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Rainwater Harvesting for Landscape Irrigation – Part 2

Mar 20, 2020
Video Length:  1:12:32
Presented By:  Mike Warren of Watertronics

In Part 2 of the Rainwater Harvesting for Landscape Irrigation series, we'll take a look at a pump station's role in a rainwater harvesting system and how it applies to design. Presenter Mike Warren of Watertronics will discuss and outline the pros and cons of pumps and pumping applications, including submersible, flooded suction, and suction lift. He'll also go over level controls, secondary backup water, discharge filtration, and treatment. Mike will then analyze the need for a disinfection component in an irrigation system before concluding with a few case study installation examples.

Webinar Contents:

Note: The following catalog of content covered in this webinar is time stamped to allow you to follow along or skip to sections of the video that are relevant to your questions. You can also search for content on this page using the FIND command in your browser (CTRL + F in Windows, Command + F in Mac OS.)

  • Intro/TOC
  • Pump Station’s Role (Controls)
  • Backup Water Supply and Level Controls
  • Post Filtration and Treatment
  • Direct Style vs. Day Tank Style
  • Example Projects

0:00 – 12:02: Intro/TOC

Recap of Mike’s previous webinar, Rainwater Harvesting for Landscape Irrigation, part 1 (2:41)

 

Goal of a rainwater system: Develop a water collection and distribution system that harvests water from multiple sources and delivers it efficiently to multiple applications, automatically (3:37)

 

Major components of water harvesting (recap) (4:20):

  • Catchment
  • Pre-filtration
  • Storage
  • Pumping water
  • Controls
  • Post-filtration

 

Recap of potential collection sources and filtration components (5:27)

 

The three main components of a rainwater harvesting system (recap) (8:30):

  • Pre-filter
  • Storage tank
  • Pump controls and treatment system

 

Pre-filter components (recap) (9:00):

  • The best way to filter the water is at the source. The sooner we incorporate filtration, the better the rest of the system operates.
  • Primary particle filtration (TSS – total suspended solids)
  • Oil/water separation (stormwater only – hydro-dynamic separator

 

Green roofs and other surfaces (recap) (10:20)

 

Storage components (recap) (10:50):

  • Storage can consist of any vessel that can hold or retain water.
  • Tanks or ponds
  • Separate containment, or built into building foundation
  • Below or above ground (note anti-floatation when below ground)

12:03 – 25:29: Pump Station’s Role (Controls)

Pumping/controls (12:03):

  • The heart of the water harvesting system
  • Submersible or above-grade pumps
  • Controls all peripheral components (level, flow, pressure, and filter)
  • Make a water manager out of the end user
  • Quantify ROI and contain data about the system

 

Types of pumps (13:10)

 

Submersible pumps (13:50)

 

Flooded suction pumps (14:48)

 

Submersible pros and cons (16:06)

Submersible pumps are more efficient but potentially require more maintenance.

 

Suction life pumps (16:55)

 

Controls (18:40)

 

Parts of a control panel (20:58)

  • PLC 24V DC
  • 460V disconnect
  • Circuit breakers (control power, touch screen, PLC)
  • Surge suppressors (analog sensors)
  • Lightning arrestor
  • 460/24VAC transformer
  • 24V DC relays
  • Phase monitor and circuit breaker
  • 460/120 AC transformer
  • VFD fuses
  • VFD

 

Operator interface: example (23:21)

25:30 – 42:14: Backup Water Supply and Level Controls

Level controls: How to integrate a backup water source (25:30)

  • Do we need a backup water source?
  • Will the backup water source go to the reservoir or direct to the water distribution system?
  • Does the backup water source have the proper flow and pressure to satisfy the water distribution system demand?
  • The backup water source requirements change based on the following possible scenarios:
    • Backup water will go to the reservoir
    • Backup water will go direct to the water distribution system

 

Tank fill (26:56)

  • Backup water must have the proper flow to the tank. (Pressure is not important.)
  • Controls must maintain a low water level in the tank, leaving the most possible room to capture the next rain event. Do not set the fill valve to fill the tank to its full level.

 

Direct to distribution (31:38)

  • Local codes must allow for this type of connection.
  • Backup water must have the proper flow and pressure at the connection to the rainwater system.
  • Controls must have switch back to rainwater based up availability in the tank.

