SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: https://read.dmtmag.com/i/56877
Irrigation&Drainage | Dr. M. Ali Harivandi A contemporary view of recycled water irrigation M ost of us are familiar with the term "Black Gold" as another name for oil, and we may have heard of "Blue Gold" used in some quarters in reference to water. Without question, human- ity is polluting and wasting water even as its need for water grows with increasing population. Thus, just as it appears that wars today are fought over oil, future wars may be fought over water. Agronomists generally do not play the roles of economist, diplomat, or soldier. We can, however, try to educate, and sometimes the topics we broach have large consequences. The use of recycled or reclaimed water is, I be- lieve, such a topic. And considering the critical water needs of today's world, I would like to as- sign to recycled water the term Purple Gold, after the color officially used to designate all equipment contacting it. Having worked with this resource for over 30 years, evaluating its potential for turfgrass and landscape irrigation, I have witnessed its quality increase significantly. As quality has in- creased, both the value and the use of recycled water have also risen dramatically. I believe re- cycled water, already deserving of the name Purple Gold, will be recognized as such society- wide in the near future. Already, in the face of increasingly common drought, habitat erosion, and the escalating cost of potable water, recy- cled water is the Purple Gold of urban land- scape irrigation. In light of recycled water's importance, a review of its qualities and of the management practices needed to use it success- fully is in order. Although three-quarters of the earth's sur- face is covered with water, only a minute frac- tion of all the water on earth is both readily available and of sufficient quality to be suitable for human use, including irrigation of agricul- tural crops and landscape plants. In fact, it is es- timated that only 0.02% of all water on earth is fresh and immediately available, i.e., could be used with relative ease and with minimal energy input and expense. That small fraction of earth's water includes rain and snow-melt stored in lakes and reservoirs, as well as water available in rivers. More than 99% of earth's water is in its oceans or locked in polar ice caps and glaciers. Converting water from these sources to potable form is highly energy-dependent and expensive. Yet fresh surface and ground water together are being rapidly depleted due to industrial and 34 SportsTurf | March 2012 agricultural use and direct human consump- tion. Population growth accelerates and exacer- bates the potable water scarcity. In most cases, turf and landscape irrigation is not a priority for municipalities during droughts. Severe restrictions on turfgrass and landscape irrigation during droughts are com- mon, including complete shutdown of golf course or park irrigation. Irrigation with recy- cled water is therefore a viable means of coping with drought, water shortages, and/or the rising cost of potable water. Currently, large volumes of recycled water are used to irrigate golf courses, parks, roadsides, landscapes, cemeter- ies, athletic fields, sod production farms, and other landscape sites. Interest in recycled water irrigation also increases as more and better- quality treated sewage water becomes available. Today, most sewage treatment plants pro- duce high-quality recycled water suitable (as far as human-pathogen content is concerned) for additional uses such as golf courses, parks, ath- letic fields, and other urban landscape sites. In certain southwest desert areas of the United States, most golf courses (and associated land- scapes) may use only recycled (or other de- graded-quality) water for irrigation. In a larger context, recycled water is now the irrigation source for approximately 15% of US golf courses and close to 35% of courses in south- western states. These figures are rapidly increas- ing, as are those for all other commercial, institutional, and industrial sites irrigated with recycled water. "Recycled water" refers to water that has un- dergone one cycle of (human) use and then re- ceived significant treatment at a sewage treatment plant to be made suitable for various reuse purposes, including turfgrass irrigation. Several other terms are also used for recycled water, among them: reclaimed water, reuse wastewater, effluent water, and treated sewage water. Sewage treatment takes raw sewage with all of its suspended matter and pathogenic or- ganisms and converts it into clear, reclaimed water that looks as good to the human eye as any potable water. In almost all cases, recycled water is thoroughly disinfected before leaving the treatment plant. Disinfection greatly re- duces (or entirely eliminates) the human dis- ease-causing organisms and expands the irrigation uses of recycled water. However, "dissolved" solids (salts) still re- main and are of concern if the water is to be used for irrigation. It is technically possible to remove all of the dissolved salts from sewage water, using techniques such as reverse osmosis. Reverse osmosis, in fact, is used on a small scale at a few golf courses to remove almost all dis- solved solids from water. However, the expense is such that very few treatment plants in the world currently use it. Therefore, most of the recycled water available for irrigation is only tertiary treated and may contain high concen- tration of salts. Turfgrass is particularly well suited to irriga- tion with recycled water. Among landscape plants, turfgrasses can absorb relatively large amounts of nitrogen and other nutrients often found in elevated quantities in recycled water, a characteristic that may greatly decrease the odds of groundwater contamination by recycled water. Equally important, turfgrass plantings are generally permanent and their growth is continuous, providing a stable need for contin- uously produced recycled water. Presently, most of the turfgrass irrigated with recycled water grows on golf courses. However, recycled water irrigation is increasing on sports fields, in parks, on many industrial and institutional landscapes, and on sod production farms. Most municipalities require signage (usually colored purple) to inform the public of the presence of recycled water. These efforts are in- tended to prevent anyone from ingesting or otherwise using the water directly, to avoid any risk, however slight, of contact with human pathogens. The color purple is now broadly ac- cepted as the official color for recycled water conveyance equipment. Almost all irrigation system components are now available in purple, including pipes, sprinkler heads, valves, and ir- rigation boxes. POTENTIAL CHALLENGES Despite sound reasons for using recycled water for turfgrass irrigation, there are legiti- mate concerns about possible injury to turfgrass and other landscape plants due to the salt con- tent and other characteristics of reclaimed water. During irrigation, dissolved salts and other chemical constituents move with water into the plant rootzone. Recognizing the prob- www.sportsturfonline.com By