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ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011). ‘Physical Treatment Processes of Industrial Waste’ (Part B). By; Mrs Hafiza Binti Shukor. OVERVIEW OF WASTE TREATMENT UNIT OPERATIONS. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011).

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ERT 417/4 WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

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  1. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011) ‘Physical Treatment Processes of Industrial Waste’ (Part B) By; Mrs Hafiza Binti Shukor

  2. OVERVIEW OF WASTE TREATMENT UNIT OPERATIONS ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  3. PHYSICAL TREATMENT PROCESS • Treatment methods in which the application of physical forces predominates are known as physical unit operations. • Because most of these methods evolved directly from man’s first observations of nature, they were the first to be used for wastewater treatment. • Screening, mixing, flocculation, sedimentation, flotation, filtration, and gas transfer are typical unit operations. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  4. CHEMICAL TREATMENT PROCESS • Treatment methods in which the removal or conversion of contaminants is brought about by the addition of chemicals or by other chemical reactions are known as chemical unit processes. • Precipitation, adsorption, and disinfection are the most common examples used in wastewater treatment. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  5. BIOLOGICAL TREATMENT PROCESS • Treatment methods in which the removal of contaminants is brought about by biological activity are known as biological unit processes. • Biological treatment is used primarily to remove the biodegradable organic substances (colloidal or dissolved) from wastewater. • Basically, these substances are converted into gases that can escape to the atmosphere and into biological cell tissue that can be removed by settling. • Biological treatment is also used to remove nutrients (nitrogen & phosphorus) from wastewater. • With proper environmental control, wastewater can be treated biologically in most cases. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  6. A) PHYSICAL TREATMENT PROCESS ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  7. 1) SEDIMENTATION PROCESS • Gravity separation • Employ for removal of SS from WW • 3 basic classification • Discrete (Type I) • Flocculent (Type II) • Zone (Type III) • Common operation and found in almost all WWTP • LESS COSTLY than many other treatment processes ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  8. SEDIMENTATION PROCESS (continue…….) Particle Settling Velocity Before a settling basin to settle particle is DESIGN, the settling velocities of the particles MUST be KNOWN. PHYSICAL CHARACTERISTICS of the particles determine its SETTLING VELOCITY. Consider a PARTICAL FALLING in a body of FLUID with the following ASSUMPTION. • Assumption………. • The particle is discreet & its sizes/shape not change • Infinite size vessel • Viscous fluid • Single particle • Quiescent fluid ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  9. SEDIMENTATION PROCESS (continue…….) Particle Settling Velocity The knowledge of settling velocity of particle is used to determining the depth of a treatment unit to separate the suspended solids (particulate matter) by gravity settling and for checking the adequacy of length or diameter of a tankto remove particles before the effluent flows out of the basin. Assumption………. A sand particle of 0.2mm size with specific gravity of 2.65 is observed to settle at a rate of 2.3cm/s ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  10. SEDIMENTATION PROCESS (continue…….) The force acting on the particle are the EFFECTIVE GRAVITATIONAL FORCE and DRAG FORCE, caused by FLUID RESISTANCE. The FFECTIVE GRAVITATIONAL FORCE, Fn (downward) is the DIFFERENCE between the GRAVITATIONAL FORCE (Fg) and the BUOYANT FORCE (Fb). The density of the water The density of the particle Fb (buoyant) FD (drag) Net downward force @ effective gravitational force The volume of the particle Fg (gravity) ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  11. SEDIMENTATION PROCESS (continue…….) A) TYPE 1 Sedimentation (discrete) Particle MAINTAINCE its INDIVIDUALITY and does NOT CHANGE in size, shape and density during the settling process. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  12. SEDIMENTATION PROCESS (continue…….) Settling zone Inlet zone Settling zone Inlet zone Outlet zone Outlet zone Outlet zone Inlet zone Sludge zone Sludge zone UPFLOW BASIN CERCULAR BASIN RECTANGULAR BASIN Outlet zone Inlet zone Settling zone Idealized discrete particle settling in 3 DIFFERENT TYPE OF BASINS is illustrated below: ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  13. SEDIMENTATION PROCESS (continue…….) Inlet flow V1 H Vo V2 h Sludge zone B L Definition sketch for the analysis of ideal discrete particle settling H = the effective depth of the settling zone V =settling velocity B = the width of the basin Outlet flow V1 and Vo – apply to 2 different particles ‘ENTERING AT TOP’ of basin. V2 – applies to a particles ‘ENTERING THE SETTLING ZONE at high “h” ‘of basin (above the sludge zone) • DESIGN VOLUME – must be related to the influent flow rate and particle settling velocity. • The particles that take LONGEST TIME to remove (settle), will be the one that enters AT THE TOP of the effective settling zone. • The design settling velocity is Vowhich is the settling velocity of the particle that settle through the total effective depth of the tank in the theoretical retention tank. