Instrumentation For Process Control 09
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  • A consdieration in any process for water production and/or treatment is the best use of data accumulation whether it comes from laboratory analysis or from online continuous monitoring. Each type of analysis has its own advantages and disadvantages. The user must decide what combination works the best.
  • Online, continuouos monitoring provides more timely data for quicker reaction to problems.
  • Laboratory analysis always has a place even when on-line process analyzers are in use.
  • 1) The Series 5000 silica performs 96 tests/day in the long cycle and almost twice as many in the short cycle. The CL17 performs an analysis every 2.5 minutes, for a total of 576 tests per day. The cycle-times on other instruments will vary. 2) If a lab test is only performed twice a shift, problems in a process can occur between tests without being noticed. With on-line instrumentation, problems will show up almost immediately. Delays can cause major problems in a process. 3) The CL17 and EC 1000 can be used to operate chemical feed pumps. 4) In most cases, all an operator must do is change reagents and perform routine maintenance. Time is not spent collecting and running samples. 5) Lab tests leave room for errors between technicians and within a technician. Sample collection errors , dilutions, contamination, dirty glassware, etc., can all occur when performing lab tests. 6) If many lab tests are being run, in some cases reagent costs can be reduced when using a process instrument.
  • 1) One of the reasons a process instrument is used, is to reduce the time and effort spent monitoring a process. If an instrument requires a great deal of maintenance, it defeats the purpose of having the analyzer. Hach Company has been trying to reduce maintenance on our instruments. Compare maintenance for the Series 5000 to a PCA. 2) Get the specifications on an analyzer and make sure it meets the needs of the customer. Be sure to look at detection limits, range, accuracy, resolution and repeatability. 3) Is the instrument reliable for the application? If the samples are dirty, there will be more problems than with clean samples. Check with others in the industry who have similar applications. Check with Hach Regional Managers or Hach Dealers for information. 4) Is the instrument easy for the operator to use? Is it easy to read and understand the display? Is the manual easy to read and understand? 5) Take a look at the features of the analyzer. Is everything that the customer needs and wants there? Are there a lot of features that are not really needed, or is the customer paying extra for features he will never use? 6) Cost should be last on the list of considerations. Consider both the cost of operation and of the analyzer itself, but cost shouldn’t be the determining factor in buying an instrument. If it is necessary to pay a little more to get what is wanted and needed, then do it.
  • 1) One of the reasons a process instrument is used, is to reduce the time and effort spent monitoring a process. If an instrument requires a great deal of maintenance, it defeats the purpose of having the analyzer. Hach Company has been trying to reduce maintenance on our instruments. Compare maintenance for the Series 5000 to a PCA. 2) Get the specifications on an analyzer and make sure it meets the needs of the customer. Be sure to look at detection limits, range, accuracy, resolution and repeatability. 3) Is the instrument reliable for the application? If the samples are dirty, there will be more problems than with clean samples. Check with others in the industry who have similar applications. Check with Hach Regional Managers or Hach Dealers for information. 4) Is the instrument easy for the operator to use? Is it easy to read and understand the display? Is the manual easy to read and understand? 5) Take a look at the features of the analyzer. Is everything that the customer needs and wants there? Are there a lot of features that are not really needed, or is the customer paying extra for features he will never use? 6) Cost should be last on the list of considerations. Consider both the cost of operation and of the analyzer itself, but cost shouldn’t be the determining factor in buying an instrument. If it is necessary to pay a little more to get what is wanted and needed, then do it.
  • 1) One of the reasons a process instrument is used, is to reduce the time and effort spent monitoring a process. If an instrument requires a great deal of maintenance, it defeats the purpose of having the analyzer. Hach Company has been trying to reduce maintenance on our instruments. Compare maintenance for the Series 5000 to a PCA. 2) Get the specifications on an analyzer and make sure it meets the needs of the customer. Be sure to look at detection limits, range, accuracy, resolution and repeatability. 3) Is the instrument reliable for the application? If the samples are dirty, there will be more problems than with clean samples. Check with others in the industry who have similar applications. Check with Hach Regional Managers or Hach Dealers for information. 4) Is the instrument easy for the operator to use? Is it easy to read and understand the display? Is the manual easy to read and understand? 5) Take a look at the features of the analyzer. Is everything that the customer needs and wants there? Are there a lot of features that are not really needed, or is the customer paying extra for features he will never use? 6) Cost should be last on the list of considerations. Consider both the cost of operation and of the analyzer itself, but cost shouldn’t be the determining factor in buying an instrument. If it is necessary to pay a little more to get what is wanted and needed, then do it.
  • 1) One of the reasons a process instrument is used, is to reduce the time and effort spent monitoring a process. If an instrument requires a great deal of maintenance, it defeats the purpose of having the analyzer. Hach Company has been trying to reduce maintenance on our instruments. Compare maintenance for the Series 5000 to a PCA. 2) Get the specifications on an analyzer and make sure it meets the needs of the customer. Be sure to look at detection limits, range, accuracy, resolution and repeatability. 3) Is the instrument reliable for the application? If the samples are dirty, there will be more problems than with clean samples. Check with others in the industry who have similar applications. Check with Hach Regional Managers or Hach Dealers for information. 4) Is the instrument easy for the operator to use? Is it easy to read and understand the display? Is the manual easy to read and understand? 5) Take a look at the features of the analyzer. Is everything that the customer needs and wants there? Are there a lot of features that are not really needed, or is the customer paying extra for features he will never use? 6) Cost should be last on the list of considerations. Consider both the cost of operation and of the analyzer itself, but cost shouldn’t be the determining factor in buying an instrument. If it is necessary to pay a little more to get what is wanted and needed, then do it.
  • This slide is the flow diagram for the production of potable (drinking) water, and the various parameters and sampling points for monitoring.

