NH3-N Removal from Wastewater Lagoon System
Frank
(hereinafter referred to as ammonia) out of our wastewater-effluent. I have
heard that a properly operating aerobic lagoon system will remove the
ammonia naturally. Well, 'my' system doesn't. Not during the Winter and
Spring anyway. It gets the ammonia down as low as 0.67 mg/L during the
Summer and Fall when temps are up and algae is abundant, but come old-man
Winter and it rockets up as high as 20 mg/L. So, if you will, please tell me
what I am doing 'improperly' and point out any discrepancies you can think
of...and sorry for the length but I wanted to give a little more info than
some posts I've read, lol.
The system is a natural-process, 3-lagoon system that has no capability for
mechanical aeration or recirculation. The first lagoon is faculative and the
second two are aerobic stabilization ponds. The lagoons have a capacity of
about a million gallons each and the system is designed to maintain a 30-day
detention-time at the design-flow of 0.06MGD (60,000 gallons per day). Since
we have the lengthy detention-time, the State doesn't make us chlorinate or
dechlorinate the effluent. As far as operating procedures go...
The bar-screen is cleaned once a day, every day of the week; usually around
10am.
The grit-channel is cleaned once a week, usually on Mondays (or as needed,
such as after a storm).
Floating debris (grease, plastic, etc) are skimmed from the wet-well every
two days or so.
All three pairs of lagoon-effluent baffles are cleaned weekly and checked
for level to make sure the baffles are flowing equally to minimize
short-circuiting.
All pond-embankments are regularly mowed and the plant is kept a lot neater
and cleaner than a lot of yards in town.
All ponds are skimmed with the grease-net whenever floating debris are
visible.
The final-effluent weir-box is brushed and stirred daily to prevent
buildup...except on sample-collection day! lol
I also skim all floating debris from the surfaces of all five of our lift-st
ations in town.
The City recently let me buy a pH/Dissolved-Oxygen Meter (about a month ago)
so I'm starting to get some numbers built-up. I've been taking measurements
at the influent, the effluent of each lagoon, and at the plant-effluent
weir-box, to determine the numbers in each phase of the process. The DO
seems to vary widely in the first two lagoons 0.5-4.0 mg/L in pond1 and
1.2-20 mg/L in pond2. Pond 3 has stayed between 6.8-10 since I started
testing. I only have 3ft probes so I can't test at depth in the faculative
lagoon. I do know that the faculative pond doesn't have any sludge build-up
because my Sludge-Judge keeps coming-up with light-green or light-tan water
all the way to the bottom (the water color turns tan after a storm and
usually stays that way for a week or two. I don't know if the lack of sludge
is due to the enzymes I add to the system, because we didn't have a
Sludge-Judge until a year after we started adding enzymes to the
lift-stations and plant-influent; I just know I haven't found any sludge
yet. Next time I do a SJ, I'm going to check near the effluent-baffles to
see if sludge is building-up near the outlet-ends of the pond.
I know I have omitted some things, like periodically checking the
belt-tension or oil-level in the Gorman-Rupp pumps, or checking the
emergency-generator for proper fluid-levels or adequate propane-supply, or
retightening all electrical terminals at least once a year, but I think you
can get a pretty good idea of this plant from what I've said so far. Our
effluent BOD is great, as is the TSS, pH, and Dissolved Oxygen. All these
run well below our permit-limits; it's just the ammonia and that is for
about half the year. Our design-engineer says the system is not designed to
meet our ammonia permit-limit and has recommended that we install a
"Bio-Tower" (or, an aerobic biological reactor as I've also heard it called)
but I would really like to ask him why it wasn't designed to remove ammonia
when he designed it about 4 years ago; but I guess that would be rude, lol.
And what if the State decides to strap us with a nitrate or nitrite
permit-limit during the next round of permit-renewals in March06? Hey, it
could happen. And am I correct in thinking the Bio-Tower will convert
ammonia into nitrates and nitrites? I also think ammonia can be pH-raised to
~12 then air-stripped and pH-lowered...or we could just run all of our
effluent through a cation-exchange unit (as if we could ever afford to do
either of those things, lol).
I have a meeting with the engineer this Fri, to discuss the ($100K)
Bio-Tower and the ammonia problem in general. Another local utility has a
similar unit and their operator says it is useless Winter-Spring, and that
is when our system needs the help! Anyway, I only have 1-1/2 years
experience in the wastewater field and any suggestions a knowledgeable
person can offer would be greatly appreciated. I know we will have to
eventually install an extended-aeration system, or a full-blown
activated-sludge system, but hey, if I can find a reliable solution for less
money...
Best Regards,
Frank
PS for Walt: I 'lost' my old computer (again) and just got back on-line
today. I don't have your email anymore so I can't return your message...
Mike Honeyman
<fhowell@?.com.invalid> writes
It does sound likely that temperature is inhibiting your nitrification.
I'm not familiar with lagoon treatment but have had biological filters
(I think the UK name for the equivalent of your Bio-Tower, not a filter
at all but that's us Brits for you!). The answer I have used is to keep
the recirculation relatively high. The BOD removal efficiency may drop a
little but you should, if the system is designed right, keep your
ammonia removal in the winter.
