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Pool water quality - Automatic on-demand filtration

  • 1.  Pool water quality - Automatic on-demand filtration

    Posted 17 September 2018 02:13
    Hi everyone,

    I'm exploring automating the pool water flow rate through our filtration system, to ramp up or down depending upon the pool water quality. The filtration flow rates are currently controlled by two set points on the pumps VSDs, one for operating hours and one for outside operating hours, however there are times when the pool is practically empty during the day and the current set points have to take into account the worst case. The aim is to achieve high efficiency of the system by lowering pumping requirements, and thus lower electricity consumption, whilst maintaining the desired water quality.

    I'm hoping that someone in this forum has experience with how best to measure real-time water quality so the system can respond appropriately. I am thinking that combined chlorine (via chlorine dosing system) and turbidity (via UV systems) could be the key indicators, however there may be a lag between when the water quality drops in the pool and the system responds (ramps up).

    We have 50m, 25m, dive and recreation pools, all indoors. The filtration system consists of basket strainers, Diatomaceous Earth (DE) pool filters, chlorine and hypo dosing systems, and Ultraviolet. The heating system has already been made independent of the filtration, and is controlled on a demand-response arrangement with VSD controlled pumps through plate heat exchangers. The UV units have the ability to ramp up and down and a HLI (high level interface) can be installed to get real-time feedback of water quality. The chlorine dosing system is already communicating with our Building Management System.

    If anyone has any experience/practical applications of something remotely similar to what I'm looking for I'd be very interested to find out more information.

    Bill Hanley
    Building Asset Engineer, City of Hobart

  • 2.  RE: Pool water quality - Automatic on-demand filtration

    Posted 17 September 2018 21:33
    ​Hi Bill ,

    Be very interested to see your findings with this issue !
    I think the best to ask maybe Trisleys or Hydrocare who may have some experience in this type of automation.


    Tony Micallef

    Cumberland Council
    Swim Centre's Operations Manager


  • 3.  RE: Pool water quality - Automatic on-demand filtration

    Posted 02 October 2018 21:36
    Hi Bill,
    there are a couple of areas here of consideration, which may or may not be relevant depending on regulations in your State (TAS). In WA, depending on the volume of your pool, your pumps must turn over that volume in a set period of time X amount of times. Pumps obviously are interconnected with the filtration system. So you will want to check this first before attempting any adjustments.
    You may want to do a full health check on your water ie. the calcium levels, the alkalinity and not just PH and Chlorine as this will have an affect on the chlorine levels. If your staff aren't all over this then they need training properly as this will affect water quality and chlorine levels.
    When the facility was constructed there would have been a diagram of all of your pipes, pumps, filters, heat exchanges etc. Do you have a BMS system controlling the flow rates and the temps?
    You can increase the efficiency of the heat exchange plates by expanding them out ie. adding more plates. You should also have them cleaned at least every 12 months. Easiest way is to have a spare set and swap them out, as the cleaning has to be done offsite.
    Reading the water quality ie. the Pool Managers should not be taking the reading out of the pool water (the old way) but as to the manufacturers guide, which usually at the dosing pump there is a little release area to sample the water quality, which is where the dosing pumps should be calibrated from. If the dosing pump is calibrated from water taken directly out of the pool it will be wrong and then your reading and dosing pump is always out.
    Are all of the pools independent of heating or are they all working off a single heating system, as sometimes demand on the heating systems vs setpoints can be an issue?
    You have listed quite a few issues, perhaps because they feed they are all interconnected. If you can split them up and prioritise where the main issues are ie. temperature, cost of chlorine, or even send me the diagrams/plans of your facility, happy to have a look through for comment.

    Hayley Bringdal
    Town of Mosman Park

  • 4.  RE: Pool water quality - Automatic on-demand filtration

    Posted 21 March 2019 16:32
    ​Hi everyone, and thanks for your replies.

    I've been doing some research and thinking about how to undertake any efficiency improvements here and have come up with the following:
    - The idea is to maintain the minimum standards for turn over rates that a low load pool will require, based on previous performance of the filtration system and routine water quality testing, for as long as possible during any 24 hour period.
     - Increase the filtration rate based upon pool use, which might take the form of people counters or types of bookings (i.e. swim meets, water sports rosters, etc.). We're going to investigate people counters via smart cameras who can count swimmers but his will require more thought and testing. Sampling every 5 minutes for instance, increasing incrementally based on the load on the pool. This gets us away from pre-determined filtration set-points based on 'worst case'/highest load scenarios.

    The outcome should be a demand based filtration rate with a minimum filtration that meets all standards and water quality measures, and increasing incrementally based on the load on the pool. Because our pool use is generally peaky (morning, midday and evening) I anticipate about a 50% increase in the amount of time our filtration system is at the minimum flow rate, which should see a good efficiency gain.

    For info:
     - Our pools are separated in terms of filtrations systems (50m and dive, 25m and recreation, spas).
     - Our heating systems are independent from filtration (recent upgrades) and dosing systems.
     - We have a new BMS which is very flexible and easily programmable by contractors and can connect to almost anything.

    I'll post the outcome of the project in the future. It's not forecast to be implemented until sometime later, but I'll try to keep this discussion open for interested parties.

    Bill Hanley
    City of Hobart