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  14. SEDIMENTATION PROCESS (continue…….) B) TYPE 11 Sedimentation (flocculent) Particle velocity of the particle is HIGH as it settles through the tank depth because of COALESCENE with OTHER PARTICLES. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  15. SEDIMENTATION PROCESS (continue…….) V Outlet flow Inlet flow Vo Sludge zone Increasing the SETTLING RATE yielding a LINEAR CURVE settling path. MOST of SS in INDUSTRIAL WW are FLOCCULANT NATURE For discrete particles, the efficiency of removal is related only to the OVER FLOWRATE but when flocculation occurs, both ‘overflow rate’ and ‘detention time’ become significant. Outlet flow Inlet flow V Vo Sludge zone Flocculent Settling (Type 11) Discrete Settling (Type 1) Detention Time(hydarulic retention time, HRT) : length of time a particle or unit volume of ww remains in a reactor. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  16. SEDIMENTATION PROCESS (continue…….) water Solid settle B) TYPE 111 Sedimentation (zone) The floc particles adhere together and the mass settle as a blanket, forming a distinct interface between the floc and supernatant. It is characterized by ACTIVATED SLUDGE & FLOCCULATED CHEMICAL/ SUSPENSION when the concentration of solid exceed + 500mg/L ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  17. SEDIMENTATION PROCESS (continue…….) High of sludge liq interface B B Transition zone B A A A Transition Zone Compression Zone C Settling Zone C D Dense solid D D Settling properties of flocculated sludge Initially, all the sludge is at uniform concentration A A settling proceeds, the collapsed solid on the bottom of the settling unit (D) build up at constant rate. C is zone of transition through which the settling velocity decrease as a result of high conc. of solid. Through the transition zone C, the settling velocity will decrease bcz of the increasing density & viscosity of the suspension surrounding the particles. When the rising layer of settle solid reaches the interface, a compression zone occur. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  18. SEDIMENTATION PROCESS (continue…….) DESIGN CRITERIA The following design criteria are generally assumed to design a Primary Settling Tank / Sedimentation A) GENERAL ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  19. SEDIMENTATION PROCESS (continue…….) B) DIMENSIONS C) TECHNICAL ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  20. 2) CLARIFICATION PROCESS clarifiers are primarily used in the water and wastewater treatment industries to separate solids from liquids in effluent streams • Criteria for sizing clarifier (settling tank) are: • Overflow rate (surface settling rate) • Tank depth at the side wall • Detention time ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  21. 2) CLARIFICATION PROCESS (continue………….) A) Overflow rate (Surface Settling Rate) -defined as the average daily flow rate divided by the surface area of the tank Where, Vo = overflow rate (surface settling rate) Q = average daily flowrate (m3/day) A = total surface area of the tank (m2) ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  22. 2) CLARIFICATION PROCESS (continue………….) B) Depth of Tank -taken as the water depth at the side wall measuring from the tank bottom to the top of the overflow weir. - then exclude that additional depth resulting from slightly sloping bottom that is provided in both circular and rectangular clarifiers. Effluent weir Influent Influent H Occupied with sludge ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  23. 2) CLARIFICATION PROCESS (continue………….) Effluent weir loading is equal to quantity of ww flowing divided by the total weir length, Lw. C) Detention Time -is compute by dividing tank volume by influent flow. Where, td = detention time V = tank volume Q = average daily flowrate ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  24. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  25. EXAMPLE 1: CLARIFIER DESIGN Two primary settling tank are 27.4m in diameter with a 2.1 side water depth. Single effluent weirs are located on the peripheries of the tank. For a wastewater flow of 2.65 x 104 m3/day, calculate the overflow rate, detention time, and weir loading. Ans: overflow rate=22.5 m3/m2.day detention time = 134.54 min weir loading = 2008m3/m.day ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  26. 