ammonia analyzer provides real time process control capability pwo operator seminar – february 22,...

Ammonia Analyzer Ammonia Analyzer Provides Real Time Provides Real Time

Process Control CapabilityProcess Control CapabilityPWO Operator Seminar – February 22, 2002PWO Operator Seminar – February 22, 2002

Greg Farmer - Littleton / Englewood WWTPGreg Farmer - Littleton / Englewood WWTPGary Girolimon - Ted Miller and AssociatesGary Girolimon - Ted Miller and Associates

Littleton / Englewood WWTPLittleton / Englewood WWTPProcess SchematicProcess Schematic

Before Automating Process ControlBefore Automating Process Control

Diurnal ammonia variations led to:Diurnal ammonia variations led to:

Breakpoint chlorinationBreakpoint chlorination Inconsistent fecal coliform counts Inconsistent fecal coliform counts

BenefitsBenefits

Dial in Final Effluent Ammonia ConcentrationDial in Final Effluent Ammonia Concentration Centrate Return Timing FeedbackCentrate Return Timing Feedback Maximize Nitrifying Trickling Filter (NTF) Maximize Nitrifying Trickling Filter (NTF)

EfficiencyEfficiency More Consistent Fecal Coliform Counts Through More Consistent Fecal Coliform Counts Through

Control of Ammonia to Chlorine RatioControl of Ammonia to Chlorine Ratio Only 2-3 hours/month MaintenanceOnly 2-3 hours/month Maintenance

Ammonia ControlAmmonia Control

Nitrifying Trickle Filters Nitrifying Trickle Filters

NTF Effluent Ammonia NTF Effluent Ammonia Control ModesControl Modes

By-Pass Valve ControlBy-Pass Valve Control 24 / 7 Effluent ammonia goal 24 / 7 Effluent ammonia goal

is 2.0 mg/lis 2.0 mg/l Valve opens incrementally Valve opens incrementally

when ammonia is below 2.0 when ammonia is below 2.0 mg/l mg/l

Valve closes incrementally Valve closes incrementally when ammonia above 2.0 when ammonia above 2.0 mg/lmg/l

Pump ControlPump Control If ammonia level increases If ammonia level increases

above 7.0 mg/l, NTF pump above 7.0 mg/l, NTF pump speeds increasespeeds increase

When ammonia falls below 5.0 When ammonia falls below 5.0 mg/l pump speeds decrease.mg/l pump speeds decrease.

Pumps cannot go below a Pumps cannot go below a preset speed so that the preset speed so that the minimum hydraulic loading is minimum hydraulic loading is maintained.maintained.

By-Pass Valve ControlBy-Pass Valve Control

If the analyzer detects ammonia level below the set point, the by-pass valve opens incrementally.

If the analyzer detects ammonia levels above the set point, the by-pass valve closes incrementally.

By-Pass Valve OperationBy-Pass Valve Operation

Ammonia >

Valve closes when ammonia level increases above set point of 2 mg/l.

Valve opens when ammonia level decreases below set point of 2 mg/l.

< Valve position

Nitrate >

Pump Speed ControlPump Speed Control

If the analyzer detects ammonia levels below a set point the NTF pumps speeds decrease.

Pump speed cannot go below a selected value so that the minimum hydraulic loading is maintained.

If the analyzer detects ammonia levels above a set point the NTF pump speeds increase.

Pump Speed Control OperationPump Speed Control Operation

By-pass valve

Position >

< NTF Pump Output

Nitrate >

< Ammonia

ChlorinationChlorination

Controlled Chlorine to Ammonia Controlled Chlorine to Ammonia RatioRatio

Fecal Coliform CountsFecal Coliform Counts

Analyzer AccuracyAnalyzer Accuracy

Instrument AccuracyInstrument AccuracyAnalyzer vs. LabAnalyzer vs. Lab

Instrument values are extracted daily at 8:00 am and logged to the historical data server. Operators collect a sample near the analyzer at ~8:00 am for analysis by the lab.

Final Effluent AmmoniaFinal Effluent Ammoniavs.vs.

STIP Daily AverageSTIP Daily Average

Nitrate BuoyNitrate Buoy

<---- Calibrated Properly ----->

Recalibrated During Regular Maintenance - Suspect Poor

Quality 3rd party Reagent

ISCO/STIP ISCO/STIP Process BuoyProcess Buoy

STIP Process BuoySTIP Process Buoy

Operates by being Operates by being placed directly in placed directly in wastewater (even wastewater (even activated sludge)activated sludge)

Separate buoys for Separate buoys for ammonium and ammonium and nitratenitrate

STIP Process BuoySTIP Process Buoy

Follows EPA approved Follows EPA approved methods of analysismethods of analysis

Operates in a batch Operates in a batch analysis mode with typical analysis mode with typical analysis times of 3 to 5 analysis times of 3 to 5 minutesminutes

Measuring range of 0.1 - 50 Measuring range of 0.1 - 50 mg/l as N for both nitrate mg/l as N for both nitrate and ammoniumand ammonium

Method of Analysis - GeneralMethod of Analysis - General

Solenoid valve opens permitting Solenoid valve opens permitting sample to fill settling chamber via sample to fill settling chamber via hydrostatic pressurehydrostatic pressure

Sludge settles for pre Sludge settles for pre programmed time periodprogrammed time period

Ammonium and nitrate measured Ammonium and nitrate measured with ion selective electrodes (ISE)with ion selective electrodes (ISE)

Solenoid valve reopens permitting Solenoid valve reopens permitting supernatant to fill measurement supernatant to fill measurement chamberchamber

Method of Analysis - NHMethod of Analysis - NH44NN

Caustic (NaOH) added till Caustic (NaOH) added till pH>11.5pH>11.5

Ammonium is converted Ammonium is converted to Ammonia (gas)to Ammonia (gas)

Ammonia measurement Ammonia measurement taken with gas selective taken with gas selective electrodeelectrode

Method of Analysis - NOMethod of Analysis - NO33NN

Conductivity sensor used Conductivity sensor used to add reagent (ion to add reagent (ion suppression) to adjust suppression) to adjust ionic strength of solutionionic strength of solution

Concentration measured Concentration measured with nitrate selective with nitrate selective electrodeelectrode

Method of Analysis - SchematicMethod of Analysis - Schematic

CalibrationCalibration

Buoy calibration is Buoy calibration is done using three done using three step standard step standard addition methodaddition method

Calibrated Calibrated automatically automatically once per dayonce per day

Buoy Bulkhead LayoutBuoy Bulkhead Layout

Process Buoy In Open PositionProcess Buoy In Open Position

ShowsShows Settling ChamberSettling Chamber Measuring ChamberMeasuring Chamber ElectrodesElectrodes ValvesValves AmplifiersAmplifiers

Process Buoy Without Stainless Process Buoy Without Stainless Steel HousingSteel Housing

ControllerController

One controller can operate One controller can operate two buoystwo buoys

LCD screen displays current LCD screen displays current reading and graph of last 6-reading and graph of last 6-hours of operationhours of operation

Outputs:Outputs: 4-20 mA4-20 mA Bi-directional RS 232 Bi-directional RS 232

The EndThe End