环境工程专业英语.ppt

Environment环境工程专业英语主讲人：杨卫华主讲人：杨卫华河北工程学院城建系环境教研室河北工程学院城建系环境教研室 Environment成绩评定成绩评定Quiz Quiz（1010）Performance in classPerformance in class（1010）Seminar Seminar（2020）Test Test（5050）check on work attendance check on work attendance（1010）Environment课时安排课时安排 Environment Environment Environment EnvironmentEngineering Interactions with the Environment February Engineering Interactions with the Environment February 20042004The Microbiology of Activated SludgeThe Microbiology of Activated Sludge EnvironmentWaterTreatmentWastewaterTreatmentRun-offSurface waterPotableWaterRawSewageAbstractionInfiltrationRainwaterGroundwaterMaterial Inputse.g.food&energySludgeSludgeMaterial Outputs EnvironmentIntroductionIntroductionActivated sludge can be defined as a mixture Activated sludge can be defined as a mixture of of microorganismsmicroorganisms which contact and digest which contact and digest bio-degradable materials(food)from bio-degradable materials(food)from wastewater.wastewater.Activated sludge is Activated sludge is microorganismsmicroorganisms.The Activated sludge process is a biological The Activated sludge process is a biological process.process.To properly control the activated sludge To properly control the activated sludge process,you must properly control the growth process,you must properly control the growth of of microorganismmicroorganism.This involves controlling the.This involves controlling the items which may affect those items which may affect those microorganismsmicroorganisms.EnvironmentEngineering Interactions with the Environment February Engineering Interactions with the Environment February 20042004BacteriaBacteria EnvironmentMake up about 95%of the activated sludge Make up about 95%of the activated sludge biomass.biomass.These single celled organisms grow in the These single celled organisms grow in the wastewater by consuming(eating)bio-wastewater by consuming(eating)bio-degradable materials such as proteins,degradable materials such as proteins,carbohydrates,fats and many other carbohydrates,fats and many other pounds.BacteriaBacteria EnvironmentEnzymes are compounds that are made by living Enzymes are compounds that are made by living organisms.Their purpose is to help biochemical organisms.Their purpose is to help biochemical reactions to occur.Almost all biochemical reactions reactions to occur.Almost all biochemical reactions require the presence of enzymes to cause the reaction require the presence of enzymes to cause the reaction to occur.to occur.Enzymes help bacteria in the process of breaking down Enzymes help bacteria in the process of breaking down nutrients,and in rebuilding broken down nutrients into nutrients,and in rebuilding broken down nutrients into the new compounds that they require for growth and the new compounds that they require for growth and reproduction.reproduction.Enzymes only do what they are supposed to when Enzymes only do what they are supposed to when environmental conditions are right.If the conditions are environmental conditions are right.If the conditions are not right the enzymes will not function properly,thus,not right the enzymes will not function properly,thus,the bacteria will not function properly,and they will not the bacteria will not function properly,and they will not survive.If conditions are right the bacteria will live and survive.If conditions are right the bacteria will live and prosper.prosper.The Role of EnzymesThe Role of Enzymes EnvironmentWhen there is plenty of food available,bacteria use the When there is plenty of food available,bacteria use the food mostly for growth and some for energy.food mostly for growth and some for energy.A growing bacterium have flagella(hair-like A growing bacterium have flagella(hair-like structures on the outside of the cell)which makes it structures on the outside of the cell)which makes it motile,able to move in search of food.motile,able to move in search of food.A bacterium reproduces into two bacteria.The cell A bacterium reproduces into two bacteria.The cell splits into two smaller cells and this process occurs splits into two smaller cells and this process occurs over and over again.over and over again.When there is very little food available,the bacteria When there is very little food available,the bacteria use the limited food to produce energy and to use the limited food to produce energy and to maintain the cell.Very little is available for growth maintain the cell.Very little is available for growth so less reproduction occurs.so less reproduction occurs.With little food available,and in an attempt to With little food available,and in an attempt to conserve energy,the bacterium loses it flagella and conserve energy,the bacterium loses it flagella and thus,its motility.thus,its motility.The waste products start to form a thick slime layer The waste products start to form a thick slime layer outside the cell wall,making the cells stick together.outside the cell wall,making the cells