Wastewater Treatment and Effluent Reuse

Among The Highest rates in the World in Water Reclamation for Agriculture Introduction

Since its establishment the State of has been confronting water shortage due to the dry climate, the desert expanse and sparse water sources. Mekorot, the national water company, has been constantly searching for solutions in order to increase the , whether by improving the utilization of the existing sources or by finding additional water sources. Within the framework of its activities, the company deals with sewage treatment and effluents reuse for agricultural purposes. Mekorot considers the improvement of the sewage treatment level and the expansion of the uses of reclaimed water as one of the most important professional and ecological challenges. The replacement of fresh water with reclaimed effluent for agricultural irrigation permits the supply of additional fresh water to the population, while maintaining environmental quality by reducing the ecological damages caused by sewage. Mekorot is responsible for about 35% of the treated sewage in Israel and approximately 60% of effluent reuse for agricultural needs in the country. The quantities and quality of the reclaimed effluents and are among the highest in the world. The company invests much capital in research and development of related areas such as effluent , treatment by membranes, and development of alternative methods to chlorine disinfection, in cooperation with leading companies throughout the world. One of Mekorot's main goals for the coming decade is to utilize all the effluents in Israel, thereby stopping the disposal of 100 million cu.m./year of effluents into the environment.

2 3 Sewage Treatment

What is the principle of sewage Secondary treatment treatment? A biological process intended to treat the dissolved organic materials in the sewage. This process takes Sewage treatment is based on a principle in which place by utilizing bacteria and microorganisms that very high concentrations of microorganisms meet with digest the waste products, while introducing oxygen into high-load sewage, under a massive supply of oxygen the liquid by mechanical means (aerators or air diffusion). (aerobic conditions). This process significantly shortens In order to remove the contaminants from the sewage, the natural duration of treatment that normally takes the bacteria population is multiplied to the extent that place in streams - from weeks and months to less than there are enough bacteria to digest the contaminants 24 hours! within a given time. The organic matter found in the sewage and the oxygen supplied are required for What are the stages in sewage these aerobic bacteria’s existence. During the digestive treatment? process the bacteria develop into larger colonies, which can be separated from the fluid using secondary Pre-treatment sedimentation. After sedimentation, high-quality effluent results, suitable for agricultural use in accordance with In this stage, coarse materials such as sand, rags, the Ministry of Health regulations. stones, wood and plastics are removed. The treatment in this stage includes coarse filtration by bar screens Tertiary treatment and removal of sand and oil in grit chambers. This advanced treatment ensures the removal of Primary treatment contaminants, suspended matter, bacterial and other microorganisms found in the secondary effluents. This A physical process intended to reduce the load on the is done by filtering the effluents through a deep granular biological (secondary) treatment , which uses great (sand) bed filtration (or ultrafiltration) and disinfection amounts of energy. During the primary treatment, by the addition of chlorine or other disinfectants. At approximately 30%-35% of the organic materials and the completion of the treatment, the result is very high- 40% to 60% of the suspended solids are removed by quality effluents, sent to the reclamation systems for gravitational sedimentation. unrestricted agricultural use, or to streams.

4 5 Sewage Treatment

What are the sewage treatment methods?

Extensive methods on the stones, which removes the organic material in the wastewater, improving the quality of the treated wastewater. Oxidation Ponds – Until the beginning of the 90s, this This method has a relatively slow biological process, and method was the cheapest and most used at the time. was therefore a more dominant method in the past. There According to this method, sewage is sent to shallow are currently very few such facilities in developed countries, ponds for several weeks, until algae grows and multiplies. where they are mainly found in small communities. The The algae release large quantities of oxygen during facilities’ maintenance costs are fairly low. photosynthesis, utilized by the bacteria to remove the organic materials in the sewage. Activated Sludge – In 1992 the Ministry of Health determined the "20/30 regulation", according to which Wetlands – Technology that demands much area each municipality is obligated to treat its sewage in order compared with the quantity of wastewater that it can treat. to obtain effluent quality of no more then 20 mg/l BOD After preliminary treatment, the wastewater is passed and no more than 30 mg/l suspended solids) As a result, through a vegetation bed which removes contaminants, many facilities have adopted themechanical-biological mostly through the roots. This technology is more suited method, that was found more advanced and efficient for low loads (usually for conventional sewage treatment), than Oxidation Ponds. With this method, a dense after which the treated wastewater is used for agriculture population of microorganisms is maintained in a constant or irrigating urban parks. state of mixture/circulation in the reactors to which the raw sewage is introduced. The microorganisms digest Intensive treatments the organic material and the nitrogen and phosphorus compounds, and utilize the oxygen supplied. In this form Trickling filters: this is a method of treatment in which the the microorganisms multiply their number at a very rapid wastewater is sprayed from a height of about one meter rate, so that the process continues for 12-18 hours only. over a pool with a stone bed overlaid by biomass into After their stay in the reactors, the multiplying bacteria which the wastewater is sprayed. This biomass absorbs (biological sludge) are separated from the effluents in air from the atmosphere and treats the sprayed sewage sedimentation clarifiers.

