Water Environment Federation (WEF) Discussion Forums / WEF Discussion Forums / Biosolids & Residuals

Biosolids

nang — Thu, 01 May 2008 20:06:57 GMT

I am trying to find out how to add ferrous to Class A biosolid drying process. The class A biosolid produced is lower in the iron concentration than the fertilizer. We would like to blend the Class A biosolid with Fertilizer. We will also like to increase the iron concentration in the Class A biosolid, so it equals to the iron concentration in Fertilizer.

Shall we add the iron (in the form of ferrous) before the centrifugal drying process or after the centrifugal drying process? Or shall we add it in the wet cake bin after the dewatering process prior the mixer?

What will be the best way to raise iron concentration in the Class A biosolid?

RE: Centrifuges....who the best?

Peter LaMontagne — Mon, 28 Apr 2008 16:36:35 GMT

You are asking a difficult question.
Every centrifuge has a market, so you have to figure out what you need
Do you have a high disposal cost? Over say...$40/wet ton
Do you expect to run the centrifuge a lot more than 30 hours per week?

If you answered no to both questions, than the lower cost, not so well known brands will probably be more cost effective.

If you answered yes, then you probably would do well to consider spending more money for a more rugged, hopefully higher performance one.

Obtain copies of the instruction books of models you are considering, and judge if they contain enough information therein to maintain them

Ask all vendors for installation lists and call several and talk to both maintenance persons and operators. Visit centrifuge installations in your area

If the fog the vendors throw up is really thick, (Here comes the crass commercial) I consult with engineers and owners to help them make such choices.

Peter LaMontagne

Centrifuges....who the best?

Dookie — Wed, 02 Apr 2008 11:57:41 GMT

Were looking to purchase two new centrifuges for dewatering our digested sludge. We are currently using a centrifuge so were familiar with them. Sure like to hear some feed back on the good,bad and the ugly.

RE: centrifuge problems

Peter LaMontagne — Mon, 28 Apr 2008 16:15:18 GMT

I am a little puzzled. I don't know what you mean when you refer to a single stage centrifuge. In general, if a centrifuge is doing poorly for mechanical reasons, it also runs very rough. If it is running smoothly, it's almost always a problem with the ancillary equipment and processes.

The polymer system can screw up, inadequate aging time, the sludge/polymer reaction is very poor.
Do a jar test to compare a polymer solution made in the lab, with a fresh grab sample from the plant make down unit. If they perform the same, the make down unit is fine.

Often the sludge has changed, and it is possible the polymer is not what you think it is. It is hard to know which, unless you have a reference sample of the polymer, taken during the polymer evaluation trials.

Peter LaMontagne 215 348 7879
Peter@thecentrifugeguys.com

centrifuge problems

andy940_00 — Fri, 04 Apr 2008 04:05:32 GMT

We seem to be having problems with our single stage centrifuge we can't seem to get a good quality dry bio- sludge i've tried adding clay and lime at different times with little results i've also adjusted the plate dams with no luck any suggestions would.be appreciated thanks. andy

RE: Arsenic

rocsmith — Mon, 28 Apr 2008 11:49:17 GMT

It is mostly dissolved from dewatering of a former plate glass manufacturing site. The concentration is 2,000 - 9,000 ug/L. The municipal WWTP is reluctant to accept the discharge because they are concerned about their biosolids land application program.

Arsenic

rocsmith — Wed, 23 Apr 2008 10:44:49 GMT

What is the fate of arsenic influent to a wastewater treatment plant, i.e. how much ends up in the sludge and how much goes out with the effluent? Does the treatment configuration have any impact, i.e. attached growth vs. suspended growth; with or without effluent filtration?

RE: Arsenic

Jeff Naumann — Thu, 24 Apr 2008 18:56:28 GMT

I would suspect the fate depends upon whether the arsenic is dissolved, or in particulate form. What does your analyses data seem to indicate? Or, is this a hypothetical question?

RE: Molybdenum contamination

mjwboofer — Thu, 17 Apr 2008 23:01:24 GMT

Aquifer Storage Recovery Well...I would assume.
http://www.asrforum.com/fatestudy/what.html

Still curious about what Mb is doing there...perhaps that's a discussion for another forum?

