Cooling Tower Cycles of Concentration
Description – Increase cooling tower optimization by increasing the cycles of concentration and reducing blowdown stream flow capacities by applying chemicals programs.
Process Being Fed – Cooling towers makeup water
Technologies Employed –
- Chemistry
- Fifth generation polymer
- On-line polymer monitor
- Silica deposit control product
- Third generation biofilm removal agent
- Feed and Control – On-line polymer monitor for fifth generation polymer
- Monitoring
Estimated Volume Saving – 0 to 40% of total inlet water
Capital Cost – $0 to $50,000
Timelines for Implementation – Immediate (<2 months). A wastewater discharge permit change may be required as a result of an increase in material concentration, which may influence implementation scheduling. Additionally, Total Dissolved Solids limits may also influence timelines.
Level of Difficulty in Execution – Very easy, quick fix
Mobile Water Demineralizer
Description – Replace the onsite demineralizer with mobile trailer demineralizer water, improving quality of boiler feedwater, increasing cycles of concentration and reducing blowdown flow.
Process Being Fed – Boiler feedwater Technologies Employed – Mobile trailer to improve maintenance costs and reduce washing water usage
Estimated Volume Saving – 0 to 8% of boiler makeup
Capital Cost – $0 to $10,000
Operating Cost – $15,000/month
Timelines for Implementation – Immediate (<2 months). A wastewater discharge permit change may be required as a result of an increase in material concentration, which may influence implementation scheduling. Additionally, Total Dissolved Solids limits may also influence timelines.
Level of Difficulty in Execution – Very easy, the quickest fix
Water Reuse
Description – Use any water-consuming component on site as a potential source of water for another component.
The most common internal water sources are:
- Cooling tower blowdown water
- Boiler blowdown water
- RO reject streams
- Wastewater plant
- Process unit wastewater
Power Industry
- Ash pond discharge
- Scrubber blowdown
- Coal pile runoff
Food Industry
- Lost condensate recovery – reuse (dairy and food plants)
- Meat/poultry wash water reuse
Process Being Fed – Mostly cooling towers but the source can be routed to any water consuming component. Cooling tower blowdown can be diverted to scrubbers.
Technologies Employed –
- Biological treatment to reduce TSS, BOD, COD, organic content and other loads of contamination
- Membranes - Reverse osmosis, membrane bio reactors, ZeeWeed UF membranes for industrial water reuse
- Brine concentrator and evaporator for a zero liquid discharge
- For food processors, Entrapped Air Floatation and reverse osmosis/UF membrane for wastewater reuse, as well boiler cycles optimization using pretreatment before going into reverse osmosis.
Estimated Volume Saving – 0 to 10% of total inlet water
Capital Cost – $0 to $150,000, depending on existing infrastructure – Piping, tank and pump
Operating Cost –
- $0 for generic and power industry water reuse
- $0 to $2 for food processing specific solutions described above
- $250,000 in the case of using cooling tower blowdown for scrubbers
Timelines for Implementation – Immediate (<2 months) if infrastructure exists, 2 to 6 months otherwise. A wastewater discharge permit change may be required as a result of an increase in material concentration, which may influence implementation scheduling. Additionally, Total Dissolved Solids limits may also influence timelines.
The food processing specific solutions above are longer term projects, one year on average.
Level of Difficulty in Execution – Easy – moderate
Cooling towers can use many sources of lower quality water with proper pretreatment design and chemical treatment
Municipal Wastewater Reuse
Description – The concept behind this solution is using an alternative external source of water, municipal wastewater, to be reused, solving wastewater BOD issues. The cost of water will usually be lower using this solution. This kind of project will usually require high capital costs and long term time lines which will generate high water savings.
Process Being Fed - Facility inlet water
Technology Employed – Wastewater treatment solutions, pumping and infrastructure
Estimated Volume Saving – 0 to 100% of total inlet water
Capital Cost – $1 to $10MM depending on existing infrastructure – Piping, pumping and inlet water treatment
Operating Cost - 25 cents/ m3
Timelines for Implementation – 2 years Level of Difficulty in Execution – Difficult. This project will require government interaction, permits and infrastructure laying work.
External Industrial Wastewater Reuse
Description – The alternative external source used in this case is industrial wastewater from another plant. The benefit of choosing this option is the low cost of water and diminished dependency on municipal sources. However, this solution does creates a dependency on production and wastewater quality of the source plant.
Process Being Fed - Facility inlet water Technology Employed – Wastewater treatment solutions, pumping and infrastructure.
Estimated Volume Saving – 0 to 100% of total inlet water
Capital Cost – $1 to $10MM depending on existing infrastructure – Piping, pumping and inlet water treatment
Operating Cost - 25 cents/m3
Timelines for Implementation – 2 years
Level of Difficulty in Execution – Difficult. This project will require government interaction, permits and infrastructure laying work.
Additional Solutions that Can be Utilized
- Many facilities use once-through water to cool small heat-generating equipment. Oncethrough cooling is a very wasteful practice because water is used only a single time before being sewered. Typical equipment that uses once-through cooling includes: vacuum pumps, air compressors, condensers, hydraulic equipment, rectifiers, degreasers, X-ray processors, welders, and sometimes even air conditioners. Options for eliminating oncethrough cooling are typically very cost effective and are normally focused on reuse.
- Any water used for landscape design and irrigation is always a good source for savings.
- Installing cartridge filters on waste lines, contaminated only with TSS and reusing the stream.
- Identify a low TDS stream going to waste, then install a poly tank and pump with level control to direct flow to the cooling tower.
- Take a portion of plant effluent and add standard UF and RO membranes to reduce TDS, put treated effluent into a poly tank and pump ahead of ion exchange system. You can recover 65 to 70% of plant effluent as product water.
- Reduce wasted condensate. Remember, each gallon of condensate saved represents a reduction in water intake of 1.25 gpm and a reduction in waste plant loading, as well as heat savings.
- Look for application of multi media filter Electro Dialysis Reversal (EDR) technology. Remember, EDR can get 90% recovery of inlet flow, 95+% removal of ions, but does not remove any silica.
- Is there a plan to collect rainwater, filter it, and use it as tower makeup?
- Is desalination of brackish water an option?
- A mobile exchange trailer can be a good option for putting an RO ahead of a 2-bed demineralizer, which will reduce demineralizer waste from 20 to 24% to 2% and the RO reject can be added to the cooling tower.
