COMPARISON OF BATCH AND CONTINUOUS PROCESSES
| PARAMETERS | SBR SYSTEM | CONTINUOUS FLOW ACTIVATED SLUDGE SYSTEM (CFS)1 | REMARKS |
| Concept | Time Sequence in the same tank | Time sequence in different tanks | Time sequence can be varied in SBR; no such flexibility in CFS. |
| Inflow | Periodic - normal SBR Continuous - ICEAS |
Continuous | |
| Discharge | Periodic | Continuous | Decant period can easily be changed in SBR. Further, somewhat possible to hold effluent until it meets specific requirements. CFS - Inflexible. |
| Organic load | Cyclic normal SBR Continuous - ICEAS |
Continuous | Several variations of organic loading are possible by changing duration of cycle period. CFS - Inflexible. |
| Aeration | Intermittent | Continuous | Increased flexibility in SBR. Both the aeration and the aeration duration can be varied. CFS - Only the aeration rate can be changed. |
| Mixed liquor | Always in reactor, no recycle | Recycle through reactor and clarifier | No need for final clarifiers and RAS pumps in SBR. CFS requires above facilities. |
| Clarification | Ideal - normal SBR Not as deal - ICEAS |
Not ideal. Short-circuiting and density currents are common | Several CFS systems are known to perform unsatisfactorily because of less than ideal settling conditions present in the clarifiers. SBR free from problems. |
| Flow Pattern | Perfect plug | Complete mix or approaching plug | A perfect plug flow condition in SBR achieves rapid biodegradation of pollutants (shorter reaction time). CFS requires longer reaction time. |
| Equalisation | Inherent | None | SBR is an ideal reactor in situations with excessive diurnal variations in flow and BOD, CFS can fail under above condition. |
| Flexibility | Considerable | Limited | Operater can routinely change cycle durations, aeration/mixing strategies. CFS is somewhat limited in these areas. |
| Reactor Size | Could be larger than CFS because it has to provide space for accomoding slude blanket. | Generally smaller than SBR | In spite of larger reactor size, SBR can be more compact and require less overall space because no separate clarifiers and RAS pumps are needed. |
| Operation (Process) | Relatively easy to operate - achieved by microprocessor technology | Same as SBR | SBR ideal for small plants. CFS may not be practical in small plants with excessive diurnal flow variations. |
| (Equipment) | Fewer mechanical equipment result in easier operation | Significally more mechanical equipement result in somewhat difficult operation | |
| Effluent quality | Excellent in most case | Excellent in most case | |
| Flexibility to meet changing requirements (C, N, P removal) | Tremendous flexibility in SBR; achived by changing operational strategy (cycle duration, cycle sequence and aeration mixing strategy). Somewhat less in ICEAS. | Limited as compared to SBR |
1. Includes aeration tank(s),
clarifier(s) and RAS pumping.
*from TECHNOLOGY EVALUATION OF SEQUENCE BATCH REACTORS,
Environmental Protections Agency, September 1984
