Secondary Treatment Configurations SOP Pretreatment 2012
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Transcript Secondary Treatment Configurations SOP Pretreatment 2012
Secondary Treatment
Configurations
SOP Pretreatment Workshop
August 2011
NDWRCDP Disclaimer
This work was supported by the National Decentralized Water
Resources Capacity Development Project (NDWRCDP) with
funding provided by the U.S. Environmental Protection Agency
through a Cooperative Agreement (EPA No. CR827881-01-0)
with Washington University in St. Louis. These materials have
not been reviewed by the U.S. Environmental Protection
Agency. These materials have been reviewed by
representatives of the NDWRCDP. The contents
of these materials do not necessarily reflect the views and
policies of the NDWRCDP, Washington University, or the U.S.
Environmental Protection Agency, nor does the mention of trade
names or commercial products constitute their endorsement or
recommendation for use.
CIDWT/University Disclaimer
These materials are the collective effort of individuals from
academic, regulatory, and private sectors of the
onsite/decentralized wastewater industry. These materials have
been peer-reviewed and represent the current state of
knowledge/science in this field. They were developed through a
series of writing and review meetings with the goal of formulating
a consensus on the materials presented. These materials do not
necessarily reflect the views and policies of University of
Arkansas, and/or the Consortium of Institutes for Decentralized
Wastewater Treatment (CIDWT). The mention of trade names or
commercial products does not constitute an endorsement or
recommendation for use from these individuals or entities, nor
does it constitute criticism for similar ones not mentioned.
Pretreatment components
Section
objectives
Describe various engineered systems that
maintain high-rate aerobic digestion of
organic compounds found in domestic
wastewater
Provide an understanding of the typical issues
associated with these components
Describe basic operation and maintenance
procedures required to keep these systems
functional
Basic aerobic treatment
environments
Saturated
Suspended growth
Fixed/attached growth
Integrated fixed/activated sludge (IFAS)
Unsaturated
Media filters
Trickling filters
Saturated treatment
Suspended
growth
Fixed/attached growth
Integrated fixed/activated sludge (IFAS)
Saturated aerobic units:
Primary distinctions
Packaging
Flow
of effluent
Aeration method
Biomass management
Suspended growth reactors
Activated
sludge process
Biomass is thoroughly mixed with nutrients
and biodegradable compounds
Organisms flocculate and form active
mass of microbes - biological floc
Extended aeration to limit biomass wasting
Endogenous respiration
Suspended Growth
Suspended growth
Suspended growth
Suspended growth
USEPA Manual, 1980
Sequencing Batch Reactor
Suspended growth treatment process
Utilize a single chamber for achieving aeration,
clarification and anoxic conditions
Flow equalization chamber for dosing effluent into
the treatment chamber
Sequencing batch reactors
Sequencing batch reactors
Fixed/attached growth reactors
Fixed-film
process
Inert medium is submerged in the aeration
chamber
Effluent circulated through media and
attached microbes
Colloidal and dissolved organics
compounds absorbed by biological film
Extended aeration to limit biomass wasting
Food brought to bugs
Fixed-film reactors
Rotating Biological Contactor
(RBC)
Membrane bioreactors
Wikipedia
Flow schemes
Continuous
inflow
Batch processes
Aeration
Air
supply and delivery component
Distribution device
Venting device
Air supply delivery
Methods
Aspirator/Aerator
Compressor
Blower
Free Air
Aerator/Aspirator
Aerator/Aspirator
Spinning shaft or impeller creates a vacuum (venturi)
Vacuum pulls air into the water
Compressor
Two distinct types of
compressors
Rotary
Linear
Both types fitted with
filters
Relative to blowers:
Rotary
Greater pressure
Lower air flow
Linear
Blowers
Fitted with inlet
screens/filters
Relative to compressors:
Lower pressure
Greater air flow
Air distribution device
Introduces air into the water
Includes any supply line(s)
Various methods
Aspirator/aerator
Shaft
piping delivers
