RESEARCH METHODOLOGY. LECTURE NOTES. MTECH 1 YEAR –. DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING. MALLA REDDY COLLEGE OF ENG

1. Attached Growth Biological WW
treatment Systems

2. Biofilm Systems
• Biofilm
– a biological slime layer
– bacteria in biofilm
degrade organics
– biofilm will develop
on almost anything

3. Types of Biofilm Systems
• Trickling filters
• Rotating biological contactors
• Fluidized bed reactors
• Biofilters
• Wetlands systems
• Sequencing batch biofilm reactors
(many of these can be aerobic or anaerobic)

4. Trickling
Filters

5. Flow Diagram for Trickling Filters
Recycle
Primary
clarifier
Trickling
filter
Final
clarifier
Waste
sludge
Final
effluent
Influent

6. Trickling Filters
• Not a true filtering or sieving process
• Material only provides surface on which
bacteria to grow
• Can use plastic media
– lighter - can get deeper beds (up to 12 m)
– reduced space requirement
– larger surface area for growth
– greater void ratios (better air flow)
– less prone to plugging by accumulating slime

7. Trickling Filters
Filter Material

8. Typical Trickling Filter

9. Typical Modular and Random
Packed Plastic Media
Schematic diagrams of modular and random packed media used
in fixed-film treatment systems (Source: Bordacs and Young, 1998)

10. Random Packing
Leonard
W.
Casson,
Ph.D.,
P.E.,
DEE

11. Structured Media
Leonard
W.
Casson,
Ph.D.,
P.E.,
DEE

12. Bio-towers

13. Trickling Filter
• Tank is filled with solid media
– Rocks
– Plastic
• Bacteria grow on surface of media
• Wastewater is trickled over media, at top of tank
• As water trickles through media, bacteria degrade BOD
• Bacteria eventually die, fall off of media surface
• Filter is open to atmosphere, air flows naturally through media
• Treated water leaves bottom of tank, flows into secondary clarifier
• Bacterial cells settle, removed from clarifier as sludge
• Some water is recycled to the filter, to maintain moist conditions

14. Trickling Filter System

15. Trickling Filter Process

16. Bacteria Removal

17. Types of Trickling Filters
• Standard or low rate
– single stage rock media units
– loading rates of 1-4 m3 wastewater/m2 filter
cross-sectional area-day
– large area required

18. Types of Trickling Filters
• High rate
– single stage or two-stage rock media units
– loading rates of 10-40 m3 wastewater/m2 filter
cross-sectional area-day
– re-circulation ratio 1-3

19. Types of Trickling Filters
• Super rate
– synthetic plastic media units
• modules or random packed
• specific surface areas 2-5 times greater than rock
• much lighter than rocks
• can be stacked higher than rocks
– loading rates of 40-200 m3 wastewater/m2 filter
cross-sectional area-day
– plastic media depths of 5-10 m

20. Design Criteria for Trickling Filters
Table 10.5
Typical Design Criteria for Trickling Filters
Item Low-rate filter High-rate filter Super-rate filter
Hydraulic loading (m3/m2-d) 1 - 4 10 - 40 40 - 200
Organic loading (kg BOD5/m3-d) 0.08 - 0.32 0.32 - 1.0 0.8 - 6.0
Depth (m) 1.5 - 3.0 1.0 - 2.0 4.5 - 12.0
Recirculation ratio 0 1 - 3 1 - 4
Filter media Rock, slag, etc. Rock, slag,
synthetics
Filter flies Many Few, larvae are
washed away
Few or none
Sloughing Intermittent Continuous Continuous
Dosing intervals < 5 min < 15 s Continuous
Effluent Usually fully
nitrified
Nitrified at low
loadings
Nitrified at low
loadings