1. ERT 319 Industrial Waste Treatment
HANNA ILYANI ZULHAIMI

2. Biological Treatment: Processes of Industrial Wastes

3. INTRODUCTION Objectives of Biological Treatment:
a) Transform (i.e., oxidize) dissolved and particulate biodegradable constituent s by microorganisms into acceptable end products,
b) Capture and incorporate suspended and non-settleable colloidal solids into a biological floc or biofilm,
c) Transform and remove excess nutrients, such as nitrogen and phosphorus. (why?)
d) In some cases, remove specific trace organic constituents and compounds.

4. For industrial wastewater perspective:
To remove or reduce the concentration of organic and inorganic compounds.
 because some of the constituents and compounds are toxic to microorganism, pretreatment may be required before discharging to municipal collection.
Pretreatement here is meant by chemical treatment. Biological treatment cannot oxidize all compound since it deals with living things (microorganism).

5. Aerated lagoons (suspended growth)
Biological Processes for wastewater treatment
Activated sludge process (suspended growth)
Aerated lagoons (suspended growth)

6. Trickling filters (attached growth)
Rotating biological contractors RBC (attached growth)

7. Trickling filter

8. vi = stoichiometric coefficient
Aerobic biological oxidation of organic matters
Nutrients for microbes to
Converts organic matters to
CO2 and H2O
Biomass produced
This the general equation for aerobic biological exodation.
As u can see, in order for microbes to convert organic material (substrates), it needs nutrients to tranforms it to new cell (biomass).
Organic material = substrate = benda yang nak urai = food
Biomass = microbes (active, decay), inert particulate
vi = stoichiometric coefficient

9. Composition & Classification of Microorganisms
** Revise the cell components, compositions, structure, DNA, RNA, microbial Growth & metabolism, C & N sources …
Refer Chapter 7, page

10. COMMON TERMINOLOGY IN BIOLOGICAL TREATMENT PROCESS

11. Bacteria metabolism Aerobic, autotrophic Aerobic, heterotrophic
Heterotrophic= use organic compound to form new cell and CO2 and H20
Autotrophic = use carbon to produce new cells and no2 or no3
Anaerobic, heterotrophic

12. Bacterial reproduction:
In 30 min of generation time (time required bacteria to divide into 2 organisms)
1 bacterium would yield ~ 17 x 106 bacteria in 12 h and the mass ~ 8.4 µg
Biomass yield Y = g (biomass produced) / g (substrate consumed)
VSS- common method to measure biomass growth

13. Quiz 1 Explain the term below: Aerobic Anaerobic Heterotrophic
Autotrophic
Phototroph
Chemotroph

14. Microbial Growth Kinetics (Empirical study)
Growth kinetics govern the substrate oxidation and biomass production TSS conc. in biological reactor.
Organic compounds mostly defined as biodegradable COD (bCOD) or ultimate carbonaceous BOD (UBOD). bCOD and UBOD comprise of soluble (dissolved), colloidal and particulate biodegradable components.
Biomass solids in bioreactor = TSS & VSS
The mixture of solids resulting from combining recycled sludge with influent wastewater in bioreactor = mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS)
Solid = biomass, non-biodegradable volatile suspended solid (nbVSS) and inert inorganic total suspended solid (iTSS)

15. Rate of Utilization of Soluble Substrates
(-ve : substrate decreases with time)
r, su = rate substrate conc. change due to utilization, g/m3.d
k = max specific substrate utilization rate, g substrate/ g microbe . D
Ks = substrate conc. at one-half max substrate utilization rate g/m3
X= biomass concentration, S= limiting substrate concentration g/m3

17. 2) Rate of Biomass Growth with soluble substrate
Specific biomass growth rate, μ= rg/
3) Rate of oxygen uptake

18. 4) Effects of temperature

19. 5) Total volatile suspended solids & Active biomass

21. Example 7-5 Determine Biomass and Solids Yields
An aerobic complete mixed treatment process is used to treat an industrial wastewater. The amount of bsCOD in the influent wastewater is 300 g/m3 and the influent nbVSS concentration is 50 g/m3. The influent flowrate is 1000 m3/day, the aerobic tank biomass concentration is 2000 g/m3, the reactor bsCOD concentration is 2.4 g/m3 and the reactor volume is 335 m3. if the cell debris fraction, fd is 0.1, Determine (use the kinetic coefficient given in table 7-8)
the net biomass yield
the observed solids yield
the biomass fraction in the MLVSS

23. Aerobic Biological Oxidation
There are wide range of microorganisms used:
Aerobic heterotrophic bacteria: produce extracellular biopolymers that result in the formation of biological flocs, then separated by gravity settling.
Protozoa: consume free bacteria and colloidal particulates – aid effluent clarification.

