History:

Drip Irrigation was developed as an agricultural irrigation method. Driving this development was the need to maximize water usage. Combinations of lack of water, cost of water, quality of water and finally soils were all factors in this development stage as well as the technology needed to manufacture said equipment.

Farmers use a system described as integrated system management. As farming is profit based, an evaluation is done to ensure that the cost of maintenance is less than the cost of profit loss due to a lower level of maintenance. System flushing is labor intensive, given the typical design of an agricultural system that does not include flush manifolds, and as such each drip line is normally flushed individually. When a system flush is performed the flush needs to be maximized for cost / benefit purposes.

It is noteworthy that the agricultural irrigation industry is unregulated but the very high value of crops and resulting potential loss of crop lawsuits has all but eliminated poor system design and installation practices. Maintenance practices are entirely up to the grower / owner. This has led to much discussion (see Annex 1 by Dr. Freddie Lamm) and one published standard (see Annex 2 ASAE EP 405).

Dr. Freddie Lamm concludes with:

"In closing this message, I don't necessarily dispute anyone’s' values. However, I personally don't think the science paper trail is very convincing on this issue. Some might say that if a value seems to work, that's fine and I agree to a point. However, when the rationale behind the value gets lost, its more difficult to dispute that "rule of thumb", because you may not know what theory you can supersede with a better idea. For example, scouring (removing a coating of debris from pipe wall) probably has different physics and dynamics science requirements than flushing (moving debris along a pipe). Additionally, some materials would have greater sedimentation velocities and drag coefficients."

ASAE EP 405:

3.7 Flushing system. To assist in keeping sediment buildup at a minimum, automatic or hand flushing of all microirrigation pipelines is recommended on a regular time schedule. Filtration should be effective enough so that flushing of the system is needed no more frequently than once per week.

3.7.2 Capacity. A minimum flow velocity of 0.3 m/s (1 ft/s) is needed for flushing of lateral lines. Because only a few lateral lines can be flushed at one time, the flushing system should be adequately valved so that subunits can be flushed independently.

Bacteria multiply and mutate at an extremely high speed. The multitude of modern antibiotics is a result. Such a mutation can result in bacterial growth with unpredictable properties. An example of this is shown in the Rock Bridge Report (Annex 3), where the bacteria resisted aggressive chlorination and were finally knocked out by industrial strength Drano.

Waste Water Subsurface Dispersal Systems:

As building sites unsuitable for a conventional on-site sewage system were considered, coupled with many conventional onsite systems failing, new and innovative systems were developed for onsite treatment and dispersal.

Geoflow is one of the major manufacturers of wastewater subsurface drip dispersal system (SSDDS) components.

Geoflow is the only manufacturer that incorporates multilevel protection against the two major risks of failure of subsurface drip dispersal of sewage effluent.

Root intrusion: With subsurface drip dispersal there is always a risk of root intrusion. This risk increases if the soil is not kept in a saturated state. WASTEFLOW® drippers incorporate ROOTGUARD® that is an infusion of trifluralin (Treflan) to eliminate this risk. This patented process allows Geoflow, Inc. to warrant their SSDDS for fifteen years against root intrusion.

Bacterial and solids buildup inside the drip line tubing: With any drip system, surface or subsurface there is a risk of bacterial growth on the inside of the tube wall, in its normal life cycle "sluffing" off material that can potentially plug the drip emitters. Also there is also a certain degree of sedimentation in the tubing at the end of the lateral because as the velocity decreases towards the end of the drip line and the flow rate drops and losses its ability to transport solids. WASTEFLOW has a Geoshield® lining (containing tributyltin maleate) that covers the entire inside of the tubing as well as a being infused into the dripper itself. This anti bacterial lining not only inhibits bacterial growth it also inhibits the existing bacteria that washes through from the pre and treatment side from attaching to the wall. This is considered an internal threat to the longevity of the drip emitter. In combination with the Geoshield lining Geoflow WASTEFLOW has extra smooth walls resulting from the addition of a fluoro-polymer. (Teflon® - like) incorporated in this inner layer.

Please see Annex 4 for more information about ROOTGUARD

Please see Annex 5 for more information about Geoshield

Please see Annex 6 for more information about anti-bacterial materials

Please see Annex 7 for more information about smooth walls of WASTEFLOW with a fluoro-polymer compared to a standard polyethylene tube.

The question is asked as to how long the Geoshield will stay active. Geoflow has been using it for fifteen years with no problems developing with age. Other companies use the same chemical in many products and expect a life of up to fifty years. Please see Annex 8, Annex 9, Annex 10 and Annex 10a.

Mechanics of Flushing Drip lines

Before the discussion, some keywords need to be defined for clarification.

NOWRA is the major representative body for the On Site industry.

NOWRA definitions:

3.15 Flushing: The process by which dripperlines are hydraulically cleansed to prevent emitter clogging by increasing the velocity of water flow through the dripperlines to scour and transport solid materials that may have accumulated in or on the interior surfaces of the dripperlines.

3.28 Scouring: The process to clear a conduit of particulates by hydraulic flushing at a sufficient velocity to lift and carry particulates downstream.

From the above it can be seen that NOWRA does not seem to clearly differentiate between "Flushing" and "Scouring".

ASAE:

ASAE EP 405 recommends flushing at1 ft/s. It does not mention scouring.

We will define

Laminar Flow Flow regime based on Reynolds numbers < 2000

Transitional or Unstable Flow Flow regime based on Reynolds numbers between 2000 and 3000

Turbulent Flow Flow regime based on Reynolds numbers > 3000

Because bacteria do not adhere to the inside walls of the WASTEFLOW dripline Geoflow systems do not require any velocity in excess of the flush velocity.

Flush Velocity: The minimum required flush velocity is determined by the specific gravity and size of the particles to be moved with the water. Because the minimum pretreatment is a septic tank followed by 130 micron filtration any particles in the system will be organic and close to the specific gravity of the water and small. This is unlike agricultural systems where the impurities may be fine inorganic material.

Summary:

Geoflow WASTEFLOW is a unique product invented in the U.S.A. specifically for the wastewater dispersal market. There is no other product on the market that has the three critical patented (or patent pending) technologies of ROOTGUARD, Geoshield and the smooth inner walls. When prescriptive standards are so rigid as to prevent advanced technologies from the market place, then clearly a performance standard is required.

This is clearly a situation where a performance standard is required. Several states have resolved this issue by referring to manufacturer’s recommendations, as shown in Annex 11.

From fifteen years of field experience and the flow pattern under various Reynolds numbers combined with the Tables drawn by Dr. Sanjines (Annex 12), the later two shown below, there is no reason to flush a WASTEFLOW line at a velocity in excess of 0.5 ft/sec.