stick together.Growth CharacteristicsGrowth Characteristics EnvironmentLag-phaseLag-phase During this phase bacteria become During this phase bacteria become acclimated to their new surroundings.They are acclimated to their new surroundings.They are digesting food,developing enzymes and other digesting food,developing enzymes and other things required for growth.things required for growth.Accelerated Growth-phaseAccelerated Growth-phase The bacteria are The bacteria are growing as fast as they can,since there is an growing as fast as they can,since there is an excess of food.The cells are mostly dispersed,not excess of food.The cells are mostly dispersed,not sticking together.sticking together.Declining Growth-phaseDeclining Growth-phase Reproduction slows down Reproduction slows down because there is not an excess of food.A lot of food because there is not an excess of food.A lot of food has been eaten and there are now a large number of has been eaten and there are now a large number of bacteria to compete for remaining food,so the bacteria to compete for remaining food,so the bacteria do not have enough remaining food to keep bacteria do not have enough remaining food to keep the growth rate at a maximum.the growth rate at a maximum.Growth curve of bacteriaGrowth curve of bacteria EnvironmentStationary-phaseStationary-phase The number of bacteria is the The number of bacteria is the highest possible,but not much food is left,so the highest possible,but not much food is left,so the bacteria cannot increase in number.There is some bacteria cannot increase in number.There is some reproduction,but some cells are also dying,so the reproduction,but some cells are also dying,so the number of bacteria remain relatively constant.The number of bacteria remain relatively constant.The bacteria have now lost their flagella and have a bacteria have now lost their flagella and have a sticky substance covering the outside of the cell,sticky substance covering the outside of the cell,allowing them to agglomerate into allowing them to agglomerate into flocfloc.In fact,the.In fact,the flocfloc get big enough that if aeration and mixing were get big enough that if aeration and mixing were stopped,the stopped,the flocfloc could settle to the bottom.could settle to the bottom.Death-phaseDeath-phase The death rate increases with very The death rate increases with very little if any growth occurring.Therefore,the total little if any growth occurring.Therefore,the total number of living bacteria keeps reducing.The number of living bacteria keeps reducing.The bacteria are just trying to keep alive.bacteria are just trying to keep alive.Growth curve of bacteriaGrowth curve of bacteria EnvironmentWe measure the amount of biodegradable matter We measure the amount of biodegradable matter the bacteria use for food by measuring the amount the bacteria use for food by measuring the amount of BOD(biochemical oxygen demand)or COD of BOD(biochemical oxygen demand)or COD(chemical oxygen demand)in the influent to the(chemical oxygen demand)in the influent to the aeration basin.We estimate the weight of aeration basin.We estimate the weight of microorganismsmicroorganisms in the mixed liquor by measuring in the mixed liquor by measuring the amount of volatile suspended solids(VSS)in the the amount of volatile suspended solids(VSS)in the activated sludge.We use this information to form a activated sludge.We use this information to form a relationship called food to relationship called food to microorganismmicroorganism ratio(F/M ratio(F/M ratio).The F/M ratio tells us something about growth ratio).The F/M ratio tells us something about growth and cell condition.If the F/M ratio is high,the bugs and cell condition.If the F/M ratio is high,the bugs normally grow quite rapidly(because this means normally grow quite rapidly(because this means there is a lot of food available in comparison to the there is a lot of food available in comparison to the amount of amount of microorganismmicroorganism);if the F/M ratio is low,the);if the F/M ratio is low,the bug normally grow very slowly(because little food bug normally grow very slowly(because little food is available for growth).is available for growth).F:M(Food to Microorganism ratio)F:M(Food to Microorganism ratio)EnvironmentMicroorganismsMicroorganisms need oxygen to live.Oxygen use need oxygen to live.Oxygen use and be used to determine the activity of the and be used to determine the activity of the organisms.-Actively growing organisms are rapidly organisms.-Actively growing organisms are rapidly metabolizingmetabolizing the food,so they are use oxygen at a the food,so they are use oxygen at a rapid rate.-We measure the rate at which oxygen is rapid rate.-We measure the rate at which oxygen is used by a test called the Oxygen Uptake Rate used by a test called the Oxygen Uptake Rate(OUR),or the Respiration Rate.It is measured in mg(OUR),or the Respiration Rate.It is measured in mg O2/hr/gm of MLSS.