The use of a plug-flow process became problematic when industrial wastes were introduced because of the toxic effects of some of the discharges With the development of simple inexpensive program logic controllers(PLCs) and the availability of level sensors and automatically operated valves, the sequencing batch reactor SBR) process(see Fig. 7-1c) became more widely used by the late 1970s, especially for smaller communities. Some of the stages are not aerated (anaerobic or anoxic stages) and internal recycle flows may be used
The use of a plug-flow process became problematic when industrial wastes were introduced because of the toxic effects of some of the discharges. With the development of simple inexpensive program logic controllers (PLCs) and the availability of level sensors and automatically operated valves, the sequencing batch reactor (SBR) process (see Fig. 7-1c) became more widely used by the late 1970s, especially for smaller communities . Some of the stages are not aerated (anaerobic or anoxic stages) and internal recycle flows may be used
Recent Process Developments As noted above. numerous modifications of the activated-sludge process have evolved in the last 10 to 20 years, aimed principally at effective and efficient removal of nitrogen and phosphorus
Recent Process Developments As noted above, numerous modifications of the activated-sludge process have evolved in the last 10 to 20 years, aimed principally at effective and efficient removal of nitrogen and phosphorus
7-2 Wastewater Characterization Activated-sludge process design requires determining (1)the aeration basin volume, (2) the amount of sludge production,(3)the amount of oxygen needed, and(4)the effluent concentration of important parameters
7-2 Wastewater Characterization Activated-sludge process design requires determining (1) the aeration basin volume, (2) the amount of sludge production, (3) the amount of oxygen needed, and (4) the effluent concentration of important parameters
7-3 Fundamentals of Process Analysis and Control Selection of Reactor Type Important factors that must be considered in the selection of reactor types for the activated-sludge process include (1) the effects of reaction kinetics,(2) oxygen transfer requirements, 3) nature of the wastewater,(4) local environmental conditions,(5) presence of toxic or inhibitory substances in the influent wastewater,(6)costs, and (7) expansion to meet future treatment needs
7-3 Fundamentals of Process Analysis and Control Important factors that must be considered in the selection of reactor types for the activated-sludge process include (1) the effects of reaction kinetics, (2) oxygen transfer requirements, (3) nature of the wastewater, (4) local environmental conditions, (5) presence of toxic or inhibitory substances in the influent wastewater, (6) costs, and (7) expansion to meet future treatment needs. Selection of Reactor Type