Instrumentation For Process Control 09 Instrumentation For Process Control 09 Presentation Transcript

  • Instrumentation for Process Control Gregg Cunningham Consultant/Trainer Three Gez Consulting Email:greggacunn@comcast.net
  •  
  • Outline
    • Optimizing Process Performance
      • Lab Instruments
      • On-line Instruments
      • Know your process
      • Data analysis
  • Outline
    • Specific Cost/Energy Savings Points
      • Source water
      • Flocculation Aids
      • Filter Performance
        • Filter Effluent
        • Filter to Waste
        • Backwash
      • Disinfection control
      • Distribution
  • Outline
    • Process Instruments Hands-on/Demo
      • Effects of changing water chemistry on process instruments
    • Summary and Conclusions
  • Optimizing Process Performance
  • Lab Instruments
    • Generally used for compliance purposes
    • Lab must have a QC/QA program in place
    • Lab instruments must be capable of running the same methods as the on-line instruments
  • Lab Instruments
    • Grab Sample Points
      • MUST be representative of the process
      • Easily accessible
      • Consistently use the same point
      • Correctly locate
        • Sample tap
        • “Dip” sample point
  • Lab Instruments
    • Grab Samples
      • Flush sample container with sample at least three times (unless a preservative is added)
      • If it is a sample tap
        • Let it run to flush out the line
      • If a basin
        • Do not scrape side wall
        • Do not get surface scum
        • Try to get towards the center
  • The analysis is only as good as the sample!
  • Recommended Sample Taps X Poor , may draw sediment X Poor , avoid ells, valves, T’s and other areas of turbulence Better Poor , may draw air Best X X X
  • Lab Instruments
    • Calibration and Verification
      • Follow manufacturers recommendations
      • Follow State or USEPA regulations
      • Always use fresh standards and verify with third party standards
      • Have instrument calibrated by qualified service technician at least once a year
  • Lab Instruments
    • Use the right instrument
      • Do not use a spectrophotometer to do turbidity
        • Spec will not do 90 ° detection or forward scatter
      • Instrument must have the correct resolution
        • PCII for Cl/pH only reads to a tenth
        • Pkt Turb could only read to a tenth
  • Lab Instruments
    • Use the correct procedure
      • Monochloramine vs total chlorine
      • Correct species
        • As P or as PO 4 ?
      • Digestion
      • Distillation
      • Correct range
  • Lab Instruments
    • QC/QA
      • Control charts
      • 10% of all tests run should be QC/QA
        • Standards
        • Spikes
        • Unknowns
      • MDL’s must be established for each lab tech for each parameter reported
  • LABORATORY VS ON-LINE
    • Monitoring may be carried out by collecting grab or composite samples and then analyzing them in the laboratory.
        • Requires large amounts of time and labor
        • Possibility of inconsistent results due to variations in technique at time of sampling and/or analysis
  • LABORATORY VS ON-LINE
    • Grab or composite sampling may not detect a problem (such as underfeed or overfeed of treatment chemicals) soon enough to prevent process problems or failure.
  • LABORATORY VS ON-LINE
    • Laboratory (grab) samples can be used to supplement the on-line instrumentation
      • Parameters not needing constant measurement or control
      • Problem solving
      • Checking calibration of on-line instruments
  • LABORATORY VS ON-LINE
    • What’s better: Lab or Process?
      • Most lab errors can be tied to the “human factor” or “pilot error”
      • Process instruments are generally self-diagnosing and will tell you if there is a problem
  • LABORATORY VS ON-LINE
    • Automated Analysis (On-line) is the key to solving critical water problems and reducing labor requirements.
    • Fast detection and correction of abnormalities in each unit process can cut treatment costs and keep a plant process in control.
  • On-Line Process Instruments
  •  
  • Process Instruments
    • Automate analytical tests for on-line, continuous monitoring and control
  • ADVANTAGES:
    • Detect process problems
    • Save operator time
    • Reduce operator error
    • May save reagent costs vs lab tests
    • May be used for feed control
  • CONSIDERATIONS IN SELECTING AN INSTRUMENT
    • Does it meet your needs
      • Example: particle counter vs laser turb vs LR turb
    • Does it measure the parameter needed
      • Monochloramine vs total chlorine
    • Is it in the proper range
      • HR turb not accurate at low range
      • High or low end 5% of range is ???
  • CONSIDERATIONS IN SELECTING AN INSTRUMENT
    • Is it reliable
    • Is it easy to operate
      • User friendly interface
    • Is it low maintenance
      • APA6000
    • What are the features
      • Outputs (compatible with current and future needs)
      • Software/hardware upgradeable (field or factory)
  • CONSIDERATIONS IN SELECTING AN INSTRUMENT
    • What is the cost , not just the price
      • Get the sales rep to provide the Cost of Ownership
        • Initial cost
        • Maintenance cost (including labor)
        • Reagent cost
        • Replacement parts cost
  • Cost of Ownership
  • CONSIDERATIONS IN SELECTING AN INSTRUMENT
    • Service
      • Who can work on the instrument?
        • While under warrantee
        • After warrantee
      • What is their response time?
      • Is there a service plan available?
        • Can help to control service costs
        • Best for multiple instruments
  • Installation of On-line Instruments
  • Instrument Installation: Key to Proper Performance
    • Select proper location
      • As near to the sample point as practical
        • Reduces sampling errors
        • Reduces lag time
      • Avoid dead ends, valves, bends
        • Minimize errors due to air bubbles, turbulence, etc.
      • Level, insulated from vibration
      • Good conditions of heat and humidity - avoid direct sunlight.
      • Avoid sample pumps
  • Turbidimeter Panel
    • Measurement accuracy and response time are sacrificed for convenience and appearance.
    • Good for public relations, poor for analysis
  • Turbidimeters Mounted at Sample Point
    • Instruments should be installed as close as possible to the sample point for greatest accuracy and best response time.
    Power isolation switch Flow Control
  • Poor Installation Can Lead To Erroneous Conclusions
    • Particle counts real time
    • Turbidity measurements delayed in time approximately 15 minutes due to installation in a panel arrangement
  • Example of Sampling Error Do The Math!
    • Poor
    • Sample pipe 100’ (3048 cm)
    • ¾” (1.9 cm) pipe
    • Flow 200 mL/min
    • Optimal
    • Sample line 5’ (152 cm)
    • ¼” (0.635 cm) line
    • Flow 200 mL/min
    VS
  • Poor Sampling
  • Optimal Sampling
  • Increase flow but still Poor Sampling!
