Hi Christoph,

Thanks for the question and interest in the presentation.

I would agree with your statement that pit latrine sludge has no value for biogas production in the context of this study of pit latrines in Lusaka. As you can see from the diagram you posted the values are low and indicate most of the readily degradable organic fraction has been digested within the pit latrines.It is also worth pointing out the infrequent emptying frequency of pit latrines in the area (generally greater than 2 years since previous emptying), which is also likely to be a contributing factor for low BMP values.

Of course, this statement is not representative of all pit latrines as well as different faecal sludge types. E.g in the same study BMP values of portable toilet waste in Kumasi were analysed and methane production values were similar to that of primary sludge from conventional waste water treatment works, subsequently showing great potential for biogas production from this feedstock.

Any further questions are welcome,

Regards,
Chris

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Note by moderators: This post was made by a former user with the login name cmrose who is no longer a member of this discussion forum.

Dear Christoph,

I contacted Prof. Nakajima, the author of the presentation
Sludge accumulation and BOD removal performance in three anaerobic baffled reactors installed in Vientiane City.

His answer via mail on the questions you raised was as follows:

Thank you very much for the question. Our finding is based on the three reactors in Vientiane. I absolutely agree the idea that the indicator would be applicable in another area.

However I think the rate of the scum formation would be influenced by temperature and SS concentration in the raw water. The scum formation rate seemed a little slow in Vientiane compared to the rate in Japan where the temperature is lower than Vientiane.

So the relation between the timings of scum formation in the first chamber of the sedimentation-separation tank and sludge accumulation in the anaerobic baffled tank could be a little different in another area. But the difference would not be so large and I think the scum formation could be the indicator.

[Posted by Lasse]

Hi Christoph,
here is the link: clara.boku.ac.at/index.php/planning-tool-2
we are currently preparing the release of v1.6 (should be ready by end of February) in which a number of errors are fixed.
Best regards,
Guenter

Good morning Günter,
had a look on your presentation and a lot of questions. Therefore I wanted to check out before asking the CLARA tool which you said is for download at your pages. I did not find it. could you post me your link fo get access? I have done quite a similar study in a case lately and a planning tool would have been very nice, so I wanted to check on the results with my example.

Yours
Christoph

Thanks Christoph for pointing out that my presentation is missing.
I have attached my presentation here and will contact the organisers of the conference so that it will be uplöoaded there as well.
Best regards,
Guenter

Thank you Günter for pointing out the presentations.

I looked up some and would like to mention two (perhaps the authors are part of SUSANA?:

The biochemical methane potential of faecal sludge by the Cranfield University.

Very interesting presentation with useful information. For me very interesting as there is a lot of mentioning that pit sludge could have a biogas potential. My question is :
Your statement in the presentation is

• Anaerobic digestion of fecal sludge has the potential to provide stabilization of sludge and provide opportunities for resource recovery

There are no conclusions at the end but from the methane production (see picture below) I feel that pit sludge has no value for biogas production it would just fill up the reactor. Do you agree with that statement?



The second is

Sludge accumulation and BOD removal performance in three anaerobic baffled reactors installed in Vientiane City

Excellent presentation with a lot of clear and useful data.
my question is:
Your conclusion to control sludge build up is to measure the scum layer in the first chamber. Is this finding based on more than the 3 mentioned reactors? We have a lot of baffled reactors in operation and it would be great to have such an indicator, but I am a bit reluctant. Could you explain on that?

Thank you

Christoph

P.S. Günter, I was interested in your presentation but I did not find it on the list, could you provide it?

Dear all,
I am happy to announce that the presentations from the 12th IWA Specialized Conference on Small Water and Wastewater & 4th IWA Specialized Conference on Resource Oriented Sanitation, 2-4 November 2014, Muscat, Oman, are available online at portal.cce.edu.om/iwa2014/
Attached the final program of the conference.
Best regards,
Guenter Langergraber