BY:- dinesh Downloaded from CivilDigital.com. Contents: Why do we need this Types of odors Source of...
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ODOR MANAGEMENT BY:- dinesh Downloaded from CivilDigita l.com
BY:- dinesh Downloaded from CivilDigital.com. Contents: Why do we need this Types of odors Source of odors Movement of odorous gases Strategies for odor
Contents: Why do we need this Types of odors Source of odors
Movement of odorous gases Strategies for odor control Odor control
method Design of odor-control facilities Downloaded from
CivilDigital.com
Slide 3
Why do we need odor management?? The potential release of odors
is a major concern of public acceptance. For homo-sapiens odor is
primarily related to the psychological stress the odor cause.
Higher concentration of odorous gases can be lethal. Projects have
been rejected & some waste water agencies have been subjected
to fines and other legal action over odor violation. Downloaded
from CivilDigital.com
Slide 4
Types of odors Most of odorous compound typically contain
either sulfur or nitrogen Rotten egg smell of hydrogen sulfide is
the odor encountered most commonly ODOROUS COMPOUNDODOR THRESHOLD
ppm CHARACTERISTIC ODOR Ammonia46.8Pungent, irritating Methyl
Amine21.0Putrid, fishy Chlorine0.314Pungent, suffocating Hydrogen
sulfide0.00047Rotten egg Downloaded from CivilDigital.com
Slide 5
Source of odor 1- Waste water collection system: The biological
conversion, under anaerobic condition of O.M. containing nitrogen
& sulfur Discharge of industrial W.W. that may contain odorous
compounds Odorous gases released to the sewer atmosphere can
accumulate & be released at air release valves, cleanouts,
manholes, house vents. Downloaded from CivilDigital.com
Slide 6
LocationSource/ causeOdor potential Air release
valvesAccumulation of odorous gases released from waste water High
CleanoutsAccumulation of odorous gases released from waste water
High Access ports (man holes) Accumulation of odorous gases
released from waste water High Industrial waste water discharges
Odorous compounds may be discharged to water Variable Downloaded
from CivilDigital.com
Slide 7
2- Waste water treatment facilities: Head works &
preliminary treatment operations have the highest potential for
release of odor Side stream discharge including return flows from
filter backwashing and from sludge processing facilities are often
major source of odor Downloaded from CivilDigital.com
Slide 8
LocationSources / causesOdor potential HeadworksRelease odorous
gases generated in waste water collection system due to turbulence
in hydraulic channel and transfer points High Screening facilities
Putrescible matter removed by screeningHigh PreaerationRelease of
odorous compounds generated in waste water High Grit removalOrganic
matter removed with gritHigh Side stream returns Return flows from
bio solids processing facilities High Primary clarifiersFloating
sludge, scum, turbulence in effluent weir that release odor
Moderate Aeration basinHigh organic loading, poor mixing,
inadequate DO, solids deposit Low/moderate Secondry
clarifierFloating solids, excessive solid retentionLow/ moderate
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Slide 9
3 - sludge and Biosolids handling facilities : Typically the
most significant source of odor in a TP are sludge thickening,
anaerobic digesters and sludge load-out facilities. Shearing of
solids in mixing by dewatering causes odor release Proteinaceous
biopolymer are major mechanism once released Trimethylamine above 9
pH is a gas a can be released in air Downloaded from
CivilDigital.com
Slide 10
LocationSource/ causeOdor potential ThickenersOdor release by
turbulence, solids deposits, temperature increase High/moderate
Aerobic digestion Incomplete mixing in reactorLow/ moderate
Anaerobic digestion High sulfate contents in solids, leaking
hydrogen sulfide gas Moderate/ high Sludge storage basin Lack of
mixing, formation of scum layerModerate/ high Sludge loadout
facilities Release of odor during the transfer of bio solids High
Alkaline stabilization Ammonia generation resulting from reaction
with lime moderate Downloaded from CivilDigital.com
Slide 11
Movement of odors Odorous gases hover over the point of
generation They may be measured at great distances from point of
generation In the evening or early morning hours a cloud of odor
develop over the treatment plant unit, and then transport(even 25
km) known as puff movement Puff movement of odors developed by
Wilson(1975). To reduce the effects we install barriers to induce
turbulence and/or use wind generators Downloaded from
CivilDigital.com
Slide 12
Strategies for Odor Management Control of odor causing W.W.