  • Crank it up to equal lower lag time? Big price to pay! 35,800 ml/min = 9.46 gal/min = 13,622 gal/day
  • Know Your Process
  • Know Your Process
    • Monitor Source Water
      • Known variations
        • Seasonal
        • Diurnal
      • Unexpected upsets
        • Spills/contamination
        • Security
  • Know Your Process
    • Use lab and on-line instruments to understand the variables in chemical addition
      • pH
      • Polymer
      • Disinfectant
      • Fluoride
  • Know Your Process
    • Jar tests can be invaluable
      • Must simulate your physical process
      • Helps to optimize coagulation which will optimize the process
      • Use lab test procedures for jar tests and validate process results with both lab and on-line instruments
  • Know Your Process
    • Monitor distribution
      • Yes, it really is part of the process
      • Helps to maintain the water quality throughout the system as good as it was coming out of the plant
      • Monitor Corrosion Control
      • Identify Potential Nitrification Issues
  • Know Your Process
    • Baseline data must be established
      • The more you know about “normal” operations, the quicker you will discover when it is abnormal
  • Analyze The Data
    • SCADA
      • Min, Max, Average
      • Trends
    • LIMS
      • Min, Max, Average
      • Trends
    • Combination
      • Software packages that can import from both and analyze the data
  • Specific Cost/Energy Savings Points
  • Major Monitoring Points
    • Source Water
    • Flocculation Aids
    • Filter Performance
      • Filter Effluent
      • Filter to Waste
      • Backwash
    • Disinfection
    • Distribution
  • MIXER FLOCCULATOR CLARIFIER FILTERS CLEAR WELL Disinfectants Hardness Turbidity pH Turbidity pH pH Waste Water Backwash Turbidity Turbidity Particle Monitoring Chlorine and / or Permanganate and / or Manganese Aluminum pH Turbidity Disinfectants Hardness Alkalinity pH DRINKING WATER TREATMENT FLOW DIAGRAM Raw Water Effluent Turbidity Chlorine Alkalinity Particle Monitoring Distribution Solids Filter Effluent SCM Recycle Filter to Waste
  • Source Water
  • Source Water
    • You need to know what the water quality is coming into your plant before you can make any needed adjustments to it.
    • Baseline data is invaluable.
    • Many normal variations in water quality can easily be accommodated.
    • Serious changes can be identified and dealt with.
  • Source Water – Ground Water
    • At the minimum, with on-line instruments
      • pH (with temperature)
      • ORP
      • Turbidity
    • Additionally, with either lab or on-line instruments
      • Hardness
      • Alkalinity
      • Organics
      • Nitrates
      • Iron
      • Manganese
  • Source Water – Surface Water
    • Many more parameters to be concerned with
    • Changes can happen much quicker than with ground water
    • Need to be able to respond to those changes rapidly to adjust your process
  • Source Water – Surface Water
    • pH
      • General, overall indicator
      • Seasonal variations
        • Fall turnover
        • Summer stratification
        • Influence of precipitation events
        • Indicator of biological activity
        • Indicator of industrial pollution
  • Source Water – Surface Water
    • Turbidity
      • Indicator of physical upset (rain,wind, etc)
      • Many contaminants adhere to particles (e.g. phosphorous)
      • High turbidity water is harder to treat
      • Need to be able to respond quickly to changes in turbidity
  • Source Water – Surface Water
    • Conductivity
      • Changes in ionic species
    • ORP
      • Changes in oxidative or reducing species
    • Organics
      • Seasonal changes and contamination
    • Ammonia
      • Biological degradation
  • Source Water – Surface Water
    • Nitrate
      • Level of nutrients and ag runoff
    • DO
      • Seasonal and diurnal changes due to algae and other aquatic plants
  • Source Water Monitoring Panel
  • Flocculation Aids
  • Flocculation Aids
    • Proper dosing of flocculation aids (polymer, alum, ferric chloride, etc) will optimize your process
    • Under-dosing results in poor floc formation
    • Over-dosing is expensive
  • Flocculation Aids
    • Laboratory jar tests are invaluable as long as the apparatus is representative of your process
  • Flocculation Aids
    • Controlling the dose correctly is the key
    • Parameters to monitor
      • Turbidity can be used to track dosing
      • pH is also an important parameter to track
      • Streaming Current is generally one of the best methods of measuring effectiveness of dose
  • Streaming Current
    • On-line measurement of how well charge neutralization has occurred
    • Influenced by salinity, pH and conductivity
    • Sample point must be close to the point of injection but after it is well mixed
  • Streaming Current Monitor
  • Monitoring Filter Turbidity
  • Monitoring Filter Turbidity
    • Three points of turbidity monitoring
      • Filter effluent
      • Filter to waste
      • Backwash
  • Filter Effluent Turbidity
    • Monitors filter performance
    • Provides the method of meeting regulatory requirements
      • “15 Minute Rule”
  • The “15 Minute Rule”
    • Must conduct continuous monitoring of turbidity for each filter using an approved method.
    • Must calibrate turbs using the procedure specified by the manufacturer.
    • Must record the results every 15 minutes while the filter is contributing to the combined filter effluent.
  • Combined Filter Effluent Turbidity
    • Must be monitored at least every 4 hours.
    • Must be less than or equal to 0.3 NTU in at least 95% of the measurements taken each month.
    • Must not exceed 1 NTU at any time.
