As the demand for fresh water resources intensifies and the price of fertilizers soar, the horticulture sector is eyeing recycled wastewater as a potentially valuable resource to meet both the water and nutritional demands of urban landscaping. Wastewater is not only a valuable source of recycled water, but it is rich in nitrogen and phosphorous, two of the key nutrients found in commercial fertilizers.
The state of Florida provides a key example of how recycled water can be put to good use -- more than half of the state's reclaimed wastewater is reused for irrigating recreational facilities such as parks, sports turf, golf courses, and residential landscaping. Recent studies have shown that using recycled water for irrigation is not only an efficient use of our water resources, but offers additional benefits to turfgrass, as it is rich in nutrients that are essential for plant growth and vitality.Nitrogen-rich Recycled Water Good For Turfgrass
According to a study that was recently published in the journal HortTechnology, wastewater treatment undergoes three stages of treatment: a primary stage; a secondary stage; and an advanced stage of treatment. Reclaimed wastewater that has undergone at least the first two stages of treatment can be defined as reclaimed water. According to the study's authors, the primary difference between reclaimed water that has undergone secondary treatment compared to reclaimed water that has undergone advanced treatment is that the latter further reduces the levels of chemicals and nutrients found in the water.
"Water receiving advanced treatment typically has 25% of the nitrogen (N) and phosphorus (P) and less soluble salts than contained in secondary treatments," explained Jinghua Fan and George Hochmuth, co-authors of the study. "Increasingly, the reclaimed water used for irrigation is from advanced wastewater treatment facilities."
The interest in making use of this valuable resource for residential and urban irrigation is growing as more wastewater is reclaimed and research in this area expands. One of the key benefits of utilizing nitrogen-rich recycled wastewater is that it potentially allows for the reduction in the application of other nitrogen-rich fertilizers. However, we do need to proceed with caution, as nitrogen is a drinking water contaminant that could potentially contaminate groundwater sources.
"It is important to determine the optimum combinations of water and nutrient applications to support turfgrass production without impairing groundwater through losses of nutrients from the landscape," Fan and Hochmuth explained, noting that little research has been conducted on to what degree urban lawns could utilize the nitrogen available in reclaimed water that has undergone advanced treatment.
Results of a study conducted by researchers from the University of Florida show that irrigation water containing higher nitrogen concentrations benefited turfgrass growth, but wastewater that has undergone advanced treatment, reducing nitrogen levels significantly, has little benefit to turfgrass growth at concentrations less than 5 mg/L.
Maximizing the benefits of the nutrients in wastewater for irrigating urban landscapes without polluting underground water sources could therefore be a fine balance.
Jinghua Fan, George Hochmuth, Jason Kruse and Jerry Sartain. Effects of Reclaimed Water Irrigation on Growth and Nitrogen Uptake of Turfgrass. HortTechnology October 2014 24:565-574.