[Digestion] Help needed

[Björn Dahlroth]

In Sweden where there are several big plants digesting municipal and
industrial waste these things have been studied. It is common that the
slurry is separated and that the more firm part is composted for the reason
that you mentioned and the compost is used for mixing soil for parks and
civil works. However even after composting one can not guarantee 100.00%. It
is also very common to digest the slurry from sewage treatment plants and
the residue is actually spread on fields but also used for covering old
landfills. After spreading on fields the farmers can not cultivate any kind
of crop for some time, and there is for instance also some restriction about
letting cattle  grazing on the field for some time. However the pathogens
here are certainly not precisely the same as in your country.

Bjorn Dahlroth

 

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Från: digestion-bounces at lists.bioenergylists.org
[mailto:digestion-bounces at lists.bioenergylists.org] För Voegeli, Yvonne
Skickat: den 9 december 2010 16:49
Till: For Discussion of Anaerobic Digestion; KshanikaG at masholdings.com
Ämne: Re: [Digestion] Help needed

 

Dear Kshanika Goonesekera,

 

Our studies in Nepal and India on biogas plants treating human faeces showed
that not all pathogens get eliminated during the anaerobic mesophilic
process. Please have a look at the two reports attached. The study in Nepal
showed that the concentration of E.Coli is acceptable for restricted
irrigation by WHO-standards, but helminth eggs were not completely
eliminated.

 

Also the study from India (Kerala) shows that only restricted irrigation is
recommended regarding the concentration of E.Coli and total Coliforms (see
p.45). Unfortunately, we were not able to analyze helminth eggs or other
pathogens in India.

 

In any case, it can not be guaranteed that the slurry is free of pathogens
and safe to use as a fertilizer. See also our recommendations regarding how
to use the effluent in a safe way.

 

I hope this helps.

 

Best regards,

Yvonne

°°°
Yvonne Vögeli
Eawag / Sandec
Überlandstrasse 133
P.O. Box 611
8600 Dübendorf
Switzerland
Phone: +41 (0)44 823 54 20
Fax: +41 (0)44 823 53 99
yvonne.voegeli at eawag.ch
 <http://www.sandec.ch> http://www.sandec.ch 

 

 

  _____  

From: digestion-bounces at lists.bioenergylists.org
[mailto:digestion-bounces at lists.bioenergylists.org] On Behalf Of Kshanika
Goonesekera
Sent: Donnerstag, 9. Dezember 2010 05:55
To: paul.harris at adelaide.edu.au; For Discussion of Anaerobic Digestion
Subject: Re: [Digestion] Help needed

 

Hi All, 

 

I am in Sri Lanka where industries are starting to look at the advantages of
converting their sewage and kitchen waste treatment plants to biogas plants.
My question is; 

*	Can it be guaranteed that this slurry is free of all sewage
pathogens and hence can be safely used as fertilizer? 

 

The contractor has recommended secondary aerobic treatment to the slurry; 

*	Does the slurry leaving the AD require secondary aerobic treatment?

*	Is the BOD, COD content of the slurry adequate for aerobic treatment
with MLSS of 1500-3000?

 

The employers are not keen on using the slurry as fertilizer due to the
chance that pathogens can exist. Hence, the agreement to send the slurry
through aerobic treatment and then into an inland surface waterbody. 

 

Best regards

Kshanika Goonesekera

Sri Lanka

 

 

 

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