Batch Treatment (Sequencing Batch Reactor design/مبادئ تصميم وحدات المعالجة البيولوجية بنظام الاس.بى.ار

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Batch Treatment (Sequencing Batch Reactor

by

technolab el-bahaa group

general.dr

bahaa badr

Overview: Process Description and Applicability

Sequencing Batch Reactors (SBRs) and continuous flow activated sludge systems use similar biological treatment principles.

The primary difference is that SBRs alternately fill and-draw from a common tank.

This sequencing may occur with fixed cycle times (time-based), or depend on the time needed to completely refill each tank (level-based).

The basic process steps, and typical pattern for a three tank SBR system are shown below.

With level based controls, there is also typically an idle period after decanting since the time it takes to fill the prior tank is variable.

Smaller municipalities with fewer technical resources to operate a complex system comprise the largest market for SBR systems. While the inherent complexity of SBRs has sometimes led to problems because of this, newer systems provide better control features and are more reliable.
Theoretically, engineers can design SBR systems for carbonaceous BOD removal, nitrification, denitrification, and biological phosphorus removal. Managing sludge age with the care needed to only remove carbonaceous BOD has proven an unrealistic expectation for most SBRs to date. Accordingly, SBR design guidance in this section is based on operating the systems for complete nitrification and, to the extent feasible, denitrification. The denitrification (mixed fill) step not only to remove nitrates, but to recovers alkalinity, which reduces the need for a chemical
T3-20 August 2008 Criteria for Sewage Works Design
feed system. The mixed fill step also helps regulate filamentous bacteria growth.
Other References: Sequencing Batch Reactor Design and Operational Considerations, September 2005, New England Interstate Water Pollution Control Commission, www.neiwpcc.org contains recommended process control monitoring and a troubleshooting guide. These topics are not elsewhere covered in this section.
B.
General Advantages and Disadvantages of SBRs:
While not all systems realize these advantages, and most of the disadvantages can be overcome, some of the typical advantages and disadvantages of the SBR process are:
Table T3-4. Typical Advantages and Disadvantages of SBRs
TYPICAL ADVANTAGES
TYPICAL DISADVANTAGES:
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Eliminates primary and secondary clarifiers and return sludge pumps.
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Needs three or more reactor tanks to meet redundancy requirements.
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Lowers the overall tank volume required per gallon treated.
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Needs larger disinfection and downstream components because of batch discharges.
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Reduces costs by using rectangular tank and common wall construction techniques.
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Has a more difficult review and purchase process due to proprietary parts & systems.
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Facilitates future expansion through modular construction.
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Has poorer settling floc because there are no selector zones.
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Reduces labor costs through highly automated process controls.
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Increases initial and maintenance costs by using complex control systems and valves.
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Provides perfectly quiescent settling.
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Needs a larger peak air supply.
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Maximizes use of small sites.
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Performs poorly at high peak flows.
C.
Systems Available
1.
System Types
Several manufacturers offer proprietary SBR systems. General SBR systems types include:
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Batch systems using jet aerators and mixers. These use a number of water “jets” with forced air, or venturi effect air injection spaced around each tank’s perimeter. Operators may inspect and replace such jets without taking tanks offline, and without interfering with tank cleaning, inspection or maintenance. Sloped tank bottoms provide for easy maintenance. Jet aerators can mix to a distance of 30 to 40 feet. The same jets, without air, can provide mixing for denitrification.
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Batch systems using independent mixers and diffused air. These use diffuser arrays similar to other conventional secondary treatment systems, lowering costs and improving the availability of spare parts. Designers frequently array diffusers in banks so operators can isolate, retrieve, and service them without taking a tank off-line. Designs typically use separate mixers for the mixed fill cycle. These designs usually use less slope on the floor which helps with operator maintenance, but can make wasting sludge less efficient.
Biological Treatment August 2008 T3-21
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Continuous influent, batch discharge systems. Engineers design these systems to continuously accept influent at one end while intermittently “batch” discharging from the other. These designs use influent baffles and a greater length to width ratio to make this possible. As with other designs, the aeration and mixing are turned off to allow settling prior to decanting. Designers may also use a partition and an internal sludge recycle loop to obtain some selector effect. These systems have redundancy with two tanks instead of three, but designers must evaluate the potential for short circuiting and solids washout during high flow periods.
2.
Control Systems
Engineers could theoretically design SBR components such as decanters, aerators, valves, meters, and control logic to be interchangeable. However, most SBR systems come packaged together with proprietary controls designed to interface with their specific meters, valves, motors, and blowers. Control system technology is advancing rapidly, presenting an opportunity to economically retrofit existing SBR facilities with better controls and telemetry. This can improve economy and performance.

» مبادئ تصميم خزانات المعالجة البيولوجية بنظام الرياكتور/the principal biological reactor design
» Equipment Design Features Required for SBR Systems/اسس تصميم واختيار معدات المعالجة بنظام الاس بى ار
» مبادئ تصميم خزانات الترسيب للمعالجة البيولوجية الثانوية بطريقة الحماه النشطة/General design guidelines for secondary sedimentation as a part of the activated sludge process
» General Design Considerations FOR Continuous Flow ofActivated Sludge procesess/lfمبادئ تصميم خزانات المعالجة البيولوجية باسلوب الحماة النشطة
» التصميم العام لخزانات الاس بى ار للمعالجة البيولوجية General Design Standards for SBRs