Fresh water is a valuable, finite commodity that is becoming more costly and difficult to access every day. Water supply and demand studies have revealed several emerging problems including unsustainable water-use patterns and water-scarce regions with large at-risk populations (Amarasinghe and Smakhtin, 2014). The availability of water is dwindling rapidly, and the emerging water shortage could be the defining crisis of the 21st century as the global population continues to expand, but our water withdrawals are increasing twice as fast as population (Majsztrik et al., 2011). As a local resource, water is adequate in some locations but nonexistent in others. Increased demand by both urban and agricultural users has led to a world where large river systems no longer drain into the ocean and water rationing is required in some major cities across the globe.
This decline in fresh water availability will affect many industries. Agriculture uses more water than any other human activity; however, only 40% of irrigated water reaches crops because of inefficient irrigation techniques worldwide (Pimentel et al., 1997). This study focuses on the horticultural industry. Ornamental production uses large volumes of water per hectare for both containers and greenhouses. These operations normally pull water from local aquifers, but access may be affected by water shortages.
In general, water costs are higher in the west, particularly in California, which leads to higher production cost and reduced profit. In an effort to conserve this valuable resource, there is a strong push for agricultural and horticultural industries to recycle irrigation water (Economics Consulting Service, 2008; World Bank, 2006). Growers want to manage water without changing their production schedules and the value of their crops (Majsztrik et al., 2011). One way to manage water runoff in container production is to convey rain and irrigation runoff to a containment pond for reuse (Yeager, 2008).
Recycling irrigation runoff allows for the reuse of nutrients from containers, minimizes discharge from the nursery site, and the water can even be superior to groundwater if it is mixed with rainwater (Yeager, 2008). Growers have implemented water recycling systems because they anticipate restricted water access in the near future. Containment ponds supply a “buffer” that allows growers to reduce their reliance on wells or municipal water sources in emergencies (Powell, 2014). However, recycled water poses challenges to the industry. Runoff is collected in catch basins for reuse, where a unique ecosystem forms. The water quality of these catch basins can fluctuate greatly throughout the seasons, and can support a variety of fungal and bacterial pathogens (Hong et al., 2008). The greatest threat in the use of water runoff consists of microbial pathogens that cause waterborne diseases, putting the health of an entire nursery or greenhouse at risk if recycled water is not properly managed and disinfected (Meador et al., 2012).
Plant pathogens in recycled water could potentially harm plants and spread disease, reducing sellable yields and hurting the grower financially. Furthermore, the grower may have to increase chemical use to control disease outbreaks, further adding to production costs and potential water pollution (Stewart-Wade, 2011). Fungi and fungal-like organisms in water runoff can cause disease in various crops if that water is recycled without disinfection. Some examples of such organisms include various species of Phytophthora and Pythium, which cause root crown rots and foliage blight, respectively. Many other bacteria, fungi, nematodes, and viruses can threaten nursery and greenhouse crops and have been found in irrigation runoff (Yeager, 2008).
Proper water disinfection is a critical step to ensuring that recycled irrigation water does not spread plant pathogens and increase disease risk (Stewart-Wade, 2011). Integrated water resource management is advocated by The Global Water Partnership, which defines it as “a process that promotes the coordinated development and management of water, land, and related resources to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems” (Global Water Partnership, 2000).
A grower must decide what level of disinfection is required based on the pathogens to which the crops being grown are susceptible and must also decide on an acceptable tolerance threshold for plant loss due to disease. The grower must be dedicated to hygienic operations and frequent monitoring to ensure that proper disinfection takes place, and be willing to invest in the necessary equipment. Disinfection techniques including ultraviolet light, chlorine gas, ozone, and copper require strategic implementation to work effectively. For example, although copper is an essential element for plant growth, an excessive amount is toxic and requires careful monitoring (Zheng et al., 2004).
