Sludge Aeration

• Sludge Aeration
• Odor Control
• Mixing & Equalization

Sludge Aeration: Mixing & Equalization
And Odor Control in Open Top Basin

A commercial bakery in northern New Jersey operates its baking facility on a 24/5 day/week basis producing approximately 80,000 gpd of process and sanitation washdown wastewater a day. This wastewater is pumped into an 180,000 gallon aeration basin. Extended aeration occurs prior to transferring the liquids into a holding basin, before they are pumped into an SBR (sequencing batch reactor). Solids from the bottom of the aeration basin are decanted to the sludge basin, as well are the solids from the bottom of the SBR.

Both the aeration basin and sludge basin were the principal sources of odor complaints, which the facility received from neighbors just outside the industrial park. However, between the two sources of odors the sludge basin was the worse of the two due to high levels of floated grease and settled solids. Sludge can remain in the basin for several days before it is pumped out and trucked off site for disposal (Passaic Valley Sewerage Authority).  This is especially common over the weekends when there is little plant production and primarily hot sanitation wastewater is treated in the aerated basin.  Because of the location of the bakery in a valley adjacent to the Pompton River, it is greatly affected by temperature inversions in the hot summer months, which prevent dissipation and dispersion of the odors by the wind.  The slight prevailing wind direction in the summer months is from the southeast, blowing the odors directly into the residential neighborhood and an adjacent corporate office park.

To solve this problem a venturi aerator solution was chosen to replace the coarse air diffusers which could not supply the >1 mg/l of DO necessary to control hydrogen sulfide (H2S) and -mercaptan odor formation.  A Gorman-Rupp T-8 pump with 40 hp motor and with an 8” suction line recirculates the liquid and sludge in the sludge basin through a Model VA-1300 (1300 gpm) six-inch (6”) venturi aerator. 

The sludge being discharged from the venturi aerator is laid on the surface of the basin creating an “oxygenated blanket” preventing fugitive malodorous molecules from being released into the atmosphere. Residual DO levels in the sludge basin are >2 mg/l which is sufficient to prevent the hydrogen sulfides and –mercaptans from reforming into a malodorous molecule. The kinetic energy from the velocity of the discharge keeps the contents of the basin mixed and equalized as the suction is off the bottom bringing the most anoxic sludges into the venturi aerator wherein bottom to top mixing is occurring. In this manner all the contents of the sludge basin are turned over every hour, and this keeps the sludge fresh and odorless. Sludge in the basin varies between 2-4% solids depending on production and sanitation.

For additional information on how integrated treatment solutions and systems with venturi aerators and Gorman-Rupp pumps can solve your wastewater problems contact Venturi-Aeration, Inc. at (603) 635 8239