Download - Trickling Filter
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Clarifier
General overview of plant components
Secondary Sludge
Primary Sludge
Clarifier
Raw Wastewater Influent
PRIMARY
DISINFECTION
BiologicalTreatment
System
SECONDARY
Clean Wastewater EffluentDischarge to Receiving Waters
Preliminary Residuals(i.e., grit, rags, etc.)A
B
C
WastewaterTreatmentResiduals
BiosolidsProcessing
and Disposal
(e.g., attached-grwoth Suspended-Growth, Constructed Wetland, etc.)
Clarifier
PRELIMINARY
Usually to Landfill
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Biological wastewater (WW) treatment
• To remove the suspended solids & the dissolved organic load from the WW by using microbial populations.
• The microorganisms are responsible for– degradation of the organic matter – they can be classified into
• aerobic (require oxygen for their metabolism)• anaerobic (grow in absence of oxygen) • facultative (can proliferate either in absence or presence of
oxygen).
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Biological wastewater (WW) treatment
• If the micro-organisms are suspended in the WW during biological operation– suspended growth processes
• Recycling of settled biomass is required.
• While the micro-organisms that are attached to a surface over which they grow– attached growth processes
• The biomass attached to media (ex. rock, plastic, wood)
• Recycling of settled biomass is not required.
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Attached Growth Process
What can this process do?
1. Remove Nutrient
2. Remove dissolved organic solids
3. Remove suspended organic solids
4. Remove suspended solids
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Cross-section of an attached growth biomass film
Wastewater
Oxygen (the natural or forced draft)
Organic/ nutrient
filter media
Biomass : viscous, jelly-like substance containing bacteria
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Attached Growth Process
• Trickling filter (TF)
• Rotating biological contactor (RBC)
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Trickling Filter (TF)- side view
Wastewater
rotating distributor arms
Packing media
Underdrain
– TF consists of:• A rotating arm that sprays
wastewater over a filter medium.
• Filter medium: rocks, plastic, or other material.
– The water is collected at the bottom of the filter for further treatment.
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Trickling Filter Process
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Design consideration
• Influent wastewater characteristics• Degree of treatment anticipated (BOD & TSS removal). • Temperature range of applied wastewater• Pretreatment processes• Type of filter media• Recirculation rate • Hydraulic and organic loadings applied to the filter• Underdrainage and ventilation systems
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Trickling Filter (TF)- side view
Wastewater
rotating distributor arms
Packing media
Underdrain
– TF consists of:• A rotating arm that sprays
wastewater over a filter medium.
• Filter medium: rocks, plastic, or other material.
– The water is collected at the bottom of the filter for further treatment.
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Design consideration - Pretreatment
• Trickling filters shall be preceded by primary clarifiers equipped with scum and grease collecting devices, or other suitable pretreatment facilities.
• If fine screening is provided the screen size shall have from 0.03 to 0.06 inch openings.
• Bar screens are not suitable as the sole means of primary treatment.
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Design consideration
• Influent wastewater characteristics• Degree of treatment anticipated (BOD & TSS removal). • Temperature range of applied wastewater• Pretreatment processes• Type of filter media• Recirculation rate • Hydraulic and organic loadings applied to the filter• Underdrainage and ventilation systems
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Filter media
• Crushed rock– Durable & insoluble– Locally available– But, reduce the void spaces for passage of air– Less surface area per volume for biological growth
• Plastic media – Random packing media– Modular packing media
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Filter media
Schematic diagrams of modular and random packed media used in fixed-film treatment systems (Source: Bordacs and Young, 1998)
Cross-flow Tubular Pall rings
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Design consideration - Filter media
The ideal filter packing is material that• has a high surface area per unit of volume• is low in cost• has a high durability• has a high enough porosity so that clogging is
minimized • provides good air circulation
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Design consideration
• Influent wastewater characteristics• Degree of treatment anticipated (BOD & TSS removal). • Temperature range of applied wastewater• Pretreatment processes• Type of filter media• Recirculation rate • Hydraulic and organic loadings applied to the filter• Underdrainage and ventilation systems
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Flow Diagram for Trickling Filters
Recycle
Primaryclarifier Trickling
filter
Finalclarifier
Wastesludge
FinaleffluentInfluent
Q
Qr
Recirculation= A portion of the TF effluent recycled through the filterRecirculation ratio (R) = returned flow (Qr)/ influent flow (Q)
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Trickling Filter Process
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Design consideration - Recirculation
• Why is recirculation required?– maintain constant wetting rate – dilute toxic wastes – increase air flow – recirculation flow dilutes the strength of raw
wastewater & allows untreated wastewater to be passes through the filter more than once.
• A common range for recirculation ratio– 0.5~3.0
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Single stage
PC SCTF
PC SCTF
PC SCTF
a.
b.
c.
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Two stage
PC SCTF
PC SCTF
TF
TF SC
PC SCTFTF SC
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