-Normally a higher uptake rate is O2/hr/gm of MLSS.-Normally a higher uptake rate is associated with high F/M ratios and younger associated with high F/M ratios and younger sludges and a lower uptake rate is associated with sludges and a lower uptake rate is associated with lower F/M and older sludges.So,if you want a lower F/M and older sludges.So,if you want a higher uptake rate,more sludge should be wasted.higher uptake rate,more sludge should be wasted.Less should be wasted if you want a lower F/M ratio.Less should be wasted if you want a lower F/M ratio.The Use of OxygenThe Use of Oxygen EnvironmentThe Formation of The Formation of FlocFlocAs bacteria begin growing,they generally develop into As bacteria begin growing,they generally develop into small chains or clumps.They are very active and motile small chains or clumps.They are very active and motile and it is difficult for them to settle.They have not yet and it is difficult for them to settle.They have not yet developed the slime layer which aids in their sticking developed the slime layer which aids in their sticking together.So,when mixing occurs,the small chains or together.So,when mixing occurs,the small chains or clumps are broken up and the bugs are dispersed,and clumps are broken up and the bugs are dispersed,and they will not flocculate or settle.As the sludge is they will not flocculate or settle.As the sludge is allowed to age,the bugs lose their motility and allowed to age,the bugs lose their motility and accumulate more slime.Then the clumps and chains are accumulate more slime.Then the clumps and chains are better able to stick together.The clumps grow bigger better able to stick together.The clumps grow bigger and bigger until they form a and bigger until they form a flocfloc.If the organisms are.If the organisms are allowed to develop properly,under the right conditions,allowed to develop properly,under the right conditions,the the flocfloc get large and compact and begin to settle.The get large and compact and begin to settle.The mixing in the aeration tank tends to keep the mixing in the aeration tank tends to keep the flocfloc small small since,even though the bugs are sticky,the bond formed since,even though the bugs are sticky,the bond formed holding the organisms together is not very strong.This holding the organisms together is not very strong.This is good because it allows the cells,food,and oxygen to is good because it allows the cells,food,and oxygen to contact each other.contact each other.EnvironmentDissolved OxygenDissolved OxygenOxygen is required by these bugs to Oxygen is required by these bugs to metabolizemetabolize food for food for cell maintenance and growth.Although the bugs need cell maintenance and growth.Although the bugs need oxygen,some bugs can get along with less oxygen than oxygen,some bugs can get along with less oxygen than others.Each bug must have a dissolved oxygen of at others.Each bug must have a dissolved oxygen of at least from 0.1-0.3 mg/L to function properly.So,it is least from 0.1-0.3 mg/L to function properly.So,it is important to maintain about 2 mg/L of D.O.in the important to maintain about 2 mg/L of D.O.in the activated sludge so that the bacteria that are contained activated sludge so that the bacteria that are contained in the in the flocfloc can get oxygen.If the DO is less than 2 mg/L,can get oxygen.If the DO is less than 2 mg/L,the bugs on the outside of the the bugs on the outside of the flocfloc use the DO before it use the DO before it can get to the can get to the centercenter of the of the flocfloc.If this happens,the.If this happens,the bugs in the bugs in the centercenter may die causing the may die causing the flocfloc to break up.to break up.EnvironmentThe Effects of MixingThe Effects of MixingMixing is required to bring organisms,oxygen,Mixing is required to bring organisms,oxygen,and nutrients together,and to remove metabolic and nutrients together,and to remove metabolic waste products.If there is not enough mixing,waste products.If there is not enough mixing,proper treatment will not take place because of proper treatment will not take place because of lack of contact between the bugs,their food and lack of contact between the bugs,their food and oxygen.If too much mixing is provided,it can oxygen.If too much mixing is provided,it can cause break up of cause break up of flocfloc or formation of unstable or formation of unstable flocfloc particles.particles.EnvironmentThe Effects of pHThe Effects of pHThe enzymes which regulate many of the The enzymes which regulate many of the biochemical reaction in bacteria are very pH biochemical reaction in bacteria are very pH dependent.The optimum pH should be between dependent.The optimum pH should be between 7.0 and 7.5 for the proper activated sludge 7.0 and 7.5 for the proper activated sludge microorganismsmicroorganisms to dominate.to dominate.EnvironmentThe Effects of TemperatureThe Effects of TemperatureBiochemical reactions are v