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CDARF OABDF (eventos realizados (seminario 759, seminario residuos,…
CDARF OABDF
eventos realizados
seminario 759
seminario residuos
seminario agua
seminario energia
energia
solar
apoio, suporte, instalacao, sugestao de projeto
aeolica
hidro
agronegocio
tamanho
pequeno produtor
tipo
organico
tradicional
floresta
participacoes realizadas
fernando / conam
luciana df MP 759
Ambiental Fernando
: :
Agronegocio Leo
água luciana RJ
Link Title
))
Cibele
conam
luciana regularizacao
ronald
rodrigo
fundiaria
rural
condominios
urbana
condominios
residuos
slu, waste to energy
Waste Management
How can we dispose of waste material?
landfills
designed to reduce pollution
distance away from the water table
layers
cover the top
become
park
playground
golf course
no perfect method
cut back on wastes
buy products
not heavily packed
composting
reuse
waste - to - energy plants
convert the heat
from the incinerators
to steam
waste as energy
recycle and reuse
glass
paper
aluminum
plastics
waste collection
hazardous wastes
medical supplies
cleaning solutions
old batteries
thrown out
in a special way
reuse
solid
non-hazardous waste
usually collected
by trucks
food
decomposes
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contain
compactors
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carried out
municipal
city
level
system
collecting
disposing of waste
refuse
What happens after collection?
to make
smaller
lighter
easy to handle
composting
organic waste
decompose
become
fertilizer
soil
incineration / burning
common treatment
burn
reduce
volume of waste
more than 90%
leaving
ash
glass
metal
saneamento
Waste Water Treatment
Pre Treatment
Discharge Management
Preliminary Treatment
Flow Equalisation
Use statistical data to size tanks - 30-50 year design horizon on the basis of Dry Weather Flow (DWF)
Upstream pumps automatically spill >6DWF
Spill when full
Store >3DWF - 6DWF for 2 hours in storm tanks
Flow to full of 3DWF
Improves the efficiency of the wastewater treatment plant
Waste water flows not constant
In-line
Off-line
Treatment plant operates better at steady-state
Grit Removal
Types
Vortex Flow
Tangential inlet promotes circular flow.
Airlift pump removes the grit from the grit sump
Outlet is wider than the inlet causing a lower exit velocity than the influent velocity. This prevents the grit being drawn into the effluent flow
Effluent exits at the top of the tank
Grit settles by gravity into the bottom of the tank
Wastewater enters the chamber tangentially
Horizontal Flow
Velocity controlled channel
Dimensions of the channel - shape
Special influent distribution gates
Special weir sections at the influent end
Designed to allow sufficient retention time for particles to settle
Aerated
Uses centrifugal forces
Uses diffusers to promote spiral path
Increases path length - increases retention time
Quantity of air is adjusted to provide the roll
Heavier particles settle to the bottom
Wastewater flows through the chamber in a spiral pattern
Air is introduced along one side of the chamber
Lighter organic particles remain suspended and are carried out of the tank
Reduce the formation of deposits in channels, tanks and pipelines
Protect downstream mechanical equipment from abrasion and wear
Grit (sand, gravel, broken glass, egg shell etc.) has a settling velocity substantially greater than the organic material in wastewater
Reduce the frequency of digester cleaning that is required due to accumulated grit
Bar Racks and Screens
Removes large objects
Can be mechanical or passive
Classification based on purpose
Types
Micro-screens
Fine Screens
Very Fine Screens
Bar Racks/ Coarse Screens
Trash Racks
Coarse Solids Reduction
More difficult to deal with untreatable wastes in tiny pieces
Don't produce screenings
Use a mechanical device to shred or grind the solids and return them to the flow
Alternative to bar racks and screens
Types
Grinders
Pulverise the solids by a high-speed rotating assembly
Comminutors
Uses a stationary horizontal screen to intercept the solids in the flow and a rotating or oscillating cutting bar to shear the material
Macerators
Slow-speed grinders that use two sets of counter-rotating blade assemblies
Functions
Improvement of the performance of subsequent units
Removal of untreatable solid materials
Protection of subsequent treatment units
Tertiary Treatment
Carbon adsorption
Granular activated carbon is used in a fixed bed or moving bed column (wastewater typically being applied from the bottom of the column and the regenerated carbon from the top)
Powdered activated carbon is directly applied to the effluent of a biological treatment process or to the aeration tank
Removed by adsorbing them on powdered or granulated activated carbon
Remove soluble organic matter that is resistant to biological breakdown (refractory organics)
Membrane filtration
Biofouling is a problem - overcome by chlorination and/or chloramination of feed water
Low pressure microfiltration and ultrafiltration are generally used
Membrane bioreactor activated sludge process, no clarifiers
Separation achieved by selectively passing one or more components through a membrane while retarding the passage of one or more other components
Granular filtration
Disadvantages
Development of cracks and contraction of filter bed
Buildup of emulsified grease - increases head loss
Turbidity buildup - controlled by adding chemicals or polymers
Mudball (agglomerations of biological floc, dirt and the filter media) formation - reduces effectiveness of filtration and backwashing
Loss of filtering medium during backwash
Need to be backwashed regularly to prevent particle buildup
Typically, granular filters can reduce TSS from 10 mg/L to less than 2 mg/L and total phosphorus from 1 mg/L to less than 0.1 mg/L
Effluent travels through the filter by gravity
Filters containing fine and coarse particles or granules which adsorb pollutants
Particles can include sands, gravels, anthracite , polymeric resin fillers, Ilemnite, activated carbon etc.
