Reclaimed water: Challenges of irrigation use
If you are considering irrigating with reclaimed municipal wastewater, you must be ready to make changes in your grounds-management practices. The quality of reclaimed water is typically poorer than the original irrigation supply, and it can come with inconvenient restrictions and hidden costs. Smart irrigators learn as much as possible about their water supply and, if possible, construct a contractual agreement with the reclaimed water supplier that outlines quality and quantity expectations as well as a method for dealing with water that exceeds expected limits.
If you manage the grounds of a golf course, park, cemetery or college campus, you'll provide a service to your community by irrigating with wastewater effluent. In return, you'll generally pay less for water (not always), ensure a steady supply of irrigation water and receive some fertilizer value. However, for these benefits, you must be prepared to face new challenges associated with the use of reclaimed water.
City management usually promotes its reclaimed water based on the "it's-almost-clean-enough-to-drink test." While this seemingly lighthearted analysis is sometimes true, many waters that are "clean enough to drink" are actually poor choices for irrigation.
When it comes to water quality, water-treatment professionals do not speak the same language as those of us in the green industry. Wastewater people talk about biological oxygen demand (BOD), turbidity and bacterial counts while we horticultural types are concerned about electrical conductivity (EC) and sodium adsorption ratio (SAR).
Can't we all just get along? Grounds managers and waste-water-system operators need to begin communicating on the same wavelength. As the use of reclaimed water grows in popularity (and demand), we depend more on one another. We should get to know the people responsible for both fresh-water and wastewater treatment and make every effort to understand what is happening upstream-so to speak. Learn from where your water comes and how it has been processed before it gets to your irrigation system. Also, educate the people involved in water treatment about the intricacies of irrigating with effluent.
Beware of salinity Salinity issues cause the biggest headache for us. Total salts can include calcium, potassium magnesium and sulfate and sodium chloride. The osmotic effect that they have on plants as they accumulate in the root zone is a problem as well as the negative, sealing effect that sodium has on soil structure and permeability. Raw, fresh water may already contain salts of calcium, magnesium or sodium-and it picks up more as it travels through a municipal water system. Sometimes fresh water is immediately adulterated as it is "softened" with soda ash (sodium carbonate) to decrease hardness or to remove iron and manganese. This process raises the pH to 8.5 (or more) and substantially increases the sodium and bicarbonate content while precipitating calcium and magnesium.
Quality: To have and to hold until we pass it on Water acts as a solvent and a transport mechanism as it passes through homes and businesses. Water softening by homeowners and commercial users can add substantial amounts of sodium chloride to the water supply. Waste from your property contributes organic matter, sodium-based detergents, bleaches, soaps and other chemicals. High-pressure wash bays in municipalities use sodium-phosphate detergents to remove road salt, soil, grease and solids.
Commercial effluent can have a profound effect on the final quality of the reclaimed irrigation water. Everyone who uses municipal-water supplies contributes a variety of components to wastewater. According to Al Guernsey, district environmental administrator with the Kansas Department of Health and Environment, local water districts or municipalities typically regulate the industrial discharge in a sewer system. Your local permitting agency is responsible for making sure that the final, diluted wastewater complies with state and federal requirements for discharge into rivers and streams. Guernsey says the discharge from two identical commercial operations can vary between localities because the current load level, volume and the condition of the receiving waters dictate the discharge requirements. It is, therefore, difficult to generalize about the output of a specific industrial operation.
The effect of industrial inputs is often seasonal. Canneries and sugar refineries, for example, are sometimes allowed to use a municipal sewer system, and they only operate for a portion of the year. Some food processors use lye (sodium hydroxide) as a cleaning agent and salt (sodium chloride) as a preservative. This can be a big problem for irrigators if seasonal loading happens to occur during the heat of summer when soil-salinity problems are most pronounced. Thus, it is important to be forewarned of the flux in water quality.
Pass the salt Unfortunately, the waste-water-treatment process usually does not deal with inorganic salts. It is designed to remove solids, decrease organic matter and disinfect. If you are interested in, or currently are using recycled wastewater, you should visit the waste-water-treatment plant that supplies irrigation water in your area and become familiar with the specific processes they use. Develop a rapport with the operators and ask to look at historical records. You'll soon realize that wastewater-treatment operators often speak about primary, secondary and tertiary treatment. You won't seem ignorant if you ask them to explain each step. They know this isn't common knowledge and that variations exist among these treatments.
Primary, secondary and tertiary treatment The general purpose of primary treatment is to remove suspended solids. This is generally accomplished with screens and settling basins. Sludge settles, the system removes it and then moves it to secondary treatment.
Secondary treatment involves some sort of biological degradation. These processes typically involve aeration and a second sedimentation-settling period. Then the system disinfects the effluent with chlorine and discharges-unless it needs additional, advanced treatment.
Although this next step is uncommon, advanced-or tertiary treatment-might include removal of inorganics such as phosphorus, nitrogen or metals. Some methods dictate further disinfecting to decrease coliform bacteria before discharge. Salinity problems for golf courses
None of these steps diminish either the total salinity or the sodium content of the water. In fact, the total salinity of municipal water can increase by as much as threefold from the fresh-water source to the final effluent. The SAR may increase by a factor of 5 to 10 times.
