Detailed study of Trickling filters

1. P r e s e n t e d B y - Prof. Shreyas Satpute

2. ⦁ Thereare3 major biological treatment
techniques:
1. Attachedgrowth process(Fixedfilm process).
2. Suspendedgrowth process.
3. Combined process.

3. ⦁ Inthis processmicro organisms areresponsible for conversion
of organicmatterpresentin wastewater to gasesandcell tissues
areattachedto some inert medium such as rock, slag, ceramic
or plasticmaterial.
⦁ This process include:
1.Intermittentsandfilters
2.Trickling filters 3.Rotatingbiological
contactors
4.Packedbedreactors 5.Anaerobic lagoons.
6.Fixedfilm denitrification.

4. ⦁ Inthis processmicro organisms areresponsible for conversion
of organicmatterpresentin wastewater to gasesandcell tissues
aremaintainedin suspensionwithin theliquid in thereactor by
employingeithernaturalor mechanicalmixing.
⦁ This processinclude:
1.Activated sludgeprocess.
2.Aerated lagoons.
3.Sludgedigestion system.
4.Suspendedgrowthnitrification &
denitrification

5. ⦁ This process includesbothattachedgrowth and
suspendedgrowth process.
⦁ This process include:
1.Trickling filter, activated sludge.
2.Activated sludge, trickling filter.
3.Faculativelagoons.

6. CONSTRUCTION:
Itconsist of mainly four parts:
1.watertightholdingtank.
2.Distributionsystem.
3.Filtermedia.
4.Underdrainagesystem.

8.  The tank is either rectangular or square if fixed nozzles
are used and circular in shape if rotary distributors are
used.
 As rotary distributors are more reliable & easy to maintain
andoperate.Socircular shapeis most commonly used.
 Thewallsareeithermasonryor concretewalls
 The walls are constructed such that they should
withstand the pressure exerted by sewage from
inside.
 Thewallsaremadewatertight.

9.  The underdrainsystemis supportedbya floor which
slopesto acollectionchannel.
 Italsoconsists afiltermedia which should havehigh
specificsurfacearea,high percent voidspace,resistanceto
abrasion &insoluble in sewagewater.

10. ⦁ The sewage is allowed to sprinkle over filter media
through nozzles or rotarydistributors.
⦁ The biological purification is mainly done by aerobic
bacteria which form a bacterial film known as biofilm
or slime layer aroundfilter media.
⦁ This biofilm layeris aerobiconlyupto adepthof
0.1to 0.2mmandremainingpart is anaerobic.
⦁ The organic matter is degraded by aerobic micro organisms
on theouterportion of biofilm.

11. ⦁ Thefood concentrationis high attheouter surfaceof
biofilmhencethegrowth of micro organismsis moreat
theouter surfaceof the biofilm.
⦁ Themost diffusedoxygenis consumedby micro
organismattheouter surfacebefore it reachesto the
depth.Hencetheanaerobic environmentis developed
neartheinner surfaceof thebiofilm.

13. ⦁ Eventually there is scouring of slime layer due to flowing
liquid andfreshslime layerbegins to growon themedia.
⦁ This phenomenon of scouring of slime is called
sloughing or unloading of thefilter.
⦁ The trickling filter is always preceded by primary
sedimentationwith skimming devices to removethescum.
⦁ The effluent from the filter is then taken to secondary
sedimentation tanks for settling out organic solids oxidised
whilepassingthrough filter.