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From: R Quigley
Sent: Wed Dec 26 13:47:01 2018
To: Andy Peters
Cc: Jake Ehredt; Gerald Fisher
Subject: RE: Ammonia
Importance: Normal
Attachments: image001.jpg; Andy, Tyler has sent me a couple of emails in response to your questions about the ammonia levels you have been seeing at the WWTP. Below are his thoughts to review and consider. Let me know if you have any questions or need additional information on any of these items. I will be forwarding over another email that Tyler sent my way. He consulted with Triplepoint Environment and received some good input from them. Thanks, Ryan · Shouldn’t be a hard ammonia limit (~16.7 mg/L) to achieve. I would guess that with infiltration alone, they should almost meet the limit. · They don’t have to sample for influent ammonia, but they should pull some influent ammonia samples. We tried to get the previous operator to provide influent ammonia readings but never received them. · Check the pH, make sure that it is in the optimum range. Should be between 6-7, but ideally closer to 7. · Check the ammonia at various points in the process to identify trends. My guess is that they are not getting much ammonia reduction in aerated lagoon. Mostly BOD removal, then some nitrification in lagoons. · The monthly average ammonia limit is 16.7 mg/L. In general, this is a relatively easy limit to achieve. Raw wastewater typically has an ammonia concentration of about 17.2 mg/L, based on 120 gpcd and 0.017 lbpd. If there flows are higher than 120 gpcd, the influent ammonia concentration will be lower. There average wet weather flows are in excess of 200 gpcd, typically. · They should pull some influent samples to establish a baseline influent ammonia concentration to understand how much nitrification they need to occur. They shouldn’t have to nitrify much, if any, based on the effluent limit and typical influent ww characteristics. · With respect to effluent ammonia, they’ve normally been below 15 mg/L, but did have some values greater than 16.7 mg/L in 2014/2015. But based on my review of some past DMRs, they haven’t had trouble complying with the 16.7 mg/L monthly average and the 25.9 daily max limit. · Dissolved Oxygen. Nitrification consumes large amounts of oxygen. For every lb of BOD oxidized, 1 lb of O2 is used. For every lb of ammonia oxidized, 4.6 lb of O2 are used. In order for uninhibited nitrification to occur, a working DO level is 2.0 mg/l is suggested. · BOD Loading. Before nitrification can occur, the soluble BOD must be sufficiently reduced to eliminate this competition, generally down to 20-30 mg/l. This means that they are probably getting some BOD removal in the aerated lagoon, additional BOD removal in lagoon #1, and then some nitrification in lagoon #2. The effluent BOD at Molalla’s WWTP is typically less than 15 mg/L, suggesting that they are removing BOD to a point that nitrification can occur, again, typically in lagoon #2. · pH / Alkalinity. Nitrification is optimized at higher pH's. pH around 7 is okay, but 7.5 to 8.5 is ideal. Sufficient alkalinity must be present to buffer the acids produced during nitrification. 7.14 parts of alkalinity is required for every part ammonia nitrified. But, they shouldn’t need a lot of alkalinity because they don’t need to nitrify that much with a relatively easy limit to achieve. · Their influent pH is typically around 7, based on a cursory review of DMRs. Effluent pH is typically also around 7, indicating that they probably don’t have a problem with pH or alkalinity. · Temperature. Nitrification is influenced tremendously due to temperature. Nitrification slows down dramatically or may stop altogether at around 5 degrees C. · Detention Time. They need adequate detention time to remove BOD and nitrify. The lagoons are undersized, reducing opportunity for nitrification to occur. · Toxins. Nitrifying bacteria are very sensitive to inhibitory chemicals. Shouldn’t be an issue with dilution, but something to keep in mind. · I would hold off on bioaugmentation until they characterize the influent ww characteristics and better understand what’s occurring in the process. From: Andy Peters [mailto:apeters@cityofmolalla.com] Sent: Friday, December 21, 2018 2:18 PM To: Bob Dillard Cc: S Major; R Quigley; Jake Ehredt; Gerald Fisher Subject: RE: Ammonia Bob thanks for getting back to me! I will start assembling this information next week. I’m am completely burnt and not sure I’ve got what it takes to go through last years’ DMRS just now! I’m also talking to Biolynceus about nitrifying bac-t options, so I’ll gather what they give me next week too. Thanks! Andy Peters City of Molalla Public Works Operations Supervisor (503) 829-6855 x220 Cell: 503-793-0507 117 N Molalla Ave Molalla, OR 97038 From: Bob Dillard <b.dillard@charter.net> Sent: Friday, December 21, 2018 1:54 PM To: Andy Peters <apeters@cityofmolalla.com> Cc: 'S Major' <smajor@dyerpart.com>; 'R Quigley' <rquigley@dyerpart.com>; Jake Ehredt <jehredt@cityofmolalla.com> Subject: RE: Ammonia Andy, Could give me your ammonia readings for the last year? Along with the following information if you have it.
Lagoons usually nitrify in the summer due to nitrifying bacteria available, warm water temperatures >70 F. and long detention times. The nitrifiers will usually stay in the system unless inhibited. Are your ammonias matching up with the outside lab? The ammonia probe can fail or become fouled? It will be a challenge to get the system to nitrify during the cooler temperatures and higher flows. Sometimes one can not discharge to allow some growth in the bacteria. I doubt you have this option.
Even though your permit has limits set for ammonia it does not dictate sampling. I would think DEQ would give a lot of lenience in this matter. If you don’t won’t to clarify with DEQ we can review the information you provide and identify what might have caused the problem and look for other solutions that may include the following;
We can also evaluate what actual benefit you’re getting from the aeration basin.
I hope you have a great holiday! Merry Christmas.
Bob Dillard
2470 Ash St.
North Bend Or. 97459
541-290-9908
From: Andy Peters <apeters@cityofmolalla.com>
Sent: Thursday, December 6, 2018 2:31 PM
To: Bob Dillard <b.dillard@charter.net>
Cc: Gerald Fisher <gfisher@cityofmolalla.com>; Jake Ehredt <jehredt@cityofmolalla.com>; James Clifton <jclifton@cityofmolalla.com>
Subject: Ammonia
Bob, we are running into Ammonia issues this month. Ever test we’ve done is coming in over the daily limit. We’ve sent a split sample in to Edge Laboratories, but the test is not rocket science, and our equipment was just calibrated. We have two questions (copying Ryan Q for help).
Thanks,
Andy Peters
City of Molalla
Public Works Operations Supervisor
(503) 829-6855 x220
Cell: 503-793-0507
117 N Molalla Ave
Molalla, OR 97038
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