Charles Lin

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.

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

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

Hi everyone,

Good day to you

May i know is there any reason for using wood support structure for biogas dome? (pine wood)
I see this application is quite popular in European countries.
Some people say wood support structure is not only provide the support for biogas dome when it is flaccid but also act as a "habitat" for bacteria to grow.
This "bacteria" is thiobacillus sp. which take part in converting hydrogen sulfide to sulfur.

So far we have no experience in using wooden support structure for biogas dome,
therefore, i wish to get some advice from expert all around the world.

Please share your experience

Thanks,
Charles

Hi All,

Good day to you.

Currently, i'm looking for the calculation of surface temperature of cooling pond with medium of palm oil mill effluent (POME).
This cooling pond is operated in plug flow system with retention time of 2 days for cooling.
On the upper layer of the POME, a layer of oil was found due to poor filtration after the palm oil extraction from the factory.

Generally the process is as below:
Factory --> POME --> Cooling Pond

Since there is a layer of oil on the top of the medium, evaporation is excluded from the heat transfer calculation. Conduction, convection and radiation are the main heat transfer involved.

Heat inputs:
1. qs = short-wave solar radiation,
2. qa = long-wave solar radiation,
Outputs:
1. qsr = reflected portion of qs,
2. qar = reflected portion of qa,
3. qbr = long-wave black radiation from water surface,
4. qc = conductive heat loss.

therefore,

qt = (qs + qa)-(qsr + qar + qbr) + qc

where,
qt = net heat flux across the air-water interface (pond surface).

Question:
May i know, is there any simplified equation for the above equation? As i found the following equation, but the equation included the evaporation, which is not fit to my current condition.
[The following equation aim to calculate the exit temperature of the medium]

dqt/dt = -K (Ts - E)

where,
dqt/dt : net rate of surface heat exchange,
K : heat transfer coefficient,
Ts : pond surface temperature,
E : equilibrium temperature.

where it simplified from the equation below:
qt = (qs + qa)-(qsr + qar + qbr + qe) + qc

where,
qe : evaporation heat loss.

Appreciate if anyone can share some idea or information at here.

Advance Thanks,
Charles CL