Biology Of Secondary Treatment

Question 1

What is a trickling filter?

Answer 1

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

Question 2

Trickling Filter BOD removal (%)

Answer 2

70-85%

Question 3

What is a Rotating Biological Contactor (RBC)?

Answer 3

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

Question 4

What is activated sludge?

Answer 4

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

Question 5

What is the activated sludge process?

Answer 5

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

Question 6

Activated sludge process BOD removal (%)

Answer 6

90-99%

Question 7

What three groups can organic material be classified into?

Answer 7

Soluble; dissolved in water

Colloidal; very small particles that dont dissolve or flocculate

Particulate; large particles that can flocculate

Question 8

What are the two ways to remove organic material?

Answer 8

Partial oxidation occuring within a microorganism

Settling of flocculated sludge; microorganisms, particulate material, and colloidal material are bound together

Question 9

Describe the layers of the biomass pyramid from youngest to oldest

Answer 9

1. Kingdom Monera
2. kingdom protists protozoa
3. rotifiers
4. worms and crustaceans

Question 10

Kingdom Monera

Answer 10

Bacteria - single celled organisms that breakdown organic material to grow, reproduce, and store energy. They form the basis of all biological treatment

Question 11

Kingdom Protists Protozoa

Answer 11

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)

Question 12

Rotifiers

Answer 12

Multicellular; strictly aerobic and sensitive to toxic material; dominant in stable, older sludge

Question 13

Worms and crustaceans

Answer 13

Play no significant role in the secondary treatment process, and they appear in old sludge

Question 14

When are amoeboids dominant?

Answer 14

Only when large amounts of organic material are present such as during start up or after toxic shock

Question 15

When are flagellates dominant?

Answer 15

Under conditions of high organic material availability and the presence of few bacteria

Question 16

When are ciliates dominant?

Answer 16

In low organic material conditions with the presence of many bacteria

Question 17

Ratio of C:N:P:Fe needed for bacterial nutrition

Answer 17

100:5:1:0.5

Question 18

Three physical shapes of Bacteria

Answer 18

Spherical - desirable floc formers
Cylindrical - less desireable
Filamentous - help form stable floc in low numbers, but hinder settling in high numbers

Question 19

Absorption

Answer 19

Moving soluble organic material into the cell

Question 20

Adsorption

Answer 20

Capturing particulate matter on the pollysaccharide slime layer on the exterior of the cell where it can be dissolved then absorbed

Question 21

Cryophilic microorganisms

Answer 21

< 15 degrees C; require higher numbers or higher detention time to assimilate the same amount of food

Question 22

Mesophilic range for microorganisms

Answer 22

15-35 degrees C; about 20 degrees is optimal

Question 23

Thermophilic range for microorganisms

Answer 23

35-70 degrees C; requires less detent time but more oxygen input; produces class A biosolids

Question 24

What will effluent look like at peak development of flagellated protozoans?

Answer 24

Cloudy; high in BOD and TSS

Question 25

What will effluent look like at peak development of bacterial and free swimming ciliate populations?

Answer 25

Clear; low in BOD and TSS

Question 26

What will effluent look like at peak development of stalked ciliate and rotifer populations?

Answer 26

High in TSS - dead cells

Question 27

How is the age of microorganisms represented in a trickling filter?

Answer 27

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

Question 28

How is the age of microorganisms represented in a rotating biological contactor?

Answer 28

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

Question 29

Advantages of microscopic exam of process

Answer 29

Quick, early detection, and a way to understand “normal” for your specific process

Question 30

Saprophytes

Answer 30

Independent living creatures that feed on organic matter

Question 31

Parasites

Answer 31

Live off other organisms; pathogens originate in this manner; coliforms indicate possibility of pathogens

Question 32

How much oxygen is required to fully oxidize one part of ammonia?

Answer 32

4.6 parts oxygen

Question 33

Nitrification

Answer 33

Oxidization of ammonia to nitrite with nitrosomonas and very rapidly oxidize nitrite to nitrate with nitrobacter. Aerobic process.

Question 34

Denitrification

Answer 34

Anoxic process; heterotrophic bacteria convert nitrate into nitrogen gas

Question 35

Describe plant conditions when fungi dominate

Answer 35

Serious settling problems; found under acid conditions with low dissolved oxygen and nutrient deficiency; can cause skin rash and infections

Question 36

How can sludge bulking be controlled?

Answer 36

Use settling aids such as activated carbon, lime, alum, ferric salts, polymers, and chemical oxidants

Change plant environment to one infavorable to filaments