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.
The DNREC Division of Water reviews and prepares spray irrigation system construction and operation permits for municipal, industrial, residential, and commercial wastewater purposes. Division 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.
Spray irrigation system permits are issued under the state’s Regulations Governing the Design, Installation and Operation of On-Site Wastewater Treatment and Disposal Systems (7 DE Admin. Code 7101) available as a PDF version with exhibits and attachments.
When reclaimed water is used, regardless of whether the intent is to augment water supplies or management nutrient in treated effluent, there are several positive benefits including water conservation, groundwater recharge, reduced energy consumption, improved agricultural production, and reduced nutrient loads to Delaware’s water.
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.