Design characteristics
Specific gravity
Medium gradation
Pore or grain size
Shape
Solubility of materials used
Hardness
Depth
Disinfection
Chemical precipitation
Disadvantages
Polymers can be expensive
Large amounts of chemicals may need to be transported to the (potentially remote) treatment location
Addition of treatment chemicals, especially lime may increase the volume of waste sludge by up to 50%
Requires working with corrosive chemicals, increasing operator safety concens
Overdosing can diminish the effectiveness of the
treatment.
Competing reactions, varying levels of alkalinity and
other factors make calculation of proper chemical
dosages impossible.
Advantages
Completely enclosed systems, self-operating and low maintenance
Well-established technology with readily available chemicals
Phosphorus in wastewater promotes eutrophication
Removed by precipitation using chemicals
Ferric Chloride
Aluminium sulphate
Lime
Lime use is reducing due to increase in sludge production, pH control requirements, and operation and maintenance problems with storage, handling and feeding of lime
Improves the quality (polishing) of wastewater discharged to the environment
Primary Treatment
Sedimentation Basins
Circular
Sludge Removal
Travelling bridge
Scrapper plows the settled sludge progressively into a centrally located sludge hopper
Straight multiblade scrapper
Most common
Flow splitting
Flow is split between multiple sedimentation units so that hydraulic load and the solids load are in proportion to the design limits of the tanks
A flow splitter (weirs and notches) is used to split the flow equally
Scum removal
Rotating skimmer arm and wiper attached to the scraper mechanism
Scum is pushed over the beach plate by the wipers, and then into the scum outlet piping
Outlet Configuration
Centre Feed
Double Weir Troughs
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Submerged Orificies
V-notch Weirs
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Peripheral Feed
Inlet Configuration
Centre Feed
Velocity through the orifices of the well 0.075-0.15 m/s
Diameter of feed well 10-15% tank diameter
Most common
Wastewater is introduced to the center of the tank through a center riser into a circular feed well
Depth of feed well 1-2.5m
Peripheral Feed
Diameter
Controlled by overflow rate
Range from 3-90m diameter (12-45m typical)
Depth
Should be deep enough to accommodate sludge removal equipment, store settled solids (when desludging intermittently), avoid scour, and avoid carryover of solids in the effluent
Range from 3-5m
Main form of primary treatment
Wastewater flow is slowed down and suspended solids settle to the bottom by gravity in sedimentation
Need multiple primary tanks - maintenance/cleaning
If using chemical dosing, need dosing arrangements, coagulation and flocculation before sedimentation tank
Rectangular
Common in large-scale water treatment plants
Inlet Configuration
Inlet Structures are designed to distribute water over the entire cross-section
Stilling Wall
Prevents incoming water jetting into the tank which reduces retention time
Channel or Flume
When rectangular tanks are constructed side-by-side, water is distributed by a single channel that runs perpendicular to the flow through the tank
Width 3-24m
Length 30-60m
Floor slopes towards the sludge hopper
If numerous tanks are required, rectangular tanks with common walls are constructed
Scum removal
Returning chain-and-flight scraper at the surface of the tank (for chain-and-flight sludge removal system
A surface scraper and a scum pipe (for travelling bridge sludge removal system)
Depth 4m typical
Too deep - inefficient
Too shallow - no room for sludge collecters or settlement
Sludge Removal
Chain and flight
Combined scum and sludge removal
Travelling Bridge
Travels back and forth along the tank
Outlet Configuration
Water leaving the sedimentation basin should be collected uniformly across the width of the basin
Consists of launders running parallel to the length of the tank
V-notch weirs are attached to the launders
Physical process
Removes scum (fats, oils, grease) and inert particulate matter (remaining grit)
Removes a significant fraction of organic particulate matter (suspended solids) - reduces BOD5
Lowers oxygen demand, decreases energy consumption rate and reduces operational problems with downstream biological treatment processes
Enhanced Sedimentation
May remove too much phosphorus
Makes primary effluent nutrient deficient
May help achieve phosphorus consent
Hamper secondary biological treatment which requires nutrients
Increases removal of BOD
Increases primary tank capacity by allowing higher overflow rate - higher flow rate same performance/same flow rate higher performance
Addition of chemicals to enhance sedimentation - alum or ferric chloride are added in conjunction with anionic polymers
Increased sludge quantities from coagulants and additional suspended solids collected
Chemical handling facility required - storage, mixing delivery
Fine Screens
Used in place of sedimentation if high removal efficiencies are not required
0.25-1.5mm openings typical
Removal efficiency
5-45% for suspended solids
5-50% for BOD5
Tube and Plate Settlers
Solids settle to the plate and slide down the surface to the bottom of the tank
