7 Suspended Growth Biological Treatment Processes 7-1 Introduction to the Activated- Sludge Process Historical Development Experiments conducted at the Lawrence Experiment Station during 1912 and 1913 by Clark and Gage With air input into wastewater, growths of organisms could be cultivated in bottles and in tanks partially filled with roofing slate spaced about 25 mm(1 in)apart and would greatly ncrease the degree of purification
7 Suspended Growth Biological Treatment Processes 7-1 Introduction to the Activated-Sludge Process Historical Development Experiments conducted at the Lawrence Experiment Station during 1912 and 1913 by Clark and Gage With air input into wastewater, growths of organisms could be cultivated in bottles and in tanks partially filled with roofing slate spaced about 25 mm (1 in) apart and would greatly increase the degree of purification
Lockett found that the sludge played an important part The basic activated-sludge treatment process, as illustrated on fig. 7-la and b consists of the following three basic components:(1) a reactor in which the microorganisms responsible for treatment are kept in suspension and aerated:(2 liquid-solids separation, usually in a sedimentation tank; and 3) a recycle system for returning solids removed from the liquid-solids separation unit back to the reactor
Lockett found that the sludge played an important part. The basic activated-sludge treatment process, as illustrated on Fig. 7-la and b, consists of the following three basic components: (1) a reactor in which the microorganisms responsible for treatment are kept in suspension and aerated; (2) liquid-solids separation, usually in a sedimentation tank; and (3) a recycle system for returning solids removed from the liquid-solids separation unit back to the reactor
Fig.//Description of Basic Process
Fig. 7-1Description of Basic Process
An important feature of the activated-sludge process is the formation of flocculent settleable solIds For these applications, various modifications of conventional activated-sludge processes are used including sequencing batch reactors, oxidation ditch systems, aerated lagoons, or stabilization ponas
An important feature of the activated-sludge process is the formation of flocculent settleable solids . For these applications, various modifications of conventional activated-sludge processes are used, including sequencing batch reactors, oxidation ditch systems, aerated lagoons, or stabilization ponds
Evolution of the Activated- Sludge Process A number of activated-sludge processes and design configurations have evolved since its early conception as a result of ()engineering innovation in response to the need for higher-quality effluents from wastewater treatment plants;(2)technological advances in equipment, electronics, and process control;(3) increased understanding of microbial processes and fundamental and(4) the continual need to reduce capital and operating costs
Evolution of the Activated-Sludge Process A number of activated-sludge processes and design configurations have evolved since its early conception as a result of (1) engineering innovation in response to the need for higher-quality effluents from wastewater treatment plants; (2) technological advances in equipment, electronics, and process control; (3) increased understanding of microbial processes and fundamentals; and (4) the continual need to reduce capital and operating costs
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
