Zero Emission WWTP Constructed for Reuse Program

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The city of Winder, Ga., combined the required upgrade of its existing 1.5 mgd wastewater treatment facility with a water reuse system to provide irrigation for a new city-owned golf course.

After design considerations and cost analyses, the city of Winder selected the "Zero Emission System" developed by Seghers Better Technology. An order was issued to Water Wise Inc., a firm specializing in urban water reuse, who will work in partnership with Seghers to design, install, construct and operate the new facility.

The process selected is based on a conventional activated sludge system contained within a Seghers Unitank? system. The basic unit from which every Unitank system is derived is a rectangular tank divided into three hydraulically connected compartments. Each compartment is equipped with an aeration system. The wastewater can be introduced into each of the three compartments. The two external compartments have a weir for discharge of the effluent and an outlet for evacuation of the excess sludge. They have a dual function and can both operate consecutively as sedimentation or as aeration tanks. The central compartment is permanently aerated.

A separate clarification system and return activated sludge pump system is not required in the Unitank design.

The cyclic operation consists of a sequence of two main phases divided by two intermediate phases, which allows continuous constant-level operation without a separate sedimentation tank and recirculation devices.

In the first main phase the influent is directed to the left outer compartment. The mixed liquor flows from the left compartment via the central compartment to the right outer compartment, where the sludge settles and effluent is discharged.

In the second main phase the flow pattern is in the opposite direction, with influent entering the right compartment, flowing through the middle compartment and into the left outer compartment. This compartment functions now as a sedimentation compartment, where the sludge settles and the treated water is discharged.

The short intermediate phase between the main phases is necessary during changes in flow direction.

Prior to discharge of effluent to a filtration unit or receiving waters, the initial 10 minutes of each sedimentation cycle is diverted to a "rinse pit". During this time period, the effluent launders are washed clean of any debris or solids. The rinse pit is emptied during the next 2.5 hours of the main cycle and the flow is returned to the influent stream.

The "Zero Emission" concept is a design whereby the air above the process unit is blown through a Seghobioclean (bio-filter) system for removal of any offensive odors.

The Winder facility also incorporates a complete sludge handling system using a conventional belt press. The facility is controlled by a PLC system that controls the process, adjusts to many alarm and bypass situations, includes continuous monitoring of vital process parameters, makes process adjustments based on varying input elements, generates reports and printouts and is integrated with an external SCADA system.

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