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From: Putney.David@epamail.epa.gov

Sent: Friday, April 29, 2011 3:13 PM

To: Palazzolo, Michael A.

Cc: Green, David A.; Bahner, Mark A.

Subject: RE: PAL ICR for Massena East

Mike, your explanation of the equipment scenario at the Massena East facility was very helpful (it did change our 

perspective) - thanks for clarifying. I believe that sampling the wet scrubber blowdown alone (i.e. without also sampling 

the wet scrubber sludge) will be sufficient. Mark Bahner at RTI provided (I think) a concise and clear explanation of our 

proposed approach to estimating metals emissions from the wet scrubber - provided below. 

"Here is an outline of a procedure for estimating metals emissions from a unit with a wet scrubber, based on 

analysis of blowdown water from the scrubber, and a particulate limit (e.g., in a permit): 

1) Obtain a well-mixed sample of the scrubber blowdown. This wastewater will have both suspended solids and 

dissolved solids. Say the wastewater is 1 liter (1 kg). 

2) Measure the total solids in the wastewater (both suspended solids and dissolved solids). Let’s say the 

concentration of total (suspended and dissolved) solids is 10 grams per liter. Therefore, the total solids in that 1 

liter is 10 grams. 

3) Measure the metals content of the well-mixed wastewater. Let’s say it has a chromium concentration of 0.1 

milligrams per liter. So the total chromium in the liter is 0.1 milligrams. 

4) The concentration of the chromium in the solids is therefore 0.1 milligrams divided by 10 grams, or 0.1 

milligrams divided by 10,000 milligrams, or 10 ppm. 

5) Multiply the particulate limit in the permit by the concentration of chromium in the solids in the blowdown 

water. Suppose the particulate limit is 20 tons per year. The concentration of chromium in the solids is 10 ppm, 

so the chromium emitted is 20 tpy x 10 ppm = 0.0002 tpy = 0.4 pounds per year." 

By the way, about how much of this sludge gets removed from the wet scrubber sump during each maintenance/cleaning 

shutdown (i.e. every 6 months)? 

Thanks, 

David Putney, Environmental Engineer

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards 

Sector Policies and Programs Division

109 T.W. Alexander Drive, RTP, NC 27711

Mail Drop D243-02

Ph: (919) 541-2016 Fax: (919) 541-3207

Email: putney.david@epa.gov 
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______________________________

From: "Palazzolo, Michael A." <Michael.Palazzolo@alcoa.com>

To: David Putney/RTP/USEPA/US@EPA

Date: 04/28/2011 03:30 PM

Subject: RE: PAL ICR for Massena East

David,

We may need to discuss this further. There is no sludge that leaves the scrubber on a 

continuous basis like a typical FGD system. This scrubber uses a sodium bicarbonate 

solution and there is only a continuous scrubber blowdown stream that consists of 

sodium bicarbonate solution (containing dissolved sodium sulfate) and a minimal 

amount of solids. The solids do not immediately get separated from the blowdown 

stream for disposal. The blowdown gets combined with other site industrial wastewaters 

prior to any removal of solids. So, solids removed during treatment are not 

representative of solids in the scrubber.

There is some material that collects very slowly in the bottom of the scrubber sump over 

a six month period. This material we call a “sludge” and it only gets removed when we 

shut down the scrubber for maintenance to clean it. 

We are proposing to sample only the continuous scrubber blowdown stream in response 

to the 114 request. This stream, which includes solids and liquids from the scrubber, is 

essentially the same liquid that would escape the demister at the top of the scrubber 

and be emitted from the stack. Will this work for you? How will you use total metals in 

the blowdown stream (mg/liter of blowdown) to calculate metals composition of stack 

PM emissions?

Mike

From: Putney.David@epamail.epa.gov [mailto:Putney.David@epamail.epa.gov] 

Sent: Thursday, April 28, 2011 2:18 PM

To: Palazzolo, Michael A.

Subject: PAL ICR for Massena East

Mike,

As we discussed earlier today, see the contractors' thoughts on the need to test the scrubber sludge and blowdown in red 

and blue text below:

I tend to think in terms of mass balances. In the dry scrubber/baghouse situation we can look at the 

composition of the baghouse dust and use it to represent the composition of the particulate that escapes the 
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baghouse--then apply this composition to the PM limit in their permit to estimate emissions for risk purposes. In 

the dry scrubber/wet scrubber situation we should look at the weighted average of all of the streams that are 

discharged from the wet scrubber. I think that is the blowdown (which I thought someone said was recycled 

back to the wet scrubber after settling and never discharged, in which case it could be ignored) and the sludge 

hauled off. The composition of the sum of what leaves, on a weighted dry basis, represents the composition of 

the material that escapes the wet scrubber. We then apply that composition to the PM permit limit. The short 

answer is, if both of the streams leave the plant, we need data, including masses of each stream that leave the 

plant in any given year. 

All of this logic is imperfect but it is reasonable, as well as being relatively cheap and relatively fast.

I agree....if the scrubber sludge and the water both leave the plant (are not recycled in the process) then we need 

the HAP metal concentration in both, as well as the mass flow rate of both at the sampling points. For example, 

suppose the water in the scrubber is 100 gpm, but 90 gpm are recycled, and only 10 gpm leave the plant. We 

need the metals concentration of that 10 gpm. An example calculation would be 10 gpm at 8.33 lb/gal is 83.3 

lb/minute, times 0.5 ppm of that water being hexavalent chromium equals 83.3 x 0.0000005 = 4.16 x 10-5 

lb/min hexavalent chromium in the water.

Now let’s say 10 lb/minute (dry basis) of scrubber sludge are also leaving, and that the concentration is also 0.5 

ppm. Therefore, the lb/min of hex chrome in the scrubber sludge are 10 X 0.0000005 = 5 x 10-6 lb/minute of 

hexavalent chromium in the sludge.

So the total hex chrome leaving is 4.66 x 10-5 lb/minute, in 10 lb/minute (dry basis) of material. So the ppm on 

a dry basis is now 0.466 ppm. We should multiply their particulate emissions by 0.466 ppm, instead of just the 

concentration in the water or in the sludge.

David Putney, Environmental Engineer

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Sector Policies and Programs Division

109 T.W. Alexander Drive, RTP, NC 27711

Mail Drop D243-02

Ph: (919) 541-2016 Fax: (919) 541-3207

Email: putney.david@epa.gov