Thursday, February 26, 2009

Control of activated sludge process in paper industry.

Effluents of pulp and paper mills are relatively simple to treat by activated sludge process - in theory. Some severe problems have arisen in practice, however.

Temperatures of incoming waste waters have risen during last years. The most obvious reason for this phenomenon is the increased recirculation of process waters inside the mills. Poor sedimentation of flogs, caused by the heavy growth of filamentous bacteria, has also become to be more and more hard problem for purification plants. There may be some kind of correlation between temperature and bulking of sludge?

Another problem, potentially very hazardous, is the growth and recirculation of Legionella pneumophila inside activated sludge process. The role of Protozoa has now been established: they act as carrirs of bacteria backwards in returned sludge.

Dosing of nutrients into biological treatment steps isn't any hard task anymore because the need of phosphorus and nitrogen has been studied very deeply, and simpe AT LINE testing for the optimization of them is easy to perform in the mill labs.

Two problems, mentioned before, still exist and need R&D activities to be solved: bulking of the sludge (by filamentous organisms) and L.pneumophila.


Anonymous said...


I enjoyed reading your article and blogs. I was ondering if you could help me with a query.
I work for a large dairy herd and we have a anaerobic digester for the cow manure. We have high levels of Klebsiella pneumonia in the finished solids. We use these solids for bedding and have condsiderable problems with mastitis. Some of which are being caused by Klebsiella and coliforms.
Our digester runs at around 37.7 degrees celsius. We are suspicious that we have strains that fix nitrogen as the digester has a high retention time-
(though we do not really know much about this). We are very interested in how we can reduce the level of bacteria. we can turn the temperature up a little but would appreciate any advice.

Thank you very much

Elias Hakalehto said...

This is an interesting case. Why are the klebsiellas present in such high levels in mature manure? There should also be nitrogen well present. Is there any wooden material, such as saw dust, in the material?

Turning the temperature up may increase some problems without giving any improvement. What is the retention time approximately?

Juha V. Mentu said...

Thermophilic coliforms can grow until temperature rises over 46oC. It means that you can find both E.coli and K.pneumoniae when performing colony count analyses in 44.5oC. Our maximum growth temperature analyses have shown that 47oC is a too high temperature for all coliforms.

The ability of K.pneumoniae to fix atmospheric nitrogen is a well-known feature of this bacterium. I have found that nitrogen content of secondary sedimentation outflow can be higher as that of the inflow into the same basin.

I suggest You to refer articles by NIEMELÄ,S.I, VÄÄTÄNEN,P. and MENTU,J., published on 80s', about K.pneumoniae and E.coli in paper industry effluents. You may find some information which could help You in Your problem.