24. Stoichiometry:
Electron acceptor
Electron donor

25. Biological Nitrification
2-step biological processes;
Ammonia (NH4-N) is oxidized to nitrite (NO2-N)
Nitrite is oxidized to nitrate (NO3-N)
Why??
Ammonia & nitrite – associate DO concentration & fish toxicity
Need for nitrogen removal:
control eutrophication & water-reuse application
Total conc. of organic and ammonia nitrogen in municipal wastewater: mg/L

26. Stoichiometry: Nitroso-bacteria (Nitrosococcus, Nitrosospira, etc):
Two step oxidation of ammonia to nitrate
Nitroso-bacteria (Nitrosococcus, Nitrosospira, etc):
2NH O NO H+ + 2H2O
Nitro-bacteria (Nitrobacter, Nitrococcus, Nitrospina, etc)
Nitrate:
Safer form to
aquatic lives

28. Biological Denitrification
The biological reduction of nitrate to (nitrite) then to nitric oxide, nitrous oxide, and nitrogen gas.
Biological nitrogen removal is used in wastewater treatment :
where there are concerns for eutrophication,
and where groundwater must be protected against elevated NO3-N concentration.
2 modes of nitrate removal:
Assimilating nitrate reduction (ANR)
Dissimilating nitrate reduction (DNR)

29. ANR involves the reduction of nitrate to ammonia for use in cell synthesis (Fig 7-20)
Assimilation occurs when NH4-N is not available and is independent of DO concentration.
DNR is coupled to the respiratory electron transport chain, and nitrate or nitrite is used as an electron acceptor for the oxidation of a variety of organic or inorganic electron donors (Fig 7-20).
Microorganism for denitrification: both heterotrophic and autotrophic ( most are facultative aerobic organisms with the ability to use oxygen as well as nitrate or nitrite).
- Example: Achromobacter, Acinetobacter, Bacillus, Chromobacterium, Pseudomonas, Rhizobium, etc.

30. Biological Denitrification

31. Nitrogen cycle

32. Types of Denitrification Process
Substrate driven
Endogenous driven

33. Substrate driven
In the first flow, nitrate produced in the aeration tank is recycled back to the anoxic tank (anaerobic). Because the organic substrate in the influent wastewater provides the e- donor for oxidation-reduction reactions using nitrate, the process is termed substrate denitrification. Or because the anoxic process precedes the aeration tank, the process is known as a preanoxic denitrification.

34. Endogenous driven
In the second process, denitrification occurs after nitrification and the e- donor source is from endogenous decay. BOD removal has occurred first, and is not available to drive the nitrate reduction reaction, and called postanoxic denitrification.
It has much slower rate of reaction than preanoxic denitrification.
Often, an exogenous carbon source such as methanol or acetate is added to postanoxic processes to provide sufficient BOD for nitrate reduction and to increase rate of denitrification.

35. Anaerobic Fermentation & Oxidation
Used primarily for treatment of waste sludge and high-strength organic wastes.
As a pretreatment step due to low quality effluent.
Advantages:
Lower biomass yield
Energy (methane) can be recovered from biological conversion of organic substrate
Cost-effective; savings in energy, nutrient addition and reactor volume.

36. Anaerobic Fermentation & Oxidation
Three basic steps in anaerobic oxidation of wastes:
Hydrolysis:
particulate material is converted to soluble compounds that can then be hydrolyzed further to simple monomers that are used by bacteria that perform fermentation.
2) Fermentation (or acidogenesis):
Amino acids, sugars, and some fatty acids are degraded further.
The principle products are acetate, H2, CO2, and propionate and butyrate.
Acetate, H2, CO2  precursors of methane formation (Methanogenesis)

37. b) Hydrogen-utilizing methanogens
3) Methanogenesis:
Carried out by 2 groups of microorganisms (or Methanogens):
a) Aceticlastic methanogens
split acetate into methane and CO2
CH3COOH CH4 + CO2
b) Hydrogen-utilizing methanogens
use H2 as electron donor and CO2 as the electron acceptor to produce methane

38. How?? Nuisance Organisms in Anaerobic Fermentation
When the wastewater contains significant concentrations of sulfate.
Sulfate-reducing bacteria can reduce sulfate to sulfide (toxic to methanogenic bacteria).
Then, how to solve??
How??