Molybdenum contamination

D Shulmister — Fri, 14 Dec 2007 12:56:52 GMT

Over the past six months we've seen the molybdenum concentration in the sludge cake increase from 20 or 30 mg/kg (I think that's the correct units) to above the EPA ceiling limit of 75. In fact, we're over 100. We have been searching for possible sources, including cooling tower blow down (checked with the contractors who handle most of the county's cooling tower maintenance), odor control chemicals, and potable water. We only have about a dozen industrial users, and none of them appear to be using molybdenum products. Anyone got any other ideas??

RE: Molybdenum contamination

Rob Baur — Thu, 17 Apr 2008 11:14:30 GMT

What is an ASR?

RE: Molybdenum contamination

Christian — Thu, 17 Apr 2008 08:01:01 GMT

Not sure how it got there yet. Late last year they began seeing increased levels of moly coming from the potable ASR's.

RE: Molybdenum contamination

Rob Baur — Wed, 16 Apr 2008 16:59:22 GMT

ASR? How was the moly involved?

RE: Molybdenum contamination

Christian — Wed, 16 Apr 2008 08:02:42 GMT

Update: Molybdenum problem was traced back to the ASR wells at the County water plant.

RE: Sudden Plate and Frame Dewatering Problems

TerryF — Mon, 14 Apr 2008 17:47:35 GMT

Whislt i don't have a specific solution you need to think through the how the various coagulants etc work. Ferric chloride typically works by forming a hydroxide sludge that acts as a sweep floc whereas the polymers work by charge neutralisation and bridging.

In operation Ferric will be very pH dependent whereas the polymers , whilst pH sensitive will be less so. The initial choice of polymers is often dependant on whether the solution is acidic , or basic however.

Generally Ferric Chloride will allow a far amount of flexibility with changes in dose rates and alteration/control of pH required when conditions change. However many polys are much less tolerant of changes in conditions and may work only in a narrow window.

Your records may indicate changes to background pHs , temperature , alkalinities and these may give a hint at why certain coagulant mixes are not working. As someone else has suggested changes in background conditions may be impacting on the process.

Hope this helps although i have been deliberately general in my comments.

Regards

TerryF

Sudden Plate and Frame Dewatering Problems

Brett Ward — Mon, 14 Apr 2008 09:30:34 GMT

Help and ideas needed to trouble shoot a sudden dewatering problem with a plate and frame press. The process in an oxidation ditch followed by aerobic digestion. The WAS is first pumped to primary digester then to secondary digester from which the press is feed. Traditionally a ferric chloride poly quant blend cationic polymer has worked well in the presses, but each spring in late March or early April the process fails. Regulators have pointed the finger at an industry that used to discharge acids and oily water to the system. In past years the addition of bentonite clay always improved the press performance, but not this year. Our polymer consutlant says that the imporvement using bentonite is proof of oil in the sludge. This years jar tests are strange. We can make a floc only when the pH is above 10 su. When the pH drops the floc disperses. Jar test using anionic polymer were no better. There have been no unusual changes to the oxidation ditch and effluent quality remains good. BOD and TSS < 10, ammonia <1.0 Clould this be weather related? Thanks in advance.

RE: Sudden Plate and Frame Dewatering Problems

Milos — Mon, 14 Apr 2008 11:56:50 GMT

Try the combination of lime (first, dose to pH 8,5 - 9,0) and cationic polymer, (or cationic and anionic polymer) in the jar tests.

And different temperature conditions (in the biological tanks) may change dewatering characteristics of sludge.

RE: digester slime?

d jenkins — Sun, 13 Apr 2008 20:45:56 GMT

It sounds like biological foaming caused by either nocardioform organisms or Microthrix parvicella. I say this because of your descriptions of its properties and because of the fact that you are able to get 5%TS by DAF thickening without using any polymer. Both of these microorganisms are highly hydrophobic and act as flotation aids for the WAS especially when using DAFs. I would be happy to look at the sludge for you if you want to contact me.

David Jenkins

digester slime?

Pellet — Tue, 08 Apr 2008 15:58:19 GMT

Anybody ever hear of Slime being generated in anaerobic digesters?

RE: digester slime?

Jerry — Thu, 10 Apr 2008 10:17:24 GMT

I would have it analyzed under a microscope by someone who's has the expertise. Maybe a local College Chemistry or Biology professor can help. Look at your industries to see what products they handle.

RE: digester slime?

