Dale Barnes

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Dale Barnes Jay Rousell

• THE BENEFITS AND DIFFERENCES of SUB-SURFACE
  SYSTEMS!

ONSITE 2005
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We are here to clear up the Puzzle?

• How many types of subsurface are there?
• Is a pipe with a hole drilled in it an irrigation
  system?
• Can anyone agree on a what is an approved design?
• What is an irrigation system?
• Can they be used on all sites?
• What is the best way to use each system?
• How do they comply to the AS 1547?

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Understanding the puzzle

• Over the past decade the methods of effluent
  disposal have been made of many different types
  of systems. These have worked in most cases but
  due to different site conditions, problematic
  soils and surrounding environments they have all
  suffered some problems. This is possibly due to
  the unsuitability of that system for that
  particular application.
• This is what we wish to clear up!

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The current systems used

• In the AS15472000 it calls up six systems of
  land applications.
• Absorption trenches
• Absorption Beds
• Evapo-transpiration beds and trenches, (ETA)
• Mounds
• Subsurface irrigation
• Surface irrigation

We will be concentrating on the Irrigation areas
in this paper.
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So what is an Irrigation system?

• A pressurized system that delivers a consistent
  water, to ensure the plant grows at its optimum
  productivity.
• All irrigation systems require a set amount of
  fluid, for each plant or crop daily requirement.
• The hydraulic load for irrigation is generally
  higher than 6ltr/m2/day for turf and much higher
  for medium to large trees. But currently these
  areas only receive about 1 -3 ltr/m2/day and even
  less. This will not sustain the vegetation and in
  fact only 30 -60 of the area be effective.

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Why is it called Irrigation?

• When we have an inconsistent water supply that
  contains nutrients, bacteria, algae and salts,
  but is referred as an irrigation system. No
  irrigation system is capable of handling this
  kind water.
• Yes, we are using an irrigation principles, but
  if designed as an irrigation system it will
  suffer from degradation of the soil. To have
  these systems work more effectively, we have to
  design based on the soil being capable of
  excepting effluent water.

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So why not use the term Disposal system ?

• If effluent is to be disposed of via by a
  specifically designed, manufactured and installed
  system with manufacturer warranty, then arent we
  safe guarding the end user and limiting our
  liability.
• Allow all parties to implement, simple and proven
  installation practises. Reduce costs at each step
  down the line and possibly the amount of steps.
• This may also limit the likely-hood of litigation
  from the end user, over the loss of plants due to
  lack of water.

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Under the current A.S. 1547 we have these methods
of Disposal.
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Suitability for effluent

• Yes, non public areas only
• No, prone to run off
• No, prone to ponding
• Yes, specially Manufactured

• Spray or sprinkler
• Covered surface (mulch)
• Subsurface (trenched)
• Sub surface drip disposal

• The most important facts to consider is what has
  been manufactured primarily for the disposal of
  effluent. Many of the above have small orifices,
  no protection from blockage, manufactured for
  clean water and have no design considerations for
  effluent water.

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Evaluating the methods!

• Only two of these methods are used today in the
  Irrigation industry and in nearly all cases are
  not designed for the use with effluent water.
• Just ask the question, which one eliminates
  runoff, wind interference, uneven distribution
  and possible health risks, in addition assisting
  further treatment of the effluent via the soil.

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System comparisons

• Surface spray disposal
• Prone to run-off
• High Health risks
• Easily vandalized
• Uneven nutrient removal
• Higher Surface Loading of BOD
• Higher risk of contamination

• Low pressure disposal systems
• Uneven distribution of effluent
• Higher site costs
• Greater restrictions on all sites
• Reduced nutrient removal
• Poor percolation into soils

• Pressurized subsurface disposal
• Extra design considerations
• Low risk of contamination to public or
  surrounding sites
• Higher more even nutrient removal
• Increased treatment of effluent
• Site constraints are greatly limited

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The advantages of pressurized systems!

• Low public risk
• Even distribution over the entire area
• Nil run off to surrounding sites
• Assists in the treatment of effluent
• Lower maintenance costs
• Site restrictions reduced
• Low installation costs
• All parties have safeguards

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Design Considerations

• Site evaluation for soil types and hydraulic
  loading.
• The correct choice of tube correct, i.e. (PC or
  NPC).
• The correct pump to allow correct pressure at
  field.
• Only approved designers and/or installers.
• The right type and size of valves be installed.
• System components must be installed as per the
  manufacturers specifications.
• Filtration must be installed as near as
  practicable to the field, have large screen area
  and easily serviced.
• Installation on slopes and how best install.

