Sequencing Batch Reactor Proc he sequencing batch reactor(SBR) 如100265 reactor with complete mixing during the batch reaction step(after filling) and where the subsequent steps of aeration and clarification occur in the tank All SBr systems have five steps in common, SETTLE which are carded out in sequence as follows: (1)fill, (2)react(aeration), 1313515 (sedimentation/clarification), (4) draw(decant ), and(5)idle. Each of these steps is illustrated on Fig 7-11 and described in Table 7-5 For continuous-flow applications, at least two sbr tanks must be Fig. 7-11 SBR activated sludge process:(a)schematic diagram;(b)view provided so that one tank receives of a opical SBR; (c)wiew of movable weir used to deant contents of SBR. flow while the other completes its Weir is located on the far side of the second dividing wall shown in(b) treatment cycle. Several process modifications have been made in the times associated with each step to achieve nitrogen Sludge wasting in is anothe rtant step in the sbr operation that greatl affects performance as one o ive basic process steps because there is no set time period within the cycle dedicated to wasting. The amount and frequency of sludge wasting is determined by performance requirements, as with a conventional continuous-flow system. In an SBR operation, sludge wasting usually occurs during the react phase so that a uniform discharge of solids (including fine material and large floc particles)occurs. A unique feature of the SBr system is that there is no need for a return activated-sludge(RAS)system Tab. 7-5 Description of operational steps for the sequencing batch reactor Operational Because both aeration and settling occur in the same chamber no sludge is During the fill operation, volume and substrate(raw wastewater or primer lost in the vent) are added to the re rise from 75 a tor may be 50% of the full oyde firm bwo n Fu cal reachon moy be mixed ab react step and none has to be returned by lat the end of the idl to 100%. when Nw to maintain the solids content in the mixed and aerated to promote bide with the infuse aeration chamber. The SBr process can also be modified to operate in a During the react period, the biomass consumes the substrate under ed environmental conditions continuous-flow mode as discussed 地bwdw卿 barate from the liquid under quiescent conditions. later in this chapter. Because of the substrate concentration Decant Clarified effluent is removed during the decont period. Many types of changes with time, the substrate utilization and oxygen demand rates 可购付地闻切邮 vels. The aeration system should be designed to reflect the changing its in Process Design of SBRs. Because of the many design variables involved in an SBR design, an iterative approach is necessary in which key reactor design conditions are first assumed. A set of different design conditions can be evaluated by use of a spreadsheet analysis to determine the most optimal choice. The (1)the fraction of the tank ts removed during decanting and (2) the settle, decant, and aeration times. Because the fill volume equals the decant volume, the fraction of decant volume equals the fraction of the sBr tank volume used for the fill volume per cycle. The design procedure for the SBr system is presented in Table 7-6 Tab. 7-6 Computation approach foe the design ofa sBr 7-167-16 Sequencing Batch Reactor Process The sequencing batch reactor (SBR) process utilizes a fill-and-draw reactor with complete mixing during the batch reaction step (after filling) and where the subsequent steps of aeration and clarification occur in the same tank. All SBR systems have five steps in common, which are carded out in sequence as follows: (1) fill, (2) react (aeration), (3) settle (sedimentation/clarification), (4) draw (decant), and (5) idle. Each of these steps is illustrated on Fig. 7-11 and described in Table 7-5. For continuous-flow applications, at least two SBR tanks must be provided so that one tank receives flow while the other completes its treatment cycle. Several process modifications have been made in the times associated with each step to achieve nitrogen and phosphorus removal. Sludge Wasting in SBRs. Sludge wasting is another important step in the SBR operation that greatly affects performance. Wasting is not included as one of the five basic process steps because there is no set time period within the cycle dedicated to wasting. The amount and frequency of sludge wasting is determined by performance requirements, as with a conventional continuous-flow system. In an SBR operation, sludge wasting usually occurs during the react phase so that a uniform discharge of solids (including fine material and large floc particles) occurs. A unique feature of the SBR system is that there is no need for a return activated-sludge (RAS) system. Tab. 7-5 Description of operational steps for the sequencing batch reactor Because both aeration and settling occur in the same chamber, no sludge is lost in the react step and none has to be returned to maintain the solids content in the aeration chamber. The SBR process can also be modified to operate in a continuous-flow mode as discussed later in this chapter. Because of the substrate concentration changes with time, the substrate utilization and oxygen demand rates change, progressing from high to low levels. The aeration system should be designed to reflect the changing requirements in oxygen demand. Process Design of SBRs. Because of the many design variables involved in an SBR design, an iterative approach is necessary in which key reactor design conditions are first assumed. A set of different design conditions can be evaluated by use of a spreadsheet analysis to determine the most optimal choice. The key design conditions selected are (1) the fraction of the tank contents removed during decanting and (2) the settle, decant, and aeration times. Because the fill volume equals the decant volume, the fraction of decant volume equals the fraction of the SBR tank volume used for the fill volume per cycle. The design procedure for the SBR system is presented in Table 7-6. Tab. 7-6 Computation approach foe the design of a SBR Fig. 7-11 SBR activated sludge process: (a)schematic diagram; (b)view of a typical SBR;(c)view of movable weir used to deant contents of SBR. Weir is located on the far side of the second dividing wall shown in (b)