N.C. STATE UNIVERSITY

College of Agriculture and Life Sciences
N.C. Agricultural Research Service
N.C. Cooperative Extension Service


On-Site Treatment and Disposal of Domestic Wastewater Using Alternative Types of Septic Systems.

Prepared by: Michael T. Hoover

Long-Term Objectives

1. To understand the rates, processes, and environmental conditions that control effective on-site treatment and dispersal of household wastewater under a broad range of soil conditions.

2. To help develop and improve on-site technologies that will allow people to use their land in an economically affordable way that protects their communities health and investment as well as the environment.

3. To provide research based training and educational opportunities regarding on-site septic systems for county agents, state and local regulatory officials, private consultants, installers, operators, realtors, and the general public.


Short-Term Objectives:

1. To evaluate the effectiveness of sand filter pretreatment units and pressure distribution disposal systems for household wastewaters.

2. To assess the performance of sand lined trench systems on wet, clayey soils of the lower coastal plain in northeaster North Carolina.

3. To develop a critical mass of professionally trained on-site system operators who can keep alternative types of septic systems operating properly for the long term.


Accomplishments

1. Lack of proper maintenance was identified as the primary cause of failures of alternative on-site systems although serious design, siting, and installation problems were also identified. State rules were modified to address these concerns and require professional operation and maintenance.

2. The North Carolina Subsurface System Operators Training School was established in 1992 and over the past three years about individuals have participated in this training and passed a state certification exam to become Certified Subsurface System Operators.

3. The NCSU On-Site Wastewater Management Training Facility was established in 1989 at the Walter Bright Farm in Chatham County to provide hands-on learning opportunities. This Field Training Facility is now being duplicated at educational institutions across the country due to efforts of the newly formed Consortium of Institutes for Decentralized Wastewater Treatment.

4. An in depth assessment of sand lined trench (SLT) septic systems on wet clayey soils indicated that when these systems are used in conjunction with- well maintained drainage systems, they performed comparable to conventional septic systems used on well-drained, loamy soils.


Significance

These accomplishments have directly led to changes in state rules and the state-of-practice regarding onsite systems in North Carolina. They have resulted in people being able to build homes and safely manage wastewater on land that in the past would be turned down for a septic system permit.


Future Plans

1. Development of a second On-Site Management Training Facility in eastern North Carolina.

2. Assessment of the effect of depth and duration of saturation on wastewater treatment in wet soils.

3. Evaluation of methods to improve the siting and long-term operation of large on-site systems serving subdivisions schools and small communities.