Biology Of Secondary Treatment Flashcards
What is a trickling filter?
Process in which the wastewater trickles over media that provide the opportunity for the formation of slimes of biomass which contain organisms that feed upon and remove waste from the water being treated
Trickling Filter BOD removal (%)
70-85%
What is a Rotating Biological Contactor (RBC)?
Synthetic discs mounted on a shaft providing the opportunity for the formation of slimes of biomass that feed upon and remove waste from the water in which they turn
What is activated sludge?
A mass of particles produced in raw or settled wastewater by the growth of active bacterial organisms in an aerated tank. Each particle consists of organic materal covered with bacteria and protozoa
What is the activated sludge process?
Biological treatment in which a mixture of wastewater and microorganisms is mixed and aerated. The activated sludge is then separated from the treated wastewater by sedimentation and wasted or returned as needed
Activated sludge process BOD removal (%)
90-99%
What three groups can organic material be classified into?
Soluble; dissolved in water
Colloidal; very small particles that dont dissolve or flocculate
Particulate; large particles that can flocculate
What are the two ways to remove organic material?
Partial oxidation occuring within a microorganism
Settling of flocculated sludge; microorganisms, particulate material, and colloidal material are bound together
Describe the layers of the biomass pyramid from youngest to oldest
- Kingdom Monera
- kingdom protists protozoa
- rotifiers
- worms and crustaceans
Kingdom Monera
Bacteria - single celled organisms that breakdown organic material to grow, reproduce, and store energy. They form the basis of all biological treatment
Kingdom Protists Protozoa
Large single celled organisms that feed on bacteria or large suspended matter
Amoeboids - slow moving (young)
Flagellated - very active free swimmers (young sludge)
Free swimming ciliates (old sludge)
Stalked ciliates (old sludge)
Rotifiers
Multicellular; strictly aerobic and sensitive to toxic material; dominant in stable, older sludge
Worms and crustaceans
Play no significant role in the secondary treatment process, and they appear in old sludge
When are amoeboids dominant?
Only when large amounts of organic material are present such as during start up or after toxic shock
When are flagellates dominant?
Under conditions of high organic material availability and the presence of few bacteria
When are ciliates dominant?
In low organic material conditions with the presence of many bacteria
Ratio of C:N:P:Fe needed for bacterial nutrition
100:5:1:0.5
Three physical shapes of Bacteria
Spherical - desirable floc formers
Cylindrical - less desireable
Filamentous - help form stable floc in low numbers, but hinder settling in high numbers
Absorption
Moving soluble organic material into the cell
Adsorption
Capturing particulate matter on the pollysaccharide slime layer on the exterior of the cell where it can be dissolved then absorbed
Cryophilic microorganisms
< 15 degrees C; require higher numbers or higher detention time to assimilate the same amount of food
Mesophilic range for microorganisms
15-35 degrees C; about 20 degrees is optimal
Thermophilic range for microorganisms
35-70 degrees C; requires less detent time but more oxygen input; produces class A biosolids
What will effluent look like at peak development of flagellated protozoans?
Cloudy; high in BOD and TSS
What will effluent look like at peak development of bacterial and free swimming ciliate populations?
Clear; low in BOD and TSS
What will effluent look like at peak development of stalked ciliate and rotifer populations?
High in TSS - dead cells
How is the age of microorganisms represented in a trickling filter?
Typically higher food:mass ratio at the top of the media and the outside of the slime layer resulting in younger organisms with lower food:mass ratio deeper in the media and slime layer resulting in older organisms
How is the age of microorganisms represented in a rotating biological contactor?
High food:mass ratio & young conditions at influent end
Low food:mass ratio & old conditions at effluent end
Similar from outside to inside of slime layer
Advantages of microscopic exam of process
Quick, early detection, and a way to understand “normal” for your specific process
Saprophytes
Independent living creatures that feed on organic matter
Parasites
Live off other organisms; pathogens originate in this manner; coliforms indicate possibility of pathogens
How much oxygen is required to fully oxidize one part of ammonia?
4.6 parts oxygen
Nitrification
Oxidization of ammonia to nitrite with nitrosomonas and very rapidly oxidize nitrite to nitrate with nitrobacter. Aerobic process.
Denitrification
Anoxic process; heterotrophic bacteria convert nitrate into nitrogen gas
Describe plant conditions when fungi dominate
Serious settling problems; found under acid conditions with low dissolved oxygen and nutrient deficiency; can cause skin rash and infections
How can sludge bulking be controlled?
Use settling aids such as activated carbon, lime, alum, ferric salts, polymers, and chemical oxidants
Change plant environment to one infavorable to filaments
