Effects of Reclaimed Water on Citrus Growth and Productivity

Abstract

Sewage wastewater or effluent is often viewed as a disposal problem. However, it can be a source of water for irrigation, creating an alternative disposal method for wastewater treatment facilities, benefiting agriculture as an alternate source of irrigation water, and reducing the demand for use of surface or ground water for irrigation (Parsons et al., 2001a and b). Treated wastewater, also known as reclaimed water, is typically treated municipal sewage from which excess plant nutrients, organic compounds and pathogens have been removed. The terms wastewater, treated wastewater and reclaimed water will be used interchangeably in this chapter. The characteristics and treatment of these treated waters will be described and discussed in this chapter along with use as an irrigation source for citrus production. Potential disadvantages of using reclaimed water for agricultural irrigation include real or perceived concerns about reductions in surface and ground water quality (i.e. nutrients and heavy metals), harmful effects on workers that come in contact with treated wastewater (i.e. organic compounds and pathogens), and the safety of crops for human consumption (i.e. carcinogens and pathogens) (Parsons & Wheaton, 1996; Parsons et al., 1995). In some arid regions where freshwater supplies are limited, irrigation with reclaimed water is already commonly practices (Feigin et al., 1991). Israel was a pioneer in the development of wastewater re-use practices, but was quickly followed by many other countries (Angelakis et al., 1999). Israel and the Palestinian Autonomous Regions, for example, are projected to use 3500 million m3 of water in 2010, with 1400 million m3 (40% total water supply) used for irrigation. Treated sewage water used for irrigation would be approximately 1000 million m3 or 70% of agricultural water demand and will play a dominant role in sustaining agricultural development (Haruvy, 1994). Wastewater is a preferred marginal water source, since its supply is reliable and uniform, and is increasing in volume due to population growth and increased awareness of environmental quality (Haruvy & Sadan, 1994). Costs of this water source are low compared with those of other unconventional irrigation water sources (e.g. desalinization) since agricultural reuse of urban wastewater serves also to dispose of treated urban sewage water (Haruvy & Sadan, 1994). Total cost of supplying wastewater for agricultural reuse (i.e. treatment, storage and conveyance costs) minus total costs of alternative safe disposal (e.g. deep well injection and wetlands creation) must be