These increases in salinity have caused problems for golf courses. Mike Huck, agronomist with the USGA's Turf Advisory Service (Orange County, Calif.) visits more than 100 golf courses each year. Huck agrees that conserving water in that region is important, and it is inevitable that turf managers will have to deal with reclaimed water. However, you'll have to adjust your cultural programs to deal with problems associated with effluent use-total salinity and sodium's effect on soil. Also, he says the use of reclaimed water dictates many changes in management. The most profound changes relate to dealing with total salinity and the sodium's effect on the soils.
Huck sees more severe occurrences of black layer on effluent-irrigated golf greens. You may find soggy turf on some golf courses irrigated with reclaimed water because the superintendents apply extra irrigation water to leach salts through the root zone. It is common to apply a leaching fraction of 15 to 20 percent more water than the turf needs to meet evapotranspiration demands.
As salts accumulate in the root zone over time, you may be forced to change turf species. Poa annua golf greens perform poorly under saline conditions. On some courses, the superintendents replaced bermudagrass-which is fairly salt tolerant-even more salt tolerant with paspalum. You may need to replace sensitive trees and ornamentals due to increased salinity or toxicity from boron and chlorides.
Savings and costs Your savings from reclaimed water use can be offset by increases in retrofitting, cultivating and amending soils. Some golf courses now deep-tine aerate all irrigated turf up to twice a year. They also incur expenses for gypsum applications and acid-based water treatment.
Retrofitting your irrigation system can be expensive. You must seal off cross connections between potable and reclaimed water and install back-flow valves at various locations. You'll often need intake filters to prevent algae and suspended solids from clogging nozzles.
Warnings and precautions regarding exposure Sometimes you can use only potable water near homes, clubhouses and greens, so you must have two separate systems. In these cases, mark quick couplers and new-pipe installations with purple to indicate that reclaimed water is in use. You'll need signs in English and Spanish around the property warning people not to drink the water.
Operators of inefficient or low-capacity irrigation systems face a dilemma due to concerns about exposing the public to potential pathogens because cities often restrict sprinkler irrigation to times when the public is not present. Local health regulations normally limit sprinkler irrigation only to the nighttime hours-commonly 8 to 6. Thus, the irrigation system must be capable of completing its cycle within 8 to 10 hours. If you want to irrigate during the day-to cool turf or dissolve a fertilizer-then someone must physically man the control box and ensure no one is nearby. Larry Stowell, a certified professional agronomist with Pace Consulting (San Diego, Calif.) says, "I feel sorry for low-budget courses that cannot afford the assistance that may be needed to effectively manage these resources." Stowell recently reviewed some of the challenges at various California golf courses and is well aware of the need for a higher level of management. He recently assisted Big Canyon Country Club (Newport Beach, Calif.) in developing a contractual agreement with the Orange County Water District.
That contract binds the city of Newport Beach to pay for some of the retrofitting at the club. It outlines a minimum quantity of reclaimed water that the club must use annually and the city's capability to deliver it at the needed rate in gallons per minute. Then it specifies maximum water-quality parameters for EC, total dissolved solids (TDS), SAR, adjusted SAR (SARa), bicarbonate, boron, chloride and sodium. If the effluent exceeds these limits for an extended period, the club retains the right to disconnect from the reclaimed water supply and use potable water until the city corrects the problem. The contract also includes provisions for further reimbursement by the city if damage occurs on the golf course. Stowell regrets that they were not able to tie the price to quality, stating, "Negotiations on price and quality should begin early. What other commodity can you imagine where price is not related to the quality of the product delivered?"
He fears that, in the future, we will see litigation throughout the country over these issues based on an implied warranty. In fact, a Texas farmer who used reclaimed water for years recently filed a $2 million lawsuit against a municipality and a beef packer over damage to his land. The case was settled out of court.
Damage control Users of reclaimed water are beginning to send a serious message, and some operators of water-treatment systems are getting the hint that their waste may damage soils and plant life. The Moulton-Niguel Water District in Southern California now discourages homeowners from using water softeners. Recent research by Dr. Ali Harivandi, a turf-extension specialist at the University of California (Hayward, Calif.) shows that you can minimize turf damage if you use potassium chloride in water softeners instead of sodium chloride.
Here for the duration Reclaimed water is here to stay. Honest dialogue between grounds managers and water-treatment operators will lead to sustainable practices. If you use-or are planning to use-reclaimed water, you must learn everything possible about the source of the water, its overall quality and seasonal fluctuations that may impact your operation. Consider soil type, plant species, irrigation-system efficiency and climate when assessing the degree of impact. Wherever possible, document expectations of price, quantity and quality in writing.
John Zupancic is the founder of SoilQuest International in Dodge City, Kan. He is an independent agronomist and consultant for the golf-course industry.
Want to use this article? Click here for options!
© 2013 Penton Media Inc.