CCRO Warnings

Inputs to the Flow Calculator outside the recommended range will display warnings upon input as well as design warnings in the report. Some CCRO specific warnings not tied to a particular cycle or element. These are secondary to element warnings, simply guidelines to avoid the warnings in the first place. There are a few exceptions noted below (see Figure 1):

Figure 1: CCRO Warnings

  1. Pass Average Recovery < Min. Value
    • Guideline ONLY.
    • The recommended guideline is 75 – 98% recovery.
    • Low recovery will lead to CC Duration < Min. Value warning and potentially additional warnings.
  2. PF Feed Ratio < Min. Value
    • Guideline ONLY.
    • The recommended guideline is 110 – 150% recovery.
    • The guideline is to stay within the high-pressure pump curve flow range, a 200% PF Feed Ratio is a doubling of the flow during PF Mode (2x CC Mode feed flow).
    • Significantly higher values will lead to exceeding maximum element feed flow.
  3. PF Recovery > Max. Value (or < Min. Value)
    • Guideline ONLY.
    • The recommended guideline is 10 – 30% recovery.
    • The guideline is to decrease the recovery during PF Mode (vs CC Mode) to increase the concentrate flow per PV, since during PF there is no longer any concentrate recirculation flow.
    • Low PF recovery will increase permeate conductivity during PF Mode, increasing will improve permeate quality and extend PF duration.
    • Increasing PF Feed Ratio and decreasing PF recovery will translate into shorter PF duration, which subsequently decreases the flux during CC Mode (as there is more run time to produce the same amount of permeate); this is recommended during low recovery (to decrease the difference between average flux and CC flux).
  4. CC Duration < Min. Value
    • Significant warning!
    • The recommended min. CC duration is 5 minutes, the upper limit is not critical.
    • Decreasing the flux and/or increasing the number of spacers (by increasing the Pressure Vessel Length) will increase the sequence time by increasing the system volume. In addition, increasing the recovery will increase the duration (if possible/practical).
  5. ‘Concentrate Recycle < Min. Value’ (or > Max. Value)
    • Guideline ONLY.
    • Concentrate Recycle, input tag number 3 (‘Conc. Recycle’) in the flow calculator.
    • The guideline is much higher than in traditional multi-stage RO.
    • The input will determine the size of the circulation pump.

Note:  When making adjustments in the Flow Calculator, it is important to consider practical and efficient pump ranges. The ‘Feed Ratio’ increase will determine the size of the high pressure pump (flow range only). While ‘Conc. Recycle’ input will determine the circulation pump sizing.