Potable Water Treatment Plant resource info, references, notes

Programming notes, Sequence of Operations:

Valve V1

(Diverts incoming flow from stream intake either to WTP or to bypass, depending on water level in storage tank.)

  1. Install vertical float switch FS-1 in water storage tank, near top.  Set difference in elevation between ‘V1 Open’ and ‘V1 Close’ equal to the volume of water between the high and low water level in (one) sand filter. This is 0.4 m x 4.5 m x 1.67 m = 3 M^3 or 3,000 liters or 794 gallons or 106 ft^3.  Divide this by storage tank(s) total surface area to get required depth.
  2. If storage tank is 8′ diameter and there are two of them, surface area = 2*4^2*3.14 = 100 Ft^2. So distance between V1 open and V1 close ~ 12″
  3. Modify vertical float switch as required to get this volume.  (Or use it as is, with nom. 6″ between open/close.   In two 8′ dia tanks connected at bottom, this will be about 400 gallons.

Valve V2

(Alternates between sand filters SSF-1 & SSF-2)

  1. Install vertical float switch FS-2 in either SSF-1 or SSF-2.  Set the “pump on” level at 45 cm above the Schmutzdecke, and “pump off” level at 5 cm above — the recommended max and min water depth above the biological layer, respectively.  This is about 16″, so will require modifying the float switch. (As noted above, it is about 800 gallons.)
  2. If float switch is installed in SSF-1, set it to open valve port to SSF-1 when it reaches the bottom (opens switch) and opens port to SSF-2 when it reaches the top (closes switch).
  3. Additional functions can include monitoring cycle time (for filter maintenance due alarm, performance monitoring, etc.).  Monitor the elapsed time between valve V1 open & closed, and/or total time between SSF-1 and SSF-2 filtration.

Dosing Siphon Info

(idea rejected, included here for future reference only…)

Operation of Dual Alternating Automatic Siphons

Design, Use and Installation of Dosing Siphons for On-site Wastewater Treatment Systems

Dual Alternating Flout

AMERICAN AUTOMATIC SIPHONS (A good source for controls components as well…)

FLUID DYNAMICS auto siphon (Price quote $195 for Model 207)Don Patterson, Fluid Dynamics: 970-472-4065

Jandy Valves & Actuators (typ V-1, V-2)

Jandy Pool Products, Inc. (acquired by Zodiac)
2620 Commerce Way, Vista, CA, 92081-8438, USA
Phone: 1-800-227-1442

Vertical Float Switch (FS-1, FS-2)

Superior Pump: 1-800-495-9278
Corporate Headquarters
2301 Traffic St NE
Minneapolis, MN 55413

Price from Amazon: $30.  REPL VERTICAL FLOAT SWITCH

Telecon with tech support 11/7/2012 – who confirmed that pump turns on at ~8″ and off at ~2″. It can be minimally adjusted from that (to shorten the length only) by moving a grommet. I’d like to try extending it by replacing the rod with a longer one. If I can do this I can avoid having to buy two float switches, one for “on”, the other for “off”.

Sequence of Operation:






Diagrams are from JVA2444 installation manual. Replace “Time Clock” with “Float Switch” (FS-1 or FS-2), and replace ‘SPDT Relay’ with “PLR Output V1 or V2, respectively.

  1. PLR continuously monitors float switch FS1 (Input I1). Upon closure:
    1. Rotate valve V1 to Port A (energize output Q1),
    2. Stop Timer T2, display elapsed time,
    3. Start timer T1, dislplay elapsed time,
    4. Increment counter C1, display count.
  2. Upon FS1 (Input I1) Open:
    1. Rotate valve V1 to Port B: (open Q1, and close Q2),
    2. Stop timer T1, display elapsed time.
    3. Start timer T2, display elapsed time.
  3. PLR continuously monitors float switch FS2 (Input I3). Upon closure:
    1. Rotate valve V2 to Port A (energize output Q3),
    2. Stop timer T4, display elapsed time.
    3. Start timer T3, display elapsed time,
    4. increment counter C2.
  4. Upon FS2 (Input I3) Open:
    1. rotate valve V2 to open Port B (open Q3, and close Q4),
    2. Stop timer T3,
    3. Start timer T4

Option/Alternate Idea:  The purpose of the timers and counters is to be able to measure flow rates, time how long it takes for one dose to go through a sand filter, signal when filter backwash / maintenance is due.  For example, by multiplying the count by the known volume of water between valve open and valve closed (fill and drain level), I can accurately measure total flow without an expensive flow meter — simple digital I/O only. No analog, no A/D converters.

However: By adding an expansion module (or by replacing the 12 port PLC with a 20 port PLC, I can connect a HOBO data logger to the extra channels. Which will give me more and better information.

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