Water Environment Federation (WEF) Discussion Forums / WEF Discussion Forums / Operation & Maintenance / Very Large floc particles / Latest Posts

RE: Very Large floc particles

Robert — Wed, 16 Apr 2008 17:38:15 GMT

The exocellular coating is caused by stress factors on the bacteria. Nutrient deficiency is just one stress factor, others are pH out of ideal range, and low dissolved oxygen for the applied organic load.

RE: Very Large floc particles

pasque — Tue, 15 Apr 2008 13:45:54 GMT

We utilize fine bubble diffusers to aerate. Since I posted the original message our settleability has gone to pot. Five and 30 minute numbers are around 980 and 550 respectively. Two weeks ago they averaged 500 and 230. I'm pretty sure the runoff and the chloride it contains has a lot to do with the current settability issues (plus some M. parvi issues mixed in). I remember reading somewhere that either sodium ions or chloride can cause floc dispersion. I wish I could remember where I read that.

We are a municipal waste plant but we also deal with some I and I. I am assuming the low nutrient based on the india ink test of the large floc particles. It is clear that there is some sort of exocellular material coating the floc.

I posted the floc particle picture here:

http://picasaweb.google.com/peggileebee/April2008/photo#5189542460778161378

RE: Very Large floc particles

Wiff P — Tue, 15 Apr 2008 09:41:54 GMT

Can you supply a bit more info for us? What sort of mixed liquor settleability (5 and 30 minute) are you seeing? What kind of aeration equipment do you have, and what Mixed Liquor DO concentrations are you running? Sludge blanket levels and sludge collector type? Are you seeing any signs of denitrification in the final tanks? Wondering about sludge removal problems and anoxic or even anaerobic conditions developing in clarifiers.

Assume you are muncipal (primarily sanitary) waste plant so curious why you think you have low nutrients?

Spring run off comment implies you believe you have a fair amount of inflow from melting snow, etc. Current mixed liquor temperatures? Is snow melt and high chlorides from road salt expected at your location? High chloride levels can cause some funky things to happen with mixed liquor settleability so this can be an area to check out also.

RE: Very Large floc particles

Rob Baur — Thu, 10 Apr 2008 10:54:26 GMT

You can post a photo at photo hosting sites like Google Picassa and include a link. Not sure if this site alows links so you may need to disguise it like "picassa dot com/site"

Very Large floc particles

pasque — Wed, 09 Apr 2008 15:17:41 GMT

Hello,

I am hoping someone out there can answer a question for me. I work at a 3.0 MGD treatment facility that as of last July completed construction of a nitrification process. Twice since then (October and currently) we have gone through a period of time when unusually large floc particles appear. They are large enough that we are unable to float them in our DAF unit used to thicken our WAS prior to anaerobic digestion. We continue to nitrify just fine, but the size of these babies are immense! They are macroscopic, probably 20-30 times the size of a normal floc particle. In 19 years of working here I've never seen anything like them. They are most likely due to a lack of nutrients as we are taking in run off from the "spring" thaw. India Ink reverse staining confirms this.

Anyway my question is, is this something that other nitrifying plants go through? I am new to the whole ammonia removal thing and am just curious if other plants have seen these types of floc particles.

A little info on the plant process:

3.0 MGD Flow, 1.2 MG under aeration, MLVSS 1970 mg/l, WAS VSS 4240, WAS Flow, 0.05 MGD. Influent NH3, 20.0 mg/l. Effluent NH3, 0.25 mg/l.

FM Ratio 0.165 and MCRT of 9.6 days

(I have twice tried to insert a microscopic image but the WEF site won't let me.)

Thanks in advance.

Peg