Wastewater Treatment Technology - michigan.gov · Circular “upflow” clarifier Suspended solids...
Transcript of Wastewater Treatment Technology - michigan.gov · Circular “upflow” clarifier Suspended solids...
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April 23, 2015 Webinar
Wastewater Treatment Technology
Presented by
Brian Jankowski, P.E.Environmental Engineer
DEQ – Water Resources DivisionCadillac District Office
E mail: [email protected] 231-429-0982
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Wastewater Treatment Technology
Goal and objectives1. Familiarity with basic wastewater treatment2. Identify some advantages/disadvantages3. Recognize the need for qualified
professionals for the selection, design, and operation of treatment processes
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Wastewater - definition
Definition in DEQ’s Michigan Manufacturer’s Guide - Chapter on Wastewater:
– “Wastewater is liquid waste that results from industrial and commercial processes and municipal operations…”
– Also includes:• Sanitary sewage • Storm water in certain cases
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Waste Characterization• What’s in the wastewater ? (identify
pollutants)
• What needs to be removed from the wastewater (and to what extent) ?
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Waste CharacterizationPollutant Examples • Biochemical Oxygen Demand (BOD) • Chemical Oxygen Demand (COD)• Solids (suspended or dissolved)• Oils/Grease• Temperature• Phosphorous & Nitrogen Compounds• pH• Metals• Other elements or compounds
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Metals:� Iron, Lead, Mercury, Chromium, Copper etc…
Other chemical elements/compounds:�Arsenic, cyanide ….�Chlorine compounds, Chlorides, Chlorinated
solvents� (BTEX) benzene, toluene, ethylbenzene, and
xylene
Waste Characterization “examples”
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Definitions “Organics”
• Organic compound: large class of chemical compounds whose molecules contain carbon
• Organic matter: plant or animal, “organisms”
Waste Characterization
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Wastewater Treatment• Basic process categories
Some processes may consist of more than one type; combination of Physical, Chemical and/or Biological
Physical
Chemical
Biological
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“Rearrangement & Residuals ”• Rearrangement : Pollutants are only physically
separated, and/or chemically rearranged…
• Residuals: Treatment often results in a “residual”, a solid substance (commonly known as “sludge”) that contains the target pollutants
Sludges typically need additional treatment &/or disposal (not covered in this presentation)
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Physical Processes
– Clarification/Settling – Air flotation – Filtration (incl. activated carbon,
membrane filters/bioreactors and reverse osmosis)
– Oil/water separation– Cooling
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Clarification/Settling “sedimentation”
Circular settling tank
Rectangular settling tank
Commonly referred to as “clarifiers”
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Clarification/Settling
Settled particlesIncoming Wastewater
Settlingvelocity
vs.
Overflow velocity
Circular “ upflow” clarifier
Suspended solids settle downward
Water flow is up
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Clarification/Settling
Wastewater flow
Also a matter of settling velocity
versus overflow velocity
Suspended solids settle downward
Sludge removal
Rectangular, horizontal flow clarifier
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Clarification/Settling
• Three types of sedimentation
• Settling can be enhanced by addition of certain chemicals (coagulants) and by addition of ballast
• Baffles, typical
• Inclined plates, option
discrete
flocculating
zone
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Clarification/Settling
Notable issues/concerns
• Will only address “settleable” solids
• Impaired settling & “bulking sludge”
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Physical Processes
– Clarification/Settling – Air flotation– Filtration – Oil/water separation– Cooling
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Dissolved Air Flotation (DAF)
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Dissolved Air Flotation (DAF)
AIR
Pressure tank
Skim off surface solids
“settled SLUDGE”
Wastewater
Suspended neutrally buoyant
particle
Rising air bubble
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Dissolved Air Flotation (DAF)
• Typical application in industry: refineries, chemical/petrochemical plants, paper products, food processing, and natural gas processing plants
• Typically requires addition of certain chemical “flocculating” aids or “coagulants” (mixed in waste stream ahead of DAF unit)
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DAF Example, with recycle
Dissolved Air Flotation (DAF)
CHEMICAL MIX TANK
FLOTATION TANK
AIR
AIRTANK Recycle
pump
Effluent
water
Influent water
Chemical addition
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Dissolved Air Flotation (DAF) Benefits Lighter particles removedFaster particle removal More rapid startup Thicker sludge's
Issues/concerns Significant mechanical equipmentMore complex/more maintenance Higher-energy consumption
Compared to standard clarifier type settling
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Physical Processes
– Clarification/Settling – Air flotation – Filtration – Oil/water separation– Cooling
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Filtration
FILTER MEDIA
“Permeate or filtrate”
porous medium separates solids from liquid
“retentate” or “filtrand”
Larger particles retained on upstream side of media
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FiltrationSize of particle removed dependent on “pore” size of mediaLog scale, in microns
micron = one thousandth of a millimeter
0.001
0.01
0.1
1.0
1,00010
100
PARTICLE FILTRATION
MICRO FILTRATION
HYPER FILTR.(R/O)
NANO FILTR.
