Fwd: DIG-L: Anaerobic digestion of aldehydes and acrylates

[Sjon.Kortekaas@Algemeen.MT.WAU.NL]

Comments:

Regarding aldehyde containing wastewaters, anaerobic treatment has been shown 
to be potentially a feasible option. In the Netherlands at Caldic Europoort a 
anaerobic reactor is running treating a wastewater with a total COD of about 
40 000 mg/L, containing up to 10 000 mg/L formaldehyde (engineering Biothane 
Systems International, Delft, the Netherlands).  Thought inhibitory to 
methanogens, the fact that formaldehyde is anaerobically biodegradable, 
enables detoxification by recirculation of anaerobic effluent. 

Formaldehyde toxicity data found in literature report 50% inhibition values 
from 125-300 mg l-1. During anaerobic treatment, formaldehyde was found to be 
transformed and degraded in a biological enzymatic conversion. 

Sofar there is no clear evidence about the mechanisms of formaldehyde 
toxicity. As Formaldehyde conversion rates decline at increasing formaldehyde 
concentrations, it is hypothesized that enzymatic system is hampered at 
elevated formaldehyde concentrations. The characteristics of formaldehyde 
toxicity were independent of the methanothropic substrate used. Formaldehyde 
addition to formate, methanol and acetate consuming sludges showed similar 
trends independent of the type of sludge used. Formaldehyde toxicity was found 
to be in part reversible, because the methane production rate partially 
recovered after formaldehyde depletion. Since the recovery of the methane 
production rate after formaldehyde depletion was not complete, it can be 
concluded that formaldehyde toxicity is also in part irreversible. The 
irreversible toxicity likely can be attributed to biomass formaldehyde-related 
decay. Independent of the mode of formaldehyde addition (slug or continuous), 
a certain amount of formaldehyde irrevocably reduced the methane production 
rate to a certain extent, hence the irreversible toxicity was dependent on the 
total amount of formaldehyde added to the system. This finding suggest that in 
order to treat formaldehyde containing waste streams a balance between 
formaldehyde related decay an biomass growth should be attained (Gonzalez-Gil, 
2000).. 

Sjon Kortekaas

====================================================
Dr. Ir. Sjon Kortekaas
LETTINGA ASSOCIATES FOUNDATION
for Environmental Protection & Resource Conservation
P.O. Box  500, 6700AM Wageningen, The Netherlands

Sub-Department of Environmental Technology
Wageningen University
P.O. Box 8129, 6700EV Wageningen, The Netherlands
Tel:   +31 317 48 29 09
Fax:   +31 317 48 21 08
http://www.ftns.wau.nl/lettinga-associates/
================================================

- - - - - - - - - - - - - - Original Message - - - - - - - - - - - - - -
To:	SMTP@Mail@Alg[<digestion@crest.org>]
From:	"Sylvaine BERGER" <sylvaine.berger@solagro.asso.fr>
Date:	Tuesday, May 28, 2002 at 9:37:35 am DST
Attached:	None

Hello ,
Does anyone know something, have some experience in anaerobic digestion of
aldehydes and acrylates ?
Are those components good substrates for AD ?

thank you for answers

Sylvaine BERGER


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