discharge it below ground where it is absorbed and treated by the

soil as is percolates towards groundwater.

     Soil Absorption Systems are capable of treating organic

materials, some inorganic substances and pathogens present in the

wastewater through physical, chemical and biological processes. By

acting as a filter, exchanger, adsorber, and providing a surface on

which many chemical and biological processes may occur, Soil

Adsorption Systems are capable of enhancing treatment of wastewater

from septic tanks (U.S. EPA, 1980).

     Wastewater microbes can be effectively treated through 1.2 m

of soil if the soil is unsaturated. Unsaturated conditions enhance

the removals of pathogenic organisms and other pollutants from the

wastewater   by  increasing  their  chances  to  react   with  soil

particles.   Furthermore, under unsaturated conditions the larger

pore volumes often contain air which allows for the efficient

aerobic decomposition of many suspended and dissolved organic

substances present in the wastewater. These processes tend to work

much better under unsaturated conditions because the wastewater

movement is primarily through only the smaller pore volumes of the

soil which increases both the retention and liquid-solid contact

time. When saturated conditions exist, the water flows through the

larger pores and receives minimal treatment.

      For instance, Romero (1970) cited a number of studies in which
 the effluent intersected or was close to the water table. Elevated

 bacteria levels were temporarily detected up to 24.4 m horizontally

 away from the source.   USEPA (1980), on the other hand, reports