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117 <br /> In a community system, the effluent from the STEP tank goes first to mains, somewhat <br /> larger diameter plastic pipes (24" diameter)which typically are installed running parallel <br /> to roads. The mains coalesce into other mains that deliver the effluent to the centralized <br /> secondary treatment system. <br /> The primary feature of STEP systems, including the mains that take effluent to the <br /> secondary plant, are that they are sealed and under pressure. First, this eliminates <br /> infiltration of rainwater that would increase the volume of effluent needing to be <br /> processed. Secondly, flow is not controlled by gravity,but rather by pressure generated <br /> by the STEP tank pump. As a result, mains can go up as well as down to follow land <br /> contours. Secondary plants can be located where most convenient rather than at a lower <br /> elevation. In many cases, STEP systems are typically considerably more economical <br /> than conventional gravity sewers. <br /> STEP and secondary systems are modularized in a way that overall system design is very <br /> flexible. It is feasible to have one secondary system per house or dozens of residences per <br /> secondary system. We will typically design the complete system(to serve the maximum <br /> anticipated flow from the community), but then phase in the installation of the system as <br /> the community grows to its full potential. In this manner, additional units can be added <br /> at the plant site as effluent volume increases with community expansion. Again, the <br /> flexibility in the system will allow us to phase in the systems as the community grows. <br /> The Orenco AdvanTex system for secondary treatment consists of a series of textile <br /> filters that promote exposure of the wastewater contents to bacteria that decompose the <br /> organic matter. The large surface area of the filter enhances decomposition. The liquid is <br /> intermittently recirculated over the filter. AdvanTex units come in a variety of sizes, and <br /> multiple units can be combined to increase capacity. In my opinion, the units are <br /> relatively compact, quiet, sealed, odorless and unobtrusive. They are approved for use in <br /> many jurisdictions, including North Carolina. Advantex in NC links to a video describing <br /> one such system. <br /> A major benefit of the Advantex system is that its discharge water is clear, odorless, and <br /> has impressively low levels of fecal coliform bacteria, BODS, TSS, turbidity, as well as <br /> nutrients (see attached technical reports). Indeed, in many situations this effluent is <br /> suitable for reclaimed water applications. <br /> Beyond primary and secondary system considerations, the most important one is the <br /> means of discharging the final effluent,because this is what determines how much land <br /> will need to be set aside for this purpose. The subsurface drip dispersal (SSDD) system <br /> appears well-suited to our use. It consists of small diameter(-1/2")plastic tubing buried <br /> six-nine inches underground with "nodes" (i.e., discharge ports) located at 24 inch <br /> intervals along the tubing. Fields are laid out as parallel runs of tubing called "laterals", <br /> each connected to a supply manifold at one end and a return manifold at the other end. <br /> Individual runs are typically spaced 24 inches apart. Thus, each node supplies effluent to <br /> a 4 square foot area. The system is under pressure of typically 10-50 psi to discharge the <br /> effluent at the nodes. The tubing is considered"pressure compensating" such that all <br />