Question of the Day: Alternative Cooling Tower Makeup Sources

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Question of the Day: Alternative Cooling Tower Makeup Sources
What alternative water sources could one consider for cooling tower makeup to reduce water bills?

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  2. One increasingly common supply is secondary treated municipal wastewater (gray water), but other supplies such as deep groundwater and seawater may be options as well. These supplies often contain some impurities in much higher concentration than in fresh water. For gray water, ammonia, phosphorus, and organic compounds are notable examples. Deep aquifer water can have an exceptionally high dissolved solids concentration, with chloride, sulfate, alkalinity, sodium, calcium, and other ions contributing to the total.

  3. In 1980, large air/liquid coolers were placed in a good number of new refineries in the Middle East because there was a lack of water. That was a disaster because it was poorly conceived. The idea was to use the air coolers when the air temperatures were an advantage. What wasn't considered was the impact of sand blasting the tubes 24/7 for 5 months. Then what to do when you end up with a cooler that looks like a shower head with hydrocarbons flying out. 

    In the end, a sea water pipeline was added. The hot seawater then went to RO's and the permeate used for a variety of other uses thus taking advantage of the heat. The RO reject was sent to evap ponds.  They built a small greenhouse on one of the evap ponds. The moisture then condensed and was used for irrigation in the greenhouse. They grew Tomatoes and peppers. Pretty neat all done 39 years ago.

    1 Comment

    1. Yeah not all sand is equal.  That stuff over there is more like abrasive.  Sand blasting an air coil is not fun, true.  The seawater idea sounds pretty good, but what do when there is no sea nearby?  One had best find well water, even if pretty salty in such a case, and treat that water.

  4. I saw an RO setup once on a cooling tower, reducing the need for blow down, thereby reducing the need for make up.  Cool proof on concept.  Largely cost prohibitive due to pre-filtration requirements on an RO. I wonder if it will ever catch on?

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    1. Just for the reasons you mentioned, it is a non-starter when applied to cooling tower blow-down.  IDE has put forth their new Pulse Flow RO technology with downstream thermal crystallization unit reactor, with recycled brine semi-batch process, allowing up to 98% recovery of brackish water.  This would produce a very near ideal stream for cooling tower water, but it still is too costly for cooling tower operation.  It would make more sense maybe if dry-wet cooling hybrid is used, thereby reducing the size of the air-cooled condenser, and also reducing the size of the wet section, and the amount of water evaporated to arrive at the same condenser vacuum at the steam turbine.  Apparently, pulse flow minimizes the ability of bacteria to reproduce in the membranes, and also increases cross-flow velocity down to the membrane surface during the brine pulse, thus reducing concentration polarization scale potential.

      Membrane capacitive deionization could also be added to a system such as this to allow an even lower energy cost per volume water desalted.

      1 Comment reply

      1. James - would you mind providing some links that explain how this tech works - like the thermal crystallization unit you mentioned. 

  6. The solution to the problem should not be disruptive. We offer a plug and play solution which will increase the COC up to 10 thus reducing water consumption by almost 50%, reducing energy consumption by about 10% and possibly eliminating all of the chemical usage. Further the water can be reused as grey water for irrigation eliminating water treatment cost as well as potable water for irrigation. For more info contact me at alain.mestat@h2ovortex.com

    1 Comment

    1. You will never reduce water consumption by 50% since you completely ignore the evaporative load on the cooling tower.  This is nonsense.  Yes, you might reduce the wastewater flow by 50%, but never will you reduce the total makeup water by such an amount, and to claim so, is the work of charlatans.

  7. If water consumption is the primary concern here, you can select an alternate water supply, but this does nothing if not increase the water consumption, due to the conditions relative to treated effluent.

    If you really want to conserve water, stop using evaporation altogether as a means of cooling.

    This has severe penalties of course, when you consider the extra space required for air coolers, depending on the heat load you are dissipating.  Not only that, air cooling can never cool the water being cooled (or other process fluid) below ambient dry bulb temperature, and in fact cannot reach dry bulb temperature owing to the limits of approach temperatures.  

    If your process can suffer the penalty (in a power generation plant where steam turbine exhaust is being condensed, the penalty is about 15-20% of maximum power output), which as explained can be quite severe, and if you have sufficient space in which to place a large air cooler, then you will be successful in saving upward of 90% of water previously consumed.  This can represent a seriously worthwhile cost savings in certain cases.

    An option to consider along with dry cooling (closed heat exchange with outside air), is the use of cool air storage at night, or even heat pump produced cold air stored in high thermal mass.

  8. You can use treated water water after further treatment according to the specifications that are provided by Cooling tower supplier or equipment supplier. Using rain water is also a good option last but not the least optimize cycles of concentrations through control bleed off, use cooling tower water tretment chemicals to optimize this for further guidance you have to provide the specification of Cooling system and water quality available and max allowed limits in the system. 

    you can contact us at

    rakesh@berspl.com

    Rakesh sharma 

    Team Boundless

  9. Look up The Hub at Emory University, recycling all waste water from multiple closeby buildings to use as make up for 1000’ s of Tons of cooling towers 

  10. The most overlooked source is rainwater. It is overlooked primarily because the areas that have lots of rain also have abundant water, conceptually. The growing need to treat storm water runoff may change that since it would make far more sense to use the stormwater to a practical end than to treat it and then just release it.

  11. 90 % recovery rate , Therefore you have long running times to blow down. Your blow down water can be blended then with the RO again. Or use bypass -deinonization at around 5 to 10% continuous with filtration and also helpful an UV system in this bypass loop.

  12. I agree that Rainwater is a good alternative. Do you already reuse your process water? We could help with the design if you are interested and would like to have more information. 

    Video Tutorial on process water reuse here: https://youtu.be/BLC1R1Ux_jU

  13. Consider treating your CT blowdown to remove hardness, silica, and TSS via lime softening.  Then filter with media filter or better yet UF prior to feeding an RO.  The RO reject is discharged as a high TDS stream and the high quality permeate is returned to the tower.  This effectively increases the cycles of concentration of your tower and reduces water consumption.  This scheme can be costly, so you have to look at how much you'll save on water vs. the capital cost to see of the ROI is acceptable.  This approach is normally used is arid areas where water is in short supply (such as the US Southwest).

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  14. Rainwater is a good source of alternate makeup for cooling towers. It usually  has consistently low hardness and conductivity. It will require a large holding tank and collection system which could be supplied by roof drains. It will also need to be filtered to remove any debris present. A secondary water supply is needed as well, in case the rainfall is not enough.

  15. Apparently, your process may be reliant upon local potable water supply.  Petition your supplier to bring an additional pipeline of treated effluent from the POTW, however, you should be advised of the need to continually treat water in the pipeline from the point of origin to your makeup valve, even when your cooling system is offline, due to the high potential of biological growth that produces slimy water.