Environmental Engineering (Wastewater treatment)

Core Course

Laboratory of Environmental Engineering & Planning

Department of Civil Engineering

Aristotle University of Thessaloniki

Environmental Engineering

Course description• Introduction to urban wastewater treatment.• Introduction to environmental biochemistry and biotechnology.• Physical, chemical and biological characteristics of urban sewage.

• Mechanical treatment (screens, grit chambers, sedimentation basins).• Biological treatment (activated sludge bioreactors, trickling filters,

rotating disc contactors).

• Natural systems for sewage treatment.• Chemical treatment.• Disinfection and disposal.• Sewage sludge treatment (thickening, stabilization and dewatering).

3

Teaching

• Lectures (5 hours/week)• Labs (3 hours/semester)• Exercise (Dimensioning a WWTP)• Visit to a WWTP

• Interactive environment (Blackboard)– https://blackboard.lib.auth.gr

• Literature:– Metcalf & Eddy, Inc., “Wastewater Engineering, Treatment and Reuse”

4th edition, Revised by George Tchobanoglous, Franklin L. Burton, H. Daviv Stensel.

– Efthymios Darakas ,“Environmental Engineering” A.U.Th.

Environmental Engineering

Environmental Engineering

Biological Treatment

Suspended Biomass Treatment (Activated Sludge)

Attached Growth Treatment(Trickling filters, RBC)

5

Influent

Primary clarifierBar Grit chamber Disinfection

Effluent

Secondary clarifierBioreactor

Ο2

Sludge return

Thickening Anaerobic digestion

(Post thickening) Dewatering

Dewatered sludge

BiogasSupernatant liquor

Sludge

Mechanical Treatment

Biological Treatment

Sludge treatment

Advanced treatment

P.S.

Environmental Engineering

WWTP (Typical diagram, Activated Sludge)WWTP (Typical diagram, Activated Sludge)

Environmental Engineering

7

Mechanical Treatment

BarsInfluent Effluent

Grit chamber

Sludge

Sedimentation tank

Screenings Sand

8

Biological Treatment – Activated Sludge

Effluent

Sludge

Sludge return

Air - Ο2

Influent

Suspended biomass

Bioreactor Secondary clarifier

9

Wastewater treatment - Aeration techniques

10

Nitrification - Denitrification

Nitrification - Denitrification

11

AerobicNitrification

Secondary Clarifier

AnoxicDenitrification

Air - Ο2

Effluent

InfluentΝΗ4

+

C

N2

Sludge return

Mixed Liquor

Sludge

1

12

Influent

Effluent

Anoxic zoneDenitrification

Aerobic zone Nitrification

Aerobic zone Nitrification

Aerobic zone Nitrification

2Nitrification - Denitrification

13

InfluentΝΗ4

+

C

Ο2

Effluent

N2 N2

Secondary clarifier

Recirculation

Sludge

N2N2

3Nitrification - Denitrification

14

AerobicNitrification

Secondary clarifier

Anoxic zone

Αέρας - Ο2

Effluent

InfluentΝΗ4

+

C

N2

Recirculation

Carbon (Organic matter)

Sludge

4Nitrification - Denitrification

15

Attached Growth Treatment

16

Effluent

Ιλύς

Influent

Recirculation (Optionally)

Clarifier

Biological filters

Pebbles or gravel

Moving Bed Biofilm Reactor (MBBR) - Synthetic materials

17

Trickling filters

18

Rotating Biological Contactors (RBC)

19Sedimentation tanks

Sedimentation tanks - Clarifiers

20

21Sedimentation tank

Tertiary treatment

• Membranes

• Adsorption (activated carbon)

• Ion exchange (resins)

23

Disinfection of wastewater (Chlorination)Influent

Effluent

Disinfection tanks

Cl2

24

UV Disinfection channels

25

Ozone

Effluent

Influent

Ο3 Ο3Ο3

Ozone generator

Liquid oxygen Evaporation

unit

Ozone reactor

Gases to be destroyed

26

Sludge treatment

Drying and disposal

Dewatering

Conditioning

Stabilization (aerobic – anaerobic)

Thickening

27

Thickeners

Ευθ. Νταρακάς 28

Bioreactor Secondary sedimentation

Primary sedimentation

Stabilization tank (Aerobic)Thickener

Supernatent liquid

Sludge

Excess sludge Recirculation

Dewatering

Effluent

Sludge stabilization (Aerobic)

Anaerobic digestion of sewage sludge

29

In

Biogas

Out to dewatering

Heating elements

33- 37 oC

Cover

30

Anaerobic digesters

31

Dewatering beds

Sludge 30 cm

Sand 10 cm (0,2-0,6 mm)

Sand 10 cm (7-15 mm)

Gravel 20 cm (15-30 mm)

Drainage

32

Dewatering(Solar energy)

33

Presses

Filter presses

34

Decanters

35

Sewage sludge management