Pellet — Wed, 09 Apr 2008 12:03:06 GMT

I forgot to mention we are using disolved air flotation and not using any polymer presently. The sludge is thickening to 5% without the use of polymer. That being said the consistensy was compared to polymer, still no word on whether we can use the slime in dewatering.

RE: digester slime?

Jerry — Wed, 09 Apr 2008 10:27:58 GMT

Could be your polymer.

RE: digester slime?

Pellet — Wed, 09 Apr 2008 07:51:02 GMT

It smells like anaerobic sludge, sticks to itself, acts as a surfactant, and leads to a phenominal surface foaming. It is has weird dewatering characteristics. Even after it is dewatered to 24% it shakes like jello. The digesters are running at 95F give or take about a half a degree.

RE: digester slime?

Victor — Tue, 08 Apr 2008 16:38:54 GMT

Pellet:

Are you talking about a slime that adheres to itself? Sort of snot, taffy consistency thick gooey? Is it colored or transparent, smelly? Need to describe it a bit more in detail. What is the temperature of the anaerobic digester?

RE: centrifuge problems

Rob Baur — Mon, 07 Apr 2008 12:12:44 GMT

Is it performing below the startup performance test levels? I would call in the manufacturer to optimize and also test different polymers.

RE: WAS dewatering

SMK — Fri, 04 Apr 2008 16:44:32 GMT

It's always better to thicken the WAS separately, if possible. You can blend it afterwards with Primary to improve the WAS dewatering. Problem is that you will reduce the Primary's final dryness.

My recommendation of an optimal installation would be:
Stream A: Thicken WAS using DAF or GBT (in 2%, out 8% solids), dewater belt press (in 8%, out 14% solids) and final dewatering using Elcotech electro-dewatering (in 14%, out 40% solids).
Stream B: Thicken Primary using GBT (in 3-4%, out 10-12%), dewater Fournier Rotary Press (in 10-12%, out 35-40%).

Your final product would be in the range of 35 to 40% solids, a great product for co-generation. Automated operations, very slick, cutting-edge technology and affordable if operated automated long hours.

Would this fit with your situation?

Scott
smckay@elcotech.ca

WAS dewatering

joy — Fri, 21 Dec 2007 22:49:28 GMT

Hi. Can anyone suggest what is the best way to dewater primary sludge and WAS mixture. It is very difficulty to process it in our belt presses. Even with higher polymer dosage, the output is minimal and the pressed cake is very soft. Our clarifier level is steadily increasing and we have to take the sludge out of the system faster. We have tried reducing the WAS flow but the problem is solids build up. We also tried diverting some of the WAS back to the WWTP but we encountered more problems in the primary clarifier. The WAS seemed to have decayed, floated and caused septicity in the clarifier. Do we need other equipment to process the WAS alone so that the primary sludge will solely go the belt presses?

RE: Centrifuges....who the best?

highcountryop — Fri, 04 Apr 2008 13:54:28 GMT

Andritz makes a good one we have had luck with. They are Texas Based.

RE: Centrifuges....who the best?

mjwboofer — Fri, 04 Apr 2008 10:49:20 GMT

At the WEF biosolids show earlier this week, a presentation was given by Dr. Mohammed Abu-Orf comparing performance of Belt Filter Press and a Centrifuge at Ocean County Utilities Authority, NJ. The plant ended up going with the BFP but the recommendation was given that, if possible, piloting makes a lot of sense so a real comparison can be made for your sludge. I've heard this sentiment elsewhere. I suspect that it's a combination of varying effectiveness under different conditions in addition to the free market we enjoy that contribute to the fact that there's more than one way to skin the dewatering cat.

I know a lot of centrifuge manufacturers have pilots available...Flottweg, Alfa Laval, etc. so it might be worth seeing what it would take to get something like that going. The local reps are a good place to start. If you're not sold on a centrifuge, you could try some other technologies and see some consequences firsthand.

RE: Cannibal System

Rob Baur — Wed, 02 Apr 2008 13:33:36 GMT

My impression of the Cannibal process is that the fine screens remove toilet paper fibers etc and the cyclones remove "sugar sand" so the MLSS is composed of a much higher % of real active bugs and less organic and inorganic trash. That means for a given MLSS, Cannibal MLSS has more capacity than normal MLSS. Since loading to clarifiers can limit capacity I would think a Cannibal plant would have more capacity for a similar aeration basin and clarifier. The MLSS is aerobically digested.

