TABLE OF CONTENTS

Front Page.…………………………………………………………………...…………...(i)

Certificate ………………………………………………………………………………..(ii)

Acknowledgement ……………………………………………………………………....(iii)

List of Figures…………………………………………………………………………....(iv)

List of Tables……………………………………………………………………………..(v)

1. Introduction……………………………………………………………………………(1)

2. Biological Process ………………….…………………………………………………(3)

2.1. Activated Sludge Process (ASP).....................……………………………………(3)

2.2. Waste Activated Sludge (WAS)………………………………………….……….(3)

3. Sewage Treatment ……………………………………………………………………..(4)

3.1. Pretreatment.............................................................................................................(4)

3.2. Primary treatment.................................................................................................... (4)

3.3. Secondary treatment................................................................................................(4)

3.4. Final treatment.........................................................................................................(5)

4. Aerobic Digestion ……………………………………………………………………..(5)

4.1. Aerobic Sludge Digestion Design Criteria..............................................................(6)

5. Secondary Treatment Through Biological Fitration of Sewage.....................................(7)

5.1. Contact beds.............................................................................................................(8)

5.2. Intermittent sand filters............................................................................................(8)

5.3. Trickling filters........................................................................................................(8)

5.3.1. Definition..............................................................................................................(8)

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5.3.2. Working Mechanism of Trickling Filter..............................................................(10)

5.3.3. Classification of Trickling Filters........................................................................(10)

5.3.4. Recirculation of High Rate Trickling Filters.......................................................(10)

5.3.5. Comparison of SRTF and HRTF.........................................................................(11)

5.3.6. Advantages of Recirculation................................................................................(11)

5.3.7. Advantages and Disadvantages of Trickling Filter..............................................(12)

5.4. Miscellaneous types of filters.................................................................................(12)

6. Aerobic Treatment Processes........................................................................................(12)

6.1. Biochemical Wastewater Treatment.......................................................................(12)

6.2. Natural Process.......................................................................................................(13)

6.3. Microbial Metabolism.............................................................................................(13)

6.3.1. Fermentation and Respiration..............................................................................(14)

6.3.2. Biosynthesis.........................................................................................................(14)

6.3.3. Endogenous Respiration......................................................................................(15)

6.4. Environmental Effects............................................................................................(15)

6.4.1. Temperature.........................................................................................................(15)

6.4.2. Food to Microorganism Ratio (F/M)...................................................................(15)

6.4.3. Acid Concentration.............................................................................................(16)

7. Secondary Sedimentation.............................................................................................(16)

7.1. Analysis of hindered settling.................................................................................(16)

7.2. Area Requirement Based on Single Batch Test Result.........................................(17)

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7.3. Design of secondary sedimentation tank...............................................................(18)

8. Secondary Treatment Through Activated Sludge Process...........................................(19)

8.1. Activated sludge terminology................................................................................(19)

8.2. Activated sludge processes……………………………………………………….….(21)

8.3. Conventional activated sludge………………………………………….……………(21)

8.4. Contact stabilization processes……………………………………………….………(21)

8.5. Extended aeration process………………………………………………………..(22)

8.6. Oxidation ditch…………………………………………………………………..(23)

8.7. Sequenced batch reactor…………………………………………………….……(24)

8.8. Biological growth rate……………………………………………………………(26)

8.9. Influent flow pattern…………………………………………………………….(26)

8.10. Process control………………………………………………………………....(27)

8.11. Activated sludge microorganism……………………………………………....(.28)

8.12. Sludge problems…………………………………………………….……….....(30)

8.13. Aeration tank foam………………………………………………….…………(30)

9. Summary......................................................................................................................(31)

10. References.................................................................................................................(32)

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