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turnerpr

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Improving treatability of activated Sludge
Feb 17^th, 2005, 2:09pm

Having experienced problems trying to thermally dry activated sludge we are looking to apply any pre-treatment to the activated that would break up its cellular structure and hence release intercellular water.

Ultimately our aim is to make the subsequent sludge cake produced from the activated sludge more easy to mix and bind in with dried sludge granules as part of the subsequent thermal drying process.

We do have acess to settled sludge to blend it, however we are more interested in pre-treatment or chemical addition at this time.

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grrun

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Re: Improving treatability of activated Sludge
Reply #1 - Feb 17^th, 2005, 6:38pm

I have no experience in this area, but did a Google search for "Milorganite" that provided one clue before my eyeballs fatigued. Besides filtration to remove most of the water, the pH of the sludge is adjusted to 4.4 with sulfuric acid. You may want to look for more clues at http://www.epa.gov/owm/mtb/biosolids/index.htm and also to contact someone at the Milwaukee Sewage Commision. I also learned from the Google search that many American cities are producing a similar product.

I hope this helps, grrun Embarrassed

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« Last Edit: Feb 18^th, 2005, 3:10am by grrun »

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Victor

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Re: Improving treatability of activated Sludge
Reply #2 - Feb 17^th, 2005, 9:27pm

Turnerpr:

There have been attempts at utilizing ultrasound to lyse cellular material in order to enhance anaerobic digestion. You may want to get a hold of the following article:

"ULTRASONIC SLUDGE TREATMENT FOR ENHANCED ANAEROBIC AT ORANGE COUNTY SANITATON DISTRICT"
by Jeffrey P. Brown et al, presented at WEFTEC 2003 and available through www.wef.org

ABSTRACT
Ultrasound refers to sound energy with frequencies above the audible range; that is, starting at about 20 kHz. Using ultrasound for enhanced sludge digestion relies on inducing cavitation in the liquid to produce lysis of the cellular sludge material, thereby increasing the availability of the organic material to bacteria in anaerobic digesters. This paper presents the results from a fullscale ultrasonic trial at Orange County Sanitation District (OCSD) in 2002.
The benefits of enhanced anaerobic digestion include:
1. Increased gas production
2. Greater solids destruction
3. Improved digester stability
4. Reduced digester foaming
5. Improved biosolids dewaterability
The demonstration trial at OCSD ran for 5 months. In order that a direct comparison could be made between sonicated and unsonicated feed sludge, two digesters (test and control) were chosen for study. These were operated under identical conditions, and the proportion of TWAS fed to both digesters was maintained at 60%; 65% throughout. This enabled the results to be compared both against baseline conditions (longitudinal study) and between digesters (crosssectional study) so that conclusions could be drawn for full installation of ultrasound sludge treatment at all of OCSD’s facilities. At OCSD, the ultrasound unit was located on the thickened waste activated sludge (TWAS) feed line to the test digester. Compared to the control digester, significant enhancements of gas production (50% increase) and solids destruction (15 percentage points increase) were achieved by sonicating the secondary sludge. The increases were comparable to the results from a similar UK trial.

I have no idea how applicable this process would be for your thermal drying process. Do let me know.

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Re: Improving treatability of activated Sludge
Reply #3 - Feb 17^th, 2005, 9:37pm

In order to provide some preliminary ideas, I am assuming that the sludge is not digested. If that is the case, do you have digestion facilities onsite?
Sludge drying operations require a well digested sludge feed. For strictly waste activated sludges, aerobic digestion may be sufficient. However, combined primary and secondary sludges must be anaerobically digested.
Another possibility is to operate your activated sludge process at a very high sludge age (say 20 days and up). Be careful as this will generate an effluent high in TSS, BOD, and phosphorus which could cause a permit violation.
Undigested sludges tend to 'fluff-up' inside the dryers and also cause frequent fires due to the high volatile content. I know this from personal experience.
If digestion is not feasible, heating the WAS inside a heat exchanger using excess steam (from your boilers used in the drying process?) as the source of heat can cause the cellular mass to rupture and release the bound-water. This may be an expensive option and also cause odors.

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sobisch

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Re: Improving treatability of activated Sludge
Reply #4 - Feb 18^th, 2005, 5:29am

Dear Turnerpr,

I think the additive you are looking for is lime. When adding lime in the form of CaO in addition heat will be produced. There are some related technologies, which produce granulated material as soil amendment.
Further, theoretically, bentonite or clay should also be a benefical additive.
Cell destruction as such will make dewaterability worse. However, the option of digestion, preferably anaerobic (addition gas production), should be evaluated.

