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L11 -SECONDARY TREATMENT OF SEWAGE - TRICKLING FILTERS.pptx

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Wastewater treatment is a process used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environment or is reused for various purposes (called water reclamation).

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Wastewater Engineering SECONDARY TREATMENT OF SEWAGE – TRICKLING FILTERS REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 1

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Biological Treatment Objective ◦ Remove organic matter from the wastewater which is present in soluble and colloidal ◦ Remove nutrients such as nitrogen and phosphorous from the wastewater. Process The microorganisms (principally bacteria) are used to convert the colloidal and dissolved carbonaceous organic matter into various gases and into cell tissue. Cell tissue having high specific gravity than water can be removed in settling tank. Biological removal of degradable organics involves a sequence of steps including mass transfer, adsorption, absorption and biochemical enzymatic reactions. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 2

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Batch Process During fresh commissioning of the reactor if the microorganisms inoculated in the reactor are not adapted (acclimatized) to the type of wastewater being treated, there may be some lag phase. During this phase there will be some lag time before the substrate is being accepted by the microbes, hence to reflect in substrate depletion and microbial growth. Log growth phase: Substrate is adequate in this phase and rate of metabolism is only dependent on the ability of microorganism to utilize the substrate. Declining growth phase: The rate of metabolism and hence growth rate of microorganisms decreases due to limitations of substrate supply. This is referred as substrate limited growth condition where substrate available is not enough to support maximum growth rate of microorganisms. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 3

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Batch Process Stationary phase: When the bacterial growth rate and decay rate are same there will be no net increase or decrease in mass of microorganism. This phase is referred as stationary phase. Endogenous growth phase: The microorganisms oxidize their own protoplasm for energy (endogenous respiration) and thereby decrease in number and mass. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 4

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Aerobic Treatment of Sewage 1. Attached growth process(Fixed film process). 2. Suspended growth process. 3. Combined process. Attached Growth - micro organisms are responsible for conversion of organic matter present in waste water to gases and cell tissues are attached to some inert medium such as rock, slag, ceramic or plastic material. This process include: 1.Intermittent sand filters 2.Trickling filters 3.Rotating biological contactors 4.Packed bed reactors Suspended Growth - micro organisms are responsible for conversion of organic matter present in waste water to gases and cell tissues are maintained in suspension within the liquid in the reactor by employing either natural or mechanical mixing. This process include: 1.Activated sludge process. 2.Aerated lagoons. 3.Sludge digestion system. 4.Suspended growth nitrification & denitrification REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 5

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Trickling Filters Percolating filters or Sprinkling Filters Water trickles down with the help of spray nozzles or rotary distributors Collected from the underdrainage systems Sloughing is common. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 6

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Construction and Operation - TF Above ground (Rectangular & Circular) Rectangular – Network of pipes Circular – Rotary Distributors ( Electric Motor – Rotor Arms ( 0.5 to 2 RPM) Dosage – 3 to 5 mins and resting 5 – 10 mins. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 7

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Construction and Operation Filtering Media  Coarser Material (stones or slag also free from dust)  Size 25 mm – 75 mm  Should not change weight when exposed to Acidic and Basic Conditions  Total depth – 2 to 3 m  Honeycombed walls for free circulation  Sometimes compressed gas is blown for cleaning REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 8

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Working of a Trickling Filter • The sewage is allowed to sprinkle over filter media through nozzles or rotary distributors. • The biological purification is mainly done by aerobic bacteria which form a bacterial film known as biofilm or slime layer around filter media. • This biofilm layer is aerobic only upto a depth of 0.1 to 0.2mm and remaining part is anaerobic. • The organic matter is degraded by aerobic micro organisms on the outer portion of biofilm. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 9

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Classification of Trickling Filters Conventional trickling filter or ordinary trickling filter or standard rate or low rates trickling filter • The settled sewage is applied to the filter bed and after trickling through it, passes through the final sedimentation tank for removal of most of the stabilized solids. High Rate Filters • the settled sewage is applied at much higher rate than for the low rate filter. • the difference is that provision is made in them for recirculation of sewage through the filter by pumping a part of the trickling filter effluent to the primary settling tank (or the dosing tank of trickling filter) and re-passing it through filter. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 10

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Recirculation of High Rate Trickling Filters • To increase the load rate of trickling filter the sewage is an essential and important feature of high rate filters. The recirculation consists in returning portion of the treated or partly treated sewage to the treatment process (i.e. filter). REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 11

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Comparison of Standard Rate Trickling Filter SRTF and High Rate Trickling Filter HRTF REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 12

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Operation and Maintenance Problems REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 13

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Operation and Maintenance Problems REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 14

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Advantages and Disadvantages of Trickling Filter ADVANTAGES OF TRICKLING FILTER • Rate of Filter loading is high as required less land areas and smaller quantities of filter media for their installations. • Effluent obtained from the trickling filter is sufficient stabilized. • Working of Trickling filter is simple and does not require any skilled supervision. • They are flexible in operation. • They are self cleaning • Mechanical wear and tear is small as they contain less mechanical equipment. DISADVANTAGES OF TRICKLING FILTER The beds loss through these filters is high. • Construction cost is high • These filters cannot treat raw sewage and primary sedimentation is must. • Fly nuisance and odor nuisance may prevail. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 15

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Design of Trickling Filters REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 16

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L11 -SECONDARY TREATMENT OF SEWAGE - TRICKLING FILTERS.pptx

