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ODOR MANAGEMENT

Downloaded from CivilDigital.com. ODOR MANAGEMENT. BY:- dinesh. Contents:. Downloaded from CivilDigital.com. 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 .

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ODOR MANAGEMENT

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  1. Downloaded from CivilDigital.com ODOR MANAGEMENT BY:- dinesh

  2. Contents: Downloaded from CivilDigital.com • 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

  3. Why do we need odor management?? Downloaded from CivilDigital.com • 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.

  4. Types of odors Downloaded from CivilDigital.com • Most of odorous compound typically contain either sulfur or nitrogen • Rotten egg smell of hydrogen sulfide is the odor encountered most commonly

  5. Source of odor Downloaded from CivilDigital.com 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.

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  7. 2- Waste water treatment facilities: Downloaded from CivilDigital.com • 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

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  9. 3-sludge and Biosolids handling facilities: Downloaded from CivilDigital.com • 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

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  11. Movement of odors Downloaded from CivilDigital.com • 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

  12. Strategies for Odor Management Downloaded from CivilDigital.com • 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

  13. Control of discharge to W.W. collection system Downloaded from CivilDigital.com • 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

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  15. Odor control in wastewater collection system Downloaded from CivilDigital.com • 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

  16. Odor control in wastewater treatment facilities Downloaded from CivilDigital.com • 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

  17. Downloaded from CivilDigital.com 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

  18. Odor containment & treatment measures Downloaded from CivilDigital.com • Installation of collection hoods and air handling equipment for directing the gases to treatment units • Typical containments alternatives are reported in the table

  19. Chemical additions to W.W. for Odor control Downloaded from CivilDigital.com • 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 (-).

  20. Use of odor Masking and Neutralization Downloaded from CivilDigital.com • 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.

  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.

  22. ODOR TREATMENT METHODS Downloaded from CivilDigital.com • 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

  23. Chemical scrubbers Downloaded from CivilDigital.com • 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.

  24. Simplified scrubbing reactions: With sodium hypochlorite H2S + 4NaOCl + 2NaOH ---- Na2SO4 + 2H2O + 4NaCl H2S + NaOCl ---- S + NaCl + H2O With potassium permanganate 3H2S + 2KMnO4 ---- 3S + 2KOH + 2MnO2 + 2H2O 3H2S + 8KMnO4 ---- 3K2SO4 + 2KOH+ 8MnO2 + 2H2O With hydrogen peroxide H2S + H2O2 ------- S + 2H2O pH<8.5

  25. Downloaded from CivilDigital.com • Reaction products that can occur, depending on the local waste water chemistry , include elemental sulfur, sulfate thionates, dithionates, and manganese sulfide. • Potassium permanganate is generally used in smaller units as it is expensive. • Hypochlorite scrubbers are expected to remove oxidizable odorous gases when other gases concentration is minimal. • In case where the concentration of odorous components in the exhaust gas from the scrubber are above desired levels, multistage scrubbers are often used.

  26. Effectiveness of hypochlorite wet scrubbers for removal of several odorous gases Downloaded from CivilDigital.com

  27. Design consideration for chemical scrubbers Downloaded from CivilDigital.com

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  29. Activated Carbon Adsorbers Downloaded from CivilDigital.com • Rate of adsorption for different constituents or compounds will depend on the nature of the constituents (polar Vs. Non polar) • Removal of odors also depends on the concentration of the hydrocarbons in the odorous gas, as hydrocarbons are removed preferentially before polar compounds. • As carbon beds are limited and needs to be regenerated thereby for prolonged life it is used in two stages followed by wet scrubber • For effective use of activated carbon the composition of odorous gases to be removed must be known.

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  31. Vapor phase biological treatment Downloaded from CivilDigital.com • Two principal biological processes used for treatment of odorous gases present in the vapor phase are Bio filters Conventional biological processes

  32. Bio filters Downloaded from CivilDigital.com • As the odorous gases move through the packing in the biofilter, two processes occur simultaneously a) sorption (absorption/ adsorption) b) bio-conversion • Odorous gases are absorbed into the moist surface of biofilm layer and the surface of bio filter packing material • Than microorganisms, principally bacteria, actinomycetes and fungi oxidize the absorbed gases and renew the treatment capacity of the packing material.

  33. Downloaded from CivilDigital.com • Moisture content and temperature are important environmental conditions and must be maintained to optimize micro-organism activity • Drawback being is they require large surface area to operate

  34. Design considerations for odor-control Bio-filters Downloaded from CivilDigital.com • The type and composition of the packing material sufficient porosity and near uniform particle size particle with large surface areas ability to support large micro-flora population • Facilities for gas distribution perforated pipes prefabricated under drain system • Maintenance of moisture within the bio-filter • Temperature control

  35. Conventional biological treatment processes Downloaded from CivilDigital.com • The ability of micro-organism to oxidize hydrogen sulfide and other similar odorous compounds dissolved in the liquid under aerobic conditions is the basic concept • In the activated sludge process, the odorous compounds are introduced into the aeration basin • But a major concern with this method is high rate of corrosion in air piping and blowers that occurs due to presence of moist air containing hydrogen sulfide

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  37. Thermal processing Downloaded from CivilDigital.com • Three thermal processing techniques are in use: a) Thermal oxidation b) Catalytic oxidation c) Recuperative and Regenerative thermal oxidation

  38. Downloaded from CivilDigital.com • If the gas to be combusted does not liberate enough heat to sustain the combustion process, it is usually necessary to use an external fuel source. • As because most of the waste streams have low concentration of odorous combustible gases hence sustainable thermal oxidation is seldom possible • To maintain the combustion temperatures needed to eliminate odors, large amounts of fuel is required

  39. Downloaded from CivilDigital.com • Thermal oxidation involves preheating the odorous gases before passing them into the combustion chamber so that complete oxidation can be achieved • Catalytic oxidation is a flameless oxidation process that occurs in presence of catalyst (palladium, platinum, rubidium etc.) Decrease in temperature reduces the energy requirements significantly. As the catalyst can become fouled, the gases to be oxidized must not contain particulate matter or constituents that will result in residue

  40. Downloaded from CivilDigital.com • Recuperative and Regenerative thermal oxidation processes are used to reduce fuel consumption by preheating the incoming air. In recuperative oxidizers, thin wall tubes are used to transfer heat recovered from exhaust air to incoming air In regenerative oxidizers, ceramic packing material is used to capture the heat from the hot exhaust gases and release it to the incoming air.

  41. Selection and design of odor-control facilities Downloaded from CivilDigital.com • Determine the characteristic and volumes of the gas to be treated • Define the exhaust requirements for the treated gas • Evaluate climatic and atmospheric conditions • Select one or more odor control and treatment technology • Economic analysis

  42. References Downloaded from CivilDigital.com • Metcalf and Eddy • www.wikipedia.com • www.wateronline.com • www.omi-idustries.com • www.thomasnet.com

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