Inclined plates and tubes are generally used
Influent introduced under the plates or tubes flows to the bottom of the tank
Increase the capacity of existing tanks by increasing settling area
Can retrofit plate packs
Angle of approx 60
Difficult to clean - may need retrofitted modifications to sludge/scum removal
Secondary Treatment
A reactor is used to grow biomass on incoming substrate to remove BOD before discharge to the receiving environment
Provides further removal of suspended solids
Oxidises readily degradable BOD that escapes primary treatment
Often involves treatment of nitrogen and phosphorus
Suspended Growth
Micro-organisms are maintained in suspension by mixing using aeration or mechanical agitation
Micro-organisms are suspended in the fluid
Oxidation Ponds
Aerated Ponds
Suspended solids and organic colloidal materials (BOD) settles to the bottom to form a sludge layer that undergoes anaerobic decomposition
Mechanical diffused aerators provide oxygen and allow for a greater proportion of organic material to remain suspended
Facultative Ponds
BOD reduction by aerobic bacteria at the pond surface and by anaerobic bacteria at the bottom
The soluble BOD is aerobically stabilised and suspended and colloidal BOD tend to settle and is decomposed by anaerobic bacteria
BOD reduction 70-85%
1-2m deep
Anaerobic Ponds
Anaerobic bacteria break down the organic matter, releasing methane and carbon dioxide, which can collected as a fuel (biogas). Sludge is deposited on the bottom.
Deep ponds (2-5m) that receive high organic loadings - has a smaller footprint because don't need to worry about DO
O2 consumption rate much higher than O2 production rates which creates anaerobic conditions
Typical BOD reduction efficiency is of the order of 50-70%
Aerobic Ponds
Organic water degradation mainly through the action of aerobic bacteria
DO is maintained by algal photosynthesis
Shallow ponds less than 1m depth - DO decreases with depth
Light penetrates to the bottom maintaining algal photosynthesis during daytime and UV disinfection
Surface re-aeration by wind mixing
Activated Sludge Process
Micro-organisms are mixed thoroughly with the organic compounds present in wastewater
90-99% removal of viruses (mostly through solids settling, but also bacterial antiviral products and predation)
80-99% removal of bacteria (sunlight, temperature, aggressive micro-organisms, predation by ciliated protozoans, competition from other bacteria, adsorption to sludge solids)
BOD removal is approximately 85%
Conventional Activated Sludge
Aerator
Keeps microbes in suspension
Long, rectangular basin
Aerated for 6-8 hours
Settling Tank
Liquid-solids separation, produces sludge
Recycle System
A portion of the sludge is wasted everyday to maintain the proper amount of microbes to efficiently oxidise the biodegradable organics
Step aeration activated Sludge
Contact Stabilisation
Extended Aeration
Complete Mix Activated Sludge
Oxidation Ditch
Nutrient Removal
Growth Kinetics
Food to micro-organism ratio F/M describes the degree of starvation of the biomass
F/M > 1 log (max) rate of growth of biomass, large sludge volume generated but smaller reactor volume required
Endogenous growth: F/M <<1, amount of food availability limits the biomass growth rate , smaller sludge generation but larger reactor volume required
As the micro-organisms grow and are mixed by the agitation of air, the individual organisms flocculate to form an active mass of microbes called activated sludge
Attached Growth
Wastewater components and oxygen diffuse into the biofilm
End products diffuse out of biofilm into bulk water
Flow from the attached growth process may be passed through a sedimentation basin (humus tank)
Utilise films of micro-organisms attached to inert carrier to treat wastewater
Micro-organisms form a film on a bed,disk, or other support material (plastic materials, stones) over which wastewater is applied
Types
Trickling Filter
Advantages
Low power requirements
Low biosolids load
Simple operation
Resistant to shock loads
Disadvantages
High suspended solids in effluent (sloughing of biofilm)
Very little operational control
Relatively low BOD removal (85%)
Types
Standard or low rate trickling filter
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High rate trickling filter
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Rotating Biological Contactor
Microbes in wastewater adhere to the rotating surfaces and form a biofilm
Consists of closely spaced discs (lightweight, 3-3.5m diameter), mounted on a horizontal shaft
The discs are rotated while about 1/2 of their surface area is immersed in wastewater
Oxygen is supplied to the attached biofilm by the air while the air is out of the liquid
As the biofilm passes through the wastewater they absorb organic compounds for oxidation
Discs
Aerate the wastewater and the suspended microbial growth in the reservoir
Provide media for the buildup of attached microbial growth
Bring the biofilm into contact with the wastewater
Simple operation, short retention time due to large active surface, low power, minimal odour and low sludge production
Performance Factors
Hydraulic loading rate
Number of stages
Organic loading rate
Recirculation rate
Submergence
Rotational speeds
Oxygen levels
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