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Clogging of Pipes by Struvite  RSS feed

 
Charles Lin
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Dear All,

Clogging of pipes by struvite is a common problem happening at biogas plant, yet it still has no environmental friendly solution to solve this problem until now.

Generally, it can be solved by adjusting its pH or the ratio of the three elements: magnesium, ammonia and phosphate (1:1:1), however for biogas plant which operate at pH 7, it is hard to adjust the pH as it will affect the bacterial activity and manipulate the ratio of the three elements need additional chemical which is an added cost to the project. So, i would think of there must have a better and cost effective approach to solve this problem effectively.

Some people suggested to reduce the amount of elbow, tee etc., but this is very hard and sometimes it can't be avoided, moreover, struvite also generated at straight pipe if low flow occur at there. So, this method is not feasible to do so.

Another approach to solve this problem is by interfere the electromagnetic field of the flow in the pipeline, however there is no track record on using this approach to wastewater containing pipe other than clean water/tap water.

Besides, as biogas is a renewable energy which has environmental friendly system, therefore chemical is not suitable to use in our case and most importantly it will affect the bacterial activity to generate biogas.

Lastly, a simple mechanical approach by using water jet to wash out the struvite from clogged pipelines. This approach can only applied if the clogging of pipeline noticed at very early stage where thin layer of struvite is form. This approach is not feasible if the built up struvite is thick, where it is very hard to remove even though by shovel aided with hammer.

Therefore, i'm appreciate if anyone can share some ideas to solve this problem and make biogas sector get more smoothly.

Sincerely,
Charles CL


Picture retrieved from How to Remove Struvite
 
Charles Laferriere
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Location: Quebec, Canada - 4b/5a
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Experiencing similar issues here. Been working on a SolarCIties biogaz system. Feeding pipe clogging easily.

PS: Nice name.
 
Charles Lin
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After we took the sample for laboratory test, the result was not show the three elements: magnesium, ammonia and phosphate in the ratio of 1:1:1.
Nevertheless, struvite was still formed !

Anyway, before a new and better idea born to solve this problem, we developed open channel flow system.

It is a simple open channel drain to substitute the pipelines at high potential struvite formation zone.

This system allows you to avoid struvite formation at the same time monitor your media condition in the pipe.

You can dig out the struvite from the open channel flow system, and make it as fertilizer and sell it.


If you have any new idea, please share at here.  Thanks.


Best Regards

 
Miles Flansburg
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Location: Zones 2-4 Wyoming and 4-5 Colorado
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Howdy Charles,
Can you explain your process a little better for me. Is the clogging in a specific place in the plant flow?
I am assuming you are using a digester of some sort and collecting the gas? Is it in the gas piping or is there some sort of "waste" flow that is plugging?Could you explain that?
I was involved in making gas from woodchips and we had problems with tar plugging pipes but I am not familiar with Struvite.
Did you say it formed in low flow areas? Not in high flow?  Is there a way to recycle some of the product flow back to increase the flow through the troubled areas ?
Does heat or cold effect the formation of the crystals?
 
Charles Lin
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Miles,

Yes. It is clogged at specific place which i mentioned reduce flow area or stagnant flow area it will have high possibility to form struvite. Area where there is high kinetic energy (high turbulence), struvite formation also can occurs.

We are using palm oil mill effluent as the substrate for the biogas digester to generate the biogas. This substrate contains the 3 minerals (magnesium, ammonium and phosphate) for struvite formation. There are many kind of clogging depending on the mineral in the wastewater, for my case is struvite (NH4.MgPO4.6H2O).
There is another precipitate that could form a crystalline scale within the pipe is Vivianite precipitation (purple color). If your wastewater contains Iron(II) ion, then this precipitate is possible to form.

Therefore clogging of pipe by minerals will only happen at pipe that convey wastewater provided that the wastewater has the content of mineral for crystallization.

Regarding to your problem, you may send your crystal sample to the lab for testing of its components. First of all you need to determine your crystal is what kind of crystal and then the parameters that make it to form. You may find out its component and send your sample to lab for testing. The following link describes another kind of clogging. Link

Low temperatures foster the environment for struvite formation.

Examples of area that form struvite:
- Anaerobic digesters
- Places where there is high kinetic energy (high turbulence)
- Pipe connections – especially elbows
- Pumps are a prime location
- Valves
- Internal pumping components
- Plant overflow box of the anaerobic digester
- Wastewater Sludge transfer line
- Plant Centrifuges
- Rollers of the Belt Press

For experts, please help him if you have similar case.

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