ULTRA FILTRATION
Virus Beach sand
Pollen Atomic radius
Bacteria
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Filtration• Filter Media
– “Screens”– Sand– Diamataceous earth– Granular/multi- media– Activated carbon – Membrane– Fabric
• Filter rates– Rapid infiltration – Slow infiltration
• Filter types –Gravity–Pressure–Centrifugal force–Vacuum
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Filters: “Screens” or “bar racks”
fine through coarse screening options available
Could be called“macro” filtration, it is used for removal of larger items, rags, garbage, and debris (etc)
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• Filter Media– “Sand” or – Granular/multi-
media
Anthracite Coal, Intermediate Sand, High Density Sand, High Density Support GravelSilica Sand or GravelGarnet“Others”
Filter Media
Influent wastewater
Backwash trough (typical).
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Filtration, rapid-gravity type
Backwash valve (closed)
Filter media
Under drains
Accumulatedsolids
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FiltrationIssues and concerns
• Subject to routine plugging & bio-fouling, so influent water characteristics are critical
• Require frequent cleaning or “backwashing”
• Cleaning & operation are typically mechanized & dependent on automated and/or computer controls
• Secondary cleaning methods, chemicals or air scour
• Periodic replacement of filter media
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Filtration
Pressure type “Fabric” type
Gravity flow through submerged cloth filter disk
Filter media in pressure vessel
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Filtration: Activated carbon filter media
Granular Activated Carbon (GAC)
Granular Activated Carbon particle
Magnified GAC particle surface
uses “adsorption ” - a type of attractive force between molecules
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Filtration: Membrane biological reactors (MBR)
• Combine biological treatment with a membrane liquid-solid separation process
• Low pressure micro-filtration or ultra-filtration • Uses synthetic membranes • Can be immersed in an aeration tank
Benefits:• Eliminates need for clarification & “tertiary” filtration• Needs small land area, small “footprint”Issues/concerns• Higher building & operating costs than conventional
wastewater treatment• Highly dependent on computer control technology
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Membrane bio-reactors
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FiltrationMembrane biological reactors (MBR)
Hollow tube type, cassette
Flat plate type, cassette
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Filtration : Reverse osmosis (RO)
• A filter separation process using pressure to force a solution through a semi-permeable membrane
• RO process requires high pressure be exerted on the membrane
• Process is best known for removing salt from water
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Reverse Osmosis “detail”
R/O tube detail: Perforated
central tube
Permeate
Brine Seal
concentrate
Feed channel spacer
Membrane
R/O “sorts” at the molecular level
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Reverse OsmosisBenefits• Removes wide range of pollutants
Issues/concerns • Pretreatment . Feed water needs pretreatment to
remove particulates, influent turbidity• Scaling, fouling, and degradation of membranes • Ineffective in removal of some lighter, low molecular
weight volatile organics (such as THM's, TCE, vinyl chloride, carbon tetrachloride).
• Disposal of reject water
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Physical Processes
– Clarification/Settling – Air flotation – Filtration – Oil/water separation– Cooling
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Oil/water separatorsGravity separation device
Oil droplets rise (density and size dependent).
Design based on differences in specific gravity between oil and water.