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Installation Practices

• X

• Install depth 100 -150mm
• Lateral spacings of 60100 cm
• Lay with contour of the land
• Correct pressure at field
• Soil Hydraulic load 3-4ltr/m2/day
• Large effective filter screen areas
• Design on pump out rates
• Design on original soil tests

• Dripper space lt 60 x 60cm
• Lateral space gt1.2 mtr
• Mulching of disposal areas
• Lay laterals down a slope
• Leave trench uncompacted
• Deeper than 200mm in sand
• Less than 150mm in clays
• High flow, low head pump

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Should we design based on Nutrient instead of
hydraulic

• If designed on Nitrate a disposal area could be
  800 m² instead of 300 m².
• In this case only the 300 m² will be watered
  correctly, so how will the other 500 m² work
  under normal conditions. Will the nitrate leach
  out during higher saturations levels of the soil?
  At this stage no one has proven conclusively
  either way. However what would this level be,
  compared to the level applied to turf manually,
  it would not even come close. If it is such an
  issue to reduce such a small amount then stop
  application of fertilizer to turf areas.

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Typical components

• A drip line specifically manufactured for the
  disposal of treated effluent with lilac
  identification, regulated emitter rates and
  pressure rating gt 350 kPa.
• A filter with a screen area larger than 400cm² to
  remove suspended solids and protect system from
  internal blockages.
• Feed and Flush manifolds to give even pressure
  and distribution throughout the system (120 kPa
  minimum).
• Vacuum Breaker to allow air to enter and escape
  the system to prevent syphoning.
• Flush Valve to periodically flush the system to
  remove any foreign material.

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Typical installation costs

• Trenching approx 4 hrs_at_ 90/hr 360.00
• Labour to install 2 x 3.5 hrs _at_50/hr 350.00
• Additional fittings from AWTS Field 65.00
• Travel time approx 125.00
• In total the install cost is approx 900.00
• Combined with the 400/PC Kit, the cost is only
  2100.00 for a typical installation.
• NOTE
• These figure may vary depending on site and soil
  conditions.
• Based a 400 mtr2 area on a slightly sloping site,
  with a loam soil.

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What should happen from this point?

• Use only manufactured system with specifically
  designed principles for effluent.
• Use the manufacturers design parameters and best
  installation practices.
• Instigate specific standards for pressurized
  subsurface disposal systems.
• Begin research studies on specific pressure
  systems, so these standards can be implemented
  more effectively and clearly.

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In Summary

• Irrigation design parameters are not suitable
  with the use of effluent water.
• A pipe with holes drilled in it and laid in
  Drain-coil inside a trench is not an irrigation
  system.
• The AS 1547 uses the term Irrigation, but it is
  not an irrigation system, so change to Disposal.
• Studies need to be done on the performance
  differences between gravity feed (trenchs)
  pressure systems .
• AS 1547 needs to clarify the differences of all
  the systems currently used.
• Installation of pressurised systems must comply
  with individual manufacturers standards.

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Question Time?

• Can they be installed on a slope?
• What level of TSS BOD is best?
• How easy are they to install?
• What pressure do you require?
• What system is best?
• Can they be used on Leachate?
• Should the pump be designed as part of the
  disposal system and not with the AWTS/HSTP?

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NUTRIENT UPTAKE RATES FOR SELECTED CROPSNitrogen
(LB/ACRE-YEAR)

• Forage Crops
• Alfalfa
  201-482
• Brome Grass 116-201
• Coastal Bermuda Grass 357-602
• Kentucky Blue Grass 178-241
• Quack Grass 210-250
• Reed Canary Grass 299-401
• Ryegrass 178-250
• Sweet Clover 156
• Tall Fescue 133-290
• Orchard Grass 223-312
•  Field Crops
• Barley 112
• Corn 156-178
• Cotton 67-98
• Grain Sorghum 120
• Potatoes 205
• Soybeans 223
• Wheat 143

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To answer these questions

• No, it is a trench and has uneven water and this
  is why it can only be used on perfectly flat
  surfaces.
• No, it is not, as the vegetation will not perform
  adequately.
• No it has never been used for irrigation system
  for over 30 years.
• To our knowledge there is no Australian standard
  for irrigation system as yet.
• So what Standard applies when the 1547 calls up
  Irrigation?