39. pH near neutral are preferred ;
Environmental factors:
Anaerobic processes are sensitive to pH & inhibitory substances (ex: NH3, H2S, etc.)
pH near neutral are preferred ;
pH below 6.8  methanogenic activity is inhibited
Due to about % CO2 (high) produced in anaerobic process, high alkalinity is needed to neutralize pH
Range of alkalinity, i.e., mg/L as CaCO3 is often found.
In industrial wastewater applications which mainly contain carbohydrates, it is necessary to add alkalinity for pH control.

40. Types of Biological Process for Wastewater Treatment
Suspended Growth Process
Attached Growth Process (Biofilm)

41. SUSPENDED GROWTH BIOLOGICAL TREATMENT PROCESS

42. Suspended Growth Processes (SGP)
Microbes are maintained in liquid suspension by mixing methods
Most common SGP: Activated-sludge process (ASP)
ASP uses activated mass of microbes capable of stabilizing a waste under aerobic conditions.
mix wastewater with microbial suspension at certain contact time mechanically.
MLSS & MLVSS biomass measurement = a complete mixed system (influent + sludge)
MLSS flows to clarifier (where microbial suspension is settled and thickened) “Activated sludge”
Activated sludge is returned to aeration tank to continue
biodegradation of organic material

43. Activated Sludge Process1
Reactor- microbes are kept in suspension and aerated 2
Liquid-solids separation (ex: clarifier) 3
Recycle system – returning solids from clarifier to reactor

44. Plug-flow Activated Sludge Process

45. Complete mix Activated Sludge Process

46. Selection & Design of Physical Facilities for Activated Sludge Process
Aeration Systems
Aeration Tanks
Solids Separation
Solid Separation Facilities

47. Selection & Design for Activated Sludge Processes
Aeration System
Aeration system must be adequate to:
Satisfy the bCOD of the wastes
Satisfy the endogenous respiration by the biomass
Satisfy the O2 demand for nitrification
Provide adequate mixing
Maintain minimum dissolved O2 conc. throughout the tank
 If the O2 transfer efficiency of aeration system is known, we can design/estimate the actual air requirements for diffused air aeration or installed power of mechanical surface aerators.

48. Aeration system (Air Bubble)

49. Aeration-achieved via diffused air (diffuser) or surface aerator.
Aeration equipment must be designed with enough flexibility to:
Meet minimum dan max O2 demand
Prevent excessive aeration and save energy

50. Aeration Tanks and Appurtenances (support facilities)
Usually constructed of reinforced concrete and left open to atmosphere
Capacity if aerated with diffused air:
capacity range of 0.22 to 0.44 m3 /s  at least 2 tanks needed
capacity range of 0.44 to 2.2 m3 /s  at least 4 tanks needed
capacity range over 2.2 m3 /s  at least 6 tanks or more
Depth of wastewater in the tanks: between 4.5 and 7.5 m
Freeboard: 0.3 – 0.6 m above waterline
Width-to-depth ratio of the tanks (spiral-flow mixing): 1:1, 2.2:1 or 1.5:1 (most common)
Tank with diffusers on both sides, greater width are permissible.
Triangular baffles or fillet may be placed longitudinally in the channel to eliminate dead spot

54. 2. FLOW DISTRIBUTION
For multiple units of primary sedimentation tanks & aeration tanks
Methods of splitting or controlling the flow rate, for ex: splitter boxes equipped with weirs or control valves or aeration tanks influent control gates.
Hydraulic balancing of flow by equalizing the head loss from the primary sedimentation basins to the individual aeration tank.

55. 3. Froth control systems
Foaming: when the aerated wastewater which contains soap, detergents & other surfactants
Foaming action produces froth that contains sludge solids, grease, and wastewater bacteria.
Wind may lift & blow the froth  contaminate when it touches, slippery, and difficult to remove once it has dried.
solutions:
remove froth by spraying clear water or screened effluent through nozzles.
adding antifoaming chemical additives in spray water.

