Odour in Waste Water Treatment Plant

[Danitech]

Hi all,

I am a industrial engineer -which means i have a 'basic' knowledge in chemistry -, and i´m trying to solve some problems we have experiencing in our WWTP. The basic facts:

a)Influent to the WWTP: are generated by production of PVA emulsions, some sulphates and water generated by demineralization unit. The most important influent are the PVA and sulphates ones. High TSS and QOD/BOD. No significant heavy metals in the influent.

b)Treament: Mixing (Homog.) of influents in a 120 m3 tank, addition of Al2(SO4)3, neutralization with Ca(OH)2, addition of polyelectrolite (polyacrilamide), separation of water and sludge in sedimentation Tank; clear water goes to external biological plant, the sludge goes to a filter press; the resulting cakes go to landfill.
First problem: sometimes we have strong odor, ressembling H2S. Anearobic decomposition? Sulphates forming H2S?. I was thinking of improving our stirring system in order to avoid sludge precipitation and decomposition. I was told that a H2O2 injection could help as well. Any suggestions?
Second Problem: we need to use a lot of Ca(OH)2 in the sludge tank in order to get compact cakes. Is there another solution?
I was told that we can eliminate Al2(SO4)3 in the plant. Do you agree? Any suggestions will be very appreciated.

Regards,

Daniel

 

[BobPE]

danitech:

It sounds like you have the potential for a real problem there. Your licensed operator should be able to help you. If your operator cannot help, then I would suggest you get an engineer experienced in wastewater treatment.

Just whaqt type of process is this you are working with? Adding hydrogen peroxide is a bad thing right at the treatment plant since it is a low grade disinfectant and will kill your biological treatment. Stirring sludge? Well, you didn't tell us enough about that, but I would say aeration needs to be improved, or sludge wasting perhaps, Whats your SRT? Whats your MLSS? You may be able to change coagulants, but definately not eliminate them.


BobPE

 

[bimr]

1. I would suspect the odor is H2S which is possibly being released when the pH drops. You mentioned it happens "sometimes". H2S will be released if the pH drops under 7. The demin waste may be causing that.

2. You may be able to cut back on the lime but it depends on the type of dewatering equipment that you have. Some of the older dewatering equipment will not work well without the body feed of the lime. 3.

3. Regarding the Al2(SO4)3, you probably can substitute an iron salt for this, but you will probably have to continue to use it to get good solids separation.