Thursday, 19 June 2008

PCB sludges

Things not looking too promising for the experiment set up on Monday to test anaerobic digestion of PCB containing oily sludges in Manchester. No evidence of any gas generation as yet.

Awaiting the order for starting sampling work to establish the bast way forward for the pharma client.

Continuing to review "Elements of Environmental Chemistry". Can't see a thing wrong with it so far...

Wednesday, 11 June 2008

PCBs in oily sludges, Environmental Chemistry, Chopper Pumps and truth comes to Homeopathy

Other than designing a solution to the problems of our new pharmaceutical client, I have been reviewing a book for The Chemical Engineer magazine, and looking at carrying out an experiment to determine how well anaerobic digestion might reduce PCB levels in oily sludges.

I am having difficulty at present sourcing a small chopper pump which can be controlled by inverter to provide a better, smoother feed to the pharma client's plant without blocking concerns. No problem getting one with 75mm discharge size or above, but the small ones don't have an over-rated motor, which is recommended for variable speed drive.

The book I am reviewing is "Elements of Environmental Chemistry" by Ronald Hites. Seems like a pretty good little textbook.

The oily sludges I hope to treat with AD have been a problem at a couple of sites I provide technical cover for for years now, and it is getting increasingly difficult and expensive to dispose of them. It would be nice if we can get PCB levels down to non-hazardous numbers by this process. The experiment is fairly quick and dirty, so we should have a rough answer by August.

Something amusing I saw today on the quackery front: truth in alternative medicine at last...

Wednesday, 4 June 2008

Design Errors: Static Mixers

A quiet sort of a week in the main. Cyril continues his research into treatment of PCBs in groundwater. I have been engaged with the pharmaceutical client mentioned previously on here.

They have what must be one of the worst effluent treatment plants I have ever seen in terms of fundamental design flaws. One of the biggest of them was the use of static mixers to mix acid and coagulant with effluent, which was pumped by diaphragm pumps. This showed a fundamental misunderstanding of the nature of static mixers in the system designer. Static mixers blend fluids across the body of the mixer. If you feed them with a pulsating flow from a diaphragm pump, and an out-of synch. pulsating flow from a dosing pump, you end up with constantly varying degrees of mix in the outlet flow. The normal rule of sampling at least 10 pipe diameters downstream to get 95% degree of mix no longer applies. Your pH probe for example will see extreme variation in measures pH, and instead of gaining control to +/- 0.1pH units as you should from a system like this, you will be lucky to see +/- 0.5 pH units.