SRS Crisafulli Asks "What is Coagulation and Flocculation?"

By Laura M. Fleming, SRS Crisafulli President/CFO

What is coagulation and flocculation, and why does it matter?

Last week, SRS Crisafulli hosted a bucket demonstration of Tencate Geotube technology, presented by Gregg Lebster of WaterSolve, from Grand Rapids, Michigan, and Jim Bridges, of Clearwater Dewatering, from Nampa, Idaho.

These relationships were renewed last summer when SRS Crisafulli's Australian Dealers, Bill Kelly and Andrew Cochran, made a visit to the factory in Glendive.  Over a few beers and dinner at the Lion's Club A-Frame in Makoshika Park, we discussed Dredging Solutions' successes using Geotubes to dredge and dewater sludge from wastewater treatment lagoons. Feeding the Geotubes with their Crisafulli Flump dredge system, Dredging Solutions has accomplished biosolids of >25%.

Bill Kelly explained the art of the Geotubes in his fine Aussie manner.  In particular, Bill emphasized the science of chemical conditioning regimes to flocculate the sludge.  We had homework to do - we're a mechanical engineering outfit, not chemical engineers. 

Crisafulli dredge systems have been installed in over 30 wastewater treatment facilities, including most recently an award winning system at Natchez, Mississippi, as well as the Wastewater Treatment plants in places such as Lompoc Regional WWTP, California, the Douglas County Sewer in Zephyr Cove, Nevada, the City of Mandan, North Dakota, and the City of Bozeman, Montana.  

The communitites of Glendive and West Glendive - here in rural Eastern Montana - have 90 acres currently in lagoons, and the communities are in the process of evaluating how to address the current and future wastewater needs. 

You can't blame us for wondering if we could be of any assistance to local public works departments.

We turned to Rosa-lee Cooke, Water/Wastewater Instructor at the Mountain Empire Community College, Big Stone Gap, Virginia, who offers an online curriculum in Water and Wastewater Treatment Technology, and an Associate in Applied Science Degree with a Water/Wastewater Specialization for some background. 

"In theory and at the chemical level, coagulation and flocculation is a three step process consisting of flash mixing, coagulation and flocculation.  The primary purpose of the coagulation/flocculation process is the removal of turbidity from the water.  Water with little or no turbidity will be clear."

"The end product of a well-regulated coagulation/flocculation process is water in which the majority of the turbidity has been collected into floc, which is clumps of bacteria and particulate impurities that have come together and formed a cluster."

Time for the bucket demonstration:

1. We collected buckets of sludge from the West Glendive sewage lagoon.
   
   
   
2. We vigorously mixed the sludge.
   
   
   
3. Gregg Lebster prepared a selection of coagulant chemicals to add to the sludge.
   
   
   
4. We mixed the coagulant with the sludge to create floc - which was then poured through a small geotube fabric sample. 
   
   Dan Kramer, from Montana Rural Water Systems, Great Falls, Montana inspected Gregg's floc, and the clear water that had separated from the sludge.
   
   
5. Later in the day, we repeated the demonstration at the fire hall.  Our improvisations resulted in a small geotube - held here by Ed Trainer, Geotube marine and coastline market manager, filled with fresh floc.
   

We hear from people in the field that many communitities are being encouraged to build mechanical plants;  we also hear that mechanical plants are both labor and energy intensive, and that the passive, non-energy intensive lagoon system may yet have more useful lives.

To read more, please see Rosa-Lee Cooke's Lesson 4, Coagulation and Flocculation, Mountain Empire Community College.

To read more about the proposed improvements to the Glendive wastewater infrastructure:

Great West Engineering West Glendive Public Works Wastewater Treatment Plant Presentation, and, City of Glendive, Public Meeting Presentation, April 26, 2011, Wastewater System Improvements.