56. 4. Nocardia Foam Control
Nocardia foam is a thick layer of brown biological foams that forms on the top of aeration tanks and clarifiers.
Nocardia organisms grows and tend to trap air bubbles  float to the surface and accumulate as scum (dirty foam)
Controlled by:
Spraying chlorine solution directly into foam layer.
in some cases, spray nozzles installed within a hood located across the width of plug flow aeration tanks.
may not be effective, because it can cause floc breakup & inhibit BOD removal and nitrification.
Addition of cationic polymer.

57. Solids Separation Facilities
To provide well-clarified effluent and concentrated solid.
Sludge collector
Activated sludge settling tank types:
circular or rectangular.
Circular tank:
Diameter : 2 – 60 m (or m).
tank radius: not more than 5X side water depth.

58. Solid Separator (Clarifier)

59. Sludge collectors (rectangular):
Rectangular tank
Max length:<10 x depth, commonly 90 m.
Width=6 m, use multiple sludge collection if 6m <width <24m.
Sludge collectors (rectangular):
Chain and flight

60. Other type of settling tank : stacked clarifiers
b) Traveling bridge
Other type of settling tank :
stacked clarifiers
tube and plate settlers
intrachannel clarifiers

61. Suspended Growth Aerated Lagoons
Suspended growth aerated lagoons are relatively shallow earthen basins varying in depth from 2 – 5 m, provided with mechanical aerators on floats or fixed platforms.
Mechanical aerators:
to provide oxygen for biological treatment of wastewater ,
to keep the biological solids in suspension.
Suspended growth aerated lagoons are operated on a flow-through basis or with solid recycle.
Types of suspended growth aerated lagoon:
Facultative partially mixed.
Aerobic flow through with partial mixing.
Aerobic with solids recycle and nominal complete mixing.

62. Process Design Considerations for flow-through lagoons:
BOD Removal (the basis of design is SRT and HRT)
BOD conc: S/S0=1/1+kt
Effluent characteristics
TSS and BOD conc.
Temperature effects
Oxygen requirement
Energy requirement for mixing

63. Example 7-6 Design of a Complete-Mix Suspended Growth Process
Design a flow-through aerated lagoon to treat a wastewater flow of 3800 m3/d, including the number of surface aerators and their kilowatt rating. The treated liquid is to be held in a settling basin (lagoon) with a 2-d detention time before being discharged. Assume that the following conditions and requirements apply:
Influent TSS = 200 g/m3 (influent TSS are not degraded biologically)
Influent sBOD = 200 g/m3
Effluent sBOD = 30 g/m3
Effluent suspended solids after settling = 20 g/m3
Kinetic coefficients: Y = 0.65 g/g, Ks = 100 g/m3, k = 6.0 g/g.d, kd = 0.07 g/g.d for T = 20 to 25 ⁰C
Total solids produced are equal to computed volatile suspended solids divided by 0.85
First-order observed soluble BOD removal-rate constant k20 = 2.5 d-1 at 20 ⁰C.

64. 8. Summer air temperature = 30 ⁰C 9
8. Summer air temperature = 30 ⁰C 9. Winter air temperature during coldest month = 6 ⁰C 10. Wastewater temperature during winter = 16 ⁰C 11. Wastewater temperature during summer = 22 ⁰C 12. Temperature coefficient, θ = Aeration constants: α = 0.85, β = Aerator oxygen transfer rate = 1.8 kg O2/kWh 15. Elevation = 500 m 16. Oxygen concentration to be maintained in liquid = 1.5 g/m3 17. Lagoon depth = 3.3 m 18. Design SRT = 5d 19. Power required for mixing = 8 kW/103/m3

65. ATTACHED GROWTH BIOLOGICAL TREATMENT PROCESS

66. Attached Growth Processes
Microorganisms are attached to an inert packing material.
The organic material and nutrients are removed from wastewater flowing past the attached growth (or Biofilm).
Example of packing material : rock, gravel, slag, sand, redwood, plastics, etc.
The packing can be submerged completely in liquid or not submerged, with air or gas space above biofilm liquid layer.