  • Filter Performance Turbidity vs. Particle Counter
    • Like turbidity, particle counting is another tool
    • They are complimentary and not competing technologies
    • Each can tell part of the whole picture
  • Turbidity Measurement Particle Count Measurement Measurement of light scattered at an angle. For municipal water/wastewater applications light scattering measurements at 90º to the incident light path. Particle counting measurements can be light scattering or light blocking. Light scattering technology is appropriate for particle sizes <1µm. Light blocking technology is appropriate for particle sizes > 1µm. For municipal drinking water applications, light blocking > 1µm (typically >2µm) is appropriate. Not a specific measurement of anything, it is a qualitative measurement A quantitative measurement of particle size and particle number. Measurement is independent of volume Measurement is volume dependent Measurement is relatively independent of flow rate. Sample can be flowing or static Sample must be flowing and flowing at a constant rate. Unit of measurement is nephelometric turbidity units, NTU Unit of measurement is particle counting must state the number of particles, particle size or range of sizes and unit volume. For example 10 particles per ml > 5µm or 200 particles per ml 2-5µm. Peak wavelength response for lab, SS7 and 1720 series process is ~560nm, FT660 is 660 nm, for Accu4 ~ 850nm Wavelength is 790 nm Theoretical particle size sensitivity 10 -8 m (0.01µm) 2200 PCX sensitivity is > 2µm Turbidity Measurement Particle Count Measurement Size range from approximately 10 -8 m - 10 -3 m (large molecules to sand) For the 2200 PCX: 2-750 µm Color in water is a negative interference except for the Accu 4 Color does not interfere with particle count measurements Turbidity interferes. High turbidity is a negative interference. At high turbidity scattered light is blocked or absorbed by the large amount of turbidity and thus does not reach the detector. The turbidity will be false negative. This phenomenon is called ‘going blind.’ Turbidity interferes. High turbidity is a negative interference. Particle counters typically have a range of approximately 17,000 particles/ml > 2µm. The particle counter may be over range at turbidity between 1 and 10 NTU – typically approximately 5 NTU. The particle counts will be false negative. Light absorbing materials (i.e. activated carbon) are negative interferences. Light absorbing materials (i.e. carbon) block light well and thus are counted. They do not interfere Accuracy of measurement is influenced by particle size Accuracy of measurement is influenced by particle size Accuracy of measurement is influenced by particle shape Accuracy of measurement is influenced by particle shape Accuracy of measurement is influenced by a particle’s refractive index Accuracy of measurement is influenced by particle’s refractive index
  • Particle Sizes Practical Measurement Size in Meters 10 0 10 -10 10 -6 1 Meter- Boulders 1 Angstrom Ions Bacteria/Silt & Clay Viruses/Colloids Sand Multicell Organisms Visible Microscope Electron Microscope Turbidity Particle Counting 10 -3 10 -8
  • Turbidity vs. Particle Counter
    • What follows are examples of how they compliment each other
  • 1720C and PCX-10 Response to Fluoride and Carbon
    • About 9:21 AM both PCX and 1720C showed a deviation
      • Turb from 0.04 to 0.06 NTU
      • PCX jumped over a decade on both channels
    • Delta in turb readings seem insignificant but did respond
    • PCX definitely saw something
    • What happened?
    • Out of spec sodium silicofluoride (large particle size) was also contaminated with activated carbon, hit the system at about 9:20 AM
    • PC responded strongly to both the fluoride particles and carbon particles
    • Turb saw the fluoride particles as turbidity, but carbon particles are a negative interference. That made the response much less in intensity. Most turbs do not have the low range resolution to show a significant response.
  • Particle Counter vs. Laser Turb
    • Laser Turb particle size sensitivity down to 0.01 µm
      • Resolution in mNTU (1.0 mNTU = 0.001 NTU)
    • Particle counter size sensitivity at > 2 µm
  • Particle Counter vs. Laser Turb
    • Both track fairly well together
    • The FT660 show longer time to ripen after filter run. FT660 is still seeing the particles < 2 µm
    • Particle counter does not respond to particles < 2 µm
    • FT660 definitely responds to an anomaly that the Particle counter does not. Again probably because of particle size.
  • Particle Counter vs. Laser Turb
    • Notice that the change in the FT660 at the event is from about 24 to 31 (7) mNTU’s. That is a significant number.
    • If it were a 1720E (or C or D) that would be a change of 0.007 NTU. You probably would not even see it, let alone think it was significant.
  •  
  • Particle Counter Data
    • A particle counter is an excellent tool to judge filter performance
    • BUT, you must be willing to analyze the data…and there is a lot of it!
    • Data acquisition is inadequate, it must become data analysis .
    • Data acquired without a plan for, or means of use, is not of much value.
  • Monitoring Filter Turbidity
    • Three points of turbidity monitoring
      • Filter effluent
      • Filter to waste
      • Backwash
  • Filter To Waste
    • After backwash each filter’s water is run to waste until the filter ripens enough to bring it back on line
    • Measuring the FTW turbidity is the best method of controlling when to bring the filter on line
    • If the FTW turbidity is less than the raw water but more than the allowed filter effluent, the water could be recycled until the turbidity is low enough to bring the filter on line.
    • Difficult to do with grab samples
    • Must be done with a process turb
  • Monitoring Filter Turbidity
    • Three points of turbidity monitoring
      • Filter effluent
      • Filter to Waste
      • Backwash
  • The Importance of Backwash Monitoring for Turbidity
    • Backwashing requires a significant volume of (already treated) water (3 - 5% or more).
    • The most common problem is excessive backwash.
    • This can have a dramatic impact on
      • filter performance
      • plant operating costs
  • The Importance of Backwash Monitoring for Turbidity
    • Excessive backwash can lead to
      • Loss of filter media
      • A negative effect on the ripening phase
      • Shortened filter runs
      • Higher potential for filter break throughs
      • Degraded filter performance
  • The Importance of Backwash Monitoring for Turbidity
    • To optimize filter performance: REDUCE BACKWASHING!
  • The Importance of Backwash Monitoring for Turbidity
    • Methods used for determining termination of the backwash cycle include:
      • Timed cycle
      • Backwash volume
      • Operator judgement
      • Turbidity
  • Methods for Backwash Termination: Timed Cycle
    • Backwash cycle is just timed
    • Not a true indicator of filter cleaning
      • Does not take into account:
        • Solids loading
        • Changes in the media
        • Variations in flow
    • Typically, excess water is used to ensure the filter is clean.
  • Methods for Backwash Termination: Backwash Volume
    • A specific amount of water is used to backwash the filter
    • Same problems as with the timed cycle
    • Typically, excess water is used to ensure the filter is clean.
  • Methods for Backwash Termination:Operator Judgement
    • Operator “eye-balls” the top of the filter to determine when the backwash is done.
    • The obvious:
      • Un-scientific
      • Inconsistent
    • Often results in over-washing the filter.
  •  
  • Methods for Backwash Termination: Turbidity
    • Turbidimetric measurements are made throughout the cycle
    • Determination of the end-point is:
      • Based on good science
      • Repeatable
      • Independent of filter loading and variations
      • Un-biased
  • Methods for Backwash Termination:Turbidity
    • Studies have shown that the final turbidity at the termination of a backwash cycle directly correlates to subsequent filter performance and run time.
