Document ID: EPA-HQ-OW-2008-0667-3550
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2014-08-15T04:00Z

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  
HYPERLINK "http://water.usgs.gov/owq/hardness-alkalinity.html#hardness" 
http://water.usgs.gov/owq/hardness-alkalinity.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 once-through 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.