From: "Joe Ruocco" <JoeR@ICMINC.com> 

To: "Sarah Holman" <Sarah.Holman@erg.com> 

Date: 10/16/2006 5:50:38 PM 

Subject: RE: capacity of Bio-Methanators 

All of the above- recycled as backset, evaporated to syrup and sometimes 

sent to anaerobic treatment. 

 

________________________________ 

From: Sarah Holman [mailto:Sarah.Holman@erg.com] 

Sent: Monday, October 16, 2006 8:03 AM 

To: Joe Ruocco 

Subject: RE: capacity of Bio-Methanators 

 

Thanks, Joe. 

 

My last question then is: 

 

What happens to the stillage from the ethanol process at wet milling 

facilities? Is it typically recycled or sent somewhere other than the 

anaerobic treatment system? 

 

Thanks, 

Sarah 

 

Sarah Holman 

Chemical Engineer 

Eastern Research Group, Inc. 

703-633-1661 (phone) 

703-263-7479 (fax) 

>>> "Joe Ruocco" <JoeR@ICMINC.com> 10/15/2006 6:01:12 PM >>> 

 

 

________________________________ 

From: Sarah Holman [mailto:Sarah.Holman@erg.com] 
Sent: Friday, October 13, 2006 6:32 PM 

To: Joe Ruocco 

Subject: RE: capacity of Bio-Methanators 

 

Thanks a lot, Joe, for the wet milling information. Again, very useful. 

 

I do have some questions about the COD loadings: 

 

1. Is the COD loading range (20,000 to 100,000 ppd) for a combined 

wastewater stream that is sent to the anerobic treatment system? yes 

 

2. If so, what wastewaters are included in this combined stream? 

Steeping and washing wastewaters only, or stillage from distillation as 

well? Not stillage, but a lot of wash waters from separation and product 

washing operations 

 

3. In your experience, does COD loading correlate to ethanol production? 

So, for example, is the high end of the COD loading range (100,000 ppd 

COD) likely from the largest wet milling ethanol facilities (around 250 

MMGY)? Not really- not the way it does in dry mill plants done by the 

same designer - there is a lot more product diversity in a wet mill, 

therefore a lot of variability in the ww COD loading 

 

Thanks, 

Sarah 

 

Sarah Holman 

Chemical Engineer 

Eastern Research Group, Inc. 

703-633-1661 (phone) 

703-263-7479 (fax) 

>>> "Joe Ruocco" <JoeR@ICMINC.com> 10/9/2006 11:33:03 AM >>> 

Sarah, 

Wet mill facilities generate much more wastewater at much higher COD 

than dry mill plants. This due to steeping and washing operations. 

Details vary depending on precisely which products the mill is making. 
They typically use anaerobic systems first (larger than dry mill 

systems- much larger), followed by aerobic polishing systems to either 

directly discharge to he environment or to a city POTW. 

COD loading can be anywhere from 20,000 ppd to as much as 100, 000 ppd 

depending on the mill. 

Joe 

 

________________________________ 

From: Sarah Holman [mailto:Sarah.Holman@erg.com] 

Sent: Friday, October 06, 2006 10:14 AM 

To: Joe Ruocco 

Subject: Re: capacity of Bio-Methanators 

 

Thank you, Joe, 

 

Yes, this information is quite helpful. 

 

Since you were kind enough to respond, I will bother you about one more 

topic (the last I promise!). 

 

I have found little information about the wastewater at wet milling 

facilities. I realize that you do not typically work with wet milling 

ethanol production facilities, but I thought I would try you anyway. 

These are my questions: 

 

1. My understanding is that wet milling facilities that produce ethanol 

typically do not process the stillage (distillation bottoms) into 

co-products like distillers dried grains. I assume this is because at 

wet milling facilities, the gluten/fiber portion of corn is separated 

prior to ethanol production. In addition, wet milling facilities are 

large and typically have on-site wastewater treatment that can handle 

treating the large stillage volumes. Is this correct? 

 

2. Because the gluten/fiber portion of corn is separated prior to 

ethanol production at wet milling facilities, is the COD of the stillage 

from distillation much less than at dry milling facilities? 
 

3. Do you know if the amount of stillage from distillation is much 

different at wet milling and dry milling facilities? For example, would 

a 100 MMGPY wet milling facility produce more or less stillage from 

distillation than a 100 MMGPY dry milling facility?

 

4. Do you know if many wet milling facilities recycle the stillage from 

distillation? 

 

Please feel free to call me if you are interested in discussing anything 

about ethanol production wastewaters (703-633-1661). 

 

Thank you, 

Sarah 

 

Sarah Holman 

Chemical Engineer 

Eastern Research Group, Inc. 

703-633-1661 (phone) 

703-263-7479 (fax) 

>>> "Joe Ruocco" <JoeR@ICMINC.com> 9/29/2006 12:23:47 PM >>> 

Sarah, 

Anaerobic systems are rated in terms of COD total loading capacity- that 

is the number of pounds per day of COD fed to the reactor per day is how 

we design and discuss all anaerobic systems, including of course high 

rate Bio-Methanators such as ours. 

Yes, plant capacity dictates the amount of evaporator condensate 

produced along with total COD loading. In a typical 50 MMGPY plant flows 

tend to be 80 to 140 gpm. In a 100 MMGPY plant they tend to be 200 to 

275 gpm. Loading ranges from 2000 PPD COD to 16,000 PPD depending on 

size of the plant and the design- some designs generate more COD than 

others. 

I hope this helps. 

Joe