Does that sound right?

Cannibal System

Warner — Tue, 01 Apr 2008 17:09:43 GMT

We're considering this at a 6 Mgd Tertiary Plant (Ox ditch, clarifier, continuous backwash filter). Would like to review case studies and experiences from existing operations - particularly how other biological processes were affected - positive or negative. General real life Pros and Cons. Thanks.

RE: Centrifuges....who the best?

Rob Baur — Wed, 02 Apr 2008 13:26:41 GMT

One issue with high G centrifuges is that the high shear energy rips open cells and the nutrient then cause a regrowth of coliform and other organisms along with a serious odor problem. We rated our odor in DUs, Dead Animal units! WERF has done a bunch of research on this. It would be important to visit and/or call plants with the exact model you are thinking about using. At one plant side by side centrifuges by the same manufacturer, but different models, where the high solids one made stinky cake and the other one didn't.

RE: Cannibal System

Victor — Tue, 01 Apr 2008 17:51:56 GMT

Warner:

You may want to get a hold of the following article by John T. Novak et al, "Biological Solids Reduction using the Cannibal Process", Water Environment Research, Vol. 79, No. 12, Nov. 2007, pp 2380-2386. Use the following link to view abstract of article and other information:

Biological Solids Reduction Using the Cannibal Process

Abstract:

A laboratory study of the Cannibal process was undertaken to determine if the Cannibal system would generate less sludge compared with a conventional activated sludge system. Side-by-side sequencing batch reactors were operated—one using the Cannibal configuration and the other as conventional activated sludge. It was found that the Cannibal process generated 60% less solids than the conventional activated sludge system, without any negative effect on the effluent quality or the settling characteristics of the activated sludge. The oxygen uptake rate for the centrate from the Cannibal bioreactor showed that readily biodegradable organic matter was released from the recycled biomass in the Cannibal bioreactor. It is proposed that the mechanism for reduced solids from the Cannibal system is that, in the Cannibal bioreactor, iron is reduced, releasing iron-bound organic material into solution. When the Cannibal biomass is recirculated back to the aeration basin, the released organic material is rapidly degraded.

RE: Landowner question on trash problem(tampons, etc.)

Dookie — Mon, 31 Mar 2008 16:17:42 GMT

I didnt see mentioned the volume of liquid sludge your accepting but we have used a screening box which is similar to a 40 yard roll off but has a perforated raised floor above the actual bottom and valved discharge lines out to tap into to, also a screen can be placed inside to filter the debris. Unfortunatly the debris content in larger cities biosolids is a factor.

Landowner question on trash problem(tampons, etc.)

TexasBiosolids — Tue, 11 Dec 2007 18:00:47 GMT

I'm a landowner that has biosoilds applied to my land. I'm growing sick and tired of the trash(tampons, condoms, pens, q-tips, syringes, etc.) that ends up in the mix out here. I stopped the cake as that was an even bigger trash problem and only allow liquids now.

I voiced my concerns with the application company and they tried to help by building a screening box. Well, that helped a little, but the trash still seems to get through.

I obviously am not in the business per say, but it just seems like in this day and age, they should be able to screen out all trash at the station where they pick this stuff up at. Am I wrong to think this?

Any suggestions would be greatly appreciated!

RE: Cow Killing Biosolids

WToffey — Fri, 28 Mar 2008 13:19:09 GMT

These memos are from two reliable sources that pertain to AP's dead cow story, and provide good responses to the issues raised in that story.

FROM: Chris Peot, DCWASA Biosolids Manager & Expert Panel Member
TO: Biosolids Expert Panel
March 20, 2008
SUBJECT: Associated Press Story on Georgia Court Case

You recently received a copy of an Associated Press story and other information about a recent court case in Georgia. This story has been presented as “raising doubts” about the safety of the land application of biosolids as regulated by the Environmental Protection Agency and by the Virginia Department of Environmental Quality.

As manager of one of the largest biosolids programs in the nation, as a member of this Expert Panel, and as someone who worked closely with the AP reporters for nearly a year, I want to provide you with information that was omitted in the AP story.

