Mike Russo -
December 19 at 3:00pm
Sewage Treatment Plants and the Moving Bed BioReactor System
All other issues aside in this sewer fiasco, can we devote
some space to talk just about treatment facilities and MBBR, which Dave Clouser
proposed he would recommend if a plant was situated on the Barry property?
From what I read on the web, MBBR sounds like a highly
regarded system but I have no basis of knowledge to draw any conclusion. Can
anyone with knowledge or experience comment on MBBR and whether it would
adequately contain odors and harmful substances, such that its impact on the High
School would be negligible, as I think Dave C. was representing last night?
And besides those two chronic problems typical of treatment
plants, what about the acceptable risks aspect? Are there catastrophic
possibilities not just with MBBR but with pipes and holding tanks and leach
fields and runoff that are within worrisome probabilities that could affect the
High School population? Dave C. related information from a plant operator of a
system in Middleburgh located right next to a ball field that was problem-free
for 22 years, but this morning Steve posted a photo reminder that Middleburgh
was one of the upstate towns that were devastated by Hurricane Irene flooding.
So how did that and other treatment plants and adjoining properties fare due to
those floods? Is there any reason to think that MBBS does a better job of
containment in flood circumstances. Tim
Rogers mentioned in his public comment last night that Dominick Profaci has
expertise in this area. Nick -- can you comment?
Dominick Profaci OK,
let's see what I can do here. The MBBR is a package plant activated sludge
system. The moving bed description refers to plastic media that is contained in
the liquid column of the activated sludge to allow for more surface area for
biomass to grow on to help with the treatment of the waste. Air is diffused
into the water column of the activated sludge, as it is needed by both the
suspended and attached bomass in their conversion of the waste.
Mike Russo Nick --
is the MBBR system used for primary waste or is it typically a secondary stage
treatment?
Dominick
Profaci These systems can function very
well for their purpose; but just like any other activated ludge systems can
generate odors and volatilize potentially unhealthy organisms to the surrounding
area. I can tell you first hand, as a past treatment plant operator and
troubleshooter, that I always got colds/flus after visting waste water plants.
When you are in them regularly, your immune systems actually get stronger, but
if not working in the process every day, it is very easy to get sick -
especially if your immune systems aren't at 100%
Dominick
Profaci Odors from any waste water
facility can come from hydrogen sulfide (rotten eggs), mercaptans (rotten
cabage), or a myriad of other volatile organic and inorganic compounds. Most of
these, even after diluted by the surrounding air, are highly perceptible by the
human nose. They have extremley low odor sensory thresholds and can carry for
long distances. At best these odors are obnoxios and sometimes they can cause
nausea. These come from both the liquid waste water as well as the sludges that
are produced from the process.
Mike Russo So although MBBR uses ultraviolet light
instead of chlorine as a disinfecting agent, there still would be safety issues
simply because waste matter and sewage is being processed?
Dominick
Profaci Another real concern with
package plants are their limited abilility to deal with potentially highly
varying flows. When they are designed, they are designed based on a flow
peaking factor - utilizing assumed average daily flows. What can be problematic
is when these newly designed facilities are tied into an aged collection
system. Most of these older collection systems are no longer water tight. They
are prone to inflow (water from the surface) and infiltration (water from the
ground). During heavy rainfall events, flows can increase dramatically and
easily overwhelm a small package facility that is not designed to deal with
"combined sewers." This can lead to only partiallly treated - non
permit compliant - waste water being discharged to the receiving stream and/or
overflow of the various tankage at the plant site. Another, potentially
hazardous situation.
Mike Russo Also, in
such a compact plant design, although I understand where the fully processed
waste water would go, I don't under what happens to the fully processed sludge.
Is that simply put into the ground?
Dominick
Profaci Mike to answer some of your
questions, with small package plants like these, they typically treat all the
influent flows, minus some screening to remove very large solids, through the
one system. There isn't primary segregated from seconday treatment. As for
health and safety, yes, although the chemical hazards may be reduced by not
using strong oxidizers, like chlorine, to disnfect the effluent waste water;
the bio-hazards would still exist. And as for the sludge, I have seen systems
where they use dissolved air floatation to thicken the sludge and others where
they use gravity thickening. I don't know what is envisioned here. I also don't
know what the plan is to treat that sludge - another bio-hazard. They could
either treat on-site - too many options to list here - or store it and have it
trucked to a larger waste water facility that accepts other facility sludges
for treatment. In any case, there will be odors and potential hazards.
Dominick Profaci By
the way Mike, the sludge has to be treated as it is laden with pathogenic
organisms. It can't just "be put on the ground."
Mike Russo Forgive
my near-total ignorance on the subject. So, even after MBBR or whatever
treatment system has processed the sewage, the residual sludge after processing
is still not inert and safe?
Dominick
Profaci The MBBR, or any activated
sludge system's purpose is to remove contaminants from the water column. Some
of these contaminants end up in the resultant sludges. These sludges must then
be processed to destroy any disease causing pathogens. Hope this helps.
Mike Russo Thanks
so much, Nick for all the clarifications -- definitely a great help. It's Friday
night so people might be socializing (or in Steve G.'s case, working), but
maybe some folks will have other questions or comments on this same subject
that they want to post on this thread. If so, I would greatly appreciate any
further input and expertise you can share.
Dominick
Profaci More than happy. Have a great
weekend!
Amy Dooley
Mosbacher Thanks for this thread. It answers a lot of questions.
Eric Schwartz Wow. Way too much of a fact-based discussion
in this thread...take it down a notch or two - feel free to wildly speculate on
something. Thanks Mike, thanks Dominick.
Steve Greenfield
Thanks. We needed this.
Hadley Taylor agree. thanks so much for sharing your
expertise.
Terrence Quinn
Just to make Eric crazy... Dominick is there an assumed/typical rate of
production of the sulfides and mercapton... that is ... for every gallon of
water into the plant, how much of the outputs can we expect. I know the actual
value depends on whats in the individual waste stream, but what is assume when
they do the sizing calculatin.
Dominick Profaci
Sorry Terry, there is no rule of thumb with hydrogen sulfide or any other
odorant production from waste water. It is highly variable and dependent on the
condition of the waste stream, waste water facility type and how it is
operated, and environmental conditions (time of year and/or day, temps,
barometric pressure, wind conditions, etc, etc). When I used to do odor
studies, there was a ton of on-site analysis as well as "back in the office"
odor identification (qualitative and quantitative), with a trained odor panel.
I know, seems a bit much right? But, noxious odors that are produced in waste
water treatment can be a major issue to the community that surrounds the
facility; and unfortunately very difficult to impossible to mitigate. As an
example, I spent nearly two years at the North River WWTP in NYC as an on-site
process, operations, and odor control engineer trying to help them with odor
mitigation - among other operational issues. This facility has one of the most
advanced odor control systems available, but even today they still have regular
odor complaints.
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