February 7, 2018 Process Monitoring of Water and Wastewater Treatment MWEA 2018 JOINT EXPO AND OPERATORS DAY
Functions of a Process Monitoring System Compliance / Compliance Assurance Early Warning / Upset Detection Operational Efficiency / Process Control 2
Dissolved Oxygen (DO) Wastewater Compliance Aeration control / Energy efficiency Drinking Water Taste Corrosion control 3
Energy Efficiency D.O. 4 Source: Blum, D., High Efficiency Aeration, Clarifier, Ilinois WEA, Summer 2013
Polarographic DO Sensor O 2 H 2 O O 2 H 2 O O 2 H 2 O H 2 O e - e - O 2 H 2 O O 2 Membrane e - e - Cathode O 2 H 2 O Anode O 2 H 2 O O 2 O 2 H 2 O H 2 O O 2 O 2 H 2 O H 2 O H 2 O H 2 O Probe Solution Oxygen diffuses through membrane Oxygen reduced (consumed) at cathode Electrons flow = electrical signal (ma) Oxygen concentration proportional to signal level
Measuring Dissolved Oxygen using Luminescence The excitation fiber in the sensor emits a blue light causing the sensing element to glow, or luminesce red. 6
Measuring Dissolved Oxygen using Luminescence Oxygen is constantly moving through the Diffusion Layer, affecting the luminescence of the sensing layer. 7 The lifetime of the luminescence is measured by the sensor and compared against the reference and a stable dissolved oxygen concentration is calculated. The amount of oxygen passing through the sensing layer is inversely proportional to the lifetime of the luminescence in the sensing layer.
Water Treatment Process Monitoring Physico-chemical treatment ph Chlorine Turbidity Alkalinity Ortho-phosphate (PO 4 ) Total Organic Carbon (TOC) Sludge level Nitrate Dissolved Oxygen (DO) 8
Wastewater Treatment Process Monitoring Biological and Physico-chemical treatment Dissolved Oxygen (DO) Total Suspended Solids (TSS) Oxidation Reduction Potential (ORP) Sludge level Ammonia (NH 3 ; N -3 valence) Nitrate (NO 3- ; N +5 valence) Ortho-phosphate (PO 4 ) Chlorine ph 9
Process Monitoring System Components Universal Controller Display System settings Power supply Outputs 10
Process Monitoring System Components Sensors Measurement devices Signal processing
Instrumental Methods of Analysis / Signal Types Electrochemical Potentiometric Polarographic Optical Absorption Scattering Emission Fluorimetry 12
Ammonia / Ammonium Measurement Potentiometry ion selective electrodes (ISE) Colorimetry (absorption) cabinet analyzers 13
Potentiometry Sensor Design Ion Selective Electrode (mv) Reference electrode Membrane Junction 14
Ammonia / Ammonium Applications Wastewater Ammonia-Based Aeration Control 15
Ortho-Phosphate Detection & Measurement by Colorimetry sample with PO 4 3- reagent yellow mixing coloration photometer =420 nm
Ortho-phosphate Applications Drinking water Wastewater 17
Control of a Ferric Chloride Dosing Pump (Phosphorus Removal from Wastewater)
Turbidity, Total Suspended Solids (TSS) Detection by Light Scattering Backscatter (digested sludge) light absorbance / turbidimetry < 90 (mixed liquor) Nephelometry (clean water) 19
Turbidity / Total Suspended Solids Applications Drinking Water (compliance) Water or Wastewater (non-compliance) 20
Turbidity Measurement Standards ISO 7027 LED 860 nm DIN EN 27027 LED 860 nm US EPA Method 180.1Tungsten Filament ASTM D 1889-88 Tungsten Filament All methods: nephelometric 90 NTU = FNU = FTU 90 Use of LED 860 (nm) Weak sensitivity to very small particles No influence of colored samples Tungsten filament High sensitivity to small particles Influence by colored samples 21
Wastewater Activated Sludge Solids Monitoring System Immersion sensor in mixed liquor Insertion sensor in return activated sludge 22
Total Organic Carbon (TOC) Wastewater Surrogate parameter Water Reuse Drinking Water Disinfection byproducts 23
Basic Building Blocks of TOC Analysis Carbon Dioxide Sample Introduction Oxidation Detection Display 1. Syringe 2. Process/Online 3. Sample loop 4. Autosampler 5. Solids option 1. Combustion 2. Persulfate at 98 C 3. UV/Persulfate 1. NDIR (absorption) 2. Membrane Conductivity (electrochemistry) 1. Display 2. Printout 3. Computer 4. Strip Chart Recorder
TOC Analysis in the Drinking Water Treatment Process 25
Upstream Coagulant Control 26
Downstream DBP Mitigation 27
TOC Analysis A Different Method Carbon Dioxide Sample Introduction Oxidation Detection Display 1. Syringe 2. Process/Online 3. Sample loop 4. Autosampler 5. Solids option 1. Combustion 2. Persulfate at 98 C 3. UV/Persulfate 1. UV NDIR (absorption) 2. Membrane Conductivity (electrochemistry) 1. Display 2. Printout 3. Computer 4. Strip Chart Recorder
Direct UV Detection of TOC
TOC Monitoring for (Waste)Water Reuse Control ozone dosage Monitor treatment performance (upstream and downstream sensors) Not for compliance 30
Blanket Level Wastewater Sludge recirculation (ASP) Sludge removal Drinking Water Sludge removal 31
Sludge Blanket Depth Measurement Advantages: High resolution TSS profile Disadvantages Moving parts Limited sampling Advantages: Less fouling Continuous Long-term stability Disadvantages Fluffy sludge / ambiguous results 32 Optical Acoustic
Wastewater Activated Sludge Clarifier Q + Q ras MLSS Q Q ras 33
Contact YSI or Systems Specialties www.ysi.com E-mail robert.smith@xyleminc.com ksomsel@sysspec.com Twitter @YSIinc @DrRobYSI YouTube https://www.youtube.com/user/ysiinc Facebook https://www.facebook.com/myysi 34