The costs and benefits of various irrigation systems can shed light on the affordability of water recycling. Reclaimed water is an economical water resource if proper risk management practices are used (Chen et al., 2013). According to Alcon et al. (2012), using a mixture of reclaimed and surface water is the best option when accounting for “intangible” social and environmental benefits. A variety of technologies are available to address the major risk areas in irrigation water quality, which include salinity, pathogens, nutrients, and heavy metals (Norton-Brandao et al., 2013). Each technique has unique abilities, advantages, and disadvantages including a range of operating and investment costs. For example, ultraviolet light is recommended by several guidelines as the best disinfection technology without excessive costs, while reverse osmosis technology has both high capital and operation costs (Norton-Brandao et al., 2013).
Although the process may be complicated, recycled and properly treated water has no shortage of benefits from both economic and environmental standpoints. The process reduces the discharge of untreated water into nearby water bodies and encourages producers to treat their recycled water efficiently to protect their crops. It relieves pressure on surface waters and slows down the depletion of groundwater, which supports healthy ecosystems and decreases the need for new water supply infrastructure such as dams and wells, which can damage local habitats or be costly to drill and maintain, respectively. Recycling water also recycles fertilizer within the system and may reduce fertilizer costs. Unfortunately, many of the spillover benefits described here are difficult to measure and are therefore excluded from a typical cost–benefit analysis (Schulte, 2011).
Water management has been a concern of growers in Europe for years, and reusing irrigation runoff is a popular technique. It provides a readily available water resource when restrictions limit access to ground or surface water (Yeager, 2008). Recycled water has been safely and successfully used in Florida for over 40 years. It was initially promoted to improve surface water quality by preventing runoff pollutants from entering surface water, but it now helps meet water shortages from increasing urban demand and has delayed saltwater intrusion on wells (Parsons et al., 2010). Recycled water has become a necessity to water-scarce California, which has imposed water management laws over the last decade, and in 2009 enacted The Water Conservation Act with the goal of increasing water use efficiency through urban and agricultural water conservation. It required that agricultural water suppliers (including farmers and anybody else who digs a well) adopt water management plans by the end of 2012 and update them every 5 years starting in 2015. These regulations have several required components, including that water suppliers implement efficient management practices that reduce water waste. If water suppliers fail to meet these requirements, they are not eligible for state water grants or loans (Anonymous, 2009). This California Act has set the standard for statewide water regulation laws, which many New Jersey growers anticipate will be forthcoming in their own state. This study looked at several growers in New Jersey who have made the decision to recycle their irrigation water in response to laws imposed in other states.
Still, other operations are hesitant to recycle their irrigation water when it is not required by the government. Many fear the spread of plant pathogens, which can be brought into a greenhouse by wind, insects, soil, transplants, seeds, and humans. In a recycled system, water that runs off from an infected plant can carry the disease to other plants if it is not disinfected properly. An entire operation can be threatened by one disease outbreak if it leads to significant crop loss (Powell, 2014). One grower cited the Ralstonia outbreak in the early 2000s as a reason for their trepidation toward water recycling. Ralstonia solanacearum is a soilborne bacterial pathogen that enters the plant through the root system and causes the plant to wilt and eventually die. There are two races of the bacterium, and the occurrence of Race 3 requires federal quarantine because of the relative ease of transmission. It was found to infect common crops such as geranium (UMass Amherst Extension, 2013).
Growers throughout the United States have a decision to make whether to recycle their water now or wait for legislation that requires them to do so. The Natural Resource Conservation Service (NRCS) provides assistance to private landowners making this decision, offering financial and technical assistance to help manage natural resources in a sustainable manner without having to hire an engineer or consultant. They offer financial assistance through many programs including Agriculture Management Assistance, Conservation Stewardship Program, and the Environmental Quality Incentives Program (USDA Natural Resource Conservation Service New Jersey, 2014). These are valuable resources for growers.
The objective of this case study was to perform a cost analysis of various water disinfection techniques being used at horticultural operations in southern New Jersey. The goal was to determine the most cost-efficient disinfection method for recycled irrigation water from the Cohansey aquifer, and make policy suggestions based on the results. Only financial data reported by growers were included, so this is not a full environmental cost-benefit analysis of the practice. It is reasonable to assume that if investments such as these are profitable in strictly private terms, then net social benefits are even greater, because what will be missing from the analysis will mostly consist of hard-to-quantify environmental benefits.
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