ODOR MANAGEMENT

ODOR MANAGEMENTBY:-dineshDownloaded from CivilDigital.comContents:Why do we need thisTypes of odors Source of odorsMovement of odorous gasesStrategies for odor controlOdor control method Design of odor-control facilities

Downloaded from CivilDigital.comWhy 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.comTypes of odorsMost of odorous compound typically contain either sulfur or nitrogenRotten egg smell of hydrogen sulfide is the odor encountered most commonly

ODOROUS COMPOUNDODOR THRESHOLD ppmCHARACTERISTIC ODOR

Ammonia46.8Pungent, irritating

Methyl Amine 21.0 Putrid, fishy

Chlorine 0.314 Pungent, suffocating

Hydrogen sulfide 0.00047 Rotten egg

Downloaded from CivilDigital.comSource of odor1- Waste water collection system:The biological conversion, under anaerobic condition of O.M. containing nitrogen & sulfurDischarge of industrial W.W. that may contain odorous compoundsOdorous gases released to the sewer atmosphere can accumulate & be released at air release valves, cleanouts, manholes, house vents.Downloaded from CivilDigital.comLocation Source/ causeOdor potentialAir release valvesAccumulation of odorous gases released from waste waterHighCleanoutsAccumulation of odorous gases released from waste water

HighAccess ports (man holes)Accumulation of odorous gases released from waste water

HighIndustrial waste water dischargesOdorous compounds may be discharged to waterVariable

Downloaded from CivilDigital.com2- 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.comLocationSources / causes Odor potentialHeadworks Release odorous gases generated in waste water collection system due to turbulence in hydraulic channel and transfer pointsHighScreening facilitiesPutrescible matter removed by screeningHighPreaerationRelease of odorous compounds generated in waste waterHighGrit removalOrganic matter removed with gritHighSide stream returnsReturn flows from bio solids processing facilitiesHighPrimary clarifiersFloating sludge, scum, turbulence in effluent weir that release odorModerateAeration basinHigh organic loading, poor mixing, inadequate DO, solids depositLow/moderateSecondry clarifierFloating solids, excessive solid retentionLow/ moderateDownloaded from CivilDigital.com3-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 releaseProteinaceous biopolymer are major mechanism once releasedTrimethylamine above 9 pH is a gas a can be released in air Downloaded from CivilDigital.comLocation Source/ causeOdor potentialThickenersOdor release by turbulence, solids deposits, temperature increaseHigh/moderateAerobic digestionIncomplete mixing in reactorLow/ moderateAnaerobic digestionHigh sulfate contents in solids, leaking hydrogen sulfide gasModerate/ highSludge storage basinLack of mixing, formation of scum layerModerate/ highSludge loadout facilitiesRelease of odor during the transfer of bio solidsHighAlkaline stabilizationAmmonia generation resulting from reaction with limemoderateDownloaded from CivilDigital.comMovement of odors Odorous gases hover over the point of generation They may be measured at great distances from point of generationIn 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 movementPuff 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.comStrategies for Odor ManagementControl of odor causing W.W. discharge to collection systemOdor control in W.W. Collection and treatmentInstallation of Odor Containment and Treatment measuresChemical additions to W.W. for Odor controlUse of odor Masking and NeutralizationUse of Turbulence-inducing Structures and Facilities

Downloaded from CivilDigital.comControl of discharge to W.W. collection system

Requiring pretreatment of industrial wastewaterProviding flow equalization at the source to eliminate slug discharge of wastewaterAdoption of more stringent waste discharge ordinance and enforcement their requirements

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Downloaded from CivilDigital.comOdor control in wastewater collection system

Maintaining aerobic conditions by adding hydrogen peroxide, pure oxygen or airControlling anaerobic microbial growth by disinfection or PH controlOxidizing odorous compounds by chemical additionDesign of W.W. collection system for mass turbulenceOff-gas treatment at selected locationsDownloaded from CivilDigital.comOdor 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

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Design and operational changes include:Minimization of free fall turbulence by controlling water levelsReduction of overloading of plant processesIncreasing the aeration rate Reducing solids inventory and sludge backlogIncreasing the frequency of pumping of sludge & scumAdding chlorinated dilution water to sludge thickenersIncreasing the frequency of disposal of grit and screeningsCleaning odorous accumulations more frequentlyContainment, ventilation, and treatment of odorous gasesDownloaded from CivilDigital.comOdor containment & treatment measuresInstallation of collection hoods and air handling equipment for directing the gases to treatment unitsTypical containments alternatives are reported in the table Facility (source)Suggested control strategyWastewater sewersSeal existing access ports. Eliminate the use of structure that create turbulenceBar racks Cover existing unitsGrit chamberCover the aerated grit chamber and in conventional type reduce turbulancePrimary and secondary sedimentation tanksCover existing units, replace overflow weirs with submerged weirsSludge thickenerCover existing unitsTransfer channels Use enclosed transfer channelsDownloaded from CivilDigital.comOdors can be eliminated in liquid phase by adding chemicals to achievet 1) chemical oxidation 2) chemical precipition 3)pH controlNaOCl, 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 controlDownloaded from CivilDigital.com19Use of odor Masking and NeutralizationSometimes, 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 intensityMasking and neutralization are short term management techniques.Downloaded from CivilDigital.comUse of Turbulence-inducing Structures and FacilitiesPhysical 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.ODOR TREATMENT METHODSTreatments are used either to treat the odor producing compounds in the waste water or to treat the foul air.SOME PRINCIPAL METHODS:-Chemical scrubbersActivated carbon absorbersVapour phase biological treatmentThermal processDownloaded from CivilDigital.comChemical scrubbersDesign 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.comSimplified scrubbing reactions:With sodium hypochloriteH2S + 4NaOCl + 2NaOH ---- Na2SO4 + 2H2O + 4NaClH2S + NaOCl ---- S + NaCl + H2O

With potassium permanganate3H2S + 2KMnO4 ---- 3S + 2KOH + 2MnO2 + 2H2O3H2S + 8KMnO4 ---- 3K2SO4 + 2KOH+ 8MnO2 + 2H2O

With hydrogen peroxideH2S + H2O2 ------- S + 2H2OpH