Increase the balance of usable water
- Improve the management of aquifers
- Fully utilize the storage capacity of the aquifer
- Maximize reuse of treated effluents
- Manage the risk of floods
The artificial recharge programs have improved the quality of groundwater, and have succeeded in restoring higher groundwater levels to Israel’s Coastal Aquifer, counteracting further seawater intrusion.
They have also proven effective in balancing present and future withdrawals with the long-term average of the annual recharge. Further, by maximizing the use of aquifers as an underground water storage facility, the recharge programs minimize the loss of surface water stored in the Sea of Galilee through evaporation or overflow to the lower Jordan River.
To assure the quality of the water from these recharge plants, Mekorot has implemented intensive maintenance program, together with a monitoring program for the plants’ catchment areas as well as the recharge system.
Mekorot’s Major Recharge Plants
Menashe Artificial Recharge Plant: Mekorot’s largest artificial recharge plant is the Menashe, a facility located in Israel’s northern part of the Coastal Aquifer.
The plant’s drainage basin is 189 square kilometers, a region of hills composed of limestone and chalk. Although average rainfall in the region is 620 mm (producing a total of approximately 84 million cubic meters of water per year), only 15% becomes runoff.
Mekorot is able to capture approximately 91% of this amount, which flows into the recharge ponds by gravity due to the difference in elevation. The recharge site itself is composed of sandstone and is part of the coastal aquifer.
The average yearly recharge is 11.7 million cubic meters. As the system takes advantage of the difference in topographical elevations between the water sources and the recharge ponds, the cost of the recharge process is limited to maintenance, with pumping costs amounting to only $0.02-$0.03 per cubic meter.
The amount of water that can be recharged in the plant is limited to the level where seepages on the banks of the spreading ponds occur. Around the recharge ponds there are rings of pumping wells.
Mekorot’s policy is to pump about 40-50% more water from the aquifer than the average recharge in order to create a temporary hydrological depression that will leave enough space for artificial recharge the following winter.
Shikma Artificial Recharge Plant: The plant is located in the southern part of the Coastal Aquifer. The water source of the Shikma artificial recharge plant is the Shikma River, which has a catchments area of 750 square kilometers.
Average rainfall in the region is 400 mm. per year. The area’s semi-arid climate causes large fluctuations in the runoff amounts that reach the Shikma Plant.
The artificial recharge site includes a sedimentation reservoir and a recharge pond: the water initially enters the sedimentation reservoir where fine particles are submerged for 48 hours, and is then pumped into the recharge reservoir.
The water quality of the recharge water is excellent, with salinity less than 100 mg/l cl. To prevent the seepage of sea water into the aquifer and to avoid loss of fresh water to the sea, rings of wells have been drilled around the recharge reservoirs to allow pumping of the recharged water.