Making Clarifiers Do More For Less. Hany Gerges, Ph.D, PE July 31, 2015

Transcription

1 Making Clarifiers Do More For Less Hany Gerges, Ph.D, PE July 31, HDR, Inc., all rights reserved.

2 Presentation Agenda 1 Background 2 Grit Removal Technology 3 Primary Clarifiers 4 Experience - Case Studies 5 Secondary Clarifiers

3 Background Grit Removal Technology Field testing is a MUST. Know YOUR Grit settling velocity. Determine Design Particle Select Right Technology

4 Grit is Different than Sand.could be much slower Background Field Testing Quantity of Grit. Particle Distribution. Grit settling velocity (300 micron grit particle = 125 micron sand particle)

5 Ask yourself what size is the majority of incoming Grit Aerated grit basins Technology Selection Mechanically induced vortex grit basins Multi-tray vortex (headcell) Large footprint Complex operation High life cycle cost Good flocculation environment Small footprint High turndown Low life cycle cost Small footprint High capital cost, low O&M cost Sole-source

6 Primary Clarifiers Hydraulics Improvements Minimizing short circuiting Background Reducing sludge re-suspension Reducing solids carry over Circular Primary Flocculation Improvements Chemically Enhanced Primary Treatment (CEPT) Reduce non-settleable solids Increasing solids settling velocity Rectangular Primary

7 Primary Clarifiers The Workhorse of Treatment Plants Pound for Pound They Remove more BOD than any other treatment unit at a treatment plant

8 Primary Clarifiers Remove Settleable Solids ONLY Raw Influent sbod Non-Settle pbod Settle PST Sludge pbod Settle Primary Effluent sbod pbod Non-Settle

9 Primary Clarifiers Typical Design Designer Assumptions Over Flow Rate = 800 gpd/ft2. TSS Removal = 50 to 60 percent. BOD Removal = percent Circular Primary Not always the case!!!!

10 Effect of Non-settleable Solids Example I Inf. TSS = 300 mg/l, TSS non = 100 mg/l Max. Removal Efficiency = 67 % Example II Inf. TSS = 300 mg/l, TSS non = 50 mg/l Max. Removal Efficiency = 83 %

11 Effect of Solids Settling Velocity Design OFR = 800 gpd/ft2. Settling velocity = 0.07 ft/min. All particles with velocity greater than 0.07 ft/min will be 100 percent removed. What is the percentage of these particles in the influent..????...

12 Fraction of Solids (%) Settling Velocity Distribution Settling Velocity (ft/min) Typical Primary Influent Chemically Enhanced Primary Influent

13 How to Use SVD? Computational Fluid Dynamic Models

14 Simple Modifications Increase Wet Weather Capacity Sludge protector canopy. Easy to retrofit to existing circular tanks. Protects hopper and direct flows above blanket minimizing sludge resuspension.

15 Simple Modifications Increase Wet Weather Capacity Sludge protector canopy. Easy to retrofit to existing circular tanks. Protects hopper and direct flows above blanket minimizing sludge resuspension.

16 Simple Modifications Increase TSS and BOD Removal Efficiency Primaries performing well under very high loading rates About 19 percent reduction in TSS. About 10 percent reduction in BOD More Biogas production.

17 Secondary Clarifiers Hydraulics Improvements Minimizing short circuiting Background Reducing sludge re-suspension Reducing solids carry over Circular Secondary Flocculation Improvements Rectangular Secondary

18 Secondary Clarifiers..The Bottleneck of WWTPs Last line of defense. Limited process control (return rate only). Not Knowing the cause of poor performance. Very expensive to build.

19 Causes of Poor Performance Poor settling sludge. Hydraulic inefficiency. Poor flocculation. High Blankets. Denitrification.

20 Secondary Clarifier Elements Energy Dissipating Inlet Effluent Baffle Covered Launders SWD Spiral Scraper TowBro Suction Mechanism

21 Many Elements.. with One Objective!!!! Energy Dissipating Inlet More Than 10 Different Designs Flocculation Center Well Big or Small? Deep or Shallow? Effluent Baffles? Needed or Not Needed? Better Hydraulics No Short Circuiting

22 EDI Everyone has an EDI Envirex Different configurations WETECH Different configurations LA - EDI Multi Layer No Bottom Tub

23 Do You Really Need an EDI?

24 Performance Enhancement Feature Improves Performance

25 Secondary Clarifiers More than 80 percent of new technology is for circular seconadries. Optimal arrangements for rectangular secondaries Inlet Baffles Mid Tank baffles Effluent Launders Sludge Hopper Canopy

26 HDR State Of The Art Clarifier

27 HDR - Optimized Rectangular Secondary Clarifiers Santa Fe WWTP. Plant 1 - Orange County Sanitation District, CA. Michelson Water Reclamation Plant, Irvine Ranch, CA. Bethel Park Authority, PA. City of Vacaville, CA Stage IV- ShaTin WWTP, Hong Kong

28 Santa Fe WWTP. Proven Experience Field Testing to Pinpoint to the problem Modeling to select fixes

29 Proven Experience Santa Fe WWTP. Influent Baffles Transversal Launders Partial Blockage of effluent launders RAS modifications Avoided Building One Additional Clarifier

30 Proven Experience Michelson WRP IRWD Influent baffles Transversal launders RAS modifications Unmodified 40 % Reduction in Effluent TSS Modified

31 Hong Kong

32 Q & A

33 Making Clarifiers Do More For Less Hany Gerges, Ph.D, PE July 31, HDR, Inc., all rights reserved.

34 Settling Velocity Tests Kemmerer Sampler Measurements

35 Step 1: Lower Kemmerer sampler below the water surface, and then close by sliding the messenger down the rope. Step 2: Bring sampler to the surface and collect a sample from the bottom valve (for influent composite sample).

36 Step 3: Let sample settle for predefined time. Tests were conducted for settling times of 1, 2, 4, 8, 16, 32 and 60 minutes. Step 4: After settling time has elapsed, collect sample through middle sampling port. Step 5: Store samples in ice chests and send to laboratory for analysis.

37 The supernatant TSS of the sample that is settled 60 minutes is considered to be the Non-Settleable Solids (NSS) concentration. The contents of the bucket (which contained samples from each test) were mixed and analyzed for TSS. This sample was considered to be the influent composite sample.

38 Stone Cutter WWTP One of the Largest Primary Clarification Plant 1.2 BGD 48 Double Deck Primary Clarifiers. 1.2 billion gallon a day. More than 15 percent increase in TSS removal.

39 HDR Engineers have designed and optimized all shapes and configurations of clarifiers all over the world Hong Kong