3)FLOTATION Use for the removal of lighter SS, oil & grease. Also for the SEPARATION (separate both the fine solid and a liquid particles from the liquid phase) and CONCENTRATION OF SLUDGE The separation of particles takes place near the top of the tank, at the surface level of liquid. Thus, the operation is just the opposite of that of gravity sedimentation where particles get removed at the bottom of the tank. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  27. 3)FLOTATION (continue………..) Floatation Tank Air & solid mixture Skimmed off Retention tank air influent Pressure Reducing pump Pressuring pump Clarified Liquid Concept of Removal Mechanism • The waste flow @ portion of clarified effluent is PRESSURIZED to 345-485 kPa (3.4-4.8 atm) in PRESENT of sufficient AIR to approach SATURATION. • When this pressurized liq-air MIXTURE is released to atm pressure in the floatation unit, minuteair bubbles are released from solution. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  28. 3)FLOTATION (continue………..) 3) The sludge flocs, SSor oil globules are floated by these minute air bubbles which attach themselves to and become enmeshed in the floc particles. 4) The air-solid mixture risesto the surface where it is skimmed off. 5) The clarified liquidis removed from the bottom of the unit. 6) The bubble released after pressurization range in size from 30µm to 120m. 7) The rise velocity of a solid-air mixture vary from 2.56-12.7 cm/min and will increase with an increasing air/solid ratio. 8) Polyelectrolyte addition can improve the adhesion of bubbles of flocs. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  29. 3)FLOTATION (continue………..) Floatation Systems Depending on the method of forming the air bubbles in the tank or recycling the waste floatation is achieved by any one of the following systems: • Systems Based on Formation of Air Bubbles • i – Air Floatation : air bubbles are formed by introducing the air in the form of gas phase directly into the liquid phase either by a revolving impeller or through air diffusers at the atm pressure. • ii-Vacuum flotation: ww is first saturated with air either directly in the aeration tank or by introducing air at the pump side. Then partial vacuum is applied so that dissolved air can come out of solution as minute bubbles. The air bubbles and particles attached to them then rise to the surface forming a scum blanket. • iii-Dissolved air flotation : flotation is achieved first by dissolving the air in the ww or in a portion of treated effluent (liquid) under high pressure in the pressurizing or retention tank and then reducing the pressure of he ww through a pressure-reducing valve to atmospheric level during feeding it to the flotation tank to form the rising air bubbles. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  30. 3)FLOTATION (continue………..) • B) Systems According to Recirculation of Effluent • In cases of large treatment plants, normally 15-20% of the effluent is recycled while small treatment plants operate without recycling the effluent. • i- CASE I : WHEN EFFLUENT IS RECIRCULATED • A predetermine fraction of effluent from the flotation unit is taken to the pressurized tank where it is pressurized, and the air is dissolved below the saturation level. The flow is then mixed with the influent entering the flotation unit through a pressure-reducing valve so that air bubbles come out from the recycled flow and get attached with the particles of incoming raw wastewater that are to be removed by flotation . ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  31. 3)FLOTATION (continue………..) ii- CASE II:WHEN EFFLUENT IS NOT RECYCLED Wastewater influent is first retained for some time in the pressure tank where pressure of wastewater is increased to as high as 275-350kPa and air is dissolved in it. Then the flow is fed to the flotation unit through a pipeline having a pressure-reducing valve. As the pressure is released from wastewater, the dissolved air comes out of the solution as fine bubbles which are used for particle separation by flotation. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  32. 3)FLOTATION (continue………..) • DESIGN CONSIDERATIONS • The main factors that require due consideration in the design of flotation units are: • Concentration of particles to be removed • Quantity of air required for formation of air bubbles • Particle rise velocity or buoyant force • Solids loading rate • Air/solid ratio ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  33. 3)FLOTATION (continue………..) Dissolved air flotation units are usually designed on the basis of the air to solid ratio, A/S, using the following equations: CASE I : For system without recycle For system with recycle CASE II : Where, A=volume of air (ml) S=mass of solids (mg) 1.3=weight of 1ml of air (mg) S’a=solubility of air in (ml/L)(temp depended funct) f=fraction of air disoolved at pressure P (atm) P=operating pressure (atm) Si=influent suspended solids or sludge solids (mg/L) Qr=pressurized recycled flow (m3/d) Q=mixed liquor flow (m3/d) ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  34. 3)FLOATATION (continue………..) • DESIGN CRITERIA • Significant design criteria are as under: • Hydraulic retention time, HRT = 20-30min (for efficient primary clarification) • Rising rate or surface loading rate = 0.06 – 1.63 m3/min-m2 • Rising velocity of air-solid mix: • a)when no flocculants are used = 2.56 – 12.7 cm.min • b)when flocculants are used = 20 – 60 cm/min ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  35. 