Standardized Criteria by the American Petroleum Institute (API)
OIL
WATER
Settleable solids
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Oil/water separators “simplified example”
Influent Effluent
OIL
Solids
Baf
fle
Baf
fle
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BAFFLE
Sludge hopper
BAFFLE
EFFLUENT TRANSFER
PIPES
SCREEN COALESCER
PARALLEL PLATE
COALESCER
INLET
Oil/water separators “Additional Features”
“COALESCERS” often added to enhance separation
OUTLET
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Oil/water separatorsCommon limitationsBoth emulsified and dissolved oils cannot be removed in physical oil/water separators
Emulsions: fine oil droplets which cannot be separated from water physically because of other chemicals in the water, such as soap.
Routine maintenance! Solids and oils must be removed & properly disposed. This must occur frequently or pollutants will pass through.
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Oil/water separatorRelatively simple to operate…
…but the effluent water must often be sent on for further treatment (dissolved air flotation unit for example) to remove any residual oil, followed by biological treatment unit for removal of dissolved compounds
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Physical Processes
– Clarification/Settling – Air flotation – Filtration– Oil/water separation– Cooling
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Cooling•Many industries generate heat in their processes and often need cooling water systems
•If need to discharge to natural waters or public sewer system may be required to cool that water first
NON CONTACT COOLING WATER is water used for cooling which does not come into direct contact with any raw material, product, byproduct, or waste
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CoolingLiquid to liquid heat exchanger
• Multiple, passes
• Pipes or plates
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• Evaporative cooling systems include – cooling towers, – evaporative condensers– spray ponds– cooling ponds.
• Reduce temperature of wastewater by transfer of heat from the wastewater to another fluid or to the atmosphere
Cooling
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Counter flow Counter flow with fill
Double flow crossover
Fill media, sample
Mechanical - induced draft cooling towers
Single flow crossover
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Cooling: issues/considerationsPonds
– Large land area required– Algae/bacteria growth
Towers – Power and maintenance requirements – Impurities in process water can cause scale,
corrosion, and fouling– Water Treatment Additives (WTAs)
• May be needed to address scale, corrosion, and fouling
• May complicate suitability for discharge; WTAs require special approvals from DEQ.
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Chemical Processes
– Air Stripping – Precipitation – Ion exchange– Chemical neutralization – Disinfection
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Air stripping• Air stripping is the transfer of volatile components
of a liquid into an air stream.
• Volatile compounds with certain properties can be economically stripped from water.– Includes BTEX compounds and certain solvents – Ammonia can also be removed by air strippers,
typically enhanced by adjustment of pH & temperature of the waste stream
• Air strippers are usually towers– “Packed” or “tray” towers of packing media
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Air stripper
PUMP
Water
Air
Air blower
Wastewater
Treated water
Sprayers
Packing material
Gas & air collection &/or exhaust
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Air StrippingPacked towers– Engineered or
random plastic packings
Low profile unit
tray
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Air StrippingBenefits • Simple. Generally easily built, operated, &
maintained
Issues/concerns• Noise, very loud• Cannot remove metals, PCBs, or other chemicals
that do not evaporate• Air stripping transfers pollutants to the air
– the air exiting the stripper may require emissions control and air quality permits
• Fouling, deposits of minerals, solids, biological films
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Air StrippersTypical plastic media for packed tower
Fouled media
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Chemical Processes
– Air Stripping – Precipitation – Ion exchange– Chemical neutralization – Disinfection
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Chemical Precipitation• For removal of:
– metals, other inorganic, suspended solids, fats, oils, greases, and some other organic substances from wastewater
• Dissolved or suspended contaminants in a solution settle out of the solution as a solid precipitate
• Precipitate is then separated from the liquid by clarifiers, filters or centrifuging etc.
