I am working on recycled paper mill effluent treatment using anaerobic baffled reactor. I would really appreciate if share with me what's the relationship between the SO4 concentration and anaerobic digestion. I haven't test it and was focusing on other parameters in my work. Is that ok or what?
Yes, it has some effect on anaerobic digestion. It can effect the methanogenesis in a big way. Here i am attaching an appropriate work that discusses the relation between SO4 concentration and anaerobic digestion.
Hope it can throw some light.
Check the following lit. www.intechopen.com/download/pdf/16290, www.scielo.br/scielo.php?pid=S0104-66322011000400008&script... on anaerobic waste water treatment.
Sulfate are converted into sulfide in anaerobic conditions by sulfate reducing bacteria (SRB). Two main effects:
- Hydrogen sulfide (H2S) is an inhibitor for the biological activity;
- Since SRB are heterotrophs, The conversion of sulfate into sulfide requires a carbon source (acetate or propionate or other) and this carbon source is no longer available for methane production.
to cut things short: what basically happens in AD is this:
SO42- + 4 H2 -> H2S + 2 H2O + 2 OH-
SO42- + CH3COOH -> H2S + 2 HCO3-
so whatever your system is, sulfate will decrease your net amount of biogas as well as lower your methane concentration by competing with H2 and by taking away C-aequivalents.
I agree with Pierre and Urs. In cases where anaerobic digestion is used to treat sulphate containing wastewater as in pulp & paper mill industries, OM acts as electron donor and sulphate as electron acceptor, sulphate reducing bacteria can change available sulphate to hydrogen sulphide. However,CH4 producing bacteria are also available in the concentration and as a result, there is competition for available hydrogen and acetate. It is noteworthy, that sulphide toxicity to bacteria may affect the efficiency of the anaerobic digestion process and limit CH4 production. Increase in substrate concentration by increasing electron donors such as OM and regulation of pH could help to reduce sulphide toxicity( as well as encourage bacterial sulphide tolerance) and encourage methane production.
Thanks to Pierre, Urs and Ernest
The question I have now is "Does the pulp and paper mill wastewater or the recycled paper mill wastewater contain SO4?"
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