What is Turbidity? - ISA Northern California Section

1 StandardsCertificationEducation & TrainingPublishingConferences & ExhibitsWhat is Turbidity? John DalyISA NorCal PresidentSouth Fork Instruments, Understand what turbidity is Investigate the various methods of measurement Compare those measurements Calibration and how it is the phenomen where by a specific portion of a light beam passing through a liquid medium is deflected from undissolvedparticles. What is turbidity ?Scattered LightIncidentLightbeamThe deflection is a function of the size and shape of the particlesSize: Smaller Than 1/10 the Wavelength of LightDescription: SymmetricSize: Approximately 1/4 the Wavelength of LightDescription: Scattering Concentratedin Forward DirectionSize: Larger Than the Wavelength of LightDescription: Extreme Concentration of Scattering in Forward Direction; Development of Maxima and Minima of Scattering Intensity at Wider AnglesAbsorbance vs.

2 Scattered Light I0 IR IS I0 ID Absorbance of light:(Concentration)Dissolved SolidsScattering of light:( turbidity )Particulate and SolidsScattered Light - What are Particles ?Particles may be anything creating heterogeneous surfaces: solids in liquids(suspension) oil in water / water in oil (emulsion) gas bubbles(foam) dust in air (smoke) droplets in air(fog, aerosol) Scattered Lightzthe type of the particles (absorbance)zthe size of particleszthe concentration (the number of particles)zthe type and shape of particleszthe wavelength of the lightzthe angle of measurementThe diffusion of light caused by undissolved particlesin the medium to a lesser or greater degree of the deflection depends on:Some History - Jackson CandleTurbidity ScaleScattered Light - Formazine Standard242 NHC Formazine=1 FNU = 1 FTU = 1 NTU = 1 TU/F = 0,25 EBCstandard-formazin-solution = 4000 FNUFNU = formazine nephelometric unitFTU = formazine turbidity unitNTU = nephelometric turbidity unitTU/F= turbidity units formazinEBC = European Brewery Conventioningredients: Hexamethylentetramine + HydrazinsulfateWhat does turbidity look like?

3 Formazin turbidity Standards - NTUS cattered Light - ComparabilityA lot of suppliers with different sensors hard to compareDual Beam Forward Scattered LightLIGHTSOURCEPROCESSSTREAMWINDOWSDIRE CT BEAMDETECTORSCATTER BEAM DETECTORSCATTER BEAM DETECTORCOLIMATINGOPTICS90 degree Scatter- NepholometrySingle Detector NepholometryDual Detector NepholometryOne and Two Detector 90 degree MeasurementSingle Detector(low turbidity )Second shorter path detector (high turbidity )23 Characteristic LinesturbidityintensityBackscatter MeasurementHigh turbidity Systems 4000 FTUT ypically probe systemsDisturbing Light Effectsdisturbing light- daylight- other light- heat sources (IR) Main Disturbance: Gas Bubbles50-80% of the mistakes in turbidity measurementMany suppliers have a debubbler chamber associated with their installation Wiper Spray cleaningSpray headSensor Cleaning SystemsHow does turbidity relate to Process?

4 Each process will have a specific turbidity signature Your process will have a different particulate size distribution to Formazin so has to be correlated Standards only allow the instrument to be calibrated to the same condition Readings are TREND readings for your process If the particle size distribution changes, so does the reading!Scattered Light - Comparability, Correlation05010015020025030005010015020 0 NTU (90 )FTUF ormazineSolids 1 Solids 2 Solids 3 Scattered Light - Comparability,Correlation - againPPM readings against Nepholometry0204060801001201401600102030 40 PPMNTUR atio Measurement(Nepholometer)Single BeamNepholometerTurbidityTurbidity as Function of ConcentrationTurbidityTypical ValuesMeasured SampleWaste WaterFinal outlet sewage treatment plantWell WaterPotable waterMilkOrange juicePrimary sludgeActivated sludgeRecirculated sludgeDigested sludgeMeasured Value70-2000 NTU4-20 - 10 - NTU> 4000 NTU300 - 900 NTU6-3%(60 - 30 g/l)3-7 g/l6-8 g/l5-8%(50-80 g/l)

5 turbidity - Examples of Applications Filter Control Centrifuge/Separator Control Biomass in fermenter Cell Growth Quality Control of final product Oil in water Water in oil Catalyst concentration Diesel in water Oil in condensate Leakage control heat exchanger Fat Content in milk Yeast dosage CIP return line Interphase detection Product recognition Water control, In- and Outlet Flocculant dosage Sludge concentration Pulp concentration Content of solids Dust in gases