6 Another sludge treatment method is sequential batch that is not immersed. This technology is suitable for small reactor (SBR), a process in which the sludge is treated communities since the wastewater treatment process is in batches (filling, aerating the process, a halt for settling slow. and emptying). The advantage of this process is that it reduces the area of sewage treatment infrastructure Membrane bioreactor: a method in which the biological because it carries out the settling and the process in the reactor can also work with large biomass concentrations same reactor. because the solids separation process is not done by settling, but by membranes. The membrane enables the From the year 2000, additional technologies were flow of water and particles smaller than gradually introduced which improve the efficiency of the 1 micron. This technology produces treated wastewater process compared with conventional sludge treatment of very high quality (tertiary), but its disadvantage is its processes. The decision to choose this technology takes relatively high cost and the need for skilled manpower. into account the size of the facility, the use of space, the quality of treated wastewater needed, and the budget. Sludge treatment – the sludge treatment stream generally includes a thickening system for the sludge, Aqwise Technology: floating plastic cubes with a large before entering into the digesters, in order to concentrate internal area are placed inside the biological reactor. The the organic material. In the digesters, which are generally large interior space better exploits the reactor’s volume anaerobic, the bacterial digestion process takes place, for the contact between the biomass and the organic without oxygen, and at a temperature of 35°-37°C. The material inside the wastewater (reducing infrastructures). sludge is transferred to dewatering facilities for water Rotating Biological Contractors (RBC) technology: extraction and sludge (with 20%-25% solids content) can a technology that is basically similar to biological be disposed of in containers for agricultural use. The reactors. A rotating drum is half immersed into the gas produced in the digesters, mostly methane, can be wastewater, an affixed biomass develops on the drum utilized to generate electricity with a bio-generator. The which aerates from the atmosphere the biological residual heat of this process is used to heat the sludge in process that is on the upper side of the drum - the half the digesters.

7 Facts & Figures

Wastewater Treatment by Mekorot Mekorot handles about 35% of wastewater treated in Israel, using a range of state-of-the-art technologies. The company currently operates several sewage treatment plants, including Shafdan, the largest plant in Israel and the Middle East. The treated wastewater is used for unrestricted agricultural irrigation in the Desert. Effluents Reclamation by Mekorot Mekorot is determined to return all of Israel’s effluents to agriculture, thereby contributing water resources in the country. At present, Mekorot returns approximately 60% of the reclaimed effluent to agriculture through 9 reclamation plants which are among the largest and most advanced in Israel:

Annual consumption Hooked-up sewage (millions of Enterprise treatment plants cubic meters)

The Third Line to the Shafdan sewage treatment 140 Negev plant Kishon Complex Haifa and Afula sewage 35 treatment plants Emek Hefer Netanya sewage treatment 18 plant and local production wells Ayalon-Latrun Ayalon (Ramle-Lod) sewage 6,3 treatment plant Hadera Hadera sewage treatment 5 plant Jordan Valley Nahal Og sewage treatment 3,3 plant (wastewater from east Jerusalem) Carmiel Carmiel sewage treatment 4,6 plant Safed Safed sewage treatment plant 0,9 Etzion Bloc Eztion Bloc sewage treatment 0,2 plant Total 213.3

Drinking water consumption in the urban and industrial sectors in Israel is 800 million cu.m. per year • 520 million cubic meters of wastewater are produced annually in Israel • 470 million cubic meters of wastewater are treated annually (about 90%) • 360 million cubic meters of treated wastewater are reused annually by agriculture (about 70%) • 100 million cubic meters of treated wastewater are channeled unused to the environment (about 21%)

