:: Perc Rite System :: :: Drip Irrigation System ::The Perc-Rite ¨ system is a computer managed, drip irrigation, wastewater disposal system. Computer management allows extremely accurate flow control and operator friendliness. By using Netafim Bioline dripper tube, even and controlled wastewater dispersal is achieved over the entire disposal area. This overview of the Perc-Rite ¨ system will present general system capabilities, as well as the site-specific options that are available.
Combining state of the art computer controls with the Netafim Bioline tubing provides an unmatched level of flow control. The Perc-Rite ¨ unit measures the effluent flow to the fraction of the gallon. It is this flow measurement, which is monitored by the computer that insures that each absorption area receives the design flow of wastewater effluent. Once the effluent is measured and leaves the unit, the Netafim Bioline tubing will disperse it. The effluent is discharged below the soil surface through a patented, chemical-resisting, pressure compensating, "drip" poly-tubing. The construction of the Bioline drip tubing is unique in that the internal diaphragm and labyrinth provides for an exact amount of effluent to be discharged from each of the emitters. The emitters are normally spaced at two-foot intervals along its entire length. The "Bioline" drip tubing maintains a constant dripper flow over pressure ranges of 7 psi to 60 psi. Because the effluent is discharged at a relatively low rate, large quantities of effluent may be distributed over long periods of time without saturating the surrounding soil. This reduces the possibility of run-off or surface water ponding.
The filtration package provided with the Perc-Rite ¨ unit is unmatched industry wide. The Arkal Spin-Klin filters are matched with automatic backflushing to protect the Netafim tubing from clogging by particles from the dosing tank. The backflushing of the filters can be initiated in two ways. First, backflushing can be initiated by total flow discharged through the system. The number of gallons that will start a backflushing cycle can be customized to meet any site's needs. The second backflush triggering mechanism is a differential pressure switch. This switch acts as a fail-safe to ensure proper effluent filtration. The computer will measure differential pressure across the filter bank. When the pressure differential reaches a preset point the filters are automatically backflushed regardless of flow through the system. This feature guarantees proper effluent filtration and flow even during periods of changing effluent conditions.
When the back flushing schedule is triggered, the filter valve closes, thus blocking the flow of unfiltered effluent to the filter. After a short delay, the flushing valve opens, thereby discharging the filtered impurities into the collector manifold. The closing and opening procedure of the filter and back flush valves causes a change of flow within the filter. When the filter valve closes, the upstream pressure is blocked, while the downstream pressure reverses the flow of the filtered effluent back through the outlet of the filter. The inverted flow carries accumulated particles from the filter rings through the open back flushing valve. The water then exits through the collector manifold to the influent side of the pretreatment tank. The back flush procedure lasts approximately fifteen seconds. Then the back flushing valve closes, the filter valve opens, and the inverted flow is cut off. Only after the first filter has completed its flushing cycle, will the second filter begin its cycle of back flushing. Each subsequent filter is then flushed in the same manner.
Automatic drip field flushing is another feature unique to the Perc-Rite ¨ system. This flushing allows the tubing to be scoured free of any slimy buildup that might hinder performance. By cleaning the tubing, pipe, and manifolds, emitter clogging is eliminated. Thus the dripper lines will continue to deliver precise and accurate doses to the absorption area. The dripper lines are automatically flushed after a preset number of dosing cycles. This function is activated by the controller which opens the field flush valve, thus allowing the flushed effluent to be returned to the pretreatment tank. The duration of this cycle is approximately three minutes. The flushing action creates a high effluent velocity, which produces a cleaning action over the inside walls of the dripper tubing, P.V.C. manifolds, and emitters.
The Perc-Rite ¨ Effluent Disposal System integrates on-site monitoring with the operation of the system to produce an unmatched level of system control, operator friendliness, and environmental safety. This system also offers the unparalleled option to monitor the system from a remote location. This remote monitoring is accomplished through either a digital communications receiver located in our office or remote personal computer interface. The Telemetry Equipment monitors the following functions:
High water alarm (audio) Power out alarm (audio) Pump start control Timed back flush of filters Automatic flushing of drip system Flow variance In the event of a power outage or a high water condition, an audio alarm will sound. Immediately, the service center can be notified via optional telephone link through a digital communications receiver. Should a flow variance (plus or minus 20%) occur, a signal will be transmitted to the service center indicating this trouble. A minimum of 24 hours storage capacity is designed into the system should a power failure occur. This 24 hours of storage will insure adequate time for a service technician to be dispatched or for the power to be restored.
The data about flows can also be down loaded into a spreadsheet to aid in recording. This feature is available for use with the personal computer based units. The operator will be able to download the day's flows, as well as, historical flows from as far back as three months. This aids large systems in complying with TNRCC rules that require an accurate record of daily flows. This aids smaller flow systems in building historical data on flow per day and flow per occupant. Flow recording will also aid in trouble shooting the causes of unusually large or small flows.
In addition to simply monitoring these functions the unit can also control itself based on the data received. For example, if a line is broken in a zone and is flowing freely, the unit will record the flow variance. If the flow variance is significant enough, not only will the condition be recorded, but the zone can be automatically taken off line to prevent further environmental contamination. The overall system will continue to run to allow for wastewater disposal in the unaffected zones while awaiting repair of the affected zone. The monitoring also records the zone, time, and date for each variance. This is an invaluable aid in maintenance trouble shooting.
