Environmental experts to speak on spray irrigation in Maryland

Land application of sewage wastewater is getting a closer look. There are several proposals in Worcester County, Md. and the coastal bays watershed to use land application sites for wastewater treatment, and the county has scheduled a public information meeting for county residents to learn more about the environmentally friendly practice.

Land application, or spray irrigation, disposes of treated municipal wastewater by spraying it on land. Treated to the same level as direct discharge, sprayed wastewater evaporates into the air, is taken up by plants, percolates through the soil, and recharges groundwater.
  
Land application has advantages over conventional direct discharge to streams because the wastewater replenishes groundwater and increases base flow in streams. "Natural" treatment takes place in the soil when plants and other organisms remove nutrients (nitrogen and phosphorus) from the wastewater. This method of waste disposal essentially eliminates stream water pollution from a treatment plant.

Along with man's increasing numbers has come a more thorough understanding of the environment and significant technological advances. Sewage treatment plants are now capable of producing effluent of a much higher quality than ever before. But from a water-resources management standpoint, discharging treated municipal wastewater directly into surface waters still has a major disadvantage.

Although treated and disinfected, most wastewaters contain relatively high levels of nitrogen and phosphorous. These elements contribute to algae growth, depleted oxygen levels, and the loss of water clarity and aquatic grasses.

Although it is the preferred alternative, not all land is ideal to receive wastewater. The county and state identify proper conditions and soil types so there is no detrimental health or environmental effect to nearby communities, wells and sensitive areas. To avoid contamination of aquifers, regulators require careful placement of spray fields and monitoring of groundwater.

First, the wastewater must be treated prior to discharge either in the water or on land. Pre-treatment requires that the quantity and quality of the treated wastewater are satisfactory for application. These parameters determine how effective land treatment will be in renovating wastewater and what effect the wastewater will have on the soils and ultimately the groundwaters of the state.

Additionally, the receiving site must have satisfactory requirements in terms of geologic, soil and hydrologic characteristics that influence the ability of a site to renovate and recycle wastewater. For land treatment, there exists an optimum geology-soils-hydrology combination.

Several local development proposals are consistent with the Comprehensive Plan due to the use of spray irrigation to achieve an 80-percent reduction in nutrient loadings and for encouraging development in an area designated for growth.

The use of treated effluent for irrigation purposes is now being considered a commodity in many areas of the country and is used to water public and private lands. For example, Delaware has set a goal of having all of its wastewater land applied.

The Worcester County Commissioners have scheduled a public information meeting on spray irrigation on Tuesday, Nov. 6, at 7 p.m. in the Worcester County Government Center in Snow Hill. At the meeting, experts from the Maryland Department of the Environment and the Worcester County Department of Environmental Programs will explain the technology of land application disposal of treated wastewater as recommended in the county's comprehensive plan. In addition to explaining how spray irrigation functions, they will discuss the health and environ- mental aspects of this technology. All interested citizens are encouraged to attend. For information call 410/632-5651.