• Assisted through the use of coagulants and polymers
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• Coagulants– Cause smaller particles suspended in
solution to gather into larger aggregates
• Polymers – Contain electrically charged molecules
which allow the polymers to act as connecters between particles suspended in solution, or to neutralize particles in solution
Chemical precipitation
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Common uses• Water softening• Heavy metal removal (metal plating wastes)• Oil & grease removal from emulsified
solutions• Phosphate removal from wash-waters and
other wastewater
Chemical precipitation
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Example reaction mechanism for a divalent metal
M++ + 2NaOH M(OH) + 2Na++
Note:• Metal precipitation, solubility is pH dependent,
need to optimize pH for each metal
Chemical precipitationConverts metals to an insoluble hydroxide(the hydroxides of most metals are insoluble)
Precipitates
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Chemical Precipitation, typical design
INFLUENT
pump
Chemical controller
Treatment chemical
MIXER
sensor
Chemical precipitation tank
EFFLUENT to CLARIFIER
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Chemical precipitationBenefits• Well-established technology, readily available• Some systems can be self-operating with low
maintenanceIssues/concerns• Competing reactions, pH, alkalinity, temperature,
mixing effects, and other factors can make precipitation delicate and frustrating
• Some chemicals are hazardous and corrosive, • Transport / handling / storage of large amounts
of chemicals may needed
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Chemical Processes
– Air Stripping – Precipitation – Ion exchange– Chemical neutralization – Disinfection
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Ion Exchange
• Used to remove heavy metals from low–concentration waste streams
Ion: an atom or molecule that has lost or gained one or more valance electrons, making it positively or negatively charged
• Pass wastewater through a bed of resin • Resin has groups of ionic charge on its
surface
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Ion Exchange
RESINBED
Distributor
Wastewater influent
Treated effluent
Regenerant Solution
Used regenerant
Process steps• Treatment• Backwash• Regeneration• Rinse
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Sodium (Na) is initially attached to resin
Ion Exchange Example
RESIN with
negative charge
Na+
Na+Na+
Na+
Na+
Na+Na+ Na+
Ca++
Ca++
Ca++
Ca++
Ca++
Ca++
Na+Ca++
Exchange process “releases” sodium and “catches” the calcium (Ca)
Ca++
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Ion ExchangeBenefits • Metal contaminants
can be recovered and reused
• Selective, may be designed to remove certain metals only
Issues/concerns • Resins may be fouled
by some organic substances, oils, & polymers.
• Wash water disposal
Sample resin beads
Bead material has a structure of pores on the surface which accommodate easily trapped and released ions
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Chemical Processes
– Air Stripping – Precipitation – Ion exchange– Chemical neutralization– Disinfection
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• Eliminate either high or low pH values
– to meet discharge limits
– or prior to other treatment processes that require pH adjustment
• Add acids, such as sulfuric or hydrochloric acid, to reduce pH
• Add alkalies, such as sodium hydroxides, to raise pH values
• Typically performed in a holding tank, rapid mix tank, or an equalization tank
Chemical Neutralization
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Chemical Neutralization
ACID Chemical Neutralization Tank
CAUSTIC
INFLUENT
P
P
Neutralized effluent
wastewater
pH monitor & control
MIXER
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Chemical Neutralization
ACIDSSulfuric Acid (H2SO4)Carbonic Acid (H2CO3)Hydrochloric Acid (HCl)Phosphoric Acid (H3PO4)Nitric Acid (HNO3)
BASES Caustic (NaOH)Calcium Hydroxide (CaOH2)Calcium Carbonate (CaCO3)-Lime
Ammonium Hydroxide (NH4OH)
• Control pH between 6.5 and 9 in order to meet typical discharge limitations
• Relatively simple, but typically involves handling hazardous chemicals
Typical chemicals
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Chemical Processes
– Air Stripping – Precipitation – Ion exchange– Chemical neutralization– Disinfection
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Disinfection
Common methods
• Chlorine
• Ultraviolet light
• Ozone
Reduce or eliminate the number of microorganisms in the water to be discharged back into the environment
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Chlorination: Uses gas or liquid chemical storage & feed, mixing, and a chamber for contact and detention
Ultraviolet (UV) light: Pass the water near lamps in a channel or pipe
Ozone (O3): Generated on-site by passing oxygen (O2) through a high voltage, ozone gas then fed to a detention/contact basin
Disinfection
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• Chlorine has a residual, a positive if there is a need to minimize microbial growth in a downstream pipeline etc.
