WASTEWATER DISPOSAL WITH SUBSURFACE DRIP IRRIGATION Donald R. McDonald AgTech Pacific.
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Transcript of WASTEWATER DISPOSAL WITH SUBSURFACE DRIP IRRIGATION Donald R. McDonald AgTech Pacific.
Effluent is discharged through subsurface drip tubing often utilizing pressure compensating emission devices allowing effluent to be spread uniformly over an area.
Dosing cycles are triggered automatically several times per day with equal amounts of water supplied to each square foot. Dosing allows uniform distribution of effluent over time as well as area.
Advantages over a conventional IWS.
Can be used where a high water table will not allow use of a conventional IWS.
Or in area with excessively tight soils.
Control Options.
Computer Control interfaced with a pulsing water meter and telephone interface.
Simple Irrigation Controller with a manual read water meter.
Drip Tubing - Two products currently used successfully
Netafim Bioline – Pressure compensating
Geoflow – Non pressure compensating with Rootguard
Design Considerations Design Flow – local
regulations for IWS Soil Loading Rate – Soil
texture, refer to chart for general guidelines
Application Guidelies for the Waste Water Systems Perc-Rite System
Soil Group Soil Texture Classes(USDA Classification)
Maximum Hydraulic Loading(gal/day/ft2)
I Sands(with S or PS structure)
Sands –SLoamy Sand - LS
0.4 - 0.3
II Course Loams (with S or PS structure)
Sandy Loam –SLLoam - L
0.30 - 0.15
III Fine Loams (with S or PS structure)
Sandy Clay Loam – SCLSilt Loam – SILClay Loam – CLSilty Clay Loam - SICL
0.15 - .10
IV Clays (with S or PS structure)
Sandy Clay – SCSilty Clay – SICClay - C
0.10 - 0.03
Additional Considerations Topography Soil Compaction Low areas where ponding
might occur Restrictive Layers Setbacks required
TABLE 4–11 NUTRIENT UPTAKE FOR SELECTED CROPS
LB/ACRE – YEAR
Forage Crops:
201–28118–45233–312Orchard Grass
26827133–290Tall Fescue
8918156Sweet Clover
241–29054–76178–250Ryegrass
28136–40299–401Reed Canary Grass
24527–40210–250Quack Grass
17840178–241Kentucky Blue Grass
2031–40357–602Coastal Bermuda Grass
21936–49116–201Brome Grass
156–20020–31201–482Alfalfa a
PotassiumPhosphorousNitrogenb
Design Steps Determine Design flow in gallons
per day (GPD) – refer to local regulations
Determine Soil Loading Rate (GPD/square foot)
Determine area required = Design Flow/Soil Loading Rate
Determine dripper spacing spacing, i.e.: 2 feet
Determine tubing spacing, i.e.: 2 feet Determine amount of tubing required
= area required / tubing spacing Determine total flow rate based on
tubing requirements
Design Steps – continued
Design Steps – continued
Determine Field Layout Maximize lateral length to
Minimize flush flow Feed and collect from upper
elevations where possible
Design Steps – continued
Determine Flush Flow required – 1.6 GPM X the number of distal ends
Break field into equal zones Calculate head losses and
elevation changes Determine Pump Size
REFERENCES Netafim –
www.netafim-usa.com Geoflow –
www.geoflow.com Waste Water Systems –
www.wastewatersystems.com American Manufacturing –
www.americanonsite.com