  • Methods for Backwash Termination: Turbidity
    • AWWA recommends backwash be terminated when the turbidity is in the range of 10 - 15 NTU
    • When done so, sufficient particulate material remains above the filter to create the proper environment for an effective ripening period, which results in longer and more effective filter runs.
  • AWWA Recommended Backwash Limit (10 - 15 NTU)
  • Large Filter with a 17,000 gpm BW Rate
  • Methods for Backwash Termination:Turbidity
    • Methods for measuring backwash turbidity
      • Grab sample
        • Must be representative sample
        • Time and labor intensive
        • Requires many samples per filter run
      • On-line
        • Slip-stream (traditional)
        • In situ
  • In situ Analysis for Backwash Turbidity
    • Use a probe design
    • The probe is placed in backwash trough
    • Extremely rapid response to changes in backwash turbidity
    • Measurements are taken at frequent intervals
  • Instrumental Monitoring
    • Advantages
      • Consistent operation
      • Automated monitoring
      • All operators “see” the same thing
      • Better overall process control to lower costs
    • Disadvantages
      • Initial instrument purchase
      • Installation costs
      • Operators may feel threatened
  • Instrumental Monitoring
      • Nearly every utility implementing instrumental backwash monitoring can achieve cost savings equal to the installed cost of the instruments in a year or less
  • Location – Time is Money!
    • Analysis needs to be taken as close to the backwash as practical – seconds are important
    • If possible mount in the BW trough
    • CAUTION: Poor response and little or no savings may result if mounted as follows:
      • Manifolding multiple filters to a single monitoring sensor or point
      • Sampling the common drain line of drain galley or gullet
  • Typical Installation Configuration
    • Many controllers accept inputs from two probes
    One Sensor in Backwash Trough
  •  
  • Monitor Uniformity of Backwash
    • Use a second sensor mounted on a pole (1/2-3/4” pipe or rigid conduit) to move around the filter to check uniformity of washing
  • Sensor Mounted in Filter Bed
      • Use pipe-mounted sensor to move around filter
    Sensor Sensor Mounting
  • Sensor Mounted in Trough
    • Sensor mounted in backwash trough – more representative
    • Sensor points upstream, into the flow
    • Mount near bottom of trough
  • Self-cleaning Wiper
    • Self-cleaning
      • Adjustable wiping frequency
      • Long wiper blade life
  • Typical Data From BW Monitoring
  • Noisy Response
    • Some samples may be noisy and require sample conditioning with a stilling chamber
  • Stilling Chamber to Quiet Noise
    • Black PVC pipe
    • 6 feet long, 8 inch diameter
    • Used to ‘quiet’ the sample
  • After Installation of Stilling Chamber
  • Large Filters Filter Side A Filter Side B BW Trough/Launderer BW Trough/Launderer BW Trough/Launderer BW Trough/Launderer BW Trough/Launderer BW Trough/Launderer Flow Common Drain Gullet Mount Permanent Probe here to look into the stream Use second probe to move around the filter to assess uniformity of backwash
  • Manifold/Drain Header Mounting
    • Avoid where possible
      • Unacceptable delay
      • Non-representative sampling
    Sensor Filter 1 Filter 2 Filter 3 Filter 4 Filter 5 Filter 6 Manifold/Drain Header
  • Summary of Backwash Monitoring
    • Consistent Filter Backwash
      • Filter to Filter
      • Operator to Operator
    • Reduced Power Cost
    • Reduced Water Consumption
    • More Saleable Water
    • Lower Re-treatment Cost
    • Lower Filter to Waste Cost and Volume
    • Lower Backwash Recovery Costs
  • Case Study: Backwash Profiling at a Colorado Water Treatment Plant
    • 38 MGD
    • 12 Filter beds
    • Coagulation, sedimentation and filtration
    • Conventional dual-media filter design
    • Filter run averages 24 hours
    • Raw water 10 - 20 NTU
    • Settled water 1 - 2 NTU
    • Final effluent rarely exceeds 0.030 NTU
  • Case Study: Backwash Profiling at a Colorado Water Treatment Plant
    • The plant is a member of the Partnership for Safe Drinking Water and consistently exceeds their membership requirements.
  • Case Study: Backwash Profiling at a Colorado Water Treatment Plant
    • To profile the filters, the probe
      • was mounted 4 feet below the water line
      • 18 inches above the filter media
      • facing away from the filter wall
      • in a horizontal position
  • Case Study: Backwash Profiling at a Colorado Water Treatment Plant
    • Data collection at 5 second intervals
    • 30 second signal averaging to reduce noise levels due to turbulence above the filter media
  •  
  • Surface Wash On 4,000 gpm 6,000 gpm Surface Wash Off Surface Wash On 3,900 gpm Surface Wash Off 6,000gpm 5,300 gpm 2,000 gpm
  • Case Study: Backwash Profiling at a Colorado Water Treatment Plant
    • The profile shows two distinct peaks
    • Cycle begins with surface wash
    • Max turbidity (55 NTU) at 6000 gpm (1 O )
    • Within 6 minutes turbidity drops below 5 NTU
    • Second SW brings it up to 15 NTU (2 O )
    • Backwash flow rate is then slowly reduced
  • Case Study: Backwash Profiling at a Colorado Water Treatment Plant
    • At nine minutes turbidity is between 1 - 2 NTU
      • Same as settled water prior to filtration
    • After almost 14 minutes final turbidity is 0.081 NTU
  • Case Study: Backwash Profiling at a Colorado Water Treatment Plant
    • Conclusions
      • The filter was over-washed (0.081 vs 10 - 15 NTU)
      • AWWA would recommend terminating BW during second Surface Wash peak (15 NTU at 7 min)
      • If longer runs are desired, could terminate BW at about 9 minutes when turbidity was equal to that of settled water.
  • Case Study: Backwash Profiling at a Colorado Water Treatment Plant
    • Conclusions (continued)
      • In either case a substantial amount of BW water could be saved. (30% – 45%) = $$$$$$
      • Although subsequent filter runs were not documented in this case, other studies have shown an increase in filter runs and quicker ripening of the filter.