the air supply
Distribution relative
to pressure
Diffused air distribution
Compressor or
blower delivers air
Mode of distribution
is manufacturer
specific
Solid pipe
Perforated pipe
• Holes
• Slots
Porous material
Diffused air distribution
Perforated Pipe
Diffused air distribution
Porous ceramic diffuser
Diffused air distribution
Spargers
small interconnected passageways inside a ceramic
matrix
Oxygen transfer into solution
Small diameter
bubbles
More surface area per
unit volume
Oxygen transfer takes
place across interface
between air and water
Point of injection
Usually
near
bottom of tank
more time for oxygen
to go into solution
more hydrostatic
pressure on bubble
more mixing of
contents
“Free” air
Alternately rotates media
through air space in top
of unit and down into
effluent in basin
Water accepts oxygen
from air
Aeration and Mixing
Aeration system
also encourages
mixing
displacement of
water as air is
introduced causes
turbulence
Air supply operation
Continuous
Timed
Venting
Air entering system
Air must exit
somewhere
Unit
House vent
Biofilter
Biomass management
Returning
sludge to a previous point in
treatment system
Keeps the biological processes working
At
some point, accumulated solids will
have to be removed
Passive sludge return system
Settled material
automatically returns
to the aeration
chamber
No moving parts
Limited flexibility for
including anoxic
treatment process
Active sludge return system
Pump on bottom of
settling chamber
Control panel with timer
Timing of return
Volume returned
Location for returned
material
Proprietary configurations
Modular
units with complete configuration
Subcomponents installed in prefab tanks
Specific to proprietary products
Basic aerobic treatment
environments
Saturated
Suspended growth
Fixed/attached growth
Integrated fixed/activated sludge (IFAS)
Unsaturated
Media filters
Trickling filters
Unsaturated treatment
Media
filters
Trickling filters
Media filters
A
container or lined
excavation
containing a specific
media through which
wastewater flows
Treatment occurs in
unsaturated
conditions
Designed to follow
primary treatment
Flow regimes for media filters
Single
pass
Recirculating
Single-pass media filter
NSFC
Recirculating media filter schematic
Recirculating Media Filter
Filter
Drainage
From
House
Septic Tank
Final Effluent Tank
Recirculation Tank
To Soil
Effluent Filter
Float Valve
in Tank
Dosing Pump
Effluent Pump
Typical configuration
– 36 inches of media
Methods of distribution
24
Pressure distribution - most common
• Spray nozzles
• Driplines
Gravity
Typical configuration
Increasingly, timer-controlled dosing is being used
Usually lined to collect filtrate for external dispersal
May be configured to drain into rock pad beneath
unit in certain soil/site conditions
Typical hydraulic loading
1 – 2 gal / ft2 /day
Multiple-pass filters: up to 5 gal / ft2 /day
Increased loadings may be allowed for
certain proprietary designs
Single-pass:
Dosing frequency
Single-pass
filters:
Historically - 4 times/day
Current recommendations - as high as 12-24
times/day
Multiple-pass:
12-72+ times/day
Treatment process
Wastewater
applied in small doses
Percolates over media in thin film
Organisms on media contact wastewater
Air is maintained in media pores
Oxygen is transferred into the thin film and
to organisms
Aeration typically passive
PRO CE SSE S A T W OR K
LI Q U I D W A S T E S
O R G A N IC S
A IR
M E D IA
B IO L O G IC A L
M ASS
P A T HO G E N S
E X CE SS
CE L L M A SS
E N D PR O D U C T S
B.O .D .
SS
N U TR IE N T S
Treatment occurs by:
Filtration
and trapping
Adsorption
Biological decomposition
Biochemical transformation
Nitrification
Denitrification (especially if recirculated)
Types of media
Washed, graded sand
Gravel
Foam chips and cubes
Expanded polystyrene
Peat
Synthetic textile materials
Bottom ash from coal-fired plants
Crushed glass
Other
Sand and gravel filters
Single pass or recirculating mode
Sand/Gravel media specifications
Must (generally) be processed to provide the right
gradation
Screened for proper gradation
Washed
Must be handled carefully after processing to
maintain the specification and remain free of
fines
Cutaway demo
Single pass sand filter
with pump basin
Questions?