Case Studies:
SAF™ Treatment Process Examples

Flotation Process Demonstration – Red Bluff Wastewater Treatment Plant, California

Situation:  The 1.2 MGD capacity Red Bluff municipal wastewater treatment plant had an activated sludge secondary treatment process and anaerobic digestion for waste activated sludge. The waste activated sludge was thickened in an Eimco Dissolved Air Flotation tank with a flotation area of 6 ft. x 17 ft.

Action:  A full-scale demonstration was conducted in October 1995 using the DAF tank retrofitted to perform as a SAF™ process, with a prototype microbubble generator.  See video.

Result:  130 gpm of activated sludge mixed liquor containing 1,200 to 1,300 mg/L TSS was treated continuously in the modified DAF tank, achieving less than 2 mg/L TSS in the clarified underflow and 7% solids content in the thickened float.  The float solids were so thick that they rendered the level float ball in the solids collection hopper inoperable.  A notable characteristic of the float solids was the absence of objectionable odor, due to odor compounds being absorbed by the frothing agent used to generate the bubble suspension.



Digested Sludge Thickening Pilot Test

Situation:  Synagro’s Biosolids Recycling Facility (BRF) centrifuges and dries digested sludge from the Sacramento Regional Wastewater Treatment Plant (SRWTP).  The BRF was experiencing high polymer usage due to low and variable digested sludge solids content (as low as 1.3%).  Pilot testing of two gravity belt thickeners was unsuccessful in reducing polymer usage.

Action:  Heron Innovators placed its SAF™ Pilot Trailer No. 3 at Synagro during May and July 2008, and May and June 2010, to test flotation thickening of digested sludge.  Between 35 gpm and 60 gpm of digested sludge, with solids content in the range of 1.3% – 2.3 and dosed with polymer, were thickened in a Model CF125 ClearFloater™ flotation tank using Suspended Air^® Emulsion produced by a Model F50 SAF™ Generator.

Result:  With hydraulic loading rates between 7.7 gpm/sq. ft. and 9.4 gpm/sq. ft., flotation was effective at solids loading rates up to 40 lb./hr./sq. ft. (960 lb./day/sq. ft.).  Float solids were between 3.5% and 5.1%, with low suspended solids in the clarified underflow.  Polymer usage was reduced between 20% and 30%.  See video.

  
 SAF Synagro Trial 4-11 (.pdf, 75k)

Tallow Recovery at Two Meat Packing Plants in Kansas

Situation:  These beef packing plants are among the largest in the country. In the past, they have operated multiple DAF’s to treat the packing process wastewater. The TSS of the raw wastewater is approximately 4,000 mg/L, and a significant proportion of that is tallow. The DAF processes remove approximately 50% of the TSS, and what is removed is rendered and sold mainly as “brown tallow”.  If solids could be recovered more efficiently, it would contain a higher proportion of “bleachable tallow”, commanding many times the price of “brown tallow”.

Action:  Heron Innovators provided its 250-gpm capacity pilot trailer for a 2-month test run in early 2007. When raw wastewater was split between an FRC DAF and the pilot trailer, the FRC DAF continued to perform at 50% TSS removal, while the SAF™ system effluent TSS was between 100 and 200 mg/L. Very dense float solids were produced – early in the test run when the float skimmer was left to operate according to its on/off timer instead of running continuously, the solids were so dense that one of the skimmer drive chains broke.

Result:  This beef packer purchased a Model F100 Suspended Air® Emulsion Generator and two Model F200 generators, and retrofitted both of their DAF’s at one of their plants.  They also purchased a Model F200 generator and a Model CF2000 ClearFloater flotation tank, and replaced their entire DAF system at the other plant.  Performance of both of these installations exceeds their expectations.

 
  SAF In Kansas (.pdf, 77k)


Municipal Wastewater Pond Algae Removal – Graton Community Services District, California

Situation: During bench and pilot testing of a compressible media tertiary filter by Lescure Engineers, Santa Rosa, CA, unacceptably short filter run times (down to one-half hour) were being experienced, even though pond suspended solids (mostly algae) were below 50 mg/L. A pilot DAF was unsuccessful in reducing the turbidity of the filter influent to less than 10 NTU, as required by California wastewater reuse regulations.

