FIG. 7.52.4 Artificial underground drainage system design.
and sufficiently large to accommodate solid particles in the waste. An efficient nozzle is the 5/8-in Rainburg 1-acre nozzle.
Wastewater treatment facilities have sprayed a concentration of as much as 5% SS in the waste. The greater the volume a nozzle can spray, the less chance the nozzle will freeze up.
The ideal soil type for spray irrigation is a sandy to sandy-loam type. Clay soils pass little water and are not
suitable for spraying. Some sandy soils exhibit clay lenses or strata that act as a barrier to flow. A ground cover assures longevity of the spray field. If wastes is applied to barren or plowed soil, particle classification occurs because of the direct bombardment of soil by the liquid.
Particle classification reduces the porosity and permeability of the soil. When the soil is plowed after particle classification, the disruption eventually extends the area of decreased permeability farther down in the soil. Continued disruption of the soil causes an area of fluid-flow resistance to develop below the depth of plowing or subsoil-ing.
Once this condition has occurred, the area is useless for waste treatment. Therefore, the spray field should not be plowed, and a cover crop should be maintained. Experi
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