Pa Wastewater Module 18 (The Activated Sludge Process Part Iv)

Front 1

List the five types of nitrogen.

Back 1

Ammonium, Ammonia, Nitrite, Nitrate and Organic-N.

Front 2

List seven nitrogen removal mechanisms.

Back 2

Biological nitrification, biological denitrification, living systems, land application, ammonia stripping, breakpoint chlorination and ion exchange.

Front 3

Climates with large temperature variations can have a significant impact on denitrification. For example, the denitrification reactor volume at 10 °C would be about four times the volume required at 20 °C to achieve the same degree of nitrification. Why do you think this is the case?

Back 3

T1 = 20 degrees C

T2 = 10 degrees C

P = 0.25T2

P2 0.25(T2)2 0.25(10)2 25

= = = = 1/4

P1 0.25(T1)2 0.25(20)2 100

The denitrification rate at 10 degrees C is only 1/4 the rate at 20 degrees C and would, therefore, require 4 times the reactor volume to achieve the same degree of treatment.

Front 4

MCRT is the abbreviation for ________.

Back 4

MCRT is the abbreviation for Mean Cell Residence Time .

Front 5

The two types of aeration systems used in nitrification processes are ______ and ______.

Back 5

The two types of aeration systems used in nitrification processes are surface aerators and diffusers.

Front 6

The optimal pH range for biological nitrification is _____ to _____.

Back 6

The optimal pH range for biological nitrification is 7.8 to 8.2 .

Front 7

Nitrification in the winter months may require up to five times the detention time used during the summer.

a. True b. False

Back 7

a. True

Front 8

Single stage biological nitrification typically requires a MCRT of ___ to ___ days

Back 8

Single stage biological nitrification typically requires a MCRT of 8 to 20 days

Front 9

For biological nitrification to proceed efficiently, there must be an adequate supply of carbon, nitrogen, and phosphorous in the wastewater. If the phosphorus level is too low, it may be remedied by adding a phosphate fertilizer to the aeration tank.

a. True b. False

Back 9

a. True

Front 10

In a denitrification process, it may be necessary to add a carbon source such as methanol if the total effluent nitrogen limit is less than ___mg/L.

Back 10

In a denitrification process, it may be necessary to add a carbon source such as methanol if the total effluent nitrogen limit is less than 7.5 mg/L.

Front 11

List the four types of suspended growth biological nitrification reactors that are commonly used.

Back 11

a. conventional or plug flow .

b. complete mix .

c. extended aeration .

d. SBR .

Front 12

Given the following data, determine how many pounds of alkalinity are available for nitrification, the pounds of ammonia removed and the pounds of alkalinity required for nitrification. Based on this information, is there adequate alkalinity to achieve complete nitrification?

Influent flow = 1.5 MGD

Influent ammonia nitrogen = 40 mg/L

Effluent ammonia nitrogen = 2 mg/L

Alkalinity available for nitrification = 160 mg/L

Back 12

Pounds of alkalinity available for nitrification:

1.5 MG X 160 mg/L X 8.34 = 2001.6 lbs of alkalinity available for nitrification

Pounds of ammonia removed:

1.5 MG X 38 mg/L X 8.34 = 475.38 lbs of ammonia removed

Pounds of alkalinity required for nitrification:

475.38 lbs of ammonia removed X 7.2 lbs of alkalinity = 3422.736 lbs of alkalinity required for complete nitrification

3,423 lbs alkalinity needed – 2,002 lbs alkalinity available = 1,421 lbs alkalinity needed.

Answer: No. At least 1,421 lbs of alkalinity will need to be added.

Front 13

List the three forms of phosphorus considered important for wastewater.

Back 13

a. Orthophosphates

b. Polyphosphate (P2O7)

c. Organically Bound Phosphorus

Front 14

List four metal salts that can be used in treating water for phosphorus removal.

Back 14

a. Aluminum sulfate (or alum)

b. Ferric chloride

c. Ferric sulfate

d. Ferrous sulfate

Front 15

Using lime to remove phosphorus requires that the wastewater has a pH of about 11. After pH

removal, ______ gas can be injected into the water to lower the pH.

Back 15

Using lime to remove phosphorus requires that the wastewater has a pH of about 11. After pH

removal, carbon dioxide gas can be injected into the water to lower the pH.

Front 16

How do the three phosphorus removal mechanisms differ?

Back 16

Potential responses:

The A/O process is a “mainstream” process where phosphorus is removed along the main plant flow stream (i.e., the secondary clarifier). The PhoStrip process removes phosphorus in a “sidestream” process (i.e., in the sidestream anaerobic stripper tank).

The A/O and PhoStrip processes are biological, whereas the flocculation and precipitation processes are chemical.

The anaerobic and aerobic hydraulic retention times (HRT) for the PhoStrip process is longer than the corresponding HRTs for the A/O process.

Front 17

Explain the difference between the A2O process and the Bardenpho process.

Back 17

The A2O process is a three stage process consisting of an anaerobic stage, an anoxic stage and an aerobic stage. The Bardenpho process is a five stage process consisting of an anaerobic stage, then an anoxic stage, followed by an aerobic stage and then another anoxic and aerobic stage.

Front 18

In the spaces below, write in the typical range of values for the indicated process control parameters:

a. MCRT A2O ____ days Bardenpho ____ days

b. RAS recycle rate A2O ____% Bardenpho ___%

c. MLSS concentration A2O ____ Bardenpho ____

d. F/M ratio A2O _____

Bardenpho ____

Back 18

In the spaces below, write in the typical range of values for the indicated process control parameters:

a. MCRT A2O 4 – 27 days Bardenpho 10 – 40 days

b. RAS recycle rate A2O 20 – 50 % Bardenpho 50 – 100 %

c. MLSS concentration A2O 3000 – 5000 mg/L Bardenpho 2000 – 4000 mg/L

d. F/M ratio A2O 0.15-0.25 lb BOD / lbMLSSday

Bardenpho 0.1-0.2 lb BOD / lbMLSSday

Front 19

From the chart in Figure 3.3, determine the optimum pH range for the following processes:

a. Aerobic treatment

b. optimum for nitrifiers

c. phosphorus removal by Al3+ addition

d. phosphorus removal by Fe3+ addition

Back 19

From the chart in Figure 3.3, determine the optimum pH range for the following processes:

a. Aerobic treatment 6.5 – 8.3

b. optimum for nitrifiers 7.5 – 8.2

c. phosphorus removal by Al3+ addition 5.0 – 6.5

d. phosphorus removal by Fe3+ addition 4.0 – 6.0