ENVR 890/296 Microbe/Pathogen Survival/Reduction in the Environment, Excreta and Excreta Treatment ProcessesMicrobial Survival/Inactivation – A Kinetic PhenomenonMicroorganism survival periods in faeces, sludge and soilSome Physical Factors Influencing Microbe Survival in the EnvironmentTEMPERATUREpHMoisture Content – Drying and DessiccationPhysical Factors Influencing Survival, ContinuedAtmospheric and Hydrostatic PressureRole of Solids-Association in Microbial SurvivalSome Chemical Factors Influencing Microbe Survival in the EnvironmentChemicals and Nutrients Influence Microbial SurvivalSome Biological Factors Influencing Microbe Survival in the EnvironmentBiological Factors Influence Microbial SurvivalFactors Affecting Survival in LiquidFactors Affecting Survival in AerosolsFactors Affecting Survival on SurfacesMicrobe Survival in Liquid MediaSurvival in Liquid MediaSlide 20Slide 21MicrobeSurvival in Liquid MediaSlide 23Microbe (Virus) Survival in AerosolsMicrobe Survival in AerosolsMicrobes Survival in AerosolsSlide 27Slide 28Microbe Survival on SurfacesSlide 30Slide 31Slide 32Slide 33Factors Influencing Microbial Reductions by Wastewater Treatment ProcessesSlide 35Slide 36Slide 37Primary Treatment or Primary SedimentationEnteric Microbe/Pathogen Reductions in Secondary or Biological TreatmentWaste Solids (Sludge) TreatmentEnteric Microbe/Pathogen Reductions by Sludge Treatment Processes“Processes to Further Reduce Pathogens” “PFRP”: Class A SludgeAlternative Biological Treatment of Wastewater: Alternatives for Small and Rural CommunitiesFacultative Oxidation (Waste Stabilization) PondStabilization Ponds or LagoonsEnteric Microbe/Pathogen Reductions in Stabilization PondsSlide 47Constructed Wetlands and Enteric Microbe ReductionsSeptic Tank-Soil Absorption Systems for On-Site Sewage RxLog10 Reduction of Pathogens by Wastewater Rx ProcessesSlide 51REMOVAL OF ENTERIC BACTERIA BY SEWAGE TREATMENT PROCESSESEntamoeba histolytica Reduction by Sewage TreatmentMicrobial Reductions by Wastewater TreatmentDisinfection of WastewaterWhen Wastewater Disinfection is Recommended or RequiredWastewater ReuseSlide 58Estimated Pathogen Reductions by Sewage Treatment Processes: An ExampleENVR 890/296Microbe/Pathogen Survival/Reduction in the Environment, Excreta and Excreta Treatment ProcessesMark D. SobseyDept. of Environmental Sciences and EngineeringMicrobial Survival/Inactivation – A Kinetic Phenomenon•Microbe inactivation is best described by the rate(s) or kinetic of inactivation•Survival depends on reduction rate and time (duration of exposure)•Expressing survival in absolute terms based on time only such as days or weeks is misleading–Depends on initial and final microbe concentrations•Express extent of inactivation per unit of time at specified conditions of exposureConcentration →Time →100101.00.1Microorganism survival periods in faeces, sludge and soilSome Physical Factors Influencing Microbe Survival in the EnvironmentTEMPERATURE•Greater Inactivation/death rates at higher temperatures•Lower survival rates at higher temperatures–But, some microbes will grow or grow better at higher temperatures•Many microbes survive better at lower temperature–Some bacteria experience “cold injury” or“cold shock” and cold inactivation•Thermal inactivation differs between dry heat and moist heat–Dry heat is much less efficient than moist heat in inactivating microbes•Some microbes survive very long times when frozen–Other microbes are destroyed by freezing•Ice crystals impale them•Increased environmental temperatures can promotes pathogen spread by insect vectors (mosquitoes, flies, etc.)pH•Relative acidity or alkalinity•A measure of hydrogen ion (H+) concentration•Scale: –1 (most acidic) to 14 (most alkaline or basic)–pH 7 is neutral –Moving toward pH 1 the substance is more acidic–Moving toward pH 14, the substance is more alkaline.•Extreme pH inactivates microbes–Chemically alters macromolecules–Disrupts enzyme and transport functions–Some enteric pathogens survive pH 3.0 (tolerate stomach acidity)–Some pathogens survive pH 11 and fewer survive pH 12Microbes are most stable in the environment and will grow in some media (e.g., foods) in the mid pH rangeMoisture Content – Drying and Dessiccation•Drying or low moisture inactivates/kills some microbes–Survival depends on moisture content or “water activity”But, removing water content of some foods can preserve them•Most viruses rapidly inactivated in soil at <1% moisture; –Some inactivated rapidly at a few % moisture–Time for 90% reduction in days-weeks-months; depends on moisture level & temperature•Some protozoan parasites (Cryptosporidium parvum) are rapidly inactivated when dried (>90% reduction within hours at room temp.)•Some helminth ova (Entamoeba hystolytica) are very persistent dry•Bacteria persistence to drying and desiccation is highly variable–Most bacteria can survive for extended periods of time•Days to weeks for >90% reduction•Bacteria and fungi spores are very persistent when dryPhysical Factors Influencing Survival, Continued•Ultraviolet radiation: about 330 to 200 nm–Primary effects nucleic acids; absorbs the UV energy and is damaged•Sunlight:–Ultraviolet radiation in sunlight inactivates microbes–Visible light is antimicrobial to some microbes •Promotes growth of photosynthetic microbes•Ionizing radiation–X-rays, gamma rays, beta-rays, alpha rays–Generally antimicrobial; bacterial spores relatively resistant–Main target of activity is nucleic acid–Effect is proportional to the size of the “target”•Bigger targets easier to inactivate; a generalization; exceptions–Environmental activity of ionizing radiation in the biosphere is not highly antimicrobial–Ionizing radiation is used in food preservation and sterilizationAtmospheric and Hydrostatic Pressure•Most microbes survive typical atmospheric pressure•Some pathogens in the deep ocean are adapted to high pressure levels (hydrostatic pressures): barophiles–Survive less well at low atmospheric pressures–Spores and (oo)cysts survive pressure extremes•High hydrostatic pressure is being developed as a process to inactivate microbes in certain foods, such as shellfish–Several 100s of MPa of pressure for several minutes inactivates viruses and bacteria in a time- and pressure-dependent mannerRole of Solids-Association in Microbial
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