What are the features that should be incorporated into design? How can the deposition of solids and potential odors be controlled? Location of equalization Facilities. The best location for equalization facilities must be determined for each system. Because the optimum location will vary with the characteristics of the collection system and the wastewater to be handled, land requirements and availability, and the type of treatment required detailed studies should be performed for several locations throughout the system. Where equalization facilities are considered for location adjacent to the wastewater-treatment plant, it is necessary to evaluate ow they could be integrated into the treatment process flowsheet. In son treatmen treatment causes fewer problems with solids deposits and scum accumulation. If flow-equalization systems are to be located ahead of primary settling and biological systems. the design must provide for sufficient mixing to prevent solids deposition and concentration variations. and aeration to prevent odor In-Line or Off-Line Equalization. As shown on Fig. 5-8. it is possible to achieve considerable amping of constituent mass loadings to the downstream processes with in-line equal ization, but onl slight damping is achieved with off-line equal ization. Volume Requirements for the Equalization Basin. The volume required for flowrate equalization is plotted versus the time of day. The average daily flowrate. also plotted on the same diagram is the straight line drawn from the origin to the endpoint of the diagram. Diagrams for two typical flowrate patterns are shown on Fig 5-9 To determine the required volume, a line parallel to the coordinate axis, defined by the average daily flowrate, is drawn tangent to the mass inflow curve. The required volume is then equal distance from the point of tangency to the straight line representing the average flowrate (see Fig. 5-9a). If the inflow mass curve goes above the line representing the average flowrate(see Fig. 5-9b), the inflow mass diagram must be bounded with two lines that are parallel to the average flowrate line and tangent to extremities of the inflow mass diagram The The physical interpretation of the diagrams shown on Fig. 5-9 is as follows. At the low point of tangency(flowrate pattern A) the storage basin is empty. Beyond this point, the basin begins to fill because the slope of the inflow mass diagram is greater than that of the average daily flowrate. The basin continues to fill until it becomes full at midnight For flowrate pattern B, the basin is filled equalization at the upper point of tangency ig. 5-9 Schematic mass diagrams for Tme ot determination of the required equalization basin a)Flowrate pattem A (b) Flowrate patter日 storage volume for two typical flowrate patterns In practice. the volume of the equalization basin will be larger than that theoretically determined to account for the following factors Continuous operation of aeration and mixing equipment will not allow complete drawdown. although ecial structures can be built v Volume must be provided to accommodate the concentrated plant recycle streams that are expected. if such flows are returned to the equalization basin (a practice that is not recommended unless the basin is covered because of the potential to create odors v Although no fixed value can be given, the additional volume will vary from 10 to 20 percent of the heoretical value, depending on the specific conditions Basin Configuration and Construction. In equal ization basin design, the principal factors that must be considered are (1)basin geometry;(2) basin construction including cleaning, access, and safety; (3) mixing and air requirements; (4)operational appurtenances; and(5) pump and pump control systems Basin Geometry. The importance of basin geometry varies somewhat, depending on whether in-line or off-line equalization is used. If in-line equalization is used to dampen both the flow and the mass loadings. it is important to use a geometry that allows the basin to function as a continuous-flow stirred-tank reactor 5-105-10 ✓ What are the features that should be incorporated into design? ✓ How can the deposition of solids and potential odors be controlled? Location of Equalization Facilities. The best location for equalization facilities must be determined for each system. Because the optimum location will vary with the characteristics of the collection system and the wastewater to be handled, land requirements and availability, and the type of treatment required, detailed studies should be performed for several locations throughout the system. Where equalization facilities are considered for location adjacent to the wastewater-treatment plant, it is necessary to evaluate how they could be integrated into the treatment process flowsheet. In some cases, equalization after primary treatment and before biological treatment may be appropriate. Equalization after primary treatment causes fewer problems with solids deposits and scum accumulation. If flow-equalization systems are to be located ahead of primary settling and biological systems, the design must provide for sufficient mixing to prevent solids deposition and concentration variations, and aeration to prevent odor problems. In-Line or Off-Line Equalization. As shown on Fig. 5-8, it is possible to achieve considerable damping of constituent mass loadings to the downstream processes with in-line equalization, but only slight damping is achieved with off-line equalization. Volume Requirements for the Equalization Basin. The volume required for flowrate equalization is determined by using an inflow cumulative volume diagram in which the cumulative inflow volume is plotted versus the time of day. The average daily flowrate, also plotted on the same diagram, is the straight line drawn from the origin to the endpoint of the diagram. Diagrams for two typical flowrate patterns are shown on Fig. 5-9. To determine the required volume, a line parallel to the coordinate axis, defined by the average daily flowrate, is drawn tangent to the mass inflow curve. The required volume is then equal to the vertical distance from the point of tangency to the straight line representing the average flowrate (see Fig. 5-9a). If the inflow mass curve goes above the line representing the average flowrate (see Fig. 5-9b), the inflow mass diagram must be bounded with two lines that are parallel to the average flowrate line and tangent to extremities of the inflow mass diagram. The required volume is then equal to the vertical distance between the two lines. The physical interpretation of the diagrams shown on Fig. 5-9 is as follows. At the low point of tangency (flowrate pattern A) the storage basin is empty. Beyond this point, the basin begins to fill because the slope of the inflow mass diagram is greater than that of the average daily flowrate. The basin continues to fill until it becomes full at midnight. For flowrate pattern B, the basin is filled at the upper point of tangency. Fig. 5-9 Schematic mass diagrams for the determination of the required equalization basin storage volume for two typical flowrate patterns In practice, the volume of the equalization basin will be larger than that theoretically determined to account for the following factors: ✓ Continuous operation of aeration and mixing equipment will not allow complete drawdown, although special structures can be built. ✓ Volume must be provided to accommodate the concentrated plant recycle streams that are expected, if such flows are returned to the equalization basin (a practice that is not recommended unless the basin is covered because of the potential to create odors). ✓ Some contingency should be provided for unforeseen changes in diurnal flow. ✓ Although no fixed value can be given, the additional volume will vary from 10 to 20 percent of the theoretical value, depending on the specific conditions. Basin Configuration and Construction. In equalization basin design, the principal factors that must be considered are (1) basin geometry; (2) basin construction including cleaning, access, and safety; (3) mixing and air requirements; (4) operational appurtenances; and (5) pump and pump control systems. Basin Geometry. The importance of basin geometry varies somewhat, depending on whether in-line or off-line equalization is used. If in-line equalization is used to dampen both the flow and the mass loadings, it is important to use a geometry that allows the basin to function as a continuous-flow stirred-tank reactor