      • Process optimization is the ultimate goal
  • Will I Always Save?
    • Water
      • No. Under washing and over washing are both problems. If under washing has been a problem for very long, it will take a while to clean the filter(s) up. THEN water savings will start.
    • Operation Expense
      • Yes. Savings in power, re-treatment costs of water, labor, filter media, will yield net savings.
  • Sample Calculations of Savings
  • Calculate BW Costs (Savings)
    • Calculate Cost of Backwash:
    • The Cost of Operations (A) =
    $ Cost of Operation (A) X 1000 Gallons Saved (B) = $ Saved 1000 Gallons Backwash Cycle Backwash Cycle Total Annual Budget $ * = $ Cost of Operation 1000 Gallons Produced Annually 1000 Gallons * All costs – debit service, salaries, benefits, utilities, chemicals, maintenance, depreciation, capital expenses, consulting fees
  • Calculate BW Costs (Savings)
    • Example Cost of Operation (A) :
    • The Cost of Operations (A) =
    $ Total annual budget = $ Cost of Operation 1000 Gallons annually 1000 gallons $ 18,000,000 Annual Budget = $ 3.65 4,900,000,000 Gallons Produced Annually 1000 gallons
  • Calculate BW Costs (Savings)
    • Calculate Dollars saved per Backwash:
    • So,in1000 gallons saved/backwash cycle (B )=
    $ 3.65 (A) X 1000 Gallons saved (B) = $ Saved 1000 Gallons Backwash Cycle Backwash Cycle 1000 gallons (max rate) X Minutes Saved Minute Backwash Gallons
  • Calculate BW Costs (Savings)
    • Savings per backwash (B):
    • So, assume 4,000 gal/minute rate, 1.5 minutes saved/backwash cost of water will be:
    $ 3.65 (A) X 1000 Gallons saved (B) = $ Saved 1000 Gallons Backwash Cycle Backwash Cycle 4,000 gallons X 1.5 Minutes Saved X $3.65 (A) = $21.90 Minute Wash 1000 Gal Wash
  • Calculate BW Costs (Savings)
    • Savings in Wash water (B):
    • So, assume 4 filters, 60 hr runtimes; 8,760 hours in a year so each filter will be washed 146 times
    $ 3.65 (A) X 6000 Gallons saved (B) = $ 21.90 1000 Gallons Backwash Cycle Backwash Cycle $21.90 X 146 washes X 4 filters = $12,789.60 Wash Filter Year
  • Calculate Savings and Revenue in BW
    • Savings from saved water:
    • Savings from treating or retreating replacement water – Numerically the same as above = $ 12,789.60
    $21.90 X 146 washes X 4 filters = $12,789.60 Wash Filter Year
  • Calculate Savings and Revenue in BW
    • Savings from saved water per year:
      • figured already = $12,789.60
      • Savings from treating or retreating replacement water – $ 12,789.60 same as above
    • Total savings from saved and retreating water = $25,579.20
  • Calculate Savings and Revenue in BW
    • Revenue Value of Water Saved:
    • $Price X 1000 Gallons Saved = $ Revenue
    • 1000 Gallons
    • 1.5 mintues x 4000 gal/min = 6, 000 gallons/wash
    • or 3,504,000 gallons per year (6000x146x4)
    • Water rate = $3.75/1000 = $13,140 Revenue value
  • Calculate Savings in Power for Pumps and Blowers
    • Calculate power use for pump or blower (air wash or air scour)
    KW * Used X Hours of Pumping X Dollars = Dollars Backwash KWH * Backwash * KW = Kilowatt; KWH = Kilowatt Hour. Calculate KW from motor name plate from - KVolts X rated Amps of motor.
  • Calculate Savings in Power for Pumps and Blowers
    • Calculate power use for pump or blower (air wash or air scour)
    • Example of 1.5 minutes/backwash savings
      • 60 HP PUMP AT 24kw ONLY PUMP USED
      • Utility pays $0.07 per KWH
      • 1.5/60 = hours of pumping
    24 KW X 0.025 Hours of Pumping X $0.07 = $0.042 Backwash KWH Backwash
  • Calculate Savings in Power for Pumps and Blowers
    • Calculate power use for pump or blower (air wash or air scour)
    • Example of $.042 /backwash savings
      • $0.042 x 146 backwashes/filter/year = $6.13 / Filter
      • $6.13 / Filter x 4 = $24.52 per year
    24 KW X 0.025 Hours of Pumping X $0.07 = $0.042 Backwash KWH Backwash
  • Summary of Savings
    • Savings from using less water
      • Washwater saved $ 12,789.60
      • Retreatment saved $ 12,789.60
    • Savings in Power Cost
      • Backwash pump $25
      • Surface wash $10
      • Waste return $ 5
      • Other pumps
    • Savings in labor
      • Reduced by the percent reduction of pump usage (eg 15 hrs) X labor cost
      • TOTAL DIRECT ANNUAL SAVINGS > $25,619.20
  • Summary of Savings
    • Total Direct Annual Savings $25,604.20
    • Indirect Annual savings
      • Revenue from water saved $13,140
      • Water saved/year 3,504,000 gal
  •  
  • Disinfection Control
  • Disinfection Control
    • Ozone
    • Chlorine Dioxide
    • Chloramination
  • Ozone
    • Typically use ozone analyzer or ORP for feedback control
    • Feed forward control usually done by measuring organic loading
      • TOC
      • UV-254
  • Ozone
    • Ozone is aggressive, volatile, and has a short half-life
    • Very important to sample properly
      • Correct sample tubing material
      • Shortest line possible
      • High velocity with proper volume to instrument
  • Ozone
    • “ A short detention time is critical when ozone decay is very rapid (i.e. ozone half-life is short). Sample detention time is considered adequate if total ozone decay within the sample line is <10% for the worst-case condition, which is the most rapid ozone decay rate.”
    • (Rakness, Ozone in Drinking Water Treatment: Process Design, Operation and Optimization, AWWA 2005).