• UV, no chemicals
• Ozone, can add dissolved oxygen to effluent as a positive, secondary effect
Disinfection
Benefits
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Disinfection Concerns/issues
UV disinfection:Frequent lamp maintenance and replacement needs
Needs highly treated effluent so target organisms are not shielded from the (UV)radiation
Ozone disinfectionHigh cost of the ozone generation/equipment and requires highly skilled operators
The off-gases, if any, from the contact chamber must be treated to destroy any remaining ozone before release to the atmosphere
All of the noted disinfection types have safety issues
Chlorination:•Chlorination of residual organic material can generate some harmful, carcinogenic by-products
•Chemical dechlorination required for discharge to environment
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Biological Processes
• Applies to waste waters containing organic pollutants
• Some oils can also be treated biologically
• Biological treatment systems use microbes to consume organics
Common background & definitions
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Biological Processes
• Aerobic microbes require oxygen (O2 ) to grow
• Anaerobic microbes will grow only in the absence of O2
• Facultative microbes can grow with or without O2
Aeration is the process by which air (or oxygen) is added to, dissolved in, circulated and/or mixed in wastewater
Common background & definitions
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Additional definitions or concepts for biological processes…………..
Aerobic - uses “free” oxygen(dissolved, molecular)
Anoxic – nitrate (NO3) available, but not free oxygen
Anaerobic - no free oxygen available
Aerobic means free oxygen is (used/available) in the reactor
Anoxic condition means there is no free oxygen but nitrite/nitrate is present in the reactor
Anaerobic process is a generic term for biological processes that occur in the absence of oxygen
“Simplified definitions” In the “wastewater business”
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Respiration (very simplified)
Cellular “Respiration” – “Redox” type chemical reaction
(Oxidation/ Reduction)
– Involves electron transfer and therefore….needs and electron accepter and electron donor
In aerobic respiration the e- accepter is molecular oxygen
e−
organics + O 2➡➡➡➡CO2 +H2O+ energy
molecule, atom, or ion
e−Reduction
Oxidation
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“Anaerobic” respiration
“facultative anaerobe” bacteria can respire anaerobically using another electron acceptor instead…such as Nitrates
Strict “Anaerobes” (Obligate anaerobes)
– die in presence of oxygen
– utilize e- acceptors other than oxygen gas
Examples: sulfate nitrate, sulphur...
O2 preferred e- acceptor, but ….if O2 not available (i.e.…anaerobic conditions)
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“Anaerobic” activity/respiration
In anaerobic environments in wastewater, • Multiple stages of biological processes involved
– Organisms still obtain “energy” from breaking down organics
– Produce methane, carbon dioxide, and water, hydrogen sulfide, etc.
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• Nitrification biological oxidation of nitrogen from ammonia to nitrate
– 2 step aerobic process1. ammonia to nitrite - NO2
2. nitrite to nitrate - NO3
Each step performed by a different type of bacteria.
nitrification can be followed by…
Nitrification/denitrification
The reduction of nitrate to nitrogen gas
– Denitrification requires anoxic conditions …or the bacteria will not use the nitrates
And more definitions or concepts for biological processes…………..
Denitrification
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Biological Processes
These organisms:• Use organic compounds or matter as food
and/or energy
• Degrade (break down) these materials in metabolic processes
• Produce carbon dioxide, water and other “smaller” compounds as a result of metabolic processes
The microorganisms used are commonly referred to as the “bugs”
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Biological Processes– Lagoons/Stabilization Ponds
• Facultative• Aerated • Anaerobic
– Suspended growth• Activated Sludge• Sequencing batch reactors (SBRs)• Oxidation ditch
– Attached growth• Trickling Filters • RBCs
– Anaerobic digestion
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Lagoons/Stabilization Ponds
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Lagoons/Stabilization Ponds
Aerobic zone
Facultative zone
Anaerobic zone (bottom sludge)
Wind provides surface mixing and aeration
Sun provides energy to algae
Bacteria & algae in the pond consume organics and modify chemical byproducts
Facultative type
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Lagoons/Stabilization Ponds
Aerobic type, mechanically aerated :
Add air to increase biological activity, & extend the aerobic zone
Surface aerator
Bacteria + O2 = BOD reduction & nitrogenous compound conversion
Organic carbon is oxidized & sulfur compounds are converted also.
