316B RULE

TELEPHONE LOG

Name of Caller: John Sunda, SAIC

Date: August 25, 2009

Company Name: ProChemTech International Inc.

Street Address:

City/State/ZIP: Pennsylvania

Person Contacted: Timothy Keister

Title: Certified Water Technologist

Telephone # 814-265-0959

Called to inquire about technical, treatment chemical usage and cost issues regarding the 

impact of increasing cycles of concentration (COC) in cooling towers.

Contacted Mr Keister after reading his paper “Cooling Water Management Basic 

Principles and Technology.” 

He said they don’t have many power plants as clients but have worked with plants up to 

2000 MW. A recent client is a 90 MW plant Scrubgrass Generating plant in 

Pennsylvania.

He said that most power plant use very rudimentary treatment chemical systems for their 

cooling towers such as using biocides only. For example they may only use chlorination 

and some still use chlorine gas.

 In general as you increase the cycles of concentration the biocides costs will not vary 

that much but you will need to start using an antiscale treatment chemical like 

phosphonate and a solids dispersant like polyacrylate. If they are already treating makeup 

water for corrosion, scale, or solids increasing COC may actually reduce treatment 

chemical costs. They have found that the optimal COC with respect to chemical costs is 

in the range of 3 to 6. Also you may want to treat with acid to reduce pH. Although his 

paper does not recommend using acid this is mostly advice for smaller HVAC and 

industrial systems.

For a typical system operating around 3 to 6 cycles of concentration, the following 

dosage would be appropriate:

Phosphonate at 2-4 ppm

Polyacrylate at 4-5 ppm
The above treatment regimen including acid treatment is what they used at Scrubgrass.

For high hardness water such as in Arizona the COC limit for such a system might be 3 

but in the east it would be around 6-7. He said USGS has a hardness map to get an idea of 

distribution nationwide (found at http://water.usgs.gov/owq/hardnessalkalinity.html#hardness).

These chemicals are non-toxic and do not contain any of the priority pollutants regulated 

in the steam generation effluent guidelines so they should pose no problem with respect 

to direct discharge of cooling tower blowdown. 

There may be a small amount of COD. I asked about water quality and phosphorus 

discharge – he said this could be a problem. For example he was advising the PA DEP 

change their plans to use polyphoshates in their office towers because it might not appear 

appropriate for the PA DEP to be discharging Phosphorus into the Susquehanna when 

they are requiring others to limit discharge of P

Each chemical would require a chemical feed pump which would be relatively small in 

cost around several $1000 per pump.

They would also require costs of some labor for maintenance and the chemist to run tests. 

Most power plants have an onsite chemist. 

As described in his paper, they would also need to install a system to control the cycles of 

concentration. The simplest and most reliable is to install a meter on the makeup water 

which in turn controls the blowdown pump such that blowdown is some fraction of 

makeup. The largest cost would be for the meter which for the largest one he sells – 8 in 

for up to 1430 gpm would cost $4,000. He said they generally use a rule of thumb that 

installation will equal equipment costs

He said a full system including chemical feed and COC control for a large 2000MW 

power plant might cost $20,000 to $25,000.

I also brought up side stream filtration. With regard to solids particles in the <2 micron 

range are easily controlled with dispersants like polyacrylate. Those in the >25 micron 

range can be controlled with settling and cyclones etc. It is the solids in the 2-25 micron 

range that are the most problematic and that multimedia filters are useful if that is a 

problem. Most power plants don’t use filters but some may in the future. He said a 1,000 

gpm multimedia filter system would cost about $250,000. I asked about disposal of solids 

backwash and he said that at coal plants could easily be discharged to the ash pond.

Other benefits besides 316a & 3126b:

Chemical costs may be reduced if they are operating below the optimum COC.

The addition of better chemical treatment can reduce corrosion of equipment especially 

for the condensers by a factor of 5-6X. He said some power plant operators disregard 

corrosion because they argue the plant equipment is only expected to last 15 years.
Another benefit is that by substantially reducing the blowdown (applies both to oncethrough and closed cycle), the discharge of biocide is reduced since the volume is smaller 

and it is easier to treat (e.g., dechlorinate) smaller volumes. Same for other treatment 

chemicals since blowdown volume is reduced.