Evaluation of On-site Wastewater Disposal Systems in Mississippi Coastal Areas

Groundwater and surface water contamination have been linked to inadequate or failing on-site residential wastewater treatment and disposal systems. The potential for groundwater contamination in coastal areas with shallow water tables is higher; subsequently the ability of soil, microorganisms, and vegetation to mitigate pollutants may be reduced. This study evaluated the performance of the four types of on-site wastewater treatment and disposal systems predominantly used on the Mississippi Gulf Coast. One type of system was deemed inappropriate for this region as none of the dozens of installations examined were functioning acceptably. Of the remaining three types, subsurface water samples were collected from representative sites using lysimeters and monitoring wells. Apart from general performance evaluation of these systems, seasonal changes translating into possible variation in disposal efficiencies and groundwater contamination were investigated. Statistical analysis of variations in organics (COD and BOD₅), nitrogen (TKN and NH ₄ ⁺ ?CN), and fecal coliform concentrations was used to identify probable deficiencies in systems tested and to recommend changes to governing standards.