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Lagoons/Stabilization PondsAnaerobic type: Anaerobic “bugs” convert organic materials into stable products such as carbon dioxide & methane in a 2 phase process:
DE
EP
ER
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• Simple treatment systems, but the biology and biochemistry involved are very complex
• Different types of lagoons often combinedto achieve the best treatment
• Operated at ambient temperature, only function well in mild or warm climates
Lagoons/Stabilization Ponds“general comments”
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Issues and Concerns common to all lagoon types
• Removal of settled sludge's & grit
• Sludge reduction limited in cold climates
• Emergent vegetation, insects & burrowing animals
• Need for composite liners (expensive)
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Biological Processes– Lagoons/Stabilization Ponds
• Facultative• Aerated • Anaerobic
– Suspended growth• Activated Sludge• Sequencing batch reactors (SBRs)• Oxidation ditch
– Attached growth• Trickling Filters • RBCs
– Anaerobic digestion
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Conventional biological treatment
Suspended growth Attached growth
Two main categories
A media is immersed in wastewater, or wastewater poured over media. Microbes attached to media
Microbes mixed and suspended in wastewater
Enlarged “microbe”
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Suspended growth Biological processes
Suspended growth process variations: • Activated sludge, • Oxidation ditches• Sequencing batch reactors (SBRs)
Speed up the work of aerobic bacteria & other organisms by providing a highly aerobic environment to increase their efficiency
Removes or breaks down bio-degradable organic material & converts organic nitrogen-compounds
Air is added to the water, provides oxygen to the suspended microbial growth
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Activated sludge (typical)
Influence process/performance by control of: • sludge recycle vs. waste• micro-organisms’ residence time, • sludge density
Aeration tank Clarifier
Waste sludge
Return sludge
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Activated sludge
AERATION TANK SURFACE
AIR DIFFUSER HEADS
AIR DISTRIBUTION SYSTEM
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“aerators”
Coarser Finer BubblesSize
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Activated sludgeBenefits • Treatment units are
relatively small, requiring less space than attached growth processes
• Good process control features and options
• Process is generallyfree of odors
• Process flexibility, has many variants
Issues/concerns• Can be costly to
operate compared to attached growth units, higher energy use for aeration system
• Process can be impacted by elevated levels of toxic compounds in the wastewater
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Sequencing batch reactors (SBR) or sequential batch reactors
• Reactor tanks for treating wastewater “in batches”
• Typically, minimum of 2 identically equipped tanks
• One tank is in settle/decant mode while other is aerating and filling.
• 5 stages in the SBR treatment process:
1.Fill2.React3.Settle4.Decant5.Idle
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Aeration: can beon or off
Sequencing batch reactors (SBR) basic operation
Fill the tank
EFFLUENT
INFLUENT
2. REACT
3. SETTLE
4. DECANT
5. IDLE
1. FILL
Aeration on(Mixers/blowers on) Aerobic process“Reaction stage”
Aeration off
Clarification stage,(Gravity separation)
Aeration off
Aeration: can beon or off…depends
on how long idle time is or other factors
Withdraw the clear fluid
Waste excess sludge if needed, during idle
NO MORE INFLUENT
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SBR Fill and draw processBatch operation
treating
spare
Spare reactor , in case one unit is down, as a minimum of two is required to maintain continuity of service
While a tank is in “treatment mode” it no longer t akes in any influent flow, so that influent is directed to another tank (fill mod e). Tanks rotate/switch between treatment and fill modes.
fillingOPEN
CLOSED
CLOSED
Equalization, aeration, and clarification in a time d sequence in a single reactor basin.