  • Ozone Residual Loss in Sample Line
  • Chlorine Dioxide
    • Requires amperometric titration in lab for regulatory purposes
      • CLO 2
      • Chlorite
      • Chlorate
      • Generator performance
    • On-line instruments provide the monitoring necessary to assure CLO 2 stays within limits
  • Chloramination
    • Must use the correct instrument for the job
    • If you are making monochloramine then measure monochloramine
    • You cannot use a total chlorine test to measure monochloramine
    • WHY?
  • Chloramination
    • Back to some basics
    • Definitions
      • Total Chlorine = Free + Combined
      • Combined Chlorine = (mostly) mono-, di- and trichloramine
      • Free Chlorine = Hypochlorous acid (HOCL) + hypochlorite ion (OCL - )
  • Chloramination Curve
    • Begin adding chlorine to water containing ammonia
      • Initial addition of chlorine reacts to exhaust any chlorine demand present in the water
  • Chlorination Curve Chlorine Added Chlorine Measured
  • Chloramination Curve
    • Continue to add chlorine to the water
      • After chlorine demand is exhausted, chlorine reacts with ammonia to form monochloramine
    HOCl + NH 3  NH 2 Cl + H 2 O
  • Chlorination Curve Chlorine Added Chlorine Measured Chloramination I 5:1 Cl 2 :N Ratio
  • Chloramination Curve
    • Continue to add chlorine to the water
      • After complete formation of monochloramine, monochloramine reacts with additional chlorine to form dichloramine and nitrogen trichloride.
    HOCl + NH 2 Cl  NHCl 2 + H 2 O
  • Chloramination Curve
    • Continue to add chlorine to the water
      • As dichloramine and nitrogen trichloride form, the addition of chlorine continues to oxidize these compounds to nitrogen gas
      • The point at which all dichloramine is converted to nitrogen gas is the breakpoint .
  • Chlorination Curve Chlorine Added Chlorine Measured Chloramination I Breakpoint 9:1 Cl 2 :N Ratio II 5:1 Cl 2 :N Ratio
  • Chloramination Curve
    • Continue to add chlorine to the water
      • After the breakpoint, all chlorine added to the water remains as free chlorine
      • Breakpoint chlorination
    Cl 2 + H 2 O  HOCl + OCl -
  • Chlorination Curve Free Chlorination III Chlorine Added Chlorine Measured Chloramination I Breakpoint 9:1 Cl 2 :N Ratio II 5:1 Cl 2 :N Ratio
  • Chloramination Goals
    • Complete formation of monochloramine (stay in section I)
      • 3-5:1 Cl 2 :N optimal feed ratio
    • Avoid dichloramine formation
      • Avoid taste and odor problems
    • Minimize un-reacted ammonia
      • Control biofilm and nitrification
  • Chloramination Species
    • Curve we have been looking at is total chlorine
    • What other species are involved in chloramination and what happens to their concentrations?
  • Free Ammonia
    • Free ammonia reacts with chlorine to form monochloramine until ammonia has been consumed
  • Chloramination Species Free Chlorination III Total Chlorine Free Ammonia Chlorine Added Chlorine Measured Chloramination I II
  • Monochloramine
    • Monochloramine is equivalent to total chlorine until Section II where it reacts with chlorine to form new compounds.
    • No monochloramine remains at the breakpoint.
  • Chloramination Species Free Chlorination III Total Chlorine Free Ammonia Monochloramine Chlorine Added Chlorine Measured Chloramination I II
  • Free Chlorine
    • Free chlorine does not exist until after the breakpoint.
    • After the breakpoint, all chlorine added to the system exists as free chlorine.
  • Chloramination Species Free Chlorination III Total Chlorine Free Ammonia Monochloramine Free Chlorine Chlorine Added Chlorine Measured Chloramination I II
  • Chloramination
    • So why can’t I use total chlorine to run my chloramination process?
    • Let’s look at the results of a total chlorine test on the curve.
  • Where Am I When Total Chlorine = 3mg/L? Free Chlorination III Chlorine Added Chlorine Measured Chloramination I II
  • I Am Here! Free Chlorination III NH 2 Cl = t-DPD f-NH 3 N > 0 NH 2 Cl < t-DPD f-NH 3 N = 0 t-DPD > 0 NH 2 Cl = 0 f-NH 3 N = 0 Chlorine Added Chlorine Measured Chloramination I II
  • Chloramination
    • Chose the right instrument for the job
    • Both lab and on-line instruments are available to measure and/or calculate:
      • Monochloramine
      • Total Chlorine
      • Free Chlorine
      • Total Ammonia
      • Free Ammonia
  • Chloramination
    • Using the right instrument to measure these parameters will keep your process in control
    • Upset conditions can be dealt with in a timely manner to minimize any negative impact
  • Distribution
  • Distribution
    • Distribution monitoring is critical not only for security, but also for performance reasons.
    • The distribution system is a part of the process that has been overlooked.
    • The water leaving your plant may meet all regulated requirements, but can change dramatically in distribution.
  • Distribution
    • There are many parameters that can be monitored.
    • Through many studies, those deemed most important are:
      • pH
      • Conductivity
      • Chlorine (colorimetric)
      • Turbidity
      • TOC
  • Distribution
    • Several manufactures have developed “panels” that include these and other parameters.
    • You can build your own with discrete instruments
    • EPA suggests that at least 10 sampling points are needed throughout a system to be effective
    • The difficult part is interpreting all the data
  • Guardian Blue ™
    • Off the shelf “hardware” and communications
    • Raw data available to SCADA system
    • Contains a software algorithm that can interpret, identify and name anomalies in the system
  • Guardian Blue ™
    • Hach Laboratory testing and verification.
    • EPA/Battelle Environmental Testing Verification (ETV) program testing and certification.
    • Army Edgewood Chemical and Biological Command (ECBC) and Army Corps of Engineers Engineer Research and Development Center-Construction Engineering Research Laboratory(ERDC-CERL) Testing.
    • Real world deployment testing.
  • All of this Led to DHS Safety Act Approval
    • The SAFETY act is part of the 2002 Homeland Security Act. S upport A nti-terrorism by F ostering E ffective T echnologies Act
    • Provides litigation protection for manufacturers and end users of designated anti-terror technologies.
    • All testing data was submitted to DHS for review and approval.