67. Attached growth biological treatment process
Most common:
Trickling filter – wastewater is distributed over the top area of a vessel containing non-submerged packing material
Attached growth biological treatment process

68. Trickling Filter

70. Process flow in Trickling Filter
The wastewater is applied over the bed of supporting media (rocks, stones, ceramic pieces, slag, etc) by rotating arms.
The effluent is collected in the secondary clarifier, to separate washed out biomass solids before final disposal.
As the wastewater trickles through the filter media, growth of microorganism takes place on the surface of packing material known as bio-film or slime layer.
When the wastewater passes over this film, contact between substrates or food (waste) and microorganism is established, thus, the waste is decomposed aerobically by the attached biomass.
(Facultative bacteria attach in trickling filters, decompose the organic material in the wastewater along with aerobic and anaerobic bacteria).
Then, a stage comes when anaerobic conditions are developed nearer to the media surface and the microorganisms cannot remain attached or fixed to the media.
the slime layer then eventually peels off (or washed out) and removed from the filter along with (next) flow.
the washed out of slime layer is called sloughing.

72. Typical trickling filter process flow diagram
Single stage

73. Two stage

75. Design Criteria of Trickling Filter
Dosing rate
Loading criteria

76. Design Criteria of Trickling Filter
Dosing rate
Dosing rate in trickling filter is the depth of liquid discharged on top of packing for each pass of the distributor.
For higher distributor rotational speeds, the dosing rate is lower.
With 2 or 4 arms, TF is dosed for every 10 – 60s.
Investigations show that reducing distributor speed results in better filter performance
improve BOD removal
reduce Psychoda & Anisopus fly population
biofilm thickness, and odors.

77. Higher Dosing Rate Larger water volume applied / revolution
Greater agitation – causes more solids to flush out
Greater wetting efficiency
Wash away fly eggs
Thinner biofilm – increase surface area & more aerobic biofilm

78. Loading criteria
Quantifying biomass / biological & hydrodynamic properties in Trickling filter are not possible. Why ??
Attached growth is not uniformly distributed in TF.
The biofilm thickness can vary.
Biofilm solids concentration may range from 40 to 100 g/L.
The liquid does not uniformly flow over the entire packing surface area.
Hence, use broader parameters such as: volumetric organic loading, unit area loadings, and hydraulic application rates  used as design / operating parameters to relate treatment efficiency

79. ROTATING BIOLOGICAL CONTACTORS (RBC)
RBC consists of series of closely spaced circular disks (polystyrene or polyvinyl chloride) submerged (typically 40%) in wastewater and rotated through it.
The disks are attached to a horizontal shaft.
 The assembly of shaft, disks and rotating equipments is called one module. Normally in industrial waste treatment, more than 3 modules arranged in series or parallel.

82. Removal Mechanism of RBC
As the shaft rotates, the surfaces of rotating disks alternately come in contact with the microorganisms and organic content of wastewater and atmosphere.
During the rotation, the microbes get attached to the disks, and O2 from atmosphere is transferred to the wastewater to maintain aerobic condition.
The microbes attached to the disks surface grow in the form of biological film and consume organic content in the wastes.
After some times, as the bio-films thickens, an anaerobic condition develops nearer to the disks surface , then the slime layer gets washed out (sloughing) by incoming waste water flow.
the sloughed bio-films is ultimately removed in the secondary clarifier before
final disposal of treated effluent.
………>> Similar mechanism to Trickling filter <<…………

83. Schematic Diagram of RBC Mechanism

84. Process Design Consideration for RBC
Staging of RBC unit- why?
Loading criteria
Assume first stage 12-20g sBOD/m2d
Total BOD loading 24-30g BOD/m2d
Effluent characteristics
- Refer Table 9-8
Secondary clarifier design
Similar with those used in trickling filter

86. Example 9-7 Design of staged RBC for BOD Removal
Given the following design conditions, develop a process design for a staged RBC system
Parameter
Unit
Primary Effluent
Target Effluent
Flowrate
BOD
sBOD
TSS
m3/d
g/m3
4000
140 90 70 20 10

87. Solution: Page 938
Follow step in page 937
Determine influent and effluent sBOD conc. and WW flowrate
Determine RBC disk area for the first stage based on max SBOD of g sBOD/m3d
Determine number of RBC shaft using standard disk density m2/shaft
Select number of trains, flow,number of stages,disk area/shaft
Based on assumption in Step 4, calculate the sBOD in each stage. If the effluent sBOD is met, calculate the organic and hydraulic loading.

88. THANK YOU!