Since the Perc-Rite ¨ system uses Netafim dripper line for wastewater disposal, this system can be installed in areas that would be unthinkable for another system. The field distribution lines are installed very near the surface and in small plow trenches, therefore, causing minimal soil disturbance. Also, effluent discharge volume from each emitter hole is small allowing installation of the system to have very little site impact even in established lawns and gardens. There are few visible indications that the installation site is being used for disposal purposes. The primary indication will be a faint green striping of the vegetation directly above the subsurface dripper lines. This will permit waste water disposal in land areas that are used for such purposes as parks, athletic fields, grove, and highway rights of way. This system is especially suited for landscaped or wooded areas around commercial buildings, schools, trailer parks, apartment complexes, or residential subdivisions.
A soil absorption bed designed around a Perc-Rite ¨ System has many distinct advantages over other forms of disposal. Problems from local overloading are decreased when effluent is distributed over the entire absorption area rather than concentrated in a few discrete areas. Dosing and resting cycles help maintain aerobic conditions in the soil, improving treatment. Shallow dripper line placement increases the vertical separation from the system to any restrictive horizon or seasonally high water table.
The Perc-Rite ¨ disposal system can also incorporate a wide variety of site customized options. A few of the many custom options will be discussed below. This unit can be used with many different pretreatment options. These treatment options range from a septic tank to an aerobic package plant. The Perc-Rite ¨ unit can also be used to control dosing to a sand or gravel filter to aid in secondary treatment. The Perc-Rite ¨ unit can also incorporate moisture sensors in the disposal fields to prevent over saturation. A domestic water source can also be controlled by the Perc-Rite ¨ unit which will supplement irrigation in time of low effluent production. This is especially useful at schools where playing fields have been used as disposal areas. In the summer months when activity is low, the domestic water can be used to keep the vegetation alive.
For existing or new treatment facilities - residential, commercial, industrial, or municipal - our filtering and sub-surface distribution system can be a viable alternative to land application techniques (spray), direct stream discharge, or other subsurface disposal methods.
Site and Soil Requirements for Perc-Rite ¨ Systems
(General Guidelines)
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The suitability of a Perc-Rite ¨ System for a given site is usually determined by five basic criteria. First, a site must be of suitable size to provide adequate disposal area and to adhere to all setbacks. Next, a disposal area must have soil of adequate quality and depth to provide good wastewater treatment. Third, the topography of a site must allow for level dripperline installation. Fourth, the site must have good drainage away from the disposal field to prevent saturation due to surface water runoff. Finally, a site must support vegetation to prevent soil erosion and to aid in disposal by evapotranspiration.
General Space Requirements
The drip field network of lateral lines for a Perc-Rite ¨ System can occupy 1,000 square feet up to several acres of area depending on design wastewater load. The positioning of all facets of the wastewater system is also an important consideration. Positioning the system to provide adequate disposal area, as well as adhering to all set back requirements is the first major challenge in designing a system. The septic tank, aerobic treatment unit, dosing tank, and distribution field are all subject to set back regulations to keep required distances from wells, property lines, building foundations, and bodies of water according to local regulations.
Soil Requirements
A Perc-Rite ¨ Disposal System should be situated in the best soil on the site. A licensed Site Evaluator will initially determine the suitability of the site. The site must have soil that is capable of holding and treating wastewater. Without the proper soil, the wastewater will remain untreated and either surface and runoff over the ground or migrate directly into the groundwater. The soil must have suitable texture as well as suitable structure. This generally means a Class I, Class II, Class III or Class IV soil. The classification of soils and their corresponding hydraulic loading rates will be introduced in the following chapter. The depth of the available soil is another major consideration. A minimum of 24 inches of usable soil is recommended between the bottom of the drip line tubing and any underlying restrictive horizons. These restrictive horizons can include consolidated bedrock or hardpan, a massive clay layer, or the seasonally high water table. In some cases, as determined by the soils engineer or soils scientist for the site, the minimum usable soil depth may be reduced to as little as 12 inches. The Perc-Rite ¨ drip lines may be installed as shallow as six inches depending on soil characteristics. The standard drip line installation depth is eight inches. This shallow installation depth makes minimum soil depth requirements easier to obtain than when using conventional systems. In some cases, where the depth to the seasonal high water table or the restrictive horizons is less than recommended, a modified Perc-Rite ¨ System using imported fill may be installed. Great care must be used in building these fill systems. Their design and construction are covered in this manual.
Topography
The Perc-Rite ¨ System has the unique ability to work on topographically challenging sites. The disposal area can be situated on slopes, undulating terrain, or flat open areas. The only requirement when designing a system on these challenging sites is that each individual dripper line runs along the contour lines, not across them. Normal spacing between dripper line laterals is 24 inches. On severe slopes of 20% or more, the dripper line laterals may need to be spaced wider than normal due to gravitational effects on water movement. Head loses due to elevation changes should be considered to ensure adequate pump sizing which will deliver the required flow and pressure. Since the Perc-Rite ¨ pressure compensating dripper emission rates are consistent at varying pressures, no special design requirements to ensure proper soil loading rates are needed. Topography considerations are further discussed in this design manual.
Drainage Requirements
Depressions, gullies, drainage ways, and areas of erosion should be avoided to prevent hydraulic overloading by surface runoff. Neither the septic tank, pumping chamber, nor distribution field should be located in such areas. Surface water and perched groundwater must be intercepted or diverted away from all components of the Perc-Rite ¨ System. Diverting ground water and surface runoff away from the disposal areas will prevent saturation in the absorption beds. Site modifications to the Perc-Rite ¨ System area such as berms may be required to ensure all surface or perched water will be diverted.
Site Vegetation Requirements
Immediately after installation of the disposal field, vegetation needs to be planted or reestablished. Virtually any vegetation ranging from native grasses to seed, sod, or hydromulch is suitable. This vegetation will serve to prevent erosion, as well remove some of the water from the soil through evapotranspiration.