Sunday, December 21, 2014

Frank S. Rossi

The author is a professor of horticulture at Cornell University.

Features

Reclaimed water

Cover Story

Using wastewater can be a solution for areas hit by droughts.

July 27, 2011

The recurrent droughts experienced through the United States each year have given the turf industry pause. Watershed commissions that cross state lines, water management districts that determine water needs and municipal water suppliers continue to question the use of potable water for recreational (read: non-essential) use.

The Northeast Climate Center reported that 2010 in the Northeastern U.S. was the driest in recorded history. The Southeast U.S. is in the throws of the most significant drought in the last 100 years. The Florida turf industry may soon be facing phased-in restrictions that will allow watering of lawns once per week or not at all.

With less than 1 percent of the world’s water available for human consumption and 80 percent of the fresh water consumed for agriculture, concern is growing in the industry on water used for maintaining greenspace.

Wastewater lawns. With population growth and the demand for potable water expect to increase, the turfgrass industry can no longer take a passive approach to water use issues. The Western U.S. receives only one-third of the nation’s rainfall, yet uses 80-85 percent of the nation’s fresh water.

Effluent wastewater can be delivered following primary, secondary or tertiary treatment at a wastewater treatment facility. Primary treatment mechanically removes the majority of the solid waste with screens, grinders and settling tanks.

While primary treatment involves mechanical removal of solids, secondary treatment engages biological processes to remove the majority of the remaining solids.

Secondary treatment may also involve chlorinating prior to discharge. Water for turf and landscape uses must be at least experienced secondary treatment.

Several processes may follow secondary treatment and include using chemicals to flocculate remaining solids, then through more sediment removal and various methods of filtration.

A reverse osmosis process or chlorinating can occur prior to release, producing highly purified water.

In the end, the water will likely contain a variety of nutrients (from the waste), metals (from the flocculation) and salts (from the purification) that will require careful management to minimize their impact on turf quality.

Interestingly, real estate developments are constructing their own wastewater or desalinization treatment facilities.
Several Audubon International Signature Properties are leading the way with small facilities that utilize ultra filtration and biological reactors to treat wastewater before reusing.

Estimates are that the $500,000 price tag can be recovered in a few years based on the increasing cost and restriction placed on irrigation water is South Florida.

Increased awareness.  Lawns managed with effluent water must realize that quality can be variable and will always have a variety of “contaminants” that will require specific management practices.

Professors Bob Carrow and Ronny Duncan from the University of Georgia authored “Salt Affected Turfgrass Sites” in an effort to bring together the best thinking on managing turfgrass with poor quality water. The title of the Carrow and Duncan book clearly identifies the major challenge with effluent irrigation water – high salt content. But it is not the only issue.

The major agronomic and environmental issues suggest that the first step to using effluent water is to establish a regular monitoring program.

Salty turf.  In a presentation at the 2010 Florida Turfgrass Conference, Carrow stated that “The three most important aspects of managing high salt content irrigation water is leaching, leaching, leaching.”

This is not simply a matter of copious amounts of water that keep salts moving downward, the you must know the type of salt that must be leached, rainfall amounts, turf species tolerance range and time of year.

Sodium salt can have a direct influence on plant growth in a manner similar to how dog urine burns leaf tissue (although dog urine is a different salt).

However, while the direct burn from high salt content irrigation water is rare, high sodium content soils often produce plants that have restricted rooting and develop drought stress symptoms. Depending on the water source and rainfall pattern, the long-term effects of sodium on soils is well documented.

As sodium content increases in the soil, the vital process of aggregation is disrupted. Sodium molecules absorb large amounts of water and swell.

The swelling prohibits silt and clay particles from making larger aggregates that offer a variety of pore spaces for water and nutrients.

Where to now?  Most landscape managers, especially in areas with adequate rainfall take their high quality irrigation water for granted.
If the population continues to grow, the leadership effort by the turf industry in using effluent water could be viewed as facilitating “smart growth.” In other words, communities will need landscapes as outlets for societies waste, whether it is water or compost. L&L
    
The author is an associate professor at Cornell University.

 

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