4) FILTRATION • Employ for the removal of SS, following coagulation in physical-chemical treatment or as tertiary treatment following the biological WW treatment process • SS are removed on the surface of the filter staining and through the depth of a filter by both staining and adsorption. • The efficiency of filtration process is a function of; • The conc and characteristics of the solid in suspension • Characteristic of a filter media & other filtration aid • The method of a filter operation ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  36. 4) FILTRATION (continue……..) Media filter may be either GRAVITY or PRESSURE The filter run TERMINATES when the TOTAL HEAD LOSS reaches available driving force @ when excess SS @ turbidity appears in the effluent. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  37. 4) FILTRATION (continue……..) The filter media size is chosen to PROVIDE slightly BETTER REMOVAL then is required. Filtration rate will effect the build up of HEAD LOSS and the EFFLUENT QUALITY ATTAINABLE. The optimum filtration rate is defined as the filtration rate which results in the MAX VOLUME filtrate perunit FILTER AREA while achieving an ACCEPTABLE effluent quality The head loss through the filter is related to the solid loading; Where, H = head loss (m) S = solid captured (kg/m2) a, n = constant ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  38. 5)MEMBRANE PROCESS Use to separate DISSOLVEDand COLLOIDAL constituents from WW Water @ components in water are driven through a membrane under the DRIVING FORCE of a PRESSURE @ELECTRICAL POTENTIAL @ CONC. GRADIENT. A semi permeable membrane is SELECTIVE to the species it passes. The size of the opening in the membrane are a major determinant of species that can pass because the opening present a physical barrier to any substances that are larger than openings. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  39. 5)MEMBRANE PROCESS (continue………) MASS TRANSFER through a membrane proceeds in both directions. Membrane characteristics govern the direction in which the solutes and solvent are traveling. If a pressure force is applied to the more concentrated solution, the flow of the liquid can be reversed (reversed osmosis, RO). The mass transfer of water through a membrane is proportional to the area of the membrane, the net pressure difference above the osmotic pressure and the distance over which the pressure difference occurs. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  40. Figure below gives details on the size of particles of interest in water treatment and the separation processes which can be used in their removal. • Membrane filtration is a process of separating particles from water as it passes through a physical barrier (a membrane with pores). • Particles greater than the pore size of the membrane are retained on the feed surface of the membrane. • The size of particles removed by the membrane depends on the effective pore size of the membrane. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  41. 5)MEMBRANE PROCESS (continue………) or Where, m = mass of water pressed t = time A= area of the membrane x = length Nw= flux of water (mass/area.time) kw = resistance coefficient ∆P = applied pressure ∆Po=osmotic pressure ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  42. 5)MEMBRANE PROCESS (continue………) The resistance coefficient is a function of membrane characteristics, solutes in water, temperature, fouling and other effects. Concentration Polarization – is one cause of membrane fouling. (high conc of dissolved ions on feed side of the membrane cause solubility products to be exceeded with deposition of the precipitates on the membrane. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  43. 5)MEMBRANE PROCESS (continue………) The flux of solute depends on the concentration gradient and a resistance parameter. Where, Ns = flux of solute Ks = resistance parameter for solute passage Cr = conc of solute in the feed Cp = conc of solute in the permeate. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  44. 5)MEMBRANE PROCESS (continue………) Another parameter describing the performance of a membrane is the solute REJECTION COEFFICIENT, which is a measure of the ability of membrane to reject the passage of a species i, Where, Ri = the rejection coefficient Cif = conc of species i in the feed Cp = conc of species i in permeate ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  45. 5)MEMBRANE PROCESS (continue………) Fouling of a membrane INCREASE RESISTANCE to flow and reduces the flux of water through a membrane. BACKWASHING or CHEMICAL TREATMENT may be applied to remove foulants. Irreversible fouling of membranes is the most serious problems. Oxidizing agents such as chlorine or ozone attack membranes and change their structures. ERT 417/4WASTE TREATMENT IN BIOPROCESS INDUSTRY SEM 1 (2010/2011)

  46. The End

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