REHAU POLYMERS PVT. LTD

Transcription

1 REHAU POLYMERS PVT. LTD EnviroVision 2011: 24 th November 2011

2 Contents Different Wastewater Treatment Processes Basics of Aeration Types of Aeration Equipments Basis of Selection & comparison of various Aeration systems Fine Bubble Diffuser Component & different types Installation techniques Basis of Selection Design Process Design & Layout Guidelines Case Study -Typical Design-Sizing Calculation Spread Sheet Trouble Shooting & maintenance Guideline

3 Plant Overview Physical Processes Screening Sedimentation Filtration Chemical Processes Precipitation Chlorination Biological Processes Aerobic Anaerobic

4 Aerobic Processes activated sludge process (ASP) trickling filter/solids contactor (TF/SC) sequencing batch reactors (SBR), rotating biological contactor (RBC), biological aerated filter (BAF), biological nutrient removal (BNR) membrane bioreactors (MBR) moving bed bio-film reactors (MBBR).

5 Anaerobic Processes Up flow Anaerobic Sludge Blanket (UASB) Anaerobic Filter (AF)

6 Aeration Aeration: Transferring & dissolving gas (Oxygen) to water is Aeration Aeration occurs all aerobic wastewater treatment processes, In ASP & its variants, energy consumption is more than other processes Aeration of liquids (usually water) is achieved by: Passing the water through air by means of fountains, cascades, paddle-wheels or cones. Passing air through the water

7 Aeration Passing the water through air by means of fountains, cascades, paddle-wheels or cones. Passing air through the liquid Venturi tube, Aeration turbines /Surface Aerators Compressed air through linear aeration tubing or coarse bubble diffusers Compressed air through fine bubble diffusers Subsurface Aerator /Mixers

8 Types of aeration systems Surface aerators: which use a motor at the surface to power a propeller or brush that splashes liquid into the air and induces fluid movement in the tank for mixing Aerator/Mixer: Devices that combine both mechanisms, such as turbines which have a propeller below the surface that shears large bubbles being supplied by a blower into smaller bubbles. Diffused aerators: which use porous devices below the surface. Compressed air is released through the pores or orifices or holes Jet Aerators: Compressed Air jet is premixed with water below water level Membranes that work from molecular diffusion

9 Surface Aerators

10 Surface Aerators: Lower Propeller

11 Floating Brush Aerators Floating brush aerator

12 Turbine Aerators A sparged turbine (left) uses the impeller to break the bubbles as it forces them away from the sparge ring towards the wall. The downdraft turbine (right) uses the downward fluid velocity to carry the bubbles

13 Aspirator/Mixer Aerators The rotating propeller (1) forces water outward horizontally at high velocity. This creates a vacuum drawing air down the shaft (4) into the water. Atmospheric air is drawn through intake ports (3) travels through the hollow drive shaft and disperses in a large plume

14 Jet Aerators Jet aerators find application in industries. They have low alpha factors like fine pore diffusers, generally do not foul and suffer low SAEs due to the need to pump water and compress air

15 Basis of Selection & comparison Surface Aerators Turbine Aerators Jet Aerators Aspirator Aerators Coarse Bubble OTR High Medium Medium High High High SAE/AE Low Low Medium Medium-high Medium-high High α factor High Low Low High Medium High Fouling NA NA NA NA Limited High Fine Bubble Aerators Possibility of Anoxic Zones Typical Typical May create No No No SWD in mtr <4-5 <8-10 * >2.5-3 <4-5 >2.5-3 <4-5 All All >2.8-3 Handling Difficult Moderate Moderate Easy Easy Easy Maintenance High Moderate Moderate Low Low Low

16 Diffused Aerators In Diffused aerators compressed air is released through the pores or orifices or holes Diffused aeration systems are classified as coarse bubble of fine pore. Fine pore diffusers produce 1 to 3 mm bubbles Coarse bubble are of size more than 3 mm

17 Coarse Bubble Diffusers Coarse bubble, with orifices of 5 mm to 12 mm, producing large, non-spherical, rapidly rising bubbles

