SAFETY-KLEEN SYSTEM, INC.  
The Buffalo, New York facility= s operations include the removal of water from used oil and treatment of non-hazardous oily wastewater. The facility currently processes about 25 million gallons of used oil and wastewater per year. Most of the oil processed by the facility is sent to Safety-Kleen= s oil re-refineries in Breslau, Ontario and East Chicago, Indiana. Pre-treated wastewater from the process is discharged to the Buffalo Sewer Authority sanitary sewer. The facility operates 24 hours per day and 7 days a week. The average volume of wastewater treated is 40,000 gallons daily.

 

 Contact Chamber: Influent wastewater enters the DAF unit through an influent header into the contact chamber. The recycle stream is injected into the header nozzle prior to entry into the unit, and mixes with the influent. The contract chamber serves as an internal weir which provides even distribution and mixing of the process flow across the width of the unit. The chamber has a separate drain for removal of heavy solids which settle.

Skimmings (Float) Removal System: The unit is equipped with a chain and flight top skimmings removal system driven by a low speed, gear motor assembly. The top skimmer system consists of double strands of stainless steel double pitch roller chain.  The chain supports adjustable, skimmer blades retained on stainless steel angle plates. The skimmer blades are spaced approximately every 5 ft. along the chain length.

The system is driven by a variable speed drive with a motor through a chain and sprocket system. An adjustable torque limiter with automatic re-engagement protects the equipment in case of overload. Adjustable timer controls are installed to provide for intermittent skimmer operation for flexibility in the removal of skimmings from the unit.

Effluent end: The bottoms trough is segregated from the effluent flow by a vertical baffle. A second vertical baffle directs the clarified effluent up into the header box and through and adjustable weir system. Clarified effluent overflowing the weirs collects in an internal trough and is discharged through a flanged nozzle.

Recirculation System: Clarified wastewater from the discharge is recycled through the unit by a centrifugal pump.  Air is supplied into the recycle stream via an eductor loop from the discharge of the pump to the pump intake, drawing in ambient air and forcing it into solution with the recycle stream under pressure from the pump. Compressed air is added through this system via plant air.

Air Dissolving Pipe (ADP): A stainless steel air dissolving pipe is equipped with an automatic pressure safety relief valve. Liquid level in the ADP is automatically maintained by an air release valve. Discharge pressure from the recycle pump and the ADP is controlled by a diaphragm control valve and a position indicator with a series of secondary whitewater injection points through stainless steel ball valves.

A liquid filled pressure gauge was provided for monitoring recycle pressurization performance. The ADP was equipped with a bottom drain valve and a removable handway for inspection and servicing. The recirculation pump and ADP tank was mounted to the flotation tank.

 
Our task was to plan new treatment units to add to the facility= s wastewater treatment capability and to meet the new US EPA= s CWT pretreatment standards. The addition of a dissolved air flotation unit (DAF) was determined to be the best solution. The DAF selected was manufactured by SAMCO Technologies, Inc. of Tonawanda, NY.  The unit includes the following sub-systems:

Flotation Tank: The unit consists of a flotation rank constructed of corrosion resistance coated carbon steel or  stainless steel plate. The unit is supported on a stainless steel base which is constructed to allow for easy cleaning around and under the unit.