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Treatment and Disposal of Sludge

Course: Waste Water Engineering — Practice MCQs, solutions, formulas & past entrance questions.

Courses › Waste Water Engineering › Treatment and Disposal of Sludge

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1. Biosolids are inorganic wastewater solids.

True False

False

Biosolids are defined as organic wastewater solids that can be reused after stabilization processes such as anaerobic digestion and composting. The term “biosolids” was introduced by Water Environment Federation in U.S. in 1998.

Hint Answer

2. Primary sludge constitutes which of following?

Chemical sludge Settlable solids Biological solids Biological and settlable solids

Settlable solids

Primary Sludge constitutes of settleable solids. This is mostly returned to primary clarifier. This is done in order to carry out mixing to provide a uniform mixture.

Hint Answer

3. For what range of COD level anaerobic digestion is carried out?

400-800 900-1200 1500-2000 300-400

1500-2000

The COD level would be around 1500-2000 mg/L if it is subjected to anaerobic digestion. In case if it is around 1300 mg/L n aerobic digestion is carried out. In anaerobic digestion, methane is produced.

Hint Answer

4. What is solid loading rate in kg/ m².d considered while designing a thickener to treat primary sludge?

40-50 50-100 100-150 150-200

100-150

The solid loading rate is considered as 100-150 kg/m².d for a thickener handling primary sludge. When a thickener is handling sludge from both primary clarifier and rotating biological contractor n solid loading rate is considered as 50-90 kg/m².d. This solid loading rate is used to calculate volume of a thickener to be designed.

Hint Answer

5. What is percentage of thickness that can be achieved for primary sludge?

2-3 % 4-5 % 6-8 % 8-10 %

8-10 %

Secondary sludge may be thickened to about 4 percent solids while primary sludge may be thickened to about 8 or 10 percent solids.

Hint Answer

6. What is biogas composed of?

O₂ and CO₂ CO₂ and NO₂ CH₄ and O₂ CH₄ and CO₂

CH₄ and CO₂

Anaerobic digestion is a biological process. A gas is produced that is composed of methane and carbon-dioxide which is called as biogas. These gases are produced from organic wastes such as livestock manure, food processing waste, etc.

Hint Answer

7. Which of following is an advantage of anaerobic digestion?

Capital cost Time Methane generation Space

Methane generation

Methane generation is a key advantage of anaerobic process. Its key disadvantage is long time required for process (up to 30 days) and high capital cost.

Hint Answer

8. What is thickened concentration of thickened sludge from rotating biological contractor?

1-2% 3-5% 5-7% 7-9 %

3-5%

The unthickened sludge from rotating biological contractor is around 1-3.5%. In most cases, it is considered 2%. The thickened sludge is around 3-5%. In most cases, it is considered 5%.

Hint Answer

9. How many types of sludge are present?

1 2 3 4

2

There are two types of sludge present, primary and secondary sludge. Primary sludge includes settleable solids removed during primary treatment in primary clarifiers.

Hint Answer

10. In anaerobic digestion system which of following statement holds good?

Acids are necessary to be added to make the pH neutral Alkalines are necessary to be added to make the pH neutral A flocculant is to be added to bring about flocculation A coagulant is necessary to be added in order to bring about coagulation

Alkalines are necessary to be added to make the pH neutral

Alkalines are necessary to be added to make pH neutral. The pH in se systems drops very low. Hence addition of such alkaline to increase pH becomes necessary.

Hint Answer

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All Chapters

View all Chapter and number of question available From each chapter from Waste-Water-Engineering

Wastewater Flow Rates, Collection and Conveyance of Sewage

Wastewater Flow Rates, Collection and Conveyance of Sewage

Hydraulic Design & Construction of Sewers

Hydraulic Design & Construction of Sewers

Sewer Appurtenances & Sewage Pumping

Sewer Appurtenances & Sewage Pumping

Valves, Blowers & Wastewater Characteristics

Valves, Blowers & Wastewater Characteristics

Natural Methods of Wastewater Disposal, Chemical Reaction Engineering and Waste Water Treatment

Natural Methods of Wastewater Disposal, Chemical Reaction Engineering and Waste Water Treatment

Unit Operations for Wastewater Treatment

Unit Operations for Wastewater Treatment

Preliminary Treatment

Preliminary Treatment

Types of Settling Tank

Types of Settling Tank

Sewage Filtration

Sewage Filtration

Activated Sludge Process

Activated Sludge Process

BOD Removal Methods & Miscellaneous Methods

BOD Removal Methods & Miscellaneous Methods

Treatment and Disposal of Sludge

Treatment and Disposal of Sludge

Septic Tanks, Oil and Grease Removal

Septic Tanks, Oil and Grease Removal

Advanced Wastewater Treatment

Advanced Wastewater Treatment

House Drainage

Rural Sanitation

Rural Sanitation

Corrosion control & Instrumentation

Corrosion control & Instrumentation

Topics

This Chapter treatment-and-disposal-of-sludge consists of the following topics

Treatment and Disposal of Sludge

Biosolids are inorganic wastewater solids.

Primary sludge constitutes which of following?

For what range of COD level anaerobic digestion is carried out?

What is solid loading rate in kg/ m².d considered while designing a thickener to treat primary sludge?

What is percentage of thickness that can be achieved for primary sludge?

What is biogas composed of?

Which of following is an advantage of anaerobic digestion?

What is thickened concentration of thickened sludge from rotating biological contractor?

How many types of sludge are present?

In anaerobic digestion system which of following statement holds good?

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