1. Obiain infuent wastewater characterization dato, define effluent requirements, and Staged Activated-Sludge Process 2. Select the number of sbr tank In the conventional plug-flow activated-sludge system, th 3. Select the react/oration, setting, and decant fimes. Determine the fl ime and total fime hydraulics and mixing regime may result per cyde. Determine the number of ycies per day 4. From the lotal number of cydes per day, determine the fil volume per cycle in two to four effective stages from the 5. Selec the MLSS concentration and determine the fill volume fraction relative No the lotal standpoint of biological kinetics tank volume Determine he decant depth Using the computed depths, determine the SB Activated-sludge processes can be the sRT for the SBR designed with baffle walls to intentionally 7. Determine the amount of tkn added that is nitrified create a number of complete-mix 8. Calculate the nitrifier biomass concentration and determine if the aeration time selected s activated-sludge zones operating in series 9. Adjust the design as needed-additionol iterations may be don For the same reactor volume reactors in o. Dehurm ine the decant pumping rate series can provide greater treatment 1, Determine the oxygen required and average transfer rate efficiency than a single complete-mix reactor, or provide a greater treatment 3. Calculate the F/M and BOD volumetric looy 4. Evaluate alkalinity needs activated-sludge process configurations 5. Prepare design summary are used at several full-scale installations The oxygen demand varies in staged complete-mix reactor designs and can be high enough in the first stage to challenge the volu Fig.7-12 Nitrification transfer capability of aeration equipment. With high-density fine bubble aeration diffusers, activated such as membrane aeration panels oxygen Nadily biodegradable COD(soluble transfer rates of 100 to 150 mg/Lh are possible, with some manufacturers claiming higher rates. The changes in oxygen uptake Slowly biodegradable COD (particulate) rates(OURs)in each stage of a four-stage activated-sludge process (defined as a function of oxygen needed for nitrification rbCOD removal, particulate degradable COD and endogenous respiration) are depicted on Most of the rbcod wil be consumed rst stage. and the day de iaf madema zero-order e te for nne nrst the deg rare oagis due to higer naats concentrations in the early stages. Oxygen demand for endogenous respiration will be relatively constant The detygen demand distribution may be estimated to determine the aeration design for staged processes and 10 percent, respectively, fo a staged system is to calcula d the total oxygen desided as would be done for a cmas taygen demand in ocess. and then proper selectio:出m沿购N图思中 approach outlined above is satisfactory because during the life of the process the oxygen demand wili Use of Simulation Models. The other approach involves the use of simulation models, in which kinetics and changes in constituent concentrations in each stage are taken into consideration. This activated-slud approach involves solving a set of equations in each includes COD, NH4-N, endogenous respiration, and bior concentration. Models and the effect of biological phosphorus removal on design and performance Alternative processes for bod removal and Nitrification Over the last 30 years numerous activated-sludge processes have been developed for the removal of organic material(BOD) and for nitrification 7-177-17 Staged Activated-Sludge Process In the conventional plug-flow activated-sludge system, the tank hydraulics and mixing regime may result in two to four effective stages from the standpoint of biological kinetics. Activated-sludge processes can be designed with baffle walls to intentionally create a number of complete-mix activated-sludge zones operating in series. For the same reactor volume, reactors in series can provide greater treatment efficiency than a single complete-mix reactor, or provide a greater treatment capacity. As a consequence, staged activated-sludge process configurations are used at several full-scale installations. Oxygen Demand in Staged Designs. The oxygen demand varies in staged complete-mix reactor designs and can be high enough in the first stage to challenge the volumetric oxygen transfer capability of aeration equipment. With high-density fine bubble aeration diffusers, such as membrane aeration panels oxygen transfer rates of 100 to 150 mg/L.h are possible, with some manufacturers claiming higher rates. The changes in oxygen uptake rates (OURs) in each stage of a four-stage activated-sludge process (defined as a function of oxygen needed for nitrification, rbCOD removal, particulate degradable COD, and endogenous respiration) are depicted on Fig. 7-12. Most of the rbCOD will be consumed in the first stage, and the OUR for pCOD degradation will decrease from stage to stage as a function of the degradation kinetics. Nitrification rates may be at a maximum zero-order kinetic rate for the first one to three stages due to higher NH4-N concentrations in the early stages. Oxygen demand for endogenous respiration will be relatively constant from stage to stage. The oxygen demand distribution may be estimated to determine the aeration design for staged processes. The percent of the total oxygen consumption may range from 40, 30, 20, and 10 percent, respectively, for a four-stage system. One design approach that can be used to obtain an estimate of the oxygen demand in a staged system is to calculate the total oxygen demand as would be done for a CMAS process, and then estimate the oxygen demand distribution with consideration to the various components described above. With proper selection of the type and placement of the diffusers and by providing an air supply system with DO control in each portion of the system, the air can be provided where needed. Generally, the approach outlined above is satisfactory because during the life of the process, the oxygen demand will vary across the tank as the load changes. Use of Simulation Models. The other approach involves the use of simulation models, in which the kinetics and changes in constituent concentrations in each stage are taken into consideration. This approach will typically result in a more optimal design and can be used to assess the real capacity of a given activated-sludge design. The simulation approach involves solving a set of equations in each stage for each constituent, which includes rbCOD, pCOD, NH4-N, endogenous respiration, and biomass concentration. Models also include phosphorus and the effect of biological phosphorus removal on design and performance. Alternative Processes for BOD Removal and Nitrification Over the last 30 years numerous activated-sludge processes have been developed for the removal of organic material (BOD) and for nitrification. Fig. 7-12 Changes in oxygen uptake rates for staged activated sludge process