Summary for clarifier design Discussion
Clarifier design for an ETP is discussed as a practical settling problem: the question asks for a good design to settle sludge, and Ted Mooney points to the "Wastewater Treatment Systems for Finishing Operations" chapter in the Organic Finishing issue of the Metal Finishing Guidebook for illustrations and background. He says the key elements are careful inlet dispersion, balanced sawtooth weirs to prevent short-circuiting, and a sludge removal method that avoids disturbing the settled solids. He also recommends lamella plates or slant tube modules set at about 55°, explaining that they increase effective settling by giving floc a surface to contact as water rises. However, he cautions that the "10x bigger tank" idea is only an approximation and that clarifier upsets still happen. His overall view is that lamella systems are more practical than simply building a much larger tank.
ACRONYMS:
ETP = Effluent Treatment Plant
Q. We need a good design of a Clarifier for our ETP (To settle sludge)
Srivarma Shetty
Auto Components – Bangalore, Karnataka, India
2007
A. The “Wastewater Treatment Systems for Finishing Operations” chapter of the Organic Finishing issue of the
Metal Finishing Guidebook has some good illustrations as a start. Key elements of a clarifier are:
– carefully dispersion at the inlets and carefully balanced sawtooth weirs so there are no short circuits, but rather the wastewater must very evenly and slowly flow upward, so that the floc can fall faster than the water rises;
– lamella plates or slant tube modules set at an angle of 55° or so, which allow the floc to touch a surface and agglomerate;
– a good way to get the accumulated sludge out without disturbance.
The theory of lamella plates or slant tube modules is that if they are set at a proper angle, during the time that the water rises a foot, the floc only needs to fall only an inch or so before it will touch a solid surface and agglomerate, so you get settling equivalent to a tank 10 times as big. I’ve seen enough “clarifier upsets” to realize that it’s not really the same thing as a tank 10x bigger, but lamella plates are more practical than a tank 10x as big :-)
For however long it remains online, the Metal Finishing Guidebook has some good illustrations and descriptions of metal finishing wastewater treatment equipment. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
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2007
Lamella plates in a round Sequencing Batch Reactor
September 19, 2014
Q. HI
Can anyone suggest if it’s possible to combine lamella plate and SBR? Is it feasible to install lamella plate in SBR for its clarification time or is it going to hinder the aeration process when plant operates for Fill/Aerate cycle?
Also has anyone have any experience of providing lamella plates in circular tank, rather than in rectangular
Response will be appreciated, thanks in advance.
Neha
Neha Singh
Research – Belfast, Antrim ,UK
A. Hi Neha. I haven’t seen it, but it sounds like it might somewhat work since solids would not have to fall very far before they agglomerate on the plates and, hopefully, slide down them for faster settling. I’m not experienced with whether the plates would hinder the aeration process, but quite possibly not.
I’ve never personally seen lamella plates per se, as opposed to tube modules, in a round tank — but I see no reason they would not be okay. The only thing is, the plates would probably have to be fairly short.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
September 2014