P.G.K.B. Ranathunga

RBC(Rotating Biological Contactor)

CONTENT INTRODUCTION RBC FLOW SCHEME RBC CONTROLLING PARAMETERS DESIGN GUIEDLINES USE OF TECHNOLOGY ADVANTAGES & DISADVANTAGES

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INTRODUCTION

• RBCs are a fixed film, aerobic, biological wastewater treatment system

• The primary function of these bio-reactors at WWTPs is the reduction organic matter.

Simplified Schematic of Rotating Biological Contactor

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Pretreatment

PrimaryTreatment

RotatingBiologicalContactors

SecondaryClarifiers

Solids Handling

INFLUENT

Disinfection

EFFLUENT

RBC FLOW SCHEME

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RBC CONTROLLING PARAMETERS

A. Organic Loading and Hydraulic Loading Rate The efficiency of RBC depends mainly on organic loading rate

rather than on the organic concentration or flow rate. Organic removal rate increases with increasing the Organic

Loading Rate.B. Biomass

It plays important role in removing the organic and inorganic substrate present in wastewater.

C. Speed Speed of rotation helps in transfer of oxygen and nutrient

required for growth of microorganism present in the biofilm.

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Cont.’…D. Dissolved Oxygen (DO)

In initial stage dissolved oxygen level generally reduces and slowly recovered in successive stages.

Higher the loading there is sharp decreased in DO.E. Staging

RBC in series achieve greater constituent reduction than a single stage of the same total media and hydraulic volume.

F. Temperature Important factor affecting the limiting viscosity of RBC sludge

and limiting viscosity decreased by increasing the temperature.G. Disc Submergence

Generally, partially submerged RBC’s are used for nitrification and fully submerged for denitrification.

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DESIGN GUIDELINES

• Can be oriented in two ways: series or parallel.• RBC process is typically divided into four separate stages.• Additionally, the disc design is made in such a way that large

amounts of biofilm can attach, which means that there is a large amount of biological mass present to degrade the pollutants (WSP 2007).

• The disc is made out of light-weighted material such and usually ridged, corrugated, or lattice-like to make as much as surface available for the biofilm to attach. (NSFC 2004)

• A minimum hydraulic retention time of 0.7 to 1.5 hours is necessary for BOD removal to occur

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Cont.’…• Media

Biological Slime Growth-Media is composed of high density plastic circular discs or sheets usually 12 feet in diameter.

Rotation of Media-The drum rotates about 1.5 rpm Appearance of Media-– A gray, shaggy appearing biological slime-for BOD removal– A brown, thinner, less shaggy biological slime-for nitrifying

system• Shaft

The typical maximum length is 27 feet long with a maximum of 25 feet occupied by media.• Drive Assembly

Mechanical drives and air drives. • Cover

Made of fiberglass

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USE OF TECHNOLOGY

• WhyTypically designed to reduce total BOD to approximately

15 to 30 mg/L., TSS to approximately 20 to 40 mg/L and to achieve ammonia reduction to > 2 mg/L.

• When

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ADVANTAGES & DISADVANTAGES

ADVANTAGES• Simple Operation• Low Energy Requirements• Low Head Loss• Low Solids Generation• Process Stability with Load

Variations • More Reliable Liquid/Solids

Separation • No Sludge Return • High contact time and high

effluent quality (both BOD and nutrients)

DISADVANTAGES• Lack of Flexibility• Sensitivity to Industrial

Wastes• Possible Low Dissolved

Oxygen• Limited Controls• Limited Experience and

Training

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REFERENCES

• Biological, R. et al., 2012. Review on Process, Application and Performance of., 2(7).

• http://web.deu.edu.tr/atiksu/ana52/rbcyeni.pdf• http://www.sswm.info/content/rotating-biological-contactors• http://williamsworks.com/images/pdf/ReconsideringRotatingBi

ologicalContactors.pdf• http://www.powershow.com/view/3e0dc1MTE2M/Rotating_Bio

logical_Contactor_powerpoint_ppt_presentation

THANK YOU…..

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QUESTIONS

1. What are the two types of RBC drive mechanisms? Mechanical drives and air drives

2. What are the 3 primary factors affecting performance of a RBC?

Physical, biochemical and microbiological factors.

3. Why RBC is generally covered? Because of climate condition reasons.

4. How can be oriented RBC s? Series or parallel