discharge to collection system Odor control in W.W. Collection and
treatment Installation of Odor Containment and Treatment measures
Chemical additions to W.W. for Odor control Use of odor Masking and
Neutralization Use of Turbulence-inducing Structures and Facilities
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Slide 13
Control of discharge to W.W. collection system Requiring
pretreatment of industrial wastewater Providing flow equalization
at the source to eliminate slug discharge of wastewater Adoption of
more stringent waste discharge ordinance and enforcement their
requirements Downloaded from CivilDigital.com
Slide 14
Slide 15
Odor control in wastewater collection system Maintaining
aerobic conditions by adding hydrogen peroxide, pure oxygen or air
Controlling anaerobic microbial growth by disinfection or PH
control Oxidizing odorous compounds by chemical addition Design of
W.W. collection system for mass turbulence Off-gas treatment at
selected locations Downloaded from CivilDigital.com
Slide 16
Odor control in wastewater treatment facilities Design details
to be considered to minimize release of odor at treatment plants:
Use of submerged inlets & weirs, elimination of hydraulic
jumps, elimination of physical conditions leading to formation of
turbulence, off-gas treatment etc. Addition of chemicals such as:
chlorine, hydrogen peroxide, lime or ozone Downloaded from
CivilDigital.com
Slide 17
Design and operational changes include: Minimization of free
fall turbulence by controlling water levels Reduction of
overloading of plant processes Increasing the aeration rate
Reducing solids inventory and sludge backlog Increasing the
frequency of pumping of sludge & scum Adding chlorinated
dilution water to sludge thickeners Increasing the frequency of
disposal of grit and screenings Cleaning odorous accumulations more
frequently Containment, ventilation, and treatment of odorous gases
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Slide 18
Odor containment & treatment measures Installation of
collection hoods and air handling equipment for directing the gases
to treatment units Typical containments alternatives are reported
in the table Facility (source)Suggested control strategy Wastewater
sewersSeal existing access ports. Eliminate the use of structure
that create turbulence Bar racksCover existing units Grit
chamberCover the aerated grit chamber and in conventional type
reduce turbulance Primary and secondary sedimentation tanksCover
existing units, replace overflow weirs with submerged weirs Sludge
thickenerCover existing units Transfer channelsUse enclosed
transfer channels Downloaded from CivilDigital.com
Slide 19
Odors can be eliminated in liquid phase by adding chemicals to
achievet 1) chemical oxidation 2) chemical precipition 3)pH control
NaOCl, H2O2, KMnO4, O3 will oxidize H2S and other odorous
compounds. Ferrous chloride and ferrous sulfate can also be used
for odor control by precipitation of sulfide ion as ferrous
sulfide. By increasing the pH value of W.W. it results in decreased
bacterial activity and also shifts the equilibrium so that sulfide
ion is present as HS (-). Chemical additions to W.W. for Odor
control Downloaded from CivilDigital.com
Slide 20
Use of odor Masking and Neutralization Sometimes, chemicals are
used to mask an offensive odor with a less offensive odor. Masking
chemicals are compounds having most common aromas. Neutralization
involves finding chemicals compounds which can be combined with the
odorous gases in vapour state so that combined gases cancel each
other`s odor and resulting in a gas with low odor intensity Masking
and neutralization are short term management techniques. Downloaded
from CivilDigital.com
Slide 21
Use of Turbulence-inducing Structures and Facilities Physical
facilities are used to induce atmospheric turbulence to reduce gas
phase odor turbulence. Odorous gases that develop under quiescent
conditions over the lagoons are diluted as they move away from the
storage lagoons, due to local turbulence induced by the
barriers.
Slide 22
ODOR TREATMENT METHODS Treatments are used either to treat the
odor producing compounds in the waste water or to treat the foul
air. SOME PRINCIPAL METHODS:- Chemical scrubbers Activated carbon
absorbers Vapour phase biological treatment Thermal process
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Slide 23
Chemical scrubbers Design objective is to provide enough
contact between air, water and chemicals to enable oxidation and
entrainment of odorous compounds. Most commonly used scrubbing
liquids are sodium hypochlorite, potassium permanganate and
hydrogen peroxide solutions. Sodium hydroxide is also used in
scrubbers where H2S concentration is high in gas phase. Downloaded
from CivilDigital.com