  • 1. Wastewater Engineering SECONDARY TREATMENT OF SEWAGE – TRICKLING FILTERS REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 1
  • 2. Biological Treatment Objective ◦ Remove organic matter from the wastewater which is present in soluble and colloidal ◦ Remove nutrients such as nitrogen and phosphorous from the wastewater. Process The microorganisms (principally bacteria) are used to convert the colloidal and dissolved carbonaceous organic matter into various gases and into cell tissue. Cell tissue having high specific gravity than water can be removed in settling tank. Biological removal of degradable organics involves a sequence of steps including mass transfer, adsorption, absorption and biochemical enzymatic reactions. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 2
  • 3. Batch Process During fresh commissioning of the reactor if the microorganisms inoculated in the reactor are not adapted (acclimatized) to the type of wastewater being treated, there may be some lag phase. During this phase there will be some lag time before the substrate is being accepted by the microbes, hence to reflect in substrate depletion and microbial growth. Log growth phase: Substrate is adequate in this phase and rate of metabolism is only dependent on the ability of microorganism to utilize the substrate. Declining growth phase: The rate of metabolism and hence growth rate of microorganisms decreases due to limitations of substrate supply. This is referred as substrate limited growth condition where substrate available is not enough to support maximum growth rate of microorganisms. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 3
  • 4. Batch Process Stationary phase: When the bacterial growth rate and decay rate are same there will be no net increase or decrease in mass of microorganism. This phase is referred as stationary phase. Endogenous growth phase: The microorganisms oxidize their own protoplasm for energy (endogenous respiration) and thereby decrease in number and mass. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 4
  • 5. Aerobic Treatment of Sewage 1. Attached growth process(Fixed film process). 2. Suspended growth process. 3. Combined process. Attached Growth - micro organisms are responsible for conversion of organic matter present in waste water to gases and cell tissues are attached to some inert medium such as rock, slag, ceramic or plastic material. This process include: 1.Intermittent sand filters 2.Trickling filters 3.Rotating biological contactors 4.Packed bed reactors Suspended Growth - micro organisms are responsible for conversion of organic matter present in waste water to gases and cell tissues are maintained in suspension within the liquid in the reactor by employing either natural or mechanical mixing. This process include: 1.Activated sludge process. 2.Aerated lagoons. 3.Sludge digestion system. 4.Suspended growth nitrification & denitrification REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 5
  • 6. Trickling Filters Percolating filters or Sprinkling Filters Water trickles down with the help of spray nozzles or rotary distributors Collected from the underdrainage systems Sloughing is common. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 6
  • 7. Construction and Operation - TF Above ground (Rectangular & Circular) Rectangular – Network of pipes Circular – Rotary Distributors ( Electric Motor – Rotor Arms ( 0.5 to 2 RPM) Dosage – 3 to 5 mins and resting 5 – 10 mins. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 7
  • 8. Construction and Operation Filtering Media  Coarser Material (stones or slag also free from dust)  Size 25 mm – 75 mm  Should not change weight when exposed to Acidic and Basic Conditions  Total depth – 2 to 3 m  Honeycombed walls for free circulation  Sometimes compressed gas is blown for cleaning REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 8
  • 9. Working of a Trickling Filter • The sewage is allowed to sprinkle over filter media through nozzles or rotary distributors. • The biological purification is mainly done by aerobic bacteria which form a bacterial film known as biofilm or slime layer around filter media. • This biofilm layer is aerobic only upto a depth of 0.1 to 0.2mm and remaining part is anaerobic. • The organic matter is degraded by aerobic micro organisms on the outer portion of biofilm. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 9
  • 10. Classification of Trickling Filters Conventional trickling filter or ordinary trickling filter or standard rate or low rates trickling filter • The settled sewage is applied to the filter bed and after trickling through it, passes through the final sedimentation tank for removal of most of the stabilized solids. High Rate Filters • the settled sewage is applied at much higher rate than for the low rate filter. • the difference is that provision is made in them for recirculation of sewage through the filter by pumping a part of the trickling filter effluent to the primary settling tank (or the dosing tank of trickling filter) and re-passing it through filter. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 10
  • 11. Recirculation of High Rate Trickling Filters • To increase the load rate of trickling filter the sewage is an essential and important feature of high rate filters. The recirculation consists in returning portion of the treated or partly treated sewage to the treatment process (i.e. filter). REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 11
  • 12. Comparison of Standard Rate Trickling Filter SRTF and High Rate Trickling Filter HRTF REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 12
  • 13. Operation and Maintenance Problems REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 13
  • 14. Operation and Maintenance Problems REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 14
  • 15. Advantages and Disadvantages of Trickling Filter ADVANTAGES OF TRICKLING FILTER • Rate of Filter loading is high as required less land areas and smaller quantities of filter media for their installations. • Effluent obtained from the trickling filter is sufficient stabilized. • Working of Trickling filter is simple and does not require any skilled supervision. • They are flexible in operation. • They are self cleaning • Mechanical wear and tear is small as they contain less mechanical equipment. DISADVANTAGES OF TRICKLING FILTER The beds loss through these filters is high. • Construction cost is high • These filters cannot treat raw sewage and primary sedimentation is must. • Fly nuisance and odor nuisance may prevail. REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 15
  • 16. Design of Trickling Filters REFERENCE – SEWAGE TREATMENT DISPOSAL & WASTE WATER ENGINEERING – P.N MODI 16