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Wastewater Solutions Part 2 – The right equipment for a dirty job.

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Written by Clark Robeson, CID |

Choosing the correct reclaimed water sprinkler for a center pivot begins with the consideration of the solids content of the reclaimed water to be applied.

Water solids content:

  • Effluent water that contains 5% to 6% solids content will barely pour from a container.
  • Effluent water with 4% solids content will have the consistency of a chocolate malt.

With solids concentrations this high, additional clear water from another source is required to thin the reclaimed water into a consistency that is appropriate for the type of sprinkler that is installed.

Not to mention the "other" stuff.

Inorganic solids frequently find their way into holding lagoons. Rubber gloves, feed bags and other objects are a sure way to plug up any center pivot effluent sprinkler package. Utilizing an appropriately sized screen on the pump inlet tube, which is designed to float below the lagoon surface, will eliminate this unwanted debris before it enters the center pivot. When submerged inlet screens are not applicable, rotating, self-cleaning screens are available to filter organic and inorganic debris from the lagoon or holding pond before it is pumped to the center pivot.

Choosing the right setup.

Various sprinkler products are available that are specifically designed to apply effluent water.

For reclaimed water with very high solids content:

  • High-volume guns installed on clamp-on saddles are a reliable solution.
  • Large-bodied plastic impact sprinklers are also a viable sprinkler to distribute reclaimed water with fewer solids content than the water that requires high volume guns.

Because of the high mounting position on the span pipeline of the center pivot and the higher pressures that both the high volume guns and impact sprinkler operate, there are environmental concerns associated with drift and odor issues. To meet the challenges of reducing drift and odor, more conventional sprinkler packages can be used.

Conventional, but effective.

Conventional sprinkler packages for reclaimed water distribution come in two basic configurations:

  • Rotating/moving distribution plate sprinklers.
  • Fixed-plate sprinklers.

Both of these styles share the same family of water orifice nozzles that are available in a variety of sizes from 1/16” diameter to the 3/8” diameter.

Rotating/moving distribution plate sprinklers have been adapted by their manufacturer with an optional, more open sprinkler body. This open architecture design allows debris to pass through more easily, alleviating the buildup of material on the rotating plate and body.

Let’s talk about psi and spacing.

Part of choosing the right sprinkler package also includes understanding what psi and spacing each package requires.

High volume guns

  • 45 psi to 90 psi operation pressure.
  • Depending on the level of water application uniformity desired, high-volume guns are spaced 80 to 120 feet apart.

Impact sprinklers

  • 40 to 60 psi operation pressure.
  • Depending on the desired uniformity of water distribution, spacing for impact sprinklers would be 45 to 90 feet apart.

Fixed plate sprinklers

  • 6 to 10 psi operation pressure.
  • When operated at low pressures, these sprinklers will provide low drift at the penalty of smaller diameters of water distribution. If uniformity of the distribution of the reclaimed water is a requirement, more sprinklers and flexible drops will be required, along with Valley spans ordered with the option 30” outlet spacing. Typically, this closer sprinkler spacing will be selected at 60” or 90”, depending on the installed elevation of the sprinklers.

Rotating/moving distribution sprinklers

  • 15 to 30 psi operation pressure.
  • With 15 to 30 psi operating pressures, rotating sprinklers can be spaced out on wider drop spacing than would be used on a fixed plate sprinkler. Sprinkler/drop spacing at the beginning of the center pivot sprinkler package could be placed at 15 to 20 feet.

Although selecting the right sprinkler package is paramount to having an effective and efficient reclaimed water application system, it is only one of several important decisions to make when developing a proper disposal for your agricultural, industrial and municipal wastewater. Your nearby Valley dealer and the Valley Irrigation water application department can team up to configure a specialized reclaimed water distribution system based on reliable Valley center pivots and linear move irrigation machines.

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