18 Coarse Bubble Diffusers Coarse bubble diffusers need little maintenance Full floor coverage can provide as much as 3%/m SOTE while a spiral roll system may be as low as 1%/m. Both systems create large circulating liquid velocities in the tank, as much as 2m/sec at the surface More suitable for mixing than Oxygen Transfer

19 Fine Bubble Diffuser On a given volume of air or liquid, the surface area, where exchange can occur, changes proportionally with drop or bubble size Utilizing extremely small bubbles or drops increases the rate of gas transfer (aeration) due to the higher contact surface area. The pores which these bubbles pass through are generally micrometer-size. The smaller the bubbles, the more gas is exposed to the liquid increasing the gas transfer efficiency.

20 Porous ceramic Fine Bubble Diffuser Porous ceramic diffusers: These are made by fusing aluminum oxide grains using porcelain bonds to form a strong, uniformly porous and homogeneous structure. The naturally hydrophilic material is easily wetted resulting in the production of fine, uniform bubbles. However due to clogging & microbial growth issues they phased out in favour of membrane diffusers

21 Components of pipe aerators COMPONENTS OF PIPE AERATOR WITH SILICONE MEMBRANE: PP support pipe Pipe Aerator with non-return valve non-return valve Silicon/EPDM seal Pipe Aerator with 11/4 thread Threaded ss rod M10 1 ¼ thread

22 Components of disc aerators COMPONENTS OF DISC AERATOR WITH SILICONE MEMBRANE: Retaining ring Silicone membrane Disc saddle Base plate Grommet NPT ¾ ss ball with seal

23 Installation Techniques of pipe aerators EPDM Membranes PU Membrane Silicon Membrane

24 Installation Techniques of pipe aerators SIMPLE & QUICK SADDLE LOCK CONNECTION STEP 1 STEP 2 Saddle lock can be easily installed and removed No risk of pipe loosening No tool required Visual inspection is possible non-return valve fastener

25 Basis of Selection of pipe aerators SAE COMPARISON BETWEEN AERATOR & SURFACE AERATOR 64mm pipe aerator 92mm pipe aerator Disc aerator DN200 Disc aerator DN300 SOTE at 5m wastewater depth 34% 36% 33% 34% SAE of REHAU aerator (kgo 2 /kwh)* SAE of surface aerator(kgo2/kwh) * blower/motor efficiency = 70% 1.5 to 2

26 Case Study: Shreyans Paper Mills WASTEWATER DATA AFTER PST & OXYGEN DEMAND INFLOW 10 MLD BOD in mg/l COD in mg/l TSS in <100 mg/l Oxygen demand 1000 kg/h DATA OF OLD AERATION SYSTEM USING SURFACE AERATORS Aeration tank no. 1 5x56kWh + 1x19kWh = 300 kwh Aeration tank no. 2 4x50kWh = 200 kwh Total power consumption using 10 surface aerators = 500 kwh AFTER UPGRADING WITH DIFFUSED AERATION A COST OF 75LACS Aeration tank no m aerators 7800 m3/h Aeration tank no m aerators ** 5200 m3/h Total airflow requirement kgf Blower power consumption Aeration tank 1 Aeration tank 2 Total power consumption using 2000 aerators Net power saving per hour Annual power saving Annual INR4/kWh 180 kwh 100 kwh 280 kwh 220 kwh 1,927,200 kwh 7,708,800 INR 77 LACS ** Diffusers of REHAU Polymer 500 kwh 280 kwh PAYBACK PERIOD FOR UPGRADE TO REHAU AERATOR IS ABOUT 1 YEAR 220 kwh 1 year

27 Types of Membranes EPDM PTTE, Teflon coated EPDM Polyurethene (PU) Silicon

28 Membrane Fouling

29 Membrane Fouling

30 Membrane Selection Criteria Tear Strength: Silicon Membrane has Up to 200% higher tear strength compared with EPDM membrane Longevity: No membrane hardening Shrinkage: No membrane shrinkage Chemical Resistance: Resistant to Chemicals, oil and grease Temperature : High temperature resistance of up to 120 C