Action: Heron Innovators provided bench testing services, and in the summer of 2006 provided a self-contained pilot trailer as pretreatment for an 18-inch square compressible media pilot filter. The trailer included a conditioning tank, a Model CF250 ClearFloater™ flotation tank, and a Model F50 Suspended Air® Emulsion generator.

Result: The pilot trailer treatment system consistently achieved the desired turbidity of less than 10 NTU, treating settling pond effluent containing between 6 and 18 mg/L TSS, and oxidation pond effluent with and without recycled filter backwash solids containing between 75 and 92 mg/L TSS, at hydraulic loading rates up to 13 gpm per square foot. Stable, gelatinous float solids were obtained, at 3.7% – 4.6% dry solids content. Float solids concentrations this high have proven to be unattainable with any DAF removing mostly algae. Lescure Engineers has sole-sourced a SAF™ treatment process including a dual compartment conditioning tank, a Model CF250 ClearFloater™ flotation tank, and two Model F50 Suspended Air® Emulsion Generators, in the Graton CSD Wastewater Treatment Plant upgrade project to be constructed in 2009.

 
  SAF at Graton (.pdf, 126k)

Winery Wastewater Treatment – Kendall-Jackson, Windsor, California 

Situation: The Kendall-Jackson Winery bottling plant at Windsor, California generates up to 35,000 gallons per day of wastewater from washing of process vessels and piping. The wastewater is treated in a series of lagoons prior to discharge to the local wastewater treatment plant. Treated wastewater suspended solids concentration was between 500 and 600 mg/L due to algae growth and solids accumulation in the final pond, exceeding the plant’s pretreatment limitation. Various attempts at treating the pond effluent using Dissolved Air Flotation were unsuccessful in significantly reducing the suspended solids.

Action: A SAF™ pilot plant trailer was provided in late summer 2004, with sufficient capacity to treat the entire permitted daily discharge of 35,000 gallons over a 4 to 6 hour period. Wastewater pumped to the flotation process was flocculated with a cationic polymer. The original one-month pilot run was extended to five months due to better than expected treatment results. Kendall-Jackson purchased a permanent skid-mounted SAF™ system, including an agitated conditioning tank, Model CF-125 ClearFloater™, and a Model F-25 Suspended Air® Emulsion Generator. It was installed in June 2005 and is achieving results similar to the pilot plant results

Result: SAF™ effluent suspended solids were reduced to between 10 and 30 mg/L, and the effluent consistently exceeds pre-treatment limitations on suspended solids by a wide margin.

  SAF at K-J (.pdf, 197k)



DAF Retrofit at a California Fruit Cannery

Situation:   A 1,000 gpm capacity FRC DAF at this large peach cannery in California's San Joaquin Valley was producing marginally acceptable effluent at low influent suspended solids concentrations when treating 700 gpm.  When influent TSS was 2,400 mg/L, all but 400 gpm had to be diverted or the treatment result was unacceptable. One of two 60-Hp Edur multi-stage pressurization pumps operated continuously, and a complete re-build or replacement of both pumps was necessary every year.

Action:  Heron Innovators provided its pilot trailer to demonstrate the SAF™ process, and replaced the DAF pressurization system with a Model F200 Suspended Air® Emulsion Generator in time for the 2007 processing season. Provision was included to inject Suspended Air® Emulsion at three different points in the FRC serpentine influent piping.

Result:  The FRC DAF operated at its rated capacity for most of the 2007 season. The 60-Hp pressurization pump was replaced by the F200’s 10-Hp recirculation pump, saving significant power and rebuild costs.  After some experience running the retrofitted DAF, it became apparent that the Suspended Air® emulsion only needed to be injected at one point rather than three.  The solids produced with the retrofitted Suspended Air® Emulsion Generator had much higher solids content than those produced by the original FRC DAF.  The retrofitted DAF operated successfully through the 2008 season.

  SAF at Cannery (.pdf, 152k)