 

Question: Is there a best or most common landscape project type that is best suited for the use of a submersible pump, a flooded suction pump, or a suction lift pump? (37:20)

Answer: It’s mostly driven off of the type of tank you plan to buy. Below-ground tanks will most likely need a submersible pump, for example.

 

Question: What is the main determination for choosing the horsepower of a pump? 40:00)

Answer: It always depends on the irrigation system. The pump needs to be designed to provide the needed flow and pressure at the start of the mainline in the worst-case scenario (the pressure needed to deliver irrigation water to the largest zone).

 

42:15 – 58:47: Post Filtration and Treatment

Discharge filtration (42:20)

Automatic screen filtration:

  • Controlled via the rainwater control panel
  • Reverses flow across the screen
  • Internal self-cleaning mechanism
  • Flushes on differential pressure, timed interval, or total gallons pumped
  • Note screen area when sizing

 

Ultraviolet disinfection basics (44:50)

  • 254nm wavelength UV light is used to render organisms inactive or unable to reproduce
  • Water is in contact with light for a period of time. Energy is transmitted to the water (mj/cm2)
  • Pick a dose (30mj/cm2) organisms require a certain amount of energy to be deactivated
  • Pick a flow rate with a given UVT% (actual UVT of water no known without water sample).

 

Water quality requirements for UV (49:20)

  • Dose: Light energy delivered into the water (mj/cm2) (see also destruction chart)
  • Ultraviolet transmittance percentage: Light’s ability to penetrate the water
  • Flow rate: Maximum GPM able to be disinfected at the criteria listed above

 

General requirements:

  • 7 grains or less of hardness
  • UVT% must be per the mfg. performance curve
  • .05 ppm of manganese (dark black metal)

 

If the UVT% of the water through the UV unit is different from what you sized the UV for, the dose is not delivered.

 

 

Chlorine injection disinfection/color (56:07)

Chlorine recirculation system on day tank (maintains 2–3 ppm residual chlorine level):

  • Uses a separate pump in day tank start/stop via timer
  • Water sent through CHL Analyzer (PH and CHL sensor)
  • Dosing pump insects to maintain a set point of CHL in PPM
  • 30-gallon holding tank (uses household bleach/pool shock)

 

Chlorine will also affect the color of water because it changes the way molecules reflect visible light to the naked eye, like a stain remover on a white T-shirt.

58:48 – 1:05:19: Direct Style vs. Day Tank Style

Direct style system (58:48)

The water in the main storage tank is pumped directly to the given application at the desired pressure. All components on the discharge side of the pump(s) are sized for max flow rate (capacity) and PSI.

 

Direct style example (59:13)

 

Transfer & day tank style system (1:00:05)

Complete rainwater system includes 2 storage tanks and 2 pump stations. Also known as “batch processing,” where a smaller transfer pump is used to treat water from a main rainwater storage tank at a lower flow rate to the “day tank,” while another pump station to deliver that water at required flow and PSI for the application.

 

Note that the transfer & day tank system doesn’t really work for irrigation.

 

Deciding factors to use direct or day tank systems (1:01:00):

  • Pressure required for application (150 PSI max rating / 125 PSI safety factor)
    • Filters and UV units have rating restrictions.
  • Flow or GPM required to application (for financial savings)
    • If the application requires 80 GPM, a day tank system that transfers water at 30 GPM offers little of no cost savings.
  • Footprint or available space
    • A direct system may be chosen even thous GPM (over 150 GPM) is high due to space constraints.
  • Application or usage profile (i.e., irrigation vs. toilet flushing)

 

Graphs: iirrigation vs. building water usage (1:02:55)

1:05:20 – end: Example Projects

City of Ocean Springs splash pad (1:05:20)

  • 3K below-ground storage tank
  • Submersible pump in tank
  • Control skid with filtration (outdoors)
  • Backup water will fill tank
  • Fully flooded excavation installation
  • Harvested splash pad water for irrigation

 

Radio Flyer irrigation (1:06:47)

  • 40K aboveground storage tank
  • Flooded suction pump with 100-micron filter
  • Backup water will fill tank
  • Cold-weather environment

 

Water harvesting (1:07:20)

  • The range of water harvesting is vast. Understanding the project intent and budget is key to a successful project.
    • Systems vary from basic to very complex with advanced controls.
    • Pricing ranges as system requirements are established.

 

Discussion of filters used in rainwater systems (1:08:50)

 

Mike Warren’s contact info:

  • Phone: +1 414-640-2496

  • Email: mike.warren@watertronics.com

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