Last May I was contacted by a reporter with AP who said he was doing a feature story on biosolids and who asked for my help. I believed this was an opportunity to share the overwhelming scientific case for the safety and benefits of biosolids and to facilitate the reporter’s search for the facts. I and many others in the biosolids profession, including government officials and farmers, provided hours of on-camera interviews, arranged tours of our facilities and arranged for the reporters and photographers to observe an actual land application process in Virginia. We then waited patiently for the story to appear. After many months, I began to inquire about the story. Each time I asked, the response was vague, usually that it was being edited or being reviewed, but that its release was imminent.

Those of us who had worked with the reporters on this story began to suspect that because the science and the experience supporting biosolids was so overwhelming — and because the story wasn’t particularly interesting — the reporters were having difficulty finding a “hook” that would grab editors’ attention and cause them to buy the story from AP.

The case in Georgia obviously provided the AP with their hook (one of the authors confirmed this with me via e-mail)—an isolated and highly disputed incident, which occurred 18 years ago, that could be used to create alarm about biosolids and, not incidentally, sell the story to subscribing newspapers and electronic media.

The true story about the Georgia case is complex, and while I’d like to give you every minute detail, I’ll submit a few of the most pertinent facts. I will be happy, however, to provide you with any of the supporting documents and more details if you desire. I believe you should be aware of the following facts:

From: Charles Hooks, Virginia Biosolids Council

In addition, the following information may also be useful in answering questions from your staff, the public and local media:

The Gaskin Study
The AP reporters are claiming that the University of Georgia study by Gaskin and others is fatally flawed because it relied on "false data" from the Augusta WWTP. In fact, the Gaskin study is based on actual soil and grass samples from land--many different farms--that received the biosolids from Augusta. The authors acknowledge that the data from the WWTP are questionable and that the metals in the biosolids were too high:

Their conclusions, however, do not rest on the data from Augusta, they rely on the actual soil and grass samples. While the plaintiff's paid consultant attacked the methods used for the samples, that does not make his opinion more valid than the peer-reviewed scientists.

The Gaskin study concluded the following:

"The study indicated that toxic levels of metals have not accumulated in the soils due to long-term biosolids application. Overall forage quality from the biosolids-amended fields was similar to that of commercially fertilized fields, however, due to the relatively high S and potential for a low Cu to Mo ratio, Cu supplements should be used to ensure ruminant health."

There are no peer-reviewed studies to indicate that the Gaskin study is flawed.

A Smoking Gun?
Then there is the "smoking gun" of the note that says the researchers should "fess up" that the data are wrong. AP claims in the story that they somehow "obtained" a draft document of the Gaskin study that contains this confession, with the implication that their investigative reporting skill resulted in this disclosure. In fact, these notes were produced by the authors of the study during the discovery phase of one of the many plaintiffs' suits.

But federal judge William Moore denied a motion by the plaintiffs to include the note in their false claims suit against the study's authors and on September 28, 2007 made the following ruling about the note:

"The note appears to be an editing comment, illustrating one scientist's attempt to ensure that the study's conclusions accurately reflect the scope of the research, and that the paper does not infer additional conclusions by use of imprecise language . The Court finds that this note, standing alone, is neither evidence of fraudulent conduct nor evidence of contamination on Plaintiffs' lands ."

The AP did not use this judge's ruling, apparently since it puts a completely different light on the claim that the Gaskin study was based on false information and was fatally flawed.

Cow Killing Biosolids

Dvant — Thu, 27 Mar 2008 11:58:39 GMT

Anyone have the skinny on the cow killing biosolids? There was an AP story about a week or two ago.

It seemed like a evil biosolids producer, good farmer story.

Me, I think it is as likely that the cheap farmer bought feed from China that had thallium in it and the cows spread it over the nice clean biosolids fields.

Just looking for someone who might know what happened.

Mark

RE: Cow Killing Biosolids

Jerry — Fri, 28 Mar 2008 10:58:23 GMT

Thallium was used in rat poison once. I wonder if the farmer had some spread around his barn?

RE: Cow Killing Biosolids

Jerry — Fri, 28 Mar 2008 10:46:33 GMT

One Engineer for the plaintif managed HazWaste sites. He wouldn't be trying to create another one for profit,would he?

RE: Cow Killing Biosolids

Dvant — Fri, 28 Mar 2008 10:36:24 GMT

I am sure we don't know the whole story.

We are talking about Augusta GA. So could it,thallium, have come from a plant that makes gopher poison for golf courses?

Mark