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Oxidation ditch
Influent
Return sludge
Sludge pumping
Secondary settling
tank
Effluent
Rotors (aeration brushes)tors
Waste Sludge
Oxidation ditch
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Oxidation ditch
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Oxidation ditch
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Biological Processes
– Lagoons/Stabilization Ponds• Facultative• Aerated • Anaerobic
– Suspended growth• Activated Sludge• Sequencing batch reactors (SBRs)• Oxidation ditch
– Attached growth• Trickling Filters • RBCs
– Anaerobic digestion
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Attached growthMicrobial growth is on the surface of media, a “film” of microbes
Media: typically made of plastic or stone
Attached Growth biological processes
Bio film“slime”
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Attached Growth biological processesAttached growth variations: • Trickling filters or towers• Rotating biological contactors (RBCs)
TRICKLING FILTER
RBC
The media is rotated in and out of the wastewater to provide oxygen
Wastewater passes over/through the media along with air to provide oxygen
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Trickling filter or tower
CLARIFIER
MEDIA
P
EFFLUENTRecycle options
Influent
Rotating distributor
Air venthole
s
Wastewater passes over media of rock, plastic spheres or blocks, or interlockingsheets of corrugated plastic
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Attached growth: RBC conventional process
“conventional” version - no recycle
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Attached growth: RBC
Air is provided by rotation of disk out of the water
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Attached growth
Benefits
• Efficient at nitrification
• Low power requirements
Issues/concerns • Additional treatment
often needed
• Accumulation of excess biomass can impair performance
• Flexibility & control are limited (compared to activated -sludge processes)
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Biological Processes
• Aerobic, anaerobic, or anoxic conditions can also be achieved in some bio-processes
• These conditions:cultivate micro-organisms that perform functions such as nitrification or denitrification
• These conditions are achieved by …
changing the treatment sequences and/or operating schemes of many of the aforementioned biological processes
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Biological Processescommon issues and concerns
Supplemental nutrients or carbon may be needed in order for the process to work properly if the waste stream is deficient in carbon or nutrients
Inconsistent waste type and loading can reduce effectiveness (of some types more than others)
Toxics can kill the biomass
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Biological Processes
– Lagoons/Stabilization Ponds• Facultative• Aerated • Anaerobic
– Suspended growth• Activated Sludge• Sequencing batch reactors (SBRs)• Oxidation ditch
– Attached growth• Trickling Filters • RBCs
– Anaerobic digestion
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Anaerobic DigestionUsed for stabilizing sludge's and industrial wastes
Digested sludge
Digesting sludge
Supernatant
Gas
INLE
TS OUTLET
Anaerobic bacteria produce methane & carbon dioxide, reducing high strength organic waste
Gas removal and use
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Anaerobic DigestionTwo Stage “High Rate” Version
GAS
ADD HEAT & MIX
STRATIFY
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Anaerobic DigestionBenefits• Low energy required compared
to aerobic versions
• Less biological sludge produced
• End product can be saleable or useable products such as biogas (methane production), soil conditioners, and fertilizer
• Suitable for high-strength industrial wastes
MIXER, in tank
GAS FLARE
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Anaerobic Digestion
Issues/concerns• Longer start-up time to develop
necessary biomass inventory • May require further treatment
with an aerobic treatment process
• Reaction rates are sensitive to lower temperatures; heating used to achieve adequate reaction rates
• Increased potential for production of odors and hazardous and corrosive gases.
Egg shaped type digester
Conventional digester design
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Likely need more than one process typically a
“Treatment train” …process examples:Carbon FILTER
Softener
RO
Resin I.E.
EQ
Neut. Precip. Coag. Floc.
CLARIFIER
Sludge holding & filter press
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Design Process, Selection of technologies
– Use a qualified consultant– Consult with DEQ staff– Consider capital & operation costs– Consider complexity of testing & reporting
requirements – Consider complexity of operation, and the
qualifications needed for operators– Operator training requirements
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Operator TrainingIndustrial/Commercial Wastewater Treatment Plant Operator Certification
Go to www.michigan.gov/deq for information
Click on “WATER” and then “Operator Training and Certification”
Certification is offered in a variety of classifications, each relating to a unit process
RULES AND REGULATIONS:Part 31 of Act 451, Industrial Rules for Industrial Wastewater Operator Certification
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Other info and resources• DEQ’s “Michigan Manufacturer’s Guide…”
contains a discussion of Wastewater Treatment Technology
• The Michigan Fruit and Vegetable Processor's Guide to Environmental Regulations, Chapter 3, Wastewater contains a detailed discussion of Wastewater Treatment Technology
It would likely be useful for sectors that manage wastewater with similar pollutants and can be found online at: www.michigan.gov/deq, more specific website location details provided in your handout
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The end
Thank you !