31 Case Study Silicon & EPDM membranes 128 pcs of RAUBIOXON pipe aerator RAUBIOXON ca. 270 min EPDM ca. 354 min Y axis: Dissolved Oxygen Concentration 24% REDUCTION IN BLOWER OPERATING TIME Test period: from 12-22pm X axis: Time in minutes *** Ref: REHAU CASE STUDY ON MASSING STP

32 Case Study Silicon & EPDM membranes ** REHAU CASE STUDY ON WEST HORNSBY STP

33 Sizing of Aerators Design Aspects: Oxygen Demand (AOR) Standard Oxygen Demand (SOTR) Aeration Density Depth of Immersion Standard Oxygen Absorption (SOA) Standard Oxygen Transfer efficiency (SOTE) Constants like α, β & θ AOR/SOR ratio

34 Sizing of Aerators Major Design Data: Type of Treatment process Tank size & geometry Plant details, location/altitude/atm. Temp. Side Water depth(swd)/average SWD Oxygen Demand (AOR) Type of Effluent TDS/TSS/MLSS/Salinity/Chloride content etc DO level to maintained Type & size of diffuser

35 Design Flowchart Given Design Inputs & AOR Calculate SOR STEP 1 Trial Configuration with Sp. Air Flow & Density Calculate Air flow & Diffused Area Estimate Trial SOA based on trial configuration from test curves

36 Design Flowchart Estimate No. of Diffusers Not Matching go back to step 1 & adjust the configuration Match against Trial Configuration with Sp. Air Flow & Density Match Adjust for Layout fine tune

37 Design Guidelines SOTE Value : Directly Proportional to depth of immersion Directly Proportional to Aeration Density Inversely proportional to specific Air flow rate Specific Airflow rate: Should maintained between 4-10 Nm 3 /hr/mtr for 64mm & 6-13 Nm 3 /hr/mtr for 92mm Sufficient margin(about 50%) to be kept for peak flow situation, fouling etc. Never design at minimum or maximum high limits

38 Design Guidelines Aeration density: Minimum 4-5% Ideal is 10-15% Mixing requirements to be observed 2.2m3/hr-m2 Layout Guideline: Should maintained between 4-10 Nm 3 /hr/mtr for 64mm & 6-13 Nm 3 /hr/mtr for 92mm Sufficient margin(about 50%) to be kept for peak flow situation Never design at minimum or maximum high limits

39 Design Case 1 Example1 64mm Pipe Aerator Tank Area = 400m2 Aerator quantity = 200m Aerator Spacing = 1000mm < 1500mm (Check 1 Passed) ADP Spacing = 4000mm < 4500mm (Check 2 Passed) Aerator Density = 7.5% > 4.5% (Check 3 Passed) Airflow rate per unit tank = (3.5x200)/400 = 1.75Nm3/hr-m2 < 2.2Nm3/hr-m2 (Check 4 Failed) Design Specific Airflow Rate = 3.5Nm3/hr-m (Check 5 Passed) For example 1, even though the design may have achieved the process oxygen requirement, it has failed the mixing check, therefore, design specific airflow has to be increased to 5Nm3/hr-m in order to meet the mixing airflow rate per unit tank requirement of 2.2Nm3/hr-m2

40 Design Case 2 Example 2 DN300 Disc Aerator Tank Area = 400m2 Aerator quantity = 400pcs Aerator Spacing = 1000mm < 1200mm (Check 1 Passed) ADP Spacing = 1000mm < 1200mm (Check 2 Passed) Aerator Density = 6.3% > 4.5%(Check 3 Passed) Airflow rate per unit tank = (5x400)/400 = 5Nm3/hr-m2 > 2.2Nm3/hr-m2 (Check 4 Passed) Design Specific Airflow Rate = 5Nm3/hr-disc aerator (Check 5 Passed) For example 2, the design has achieved both the process oxygen requirement as well as the min. mixing requirement.

41 Cleaning Process Deposits on membrane surface can be removed by high pressure hosing

42 THANK YOU FOR YOUR ATTENTION