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1、环境工程专业英语,主讲人：杨卫华 河北工程学院城建系环境教研室,成绩评定,Quiz （10） Performance in class（10） Seminar （20） Test （50） check on work attendance （10）,课时安排,Engineering Interactions with the Environment February 2004,The Microbiology of Activated Sludge,Water Treatment,Wastewater Treatment,Run-off,Surface water,Potable Water,
2、Raw Sewage,Abstraction,Infiltration,Rainwater,Groundwater,Material Inputs e.g food & energy,Sludge,Sludge,Material Outputs,Introduction,Activated sludge can be defined as “a mixture of microorganisms which contact and digest bio-degradable materials (food) from wastewater.“ Activated sludge is micro
3、organisms. The Activated sludge process is a biological process. To properly control the activated sludge process, you must properly control the growth of microorganism. This involves controlling the items which may affect those microorganisms.,Engineering Interactions with the Environment February
4、2004,Bacteria,Make up about 95% of the activated sludge biomass. These single celled organisms grow in the wastewater by consuming (eating) bio-degradable materials such as proteins, carbohydrates, fats and many other compounds.,Bacteria,Enzymes are compounds that are made by living organisms. Their
5、 purpose is to help biochemical reactions to occur. Almost all biochemical reactions require the presence of enzymes to cause the reaction to occur. Enzymes help bacteria in the process of breaking down nutrients, and in rebuilding broken down nutrients into the new compounds that they require for g
6、rowth and reproduction. Enzymes only do what they are supposed to when environmental conditions are right. If the conditions are not right the enzymes will not function properly, thus, the bacteria will not function properly, and they will not survive. If conditions are right the bacteria will live
7、and prosper.,The Role of Enzymes,When there is plenty of food available, bacteria use the food mostly for growth and some for energy. A growing bacterium have flagella (hair-like structures on the outside of the cell) which makes it motile, able to move in search of food. A bacterium reproduces into
8、 two bacteria. The cell splits into two smaller cells and this process occurs over and over again. When there is very little food available, the bacteria use the limited food to produce energy and to maintain the cell. Very little is available for growth so less reproduction occurs. With little food
9、 available, and in an attempt to conserve energy, the bacterium loses it flagella and thus, its motility. The waste products start to form a thick slime layer outside the cell wall, making the cells stick together.,Growth Characteristics,Lag-phase During this phase bacteria become acclimated to thei
10、r new surroundings. They are digesting food, developing enzymes and other things required for growth. Accelerated Growth-phase The bacteria are growing as fast as they can, since there is an excess of food. The cells are mostly dispersed, not sticking together. Declining Growth-phase Reproduction sl
11、ows down because there is not an excess of food. A lot of food has been eaten and there are now a large number of bacteria to compete for remaining food, so the bacteria do not have enough remaining food to keep the growth rate at a maximum.,Growth curve of bacteria,Stationary-phase The number of ba
12、cteria is the highest possible, but not much food is left, so the bacteria cannot increase in number. There is some reproduction, but some cells are also dying, so the number of bacteria remain relatively constant. The bacteria have now lost their flagella and have a sticky substance covering the ou
13、tside of the cell, allowing them to agglomerate into floc. In fact, the floc get big enough that if aeration and mixing were stopped, the floc could settle to the bottom. Death-phase The death rate increases with very little if any growth occurring. Therefore, the total number of living bacteria kee
14、ps reducing. The bacteria are just trying to keep alive.,Growth curve of bacteria,We measure the amount of biodegradable matter the bacteria use for food by measuring the amount of BOD (biochemical oxygen demand) or COD (chemical oxygen demand) in the influent to the aeration basin. We estimate the
15、weight of microorganisms in the mixed liquor by measuring the amount of volatile suspended solids (VSS) in the activated sludge. We use this information to form a relationship called food to microorganism ratio (F/M ratio). The F/M ratio tells us something about growth and cell condition. If the F/M
16、 ratio is high, the bugs normally grow quite rapidly (because this means there is a lot of “food“ available in comparison to the amount of microorganism); if the F/M ratio is low, the bug normally grow very slowly (because little food is available for growth).,F:M (Food to Microorganism ratio),Microorganisms need oxygen to live. Oxygen use and be used to determine the activity of the organisms. - Actively growing organisms are rapidly metabolizing the food, so they are use ox
