WASTEWATER DISPOSAL WITH SUBSURFACE DRIP IRRIGATION Donald R. McDonald AgTech Pacific.

WASTEWATER DISPOSAL

WITH SUBSURFACE DRIP IRRIGATION

Donald R. McDonaldAgTech Pacific

TYPICAL LAYOUT

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.

Systems can be controlled by a programmed microprocessor or a simple irrigation controller.

Any level of treatment from primary through tertiary can be handled by the system.

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.

How it works

General Description

TYPICAL LAYOUT

Control Options.

Computer Control interfaced with a pulsing water meter and telephone interface.

Simple Irrigation Controller with a manual read water meter.

Self Cleaning Filtration Disc Filters Screen Filters Sand Media Filters

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

Additional Considerations Nutrient load – more of a concern

with Reuse

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

The End