1: Low Pressure Pipe (LPP) &
2: Pressure Manifold Systems

These systems are particularly useful when the drainfield is at a higher elevation than the house, because a pump tank is used. Effluent filters are required, as of 1/1/99, for ALL new systems (including conventional). Pressure systems provide better effluent distribution. Improved distribution generally provides better treatment and longer system life. LPP systems require a certified subsurface operator to periodically inspect the system.

1a: The LPP repair class students get to trouble-shoot malfunctioning systems using mock failures. Several types of failures are represented, and course participants have to determine the problem based on the symptoms presented.

3: Gravel-less Systems

Two types of gravel-less distribution field trenches are displayed at the Training Center. The chamber nitrification trench system has been reviewed and found to meet the standards of an innovative system when all of the conditions are met. Chamber systems are arched, ribbed, plastic chambers that look similar to mini quanset huts. The bottom is open and the sides are usually perforated, which allows some wastewater contact with the sidewalls. One advantage of chambers is that wastewater is in direct contact with the soil along the entire bottom of the trench, thereby greatly increasing the theoretical absorption area and the amount of oxygen that can enter the system.

The polystyrene systems have conventional 4-inch perforated distribution lines surrounded by gravel-sized pieces of polystyrene. The materials are bundled together, which makes them very transportable. It is also possible to install these lines in curves and arcs, which cannot
easily be done with conventional materials.

4: Conventional System

The conventional system consists of a septic tank, distribution box, and absorption field. The distribution box is intended to evenly split the flow from the septic tank among the absorption field laterals (trenches). The trenches consist of a perforated pipe within a gravel bed of appropriate dimensions. When the ground water table is too close to the surface, an aerial-fill (mound) absorption field may be the recommended alternative.

5: Peat Filter

These systems take septic tank effluent and pass it through Irish peat, in a manner similar to a sandfilter system, and then load the treated effluent into the soil for final treatment and disposal. The peat chambers can be installed aboveground, which is helpful in situations where it is difficult to install a totally in-ground system. The system is designed to reduce bacteria load by 95 to 99%, total suspended solids (TSS) by 95 to 99%, and biochemical oxygen demand (BOD) by 99%.

6: Intermittent Sand Filter

Sand filters are often divided into two varieties: single pass and recirculating. The filter media can consist of sand or other approved media with the appropriate size and uniformity coefficient. The media serves as structure that encourages biological growth and allows the applied effluent to "ooze" slowly through the filter, thereby giving the bacteria and other organisms time to digest the material in the septic tank effluent. In a recirculating system, the effluent passes through the filter several times. Depending upon the design, the systems can also provide nitrogen reduction.

7: Intermittent Sand Filter (cut-away view):

This model presents a cut-away view of the in-ground system, previously described.

8: Brunswick Bed

This system was developed by Brunswick County Health Department personnel.

9: Groundwater Table Monitoring Well

Groundwater table depths are known to vary with season and distance from drainage systems. The well will be used to monitor water table fluctuations at this site. The information will be compared to the physical characteristics (such as color patterns and distribution) of the soil.

Table 1: On-site system selection

System Type	Cost ($)	Selection for use
Conventional	1,500-3,000	Generally first choice; anywhere suitable
Gravel-less trench a) chamber b) polystyrene	1,500-3,000	Anywhere suitable, may be useful in areas where space limits prevent use of conventional system
Low Pressure Pipe	5,000-12,000	High water table, space limits, historic fill, drainfield is higher than the house, or better effluent distribution is needed
Brunswick Bed and Fill	4,000-6,000	High water table, space limits
Pressure Manifold	5,000-7,000	High water table, space limits, when drainfield is higher than the house
Intermittent Sand Filter a) LPP discharge b) surface disposal	7,000-18,000	High water table, space limits, improved treatment (higher quality effluent)
Recirculating Sand Filter a) LPP discharge b) surface disposal	7,000-18,000	High water table, space limits, improved treatment (higher quality effluent)
Peat Filter a) gravel discharge b) trench discharge c) surface disposal	7,000-18,000	High water table, space limits, improved treatment (higher quality effluent)

E-mail me at: diana_rashash@ncsu.edu or Mail me at: Dr. Diana Rashash Area Specialized Agent-Environmental Education North Carolina Cooperative Extension Service 604 College St., Room 8 Jacksonville, NC 28540 Phone: (910)455-5873 Fax: (910)455-0977

Southeast Regional On-site Training Center Septic System Information Websites Area Agent list Environmental Education website Onslow County Homepage

This page last revised on: 6/13/01

http://www.ces.ncsu.edu/onslow/staff/drashash/enved/sitebrochure.html

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