Sewage Water Treatments and Reuse in Israel
Many places, such as Israel, in arid and semiarid regions are characterized by long, dry summers and short, wet winters. Therefore, crop production in these regions relies mainly on irrigation. In 1990, for example, the total cultivated land in Israel was
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2.4
Sewage Water Treatments and Reuse in Israel
M. Ben-Hur
Institute of Soil, Water and Environmental Science, The Volcani Center, POB 6, Bet Dagan, 50250 Israel
2.4.1
Introduction
Many places, such as Israel, in arid and semiarid regions are characterized by long, dry summers and short, wet winters. Therefore, crop production in these regions relies mainly on irrigation. In 1990, for example, the total cultivated land in Israel was 437,100 ha, of which 205,700 ha was under irrigation. However, in recent decades, although the total cultivated land area has not been changed significantly, the area of irrigated land has been reduced, in accordance with the amount of water available for agriculture. Conventional sources of good quality water (fresh water) in arid and semiarid regions are scarce. Therefore, in these regions, in order to maintain sustainable agriculture to meet the increasing demands for food, and to combat desertification, unconventional water resources need to be used for agriculture. Additional water for irrigation can be derived from treated sewage water (effluent). Table 2.4.1.
Consumption of fresh water and effluent in agriculture in Israel Year
Agricultural consumption [million m 3/yearj Effluent
Fresh water
1980
52.3
1307.5
1994
254.2
1204.7
2000
290
580
2010
490
500
In 1980, the agriculture consumed 52.3 and 1307.5 million m 3 per year of effluent and fresh water (FW), respectively (Table 2.4.1). In contrast, in 2000, the agricultural consumption of effluent increased to 290 million m 3 per year, and that of FW decreased to 580 million m 3 per year. It is expected that this trend will intensify in the future (Table 2.4.1). This decrease in the consumption of FW for agriculture (Table 2.4.1) was mainly a result of increased demands for FW in the domestic and the industrial sectors. This chapter reviews the types and the quality of the effluents in Israel, the effects of effluent irrigation on the soil, and the accompanying hazard of contamination of the water resources. F. Zereini et al. (eds.), Water in the Middle East and in North Africa © Springer-Verlag Berlin Heidelberg 2004
168
2.4.2
M. Ben-Hur
Sewage water treatments and quality
Sewage effluent comprises 99.9% water and 0.1 % organic and inorganic solids in suspended and soluble forms (Feigin et al. 1991). Raw sewage water contains microorganisms that may be pathogenic (bacteria, viruses, and parasitic protozoa), and parasitic worms. Moreover, some of the chemical materials in the sewage water are toxic. Therefore, in order to protect the public both from consuming contaminated crops and from direct exposure to the effluent applied to them, and to prevent nuisance conditions, operational problems in the irrigation system and adverse effects on soil, crops, and water resources, sewage water intended for irrigation should be treated first. All the effluent that has been and is being used for irrigation in Israel has undergone at least secondary (biological) treatment. The two most commonly used secondary treatmen
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