WASTEWATER ENGINEERING 2

Flashcards covering microbiology of sewage, unit operation & unit process, and preliminary treatment.

What role do microbes play in sewage treatment?

Microbes play an extremely important role.

What is the expected range of bacterial counts in raw sewage, depending on sewage age and water dilution?

500,000 to 5,000,000 per mL

What are bacteria?

Single-celled plants that metabolize soluble food and reproduce by binary fission.

What is the lag phase in bacterial growth?

Adjustment phase of microorganism.

What happens during the log growth phase in bacterial growth?

Microorganism multiply since there is an ample supply of food.

What is the declining growth phase?

The point at which the food is largely depleted and food becomes the limiting factor in further growth.

What defines the stationary phase?

Food is equal to microorganism, i.e., food = microorganism.

What happens during the endogeneous phase?

The total mass of microorganisms will slowly decrease as the cells use up all their stored reserves and slowly begin to die.

What do anaerobic bacteria do?

Oxidize organic matter utilizing electron acceptors other than oxygen.

What are the products from the oxidation of organic matter from Anaerobic Bacteria?

CO2, H2O, H2S, CH4, NH3, N2, reduced organics, and more bacteria.

What do aerobic bacteria do?

Utilize free oxygen as an electron acceptor.

What are the end products of from the oxidation of organic matter from Aerobic Bacteria?

CO2, H2O, SO4-2, NO3-, NH3, and more bacteria.

What are facultative bacteria?

Can function in both aerobic and anaerobic environments.

What do Pseudomonas denitrifying bacteria do?

Reduce NO3 to N2, important in biological nitrate removal.

What role does Zooglea play?

Helps through slime production in the formation of flocs in aeration tanks.

What does Sphaerotilus natans cause?

Causes sludge bulking in the aeration tanks.

What do Acinetobacter do?

Store large amounts of phosphate under aerobic conditions and release it under anaerobic conditions, useful in phosphate removal.

What do Bdellovibrio do?

Destroy pathogens in biological treatment.

What is the function of Nitrosomonas?

Converts NH4 into NO2; chemoautotrophic bacteria, very useful in bioremediation.

What do Nitrobacter do?

Transform NO2 to NO3.

What are algae?

Photosynthetic microorganisms which can produce oxygen and organic cell mass from inorganic chemicals; play a role in oxidation ponds.

What are protozoa?

Single-celled protists which reproduce by binary fission; can be aerobic, anaerobic, or facultative; major food source is bacteria.

What are fungi?

Multicellular non-photosynthetic plants; mostly aerobic, predominate in wastes deficient in nitrogen or low in pH.

What are rotifers?

Simplest multicellular animal; feed on bacteria and small protozoa, presence indicates relative stability of treated waste.

What are crustaceans?

Microscopic organisms with a rigid shell structure; strict aerobes, feed on bacteria and algae, important food for fish.

What are bacteria?

Single-celled prokaryotes which metabolize soluble food and reproduce by binary fission; can be aerobic, anaerobic, or facultative.

What are protozoa?

Single-celled eukaryotes that show characteristics usually associated with animals; responsible for improving effluent quality.

What are algae?

Plants containing chlorophyll, convert inorganic constituents in water into organic constituents.

What are fungi?

Simple plants lacking the ability to produce energy through photosynthesis; indicated for their superior aptitudes to produce a large variety of extracellular proteins.

What are viruses?

The smallest form of microorganisms capable of causing disease; difficult to destroy by normal disinfection practices.

What do microorganisms prefer?

Enough room to move around, just sufficient food, enough nutrients, enough oxygen to breathe.

What are coliform organisms?

Rod-shaped bacteria thriving inside the intestinal tract of man, used as an indication that pathogenic organisms may also be present

What is total coliform?

All aerobic, facultative, and anaerobic gram-negative, non-spore forming, rod-shaped bacteria that ferment lactose with gas formation within 48 hours

What is the Most Probable Number (MPN) method?

Used for determining the number of Coliform organisms, based on statistical analysis.

What is the Membrane Filter Technique (MFT)?

Used for determining the number of Coliform organisms, accomplished by passing a known volume of water sample through a membrane filter.

What are the objectives of sampling?

Evaluate performance efficiency of WTP, Compliance to DENR requirements.

What is Grab Sampling?

Sample taken at random with no particular time.

What is Composite Sampling?

Mixture of grab samples taken over a period of time.

What is Continuous Sampling?

Sample represents diversion of a small fraction of the total flow over some period of time.

What is Unit operation?

The treatment or removal of contaminant is brought about by the physical or mechanical sources.

What is Unit process?

The treatment occurs predominantly due to chemical and biological reactions.

What are Physical unit operations?

Treatment methods in which the application of physical forces predominate.

What are Chemical unit processes?

Treatment methods in which the removal or conversion of contaminants is brought about by the addition of chemicals or other chemical reactions.

What are Biological unit processes?

Treatment methods in which the removal of contaminants is brought about biological activity or action of microorganisms.

What is a Flowsheet?

Is a graphical representation of a particular combination of unit operation and processes.

What is Process loading criteria?

Key criteria used as a basis for sizing the individual unit operation and processes.

What is Solid Balance?

Is determined by identifying the quantities of solids entering and leaving each unit operation or process.

what are Hydraulic profiles?

Used to identify the elevation of the free surface of the WW.

What is Plant layout?

Is the spatial arrangement of the physical facilities of the treatment plant in the flowsheet.

What does Preliminary treatment include?

Screening, Flow measurement, Solids grinding, Grit removal, Equalization.

What is Screening?

Removal of coarse and settleable solids by interception.

What are Racks or Bar Screens?

Composed of parallel bars or rods which maybe hand cleaned or mechanically cleaned.

What is a Fine Screen?

Wire/cloth mesh; perforated plate.

Why is Flow Measurement important?

Needed for efficient operation, chemical addition, etc.

What is Average Daily Flowrate (ADF)?

Average flowrate over a period of time.

What is Peak Hourly Flowrate (PHF)?

Highest flowrate measured in 24-h period.

What is Maximum Daily Flowrate (MDDF)?

Maximum daily design flow over a period of time.

What is Turndown ratio?

The ratio of the highest operating flow rate to the lowest operating flow.

What are common Flow measuring devices?

Venturi meter, Parshall flumes, Weir (i.e. V-notch), Magnetic & Sonic meters

What is Solids grinding or comminution?

Grinding of coarse solids to a more or less uniform size.

What are Comminutors?

Devices that used to cut up the solids in wastewater.

What is a Barminutor?

Combination of a bar screen and a comminutor.

What is a Grit Chamber?

Enlarged channel where the velocity of wastewater flow is controlled to allow only the heavier solids to settle out.

What are the variation types of Grit Chamber?

Horizontal-flow grit chamber, Aerated grit chamber, Circular or Vortex type.

What is an Equalization basin?

Maintains a constant volumetric flow of wastewater from pretreatment to other downstream operation; dampens hydraulic or flowrate variations.

What are the objectives of Equalization?

Smooth out fluctuations in flow rate, Dampens the variation in the concentration of BOD5, and TSS, Decrease fluctuations in flow rate, to provide more consistent treatment