Conduct a simplified water balance
WTR01
Targeting your efforts in water conservations requires a reasonable understanding of how you currently use you water, conducting a water balance will give you this.
A water balance is a high-level, simple assessment of the input and utilization of water in your facility that can help to identify opportunities for improving water efficiency. Developing a water balance will give you a more thorough picture of overall water use at your facility. A water balance may be particularly appropriate for your facility, especially if you are just beginning your journey with water conservation and have not conducted a more detailed water audit.
A simplified water balance is a chart, table, or diagram of a facility’s water use that shows the flows of water into and out of each process or operation in the facility. If executed to fine detail the total volume of water entering the premises would equal, or balance, with all of the quantified point of water use or water loss that you have recorded, this is what gives the name water balance.
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The level of detail you include in your balance should be influenced by a number of factors –
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The scope to which you would deploy a conservation measure is typically influenced by the unit cost of that conservation measure, If for example you were to install tap aerators you are likely to apply it to all taps in the building, as they only cost a few pounds / dollars each. As such there is no value in understanding the different water consumptions of the different makes and models of taps that you have, rather you would focus on how much as total do my taps use.
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The data determined from your initial high level balance should influence where you focus your efforts. If initial data shows that 85% of your water is used by the cooling towers and all other use cases combined make up the final 15%, with say planter irrigation being 0.5% of the total it is clear that your time is best spent fully understanding your cooling tower water usage as opposed to committing time and resources analyzing your irrigation system.
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Given the above factors you can expect that the level of detail in different sections of a water balance will vary between facilities, there is no one size fits all template. To ensure you focus your efforts in the appropriate areas a two stage balance is recommended, first stage to gather the high level data, with a second stage focusing on you higher consuming areas.
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What you will need
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Understanding of all incoming water supplies into the facility
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Single line diagram / schematics of your water distribution system/s
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Past water and sewage bills
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Details of all installed water meters, including their location and schematically where in the system they are installed
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A list of all water consuming processes / activities at the facility
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Determining categories of usage
A review of your water distribution schematic, alongside your list of water using activities will identify distinct groupings of usage which can be assessed, at either an individual outlet / room level or as a category. For example, you may find that your kitchen facilities have their own supply, separate to all other piped systems, so this makes a sensible category, or you may find all of your washrooms are feed from a single water tank and you can measure the outlet from the tank to determine total washroom usage, which would be another useful category. Each building and its pipework infrastructure is unique, so develop a list of categories that is appropriate for your unique circumstances.
Determining usage data
This is another variable, the best data you can have is derived you’re your existing permanently installed water meters. After these you have a number of options, you can add additional permanent water meters, which is useful for measuring the effectiveness of your conservation measures after implementation. Alternatively you can use temporary clamp-on ultrasonic water meters to measure usage, one of the advantages of these is you can move them around your building to measure subsequent areas. The final option you have is to try and calculate water usage through the use of manufacturers data sheet for outlets and machinery, this option is likely to give you the lowest quality data.
The table below shows the initial data collected after the first round of data collection:
Using this first round of data gather it is immediately obvious that the emphasis of further data gathering should center on the cooling tower infrastructure. The degree of completeness is also of interest, the lower this percentage is the greater the volume of water you have not accounted for is, could you have missed processes? Leaks are a common factor in many installations, many of which are minor enough to go unnoticed but cumulatively these can add up to a notable volume.
Based on this first draft further data gathering would be targeted at the higher consuming areas of consumption, see below:
You can see that further investigation for what had been referred to as ‘cooling tower’ has managed to breakdown the usage down even further, potentially identifying other water using activities which had not originally been identified. Each of these has been quantified. Given the nature of cooling towers, where a high volume of water is lost through evaporation, an essential element of how the cooling tower functions, two new fields have been added – 'Total losses' accounts for water which has been input to the system but does not make its way to drainage, with the second category being volume of water discharged to the drain.
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You now have a high-level understanding of how you are using water in your facility, sufficient to allow you to target your conservation efforts on the systems and equipment where they would have most impact. While this knowledge alone does not result in a water reduction you can readily convert this knowledge into questions targeted at those responsible for the systems, what can I do to reduce water evaporation from the cooling towers? And how can I reduce the volume of water discharged from the tower or reuse it for another purpose?