[Digestion] Help needed

[Voegeli, Yvonne]

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


________________________________
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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