8 Shafdan

The Shafdan - the Dan Region Sewage Treatment Plant – the Negev (water suitable for unrestricted irrigating all types is one of the largest and complex facilities in Israel, and is of crops). This method will use membranes for surplus considered to be the largest and most advanced of its type secondary treated wastewater, surpluses that cannot be in the Middle East. The plant treats 130 million cubic meters injected into fields by the Soil Aquifer Treatment (SAT) of sewage annually, and returns about 160 million cubic method, which is currently used at Shafdan, because of meters of reclaimed water through “The Third Line to the the lack of permeation area. SAT is a different process, the Negev” reclamation system. The facility serves a population results of which achieve water quality that is close to current of about 2 million people, in the most crowded and densely tertiary treatment methods at Shafdan (treatment based on populated area in the country – the Dan Region. The facility injecting secondary treated wastewater into the aquifer via is owned by the Dan Region Association of Towns, which sand seepage reservoirs). includes seven municipalities and many other settlements. Under the Water Commission’s master plan, by 2015 Mekorot is responsible for operating the facility, guarantees agricultural use will be fulfilled, and surplus pure raw water the desired quality of the effluents; recharges them to will be created from the sewage treatment plants. Due to a confined aquifer through infiltration basins in order to the potential of the membrane treatment and the surplus of improve its quality, pumps the reclaimed water through treated wastewater, Mekorot has established facilities to test recovery wells and supplies them to the Negev at a the feasibility of treatments at Shafdan, which have examined quality permitting unrestricted agricultural crop irrigation. many factors. The R&D has yielded tools for continuous and The system is managed in a way that enables complete stable membrane treatment of secondary treated wastewater separation between the treated wastewater that is injected of low quality. The test facilities are currently examining a into the groundwater, and the natural groundwater, through number of ideas, some of which have already achieved a system of pumps which preserves a hydraulic gradient technological breakthrough. to prevent the injected water from mixing into the aquifer. Effluent Recharge and recovery In this way Mekorot provides an essential solution for After the biological treatment (secondary stage) in the Israel’s increasing water needs, by freeing more fresh Shafdan plant, the effluents are sent to infiltration fields in water to urban use. the sands of Rishon Le-Zion and Yavneh, where they are recharged into the aquifer by alternate regime of flooding and Studies on the restoring system at Shafdan drying. As it seeps through the ground, the water undergoes As part of the preparations for the provision of regular and physical, biological and chemical processes that improve high-quality water in the future, Mekorot invests in R&D on most significantly their quality. In addition, the underground new desalination and membrane treatment (using various retention time serves as a seasonal and multi-annual storage types of membranes for treating water) technologies in for large quantities of water that are used for irrigation during order to maximize the exploitation of water sources. In “dry” periods. After the transfer to the aquifer (ground water this context, the company improves treated wastewater reservoir), and during the retention and flow there, the water by secondary treatment up to drinking water quality for is pumped by about 150 recovery wells. Their purpose is to agriculture, unrestricted irrigation of crops, filling aquifers, pump the reclaimed water and prevent it from penetrating and industrial use. into other wells in the area, which are used for drinking At Shafdan, Mekorot plans a method for creating reused water supply. The quality of the reclaimed water is very high, water that is close to the quality of water in the Third Line to suitable for unrestricted irrigation.

9 The Third Line to the Negev

The Third Line to the Negev enterprise began operating in a limited format in 1977, and was inaugurated in its expanded format in November 1989. The enterprise consists of a network of pipelines, pumping stations and reservoirs, the purpose of which is to improve the quality of the Shafdan treated wastewater and transfer it to the Negev for agricultural use. The reclaimed water is suitable for unrestricted irrigation, without fear for customer’s health. The Third Line is separated from the two other pipelines that supply drinking water to the Negev (the eastern “Yarkon-Negev” and the western “Yarkon-Negev” pipelines), and is intended to transfer only reclaimed water for unlimited irrigation for all types of crops in the Negev. The system is made up of three main pipe sections, with a total length of 90 kilometers, six operational “floating” reservoirs and three end reservoirs in the Negev, in order to collect the stored reclaimed water during the winter and increase the quantity of water supplied for irrigation during the summer months.

10 By returning reclaimed water to the Negev, Mekorot has achieved the following goals:

• Full utilization of Shafdan effluents and prevention of wasting one of the most precious water resources in Israel • Improvement of the water balance in Israel by diversion of a larger quantity of fresh water for domestic and industrial use • Transferring large agricultural areas from the congested center of the country to the expanses of the Negev • Creation of green groves and fertile agricultural fields in previously arid and desolate areas • Reduction of the potential contamination of ground water and the spreading of disease to the population due to lack of appropriate sewage treatment and disposal

11 Photographers: Eli Degani, Ben David Meir, Moshe Shai, Albatross, Sky Balloons, Naftali Hilger, Chen Mika, Meganzi & Rolidor, Grey Content, Top Line Communications, Design: Anat Kamienietzky

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