Spray Irrigation Systems

Spray irrigation of reclaimed water has been in use in Delaware since the 1970s. Reclaimed water is water that has been recovered through the treatment of wastewater at wastewater treatment facilities. Once reclaimed water has been properly treated, it can be applied to agricultural fields, golf courses, forests, parks, roadway medians and cemeteries.

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Marlene Baust
Groundwater Discharges Section

The Large Systems Branch reviews and prepares spray irrigation system construction and operation permits for municipal, industrial, residential, and commercial wastewater purposes. Branch staff inspect facilities each year and receive monthly, quarterly, and annual reports from facilities. This data is reviewed annually, at a minimum, and for a five-year period at permit renewal.

Reclaimed water contains some nutrients (nitrogen, phosphorus and potassium), suspended solids, and small quantities of bacteria, salts and metals. Before it can be reused, however, wastewater must undergo significant levels of treatment and disinfection to eliminate odors and destroy pathogens (disease causing organisms), in order to protect public health and the environment.

Benefits of Using Reclaimed Water

When reclaimed water is used for irrigation, it helps to recharge groundwater and reduce the amount of wastewater discharged directly into Delaware’s rivers, streams and bays. The nutrients in reclaimed waters replace commercial fertilizer a farmer would otherwise have to buy instead of adding to the nutrient loading of Delaware surface water.

Using reclaimed water for non-drinking purposes can also help conserve and make the most efficient use of Delaware’s water supply. Potable water is saved for human use.

And spray irrigation of reclaimed water on farmlands helps to preserve agricultural lands and improve on-farm profitability. For example, at dedicated agricultural reuse sites, the farmland is explicitly set aside for the purpose of receiving reclaimed water to grow crops. Virtually all of the nutrients needed to produce the crops are supplied by the reclaimed water. Dedicated agricultural sites are often contracted for use for a 20 to 40 year period.

At voluntary reuse sites, on the other hand, highly treated reclaimed water is made available to farmers for routine agricultural purposes, saving the farmer the cost of installing and operating an expensive irrigation system, while supplying supplemental nutrients.

Treatment Requirements and Restrictions

The level of treatment required for reclaimed water depends on how it will be used and the degree of public contact the site may receive. For example, at sites where public access is not restricted (such as golf courses, nurseries, cemeteries or public lawns) the highest level of treatment is required. However, on restricted-access agricultural sites where buffers from the spray fields are at least 150 feet, and public access is restricted, treatment levels are not as stringent.

The amount of reclaimed water that may be applied to a site is limited both by hydrology (how much water the site can absorb) and the nutrient requirements of the crop or grass grown.

There are limits on what type of crops can be grown on fields using reclaimed water. Crops for direct human consumption that receive no processing prior to human consumption, and may be eaten raw, such as strawberries or tomatoes sold at local produce stands, may not be grown on sites receiving reclaimed water. However, any feed crops, ornamental flora, or vegetable/fruit crops that will be processed prior to consumption may be grown using reclaimed water.

And, depending on local factors, buffers may be required to limit access to spray irrigate lands.