Spray Irrigation
Spray Irrigation
(OP)
We have a small MBR WWTP and instead of drip irrigation I was told to do spray irrigation over a grassed area. I don't have any experience in the design of spray irrigation. Rain Bird was not helpful. I found specs on some of their pop-up heads and found something I thought was reasonable. 15' radius spray with 30psi. It will be over 1.14 acres. I figured layout of the heads and pipe sizing would be easy enough using EPANET and an emitter coeff of 0.7. So now I need to find a pump capable of delivering the flow to each zone and maintaining 30 psi. Now the questions start. Should I just use something like a Myers centrifugal pump or is there a different style better for this set up? What other fixtures are needed with the pump such as pressure regulators or dampeners or things of that nature. Another question. I was told the application rate was 0.8 gal/day/ft^2. Which is 1.28"/day. The sprinkler heads are capable of delivering this in less than an hour. Does the sprinkler need to be operated for 5 min. several times per day to prevent runoff? I know this is a confusing question but drip irrigation makes much more sense for infiltration. Any help would be greatly appreciated.





RE: Spray Irrigation
For the pop-up sprays, create a supply that provides 50GPM at 50 PSI.
If your areas are larger than 20' across however, I would recommend going to rotary sprinklers instead of sprays, you'll find this more cost effective. You'll need more pressure for these heads, plan on 50 PSI at the heads, give yourself a supply of 70 PSI.
If you're going to be using effluent water for irrigation, that's another reason to go with the rotary sprinklers, as they don't clog as easily as the sprays.
Your daily application sounds very high. Here in Colorado/Wyoming, I typically plan on applying .31 inches/day, which typically gives pop up spray sprinklers a run time of less than 10 minutes per day.
Tim Grote - The Irrigation Engineers.
www.irrigationengineers.com
RE: Spray Irrigation
I would doubt that drip irrigation would work since the nozzles would clog. Even if the water was solids free, you would probably get some biological growth and or scaling that would clog the drip nozzles.
In addition, you should be careful where this is applied. There are many areas of the US particularly in the North where such a system would not work or you would have to incorporate so much land that the system is impractical.
One such application that I have visited was installed as part of a "zero discharge" aluminum rolling mill in Tennessee. The soil was a hard pan type clay material with low water absorption capacity. As originally designed, the spray irrigation system would not work. The operator moved his spray nozzle around the site until he found an sinkhole that would take the water. Of course, that solution was illegal.
RE: Spray Irrigation
RE: Spray Irrigation
If you're trying to get rid of water instead of conserve it, then you're right, you'll want to over apply.
I created a similar system to distribute WW at a jail here in Colorado. Local agencies did not allow us to over apply for fear of contaminating the ground water, so we used a central control system hooked up to a weather station that calculated the applicable amount daily. We also incorporated moisture sensors to stop irrigation if we saturated soil below the root zone. We even had the system shut down if the wind blew too hard. If I recall correctly, the jail actually baled and sold the alfalfa crop derived from the process.
If you're running effluent water, I'd use a larger rotor (60'+) radius or even consider using an impact rotary sprinkler (less moving parts) as we used in the above system. Note that Rainbird and Hunter manufacture irrigation equipment for re-use water that includes scrubbers in valves, etc.
Tim Grote - The Irrigation Engineers.
www.irrigationengineers.com
RE: Spray Irrigation