Kind regards
T. Sobisch

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T. Sobisch
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kukkkatz Full Member Offline WaterandWastewa ter.Com is the best! Posts: 170 Gender: Company or Organization: KUKK Ltd.	Re: Improving treatability of activated Sludge Reply #5 - Feb 18^th, 2005, 5:59am Dear Turnerpr, in strengthening opinion of Sobisch there are operational recommendations to use zeolites to get water content deep below levels that can achieved by any physical treatment. The key to success is an optimal combination of adsorbents on modified zeolite basis. kukkkatz
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The_Solution

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Re: Improving treatability of activated Sludge
Reply #6 - Feb 24^th, 2005, 11:23pm

To improve the release of intracellular water from activated sludge there is a relatively well know procedure to promote cell lysis by using ultrasound (it can also be done chemically). A Purac/Atkins water JV (Sonico) process has 14 reference plants around the world - US, Singapore, UK, NZ, etc.

The main benefit is improved digester efficiency, gas production, etc.

See www.Purac.co.uk for details.

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C. Gillen God Member Offline Applied Environmental Biotechnology Posts: 643 Ireland Gender: Company or Organization: BioFuture Ltd.	Re: Improving treatability of activated Sludge Reply #7 - Feb 25^th, 2005, 1:00pm One other option to consider is thermophilic aerobic stabilisation which used to treat surplus sludge from municipal plants so that it can be used for land spreading. Best regards, Cgillen
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Yol YaBB Newbies Offline Water and Wastewater.com is the best! Posts: 12 Company or Organization: WR3 Technologies	Re: Improving treatability of activated Sludge Reply #8 - Feb 25^th, 2005, 2:19pm Hi, I suggest to consult this website: www.oxycair.com Refers to a chemical-free technology that can destroy bacterias cell walls with physical processes. You can also contact Mr Daniel Gagnon at +1 514 602-9092, he is based in Canada (Quebec province). Alain
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Brent_Cowan YaBB Newbies Offline Water and Wastewater.com is the best! Posts: 20 Company or Organization: CSC Technology, Inc.	Re: Improving treatability of activated Sludge Reply #9 - Mar 2^nd, 2005, 2:21am I have a chemical addition product (BR-M) that will reduce the amount of sludge solids by 50-75%. The details are too much to address here. If interested, please contact me. Brent Cowan 610-383-0909 csctechnology@comcast.net
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sobisch

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Re: Improving treatability of activated Sludge
Reply #10 - Mar 2^nd, 2005, 6:30am

Dear Turnerpr,

did you had any success in the meantime?
I just read in a wastewater related German publication (Wasser, Luft und Boden, http://www.industrieservice.de/vfmz_cms/industrie-service/wlb_content.nsf) about a fluidized bed process with direct injection of the sludge. Do not know if this would be of interest. The engineering firm is Andritz Fliessbett Systeme GmbH, Ravensburg.

Kind regards
T. Sobisch

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T. Sobisch
for@appliedcolloidssurfactants.info
http://AppliedColloidsSurfactants.blogspot.com
http://www.AppliedColloidsSurfactants.info
http://www.lum-gmbh.com

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Nadeem YaBB Newbies Offline Water and Wastewater.com is the best! Posts: 7 Gender: Company or Organization: WESCO	Re: Improving treatability of activated Sludge Reply #11 - Mar 4^th, 2005, 5:58pm Check out this web site. biogest.com innovum.com one of them uses high pressure and the other one electro static charge to do what you are asking for..........
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bineeshsreerangam YaBB Newbies Offline I am there to help you.. Posts: 44 DUBAI Gender: Company or Organization: AQUA STAR	Re: Improving treatability of activated Sludge Reply #12 - Feb 7^th, 2007, 5:04am dear all, some plants are dosing alum for conditioning sludge. but this is not advisable when sludge is used for gardening purpose. bineesh
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aquaseaulutions Full Member Offline Water and Wastewater.com is the best! Posts: 162 Company or Organization: AquaSeaulutions	Re: Improving treatability of activated Sludge Reply #13 - Feb 15^th, 2007, 12:44am The best available technology for that problem is the Oxycair CL5: http://www.oxycair.com/en_cl5-1.html No chemicals, great savings, reliable. Alain Berrouard AquaSeaulutions
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