    This is currently the ONLY DHS Designated and Certified on-line water anti-terror technology protecting you from system disruption and potential litigation
  • Dual Use Capabilities
    • The security aspects of the system derive from the event detection software and the agent library compiled by Hach.
    • The everyday utility derives from the event detection software and the plant library that is learned on site.
  • Plant Library
    • The learning ability and plant library can be used to correlate problems to changes in water quality.
    • System can be programmed to alert operators when such changes recur so that corrective action can be taken and the water supply is not compromised.
  • How the Algorithm Works Baseline Estimator Gain Matrix A Distance Measure Unit Vector Formation using Y(t) Vector Search X(t) Five Parameter Signal Vector Baseline Deviation Y(t) + - Resultant Vector Report Best Match Vector Libraries ( Agent, Plant ) A two-step process is used: Trigger when deviations indicate agent Classify agent in response to Trigger Is Threshold exceeded? No Yes Trigger Signal Threshold Level Trigger
  • Plant Event Defined Name: Pump Shut Off, Type: NORMAL
  • The plant uses caustic feed to control water pH and experienced an operational problem that resulted in the feed of excess caustic. That affected the pH and the conductivity of the water, causing the Event Monitor to alarm. The Event Monitor learned this Plant Event and can identify a recurrence of the event.
  • Road work near a distribution line dislodged biomass and other particulate matter from the lining of the pipe. There was a massive increase in turbidity, which not only showed up on the turbidimeter, but also showed up as an interference in the chlorine measurement ( optical ). As expected, the conductivity and pH also showed minor changes. The increase in biomass in the water was indicated by the TOC analyzer. This event illustrates the ability of the Event Monitor to detect and alarm on unanticipated events. This event also provides a signature for the materials adhering to the walls of the pipes in this location.
  • The Event Monitor is located in a building which experiences a daily variation in water pressure. The sample variation is associated with a turbidity increase that causes a Trigger. There is also a small pH decrease at that time, possible because of increased solubility of CO2 in the water, dropping the pH slightly. This pattern is recognized by the Event Monitor as a &quot;Normal&quot; event, rather than an alarm condition.
  • Effects of Variable Demand Daily events influencing turbidity, chlorine, pH and possibly conductivity are not completely understood but suspected to be caused by water demand fluctuations in the area. May indicate need for flushing and chlorine booster.
  • Ammonia Overfeed Event
    • On March 26 th , 2007, maintenance was performed at the Plant. After maintenance was completed, the plant was restarted and the system that feeds the ammonia overfed the chemical. The operator noticed an increase in pH and contacted operations at 16:25. Operations reported a problem with the ammonia feed pumps. The problem was temporarily fixed but a slug of ammonia was sent into the distribution system. Several customers called, complaining about an ammonia smell and taste coming from the tap. The exact amount of ammonia released was unknown, but was believed to be less than 10 ppm. The facility continued operation but temporarily utilizing free chlorine as a disinfectant until July 2 nd .
  •  
  • Possible Chlorine Feed Event On April 3, 2007 there was a turbidity and pH increase and a decrease in chlorine and conductivity. Operator believes that there might have been a problem with the chlorine feed at the plant. However, this cannot be confirmed. The plant was using free chlorine instead of chloramines at the time which rules out the ammonia feed problem.
  • Air Bubble Event
    • In one Northern Midwest system, every Friday, the sensors would behave extremely erratically resulting in multiple alarm signals being generated. Investigations led to the discovery of extreme amounts of entrained air bubbles being present in the systems water on Friday afternoons and evenings.
    • Further investigation revealed that school buildings that were to be vacant over the weekend had a policy of using air to blow out their water lines to prevent freezing so that the heat could be turned off over the weekend. A faulty check valve at one of the schools allowed the air to bleed into the distribution system. The valve was replaced, thus closing a possible backflow route into the system. After this the erratic readings ceased.
  • Main Break #1 The break occurred on July 30 th , 2006. The line was a 36” water main located 1.0 miles from the WDMP. Conductivity, turbidity, and chlorine spiked. There appears to be two water flow interruptions to the WDMP the night before but it’s unclear if they are related to the break on the 30 th .
  • Main Break #2 The break occurred at night on September 20 th , 2006. The exact time of the break is currently unknown, although there appears to be a flow interruption to the WDMP the previous morning. The line involved was a 12” water main which is 0.4 miles from the WDMP.
  • Main Break Event #3 August 17 at 10:30 AM Pittsburgh, PA
  • Turbidity
  • Chlorine
  • Conductivity
  • Conductivity Main Break 48 Hours Before
  • 36 Inch Main Break
    • A geyser caused by a severed 36-inch water line erupts 10:30 a.m., August 17 th . One of the largest water main breaks in the city's modern history.
                                                                                                                                                        
  • A driver who was able to rescue a vehicle follows a man on foot out of a flooded parking garage, following a water main break                                                                                                                                                                                               
  • More than 20 million gallons of water poured out and into nearby parking garages and other low-lying areas Downtown.                                                                                                                                                                                               
  • Workers move a section of new pipe into position as the broken 36-inch water main can be seen in the background.                                                                                                                                                     
  • Distribution
    • Distribution monitoring can be an effective means for protecting your customers from not only a security threat, but also from a plant or distribution system upset.
  • Questions?
  • Process Instruments Hands-On/Demo
    • Variety of instruments set up on an isolated city water supply
    • “Challenge” the instruments with
      • Caustic
      • Acid
      • Chlorine
      • Turbidity
  • Summary and Conclusions
  • Summary and Conclusions
    • Representative sample taps are a critical component of any testing protocol
    • Knowledge and understanding of your process is key to running it properly
    • Data collection is only good if you analyze it
    • From source to tap, on-line analysis is essential for safe, secure and high quality water
  • Summary and Conclusions
    • Lab instruments are essential for reporting and verification of process instruments
    • On-line instrumentation is the most effective way to keep your process in control
    • Significant cost/energy savings can be achieved using on-line instrumentation
  • Questions?
  • Acknowledgements
    • Terry Engelhardt, Hach Company
    • Mike Sadar, Hach Company
    • Chuck Scholpp, Hach Company
    • Carl Byron, Chemtrac
    • Trina Picardi, Hach Company