You are right that the ammonia will be converted to nitrate and nitrite,
but you can denitrify with a bolt on process later if required. Usually
involves some sort of carbon source eg Methanol dosing.
A Bio-Tower should be a cost effective long term option as they are
relatively simple to operate compared to some of your other options.
They are more robust when hit with shock loadings than an ASP and use
less energy than ASP or pH correction. I like them!
Mike Honeyman
UK
PS Just spotted you don't actually state what your ammonia consent is. I
would say the Bio-Tower would be good down to about 5mg/l but would want
some sort of polishing treatment downstream if you had a tighter limit.
HTH
--
Mike Honeyman
Walt
Hi Blaster, and best wishes, fer sure! I think it is fabulous that
professional and knowledgeable people on (at least) both sides of the "big
pond" can contribute to the resolution of issues of common interest, and
(also) of your interest. :) I hope the internationalism continues and
grows.
Mike brings some good experience and insights to bear on your issues.
(And, THANKS to Mike for the focus!) Particularly, I think he has
identified a "Carbon deficit" as a possible key to your issue. Without
having any sludge in your facultative pond, you will have little success
with any "Activited Sludge" process. It seems that you must have a Carbon
excess, (which will settle and be insoluble) before you can expect a
"low-energy" process to metabolize your NH3. Carbon could be charcoal, or
sawdust (watch for species problems), or dry straw or chaff (watch for
alergies!)
With a 30 day retention, you (and your community) should not have to be
forced to buy into "high-rate" technologies. I don't understand your
plant layout, and can't be more specific. But with enough C and P, in a
good sludge bed in your facultative pond, at least your nitrification
should be able to proceed throughout your Texas winter. Agreeably, colder
temperatures and lower pH's typical of winter operations, will spike your
NH3-Nitrogen content, no matter what.
Get the nitrification going well, first. Until then, don't worry about
nitrate and nitrite. When the license comes to renewal, do _NOT_ agree to
anything that you cannot meet. Focus on only the issues that are current.
If authorities feel that it is imperative for you to meet new limits,
feel free to question them thoroughly and at length. If it is a good
point, they will have good information to offer. With 30 day retention,
you have some leeway for denitrification efforts, if they are not already
sufficient, at that time.
Very glad that you are apparently alive and well, and continuing to
protect the water down there. Your neighbors should be thanking you. I
will be e-mailing you asap, as they say.
Best wishes!
--
If you want to exchange e-mail, post your e-mail address with
your request on the newsgroup, and I will reply via e-mail.
alfio trovato
In general, if the ratio BOD to nitrogen (in form of ammonia) exceedes 20,
removing ammonia biologically needs specializegd bacteria (nitrifiers) which
have a very slow growth and are very sensitive to temperature (the reason
for cold seasons diminished efficiency), to pH (must be within 6.5 to 8, as
a rule of thumb), and to dissolved oxygen (a value of 2 ppm can work
efficiently).
In case you go for an upgrade, consider that a biological treatment plant
will do the job efficiently and it can be upgraded, in case regulations ask
for nitrite-nitrate removal.
Please note that 20 ppm DO in water can not be true, it is surely wrong,
read carefully the operating manual. Reading 10 ppm means water is at 12 °C.
At that temperature biological activity is really SLOW. Nitrification is
completely stopped.
ciao
Alfio
"Frank cumbytel.com>" <fhowell@<remove> ha scritto nel messaggio
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ByzRite
If you are looking for a possible solution, try contacting Enviro Voraxial
Technology in Fort Lauderdale. They have a brand new technology that can
easily handle sludge and grit problems. They might also have an idea about
the ammonia. There number is 954-958-9968
PS
"Frank cumbytel.com>" <fhowell@<remove> wrote in message
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Frank Thomas
certainly ought to nitrify. If its not, then something is out of whack, and
I would check these things out before I start spending half million on some
high tech stuff
To nitrify, you have to have a couple of things in balance:
- your influent ammonia needs to be reasonable - check to see if your
influent TKN - ammonia + organic nitrogen - is around 40 and not around 100
ppm.
- your pH should be above 6.7, below that nitrification slows down
- you have to have enough air to nitrify, meaning you should have at least 1
mg/l DO in the aerated parts of the lagoon system.
- you need a pretty decent amount of alkalinity, it sort of depends on your
influent TKN and how you aerate, but I think you'd be looking for alkalinity
in the 100-250 ppm range.
To trouble shoot this, you need some test kits, and pull samples from each
lagoon so you can see what is going on - I would test influent ammonia,
ammonia in each basin, pH, DO etc,. in each basin.
Do you cycle your aerators? To fully nitrify, you might want to let them
run longer - your field tests will tell you if you need to, and they ought
to run for long periods per cycle, maybe 1/2 hour to an hour if you do cycle
"Frank cumbytel.com>" <fhowell@<remove> wrote in message
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jitney
sawdust (watch for species problems), or dry straw or chaff (watch for
If you can get a nearby source of rice hay, using it would do the rice
farmers and their neighbors a real favor. It is useless for animal
feed, and restrictions on burning it are showing up all over the
place.
An interesting historical aside...during the Napoleonic wars, French
farmers were required to mulch manure in a way that converted the
biomass ammonia into nitrates, which were then calcined and later
converted to potassium nitrate and used to make..black
gunpowder.-Jitney