THE VORTEX DROP STRUCTURE IMPLEMENTATION FOR …

1 THE VORTEX DROP STRUCTURE IMPLEMENTATIONFOR ODOR AND CORROSOIN CONTROLW illiam P. Moeller, Jr., , Eugene Natarius, council Environmental Services3565 Kennebec DriveEagan, Minnesota 55122-1036 ABSTRACTH ydrogen sulfide gas emissions cause extensive corrosion and odor problems in wastewaterconveyance and treatment systems. A significant source of these emissions is from drop struc-tures such as interceptor drop maintenance holes, forcemain discharges, joint structures, and wetwell drops in sewer pumping stations. The VORTEX Drop STRUCTURE (VDS), invented by EugeneNatarius, is an effective energy dissipater and aerator, which considerably improves the dropstructure.

2 It dissipates the flow energy and aerates the wastewater, preventing emission of odor-ous gases, oxidizing the hydrogen sulfides, and protecting the drop STRUCTURE from corrosion andabrasive council Environmental Services, a regional public agency serving the Minneapolis/St. Paul area, successfully implements the VDS. Four installed VDS have been working on maininterceptors with no odor complains from the public. The cost of chemical feed for odor controlhas been significantly reduced, and the structures are virtually maintenance-free.

3 Additional VDSinstallations are in progress at a pumping station wet well, and on a forcemain to measure VDS effectiveness was performed at two installations. The analysis of mul-tiple wastewater samples taken simultaneously upstream and downstream of the VORTEX DropStructures shows a significant decrease of dissolved hydrogen sulfides and a sharp rise in thedissolved oxygen concentrations downstream of the structures. The results of air qualitymonitoring around VDS installations indicate a strong effectiveness. Odor complaints fromadjacent homeowners have virtually drop STRUCTURE , gas emission, VORTEX drop STRUCTURE , odor control, corrosion control, wastewateraeration, abrasive wear control, solution, sewer drops create turbulent flow, which releases Hydrogen sulfide (H2S) gas.

4 Thisemission from the drop structures can lead to rapid, extensive damage to concrete and metalsewer piping and mechanical equipment, and is a main source for odor are beneficial aspects of vertical drops in situations where sewage is still fresh andcontains a relatively low amount of dissolved sulfides. Intensive flow turbulence and re-aerationat these drops boost the level of dissolved oxygen in such sewers. The O2 boost prevents exhaus-tion of the dissolved oxygen for a considerable length of in most practical cases, sewage contains a significant amount of potentially volatile dis-solved molecular H2S.

5 This H2S gas is released in drop structures and causes corrosion and odorproblems. Substantial physical evidence and test data show that most hydrogen sulfide emissionoccurs at the drops, rather than in the pipes. This is further confirmed by public odor complaintsmost often coming from areas neighboring the sewage to its elevation, flow upstream of the drop possesses great potential energy. This energy mustbe dissipated to solve the problem. A known method is to create a wall-hugging spiral flow in thevertical drop STRUCTURE to dissipate the energy by friction [1].

6 This VORTEX flow is formed by acircular, or volute-shaped chamber situated concentrically on top of the vertical this method to a typical drop of interceptor sewage flow is complicated by two , the upstream flow velocities are usually not enough to create a stable tangential flow on thevertical wall of a standard maintenance hole (MH). Second, quite often the MH is used forlateral connections at elevations lower than the main influent method can be improved considerably if the influent flow is accelerated and directed into ashaft of a predetermined diameter installed in the drop STRUCTURE ( VORTEX Shaft) See ( pending).

7 The VORTEX form with a VORTEX channel of decreasing radius creates accelerating spinning accelerating flow is directed through a special top cut into a VORTEX shaft, with a muchsmaller diameter, installed inside of a sewer drop STRUCTURE . The flow continues spiraling down-ward in a combined field of gravity and centrifugal forces. Due to the sharp reduction in diameterand significant increase of centrifugal forces, the flow maintains intimate contact with the vortexshaft wall creating a stable air core without loosing its integrity.

8 In the VORTEX shaft, the flowdrags air down creating a slightly negative air pressure above the VORTEX . This effect prevents gasfrom escaping up above the VORTEX form. The air is entrained and mixed with the flow. The mostintensive processes of vigorous mixing and aeration occur in the submerged part of the vortexshaft. The flow exits the VORTEX shaft at the bottom into an energy-dissipating pool. Theremaining flow energy is dissipated through mixing and internal friction. A tranquil flow satu-rated with air exits the energy dissipating pool to the effluent VORTEX flow acceleration combined with its direction into a much smaller diameter innershaft provides effective energy dissipation with intensive airflow mixing and aeration before theemission occurs.

9 This method yields the following benefits: Elimination of odorous gas emission Protection of the STRUCTURE and pipes from intensive corrosion Aeration of wastewater flow Effective energy dissipation eliminating abrasive wear of the STRUCTURE Creation of conditions for boosting dissolved oxygen and oxidation of dissolved sulfides Reliable function independent of flow fluctuations Elimination of the need for air treatment Significant improvement of existing drop STRUCTURE rehabilitation DROP IMPROVEMENTSThe metropolitan council Environmental Services (MCES)

10 Has used the new VORTEX method tocontrol odor and improve collection system flow drop structures situated on main MCES is a regional public agency that provides wastewater collection treatment to a seven-county metropolitan area surrounding Minneapolis and St. Paul, first VORTEX drop STRUCTURE constructed by MCES is located in Minneapolis on HumboldtAvenue South. The STRUCTURE has a 15-foot flow drop and is located at a MH downstream of thedischarge point of a 27,000-foot long forcemain (FM). This FM has an average flow (ADF) million gallons daily (MGD).