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Visit us at: www.ci.englewood.co.uswwtpdefault.htm. K. I. S. S. K Chemical I njection S ystem S implified. Presented by. Kirk Petrik - Project Manager, Brown and Caldwell Darwin Barrie - Maintenance Supervisor, Littleton / Englewood WWTP
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K. I. S. S. KChemical Injection System Simplified
Presented by • Kirk Petrik - Project Manager, Brown and Caldwell • Darwin Barrie - Maintenance Supervisor, Littleton / Englewood WWTP • Greg Farmer - Operations Supervisor, Littleton / Englewood WWTP • James Widner - Brown and Caldwell
History • 1991- Liquid chemical disinfection system replaced gas system • Cost - $466,000 • Complexity increased through design • Temporary system - designed to last 5 years
L / E WWTP Action Team Research • Records • Operations log entries • Maintenance work orders • www.wef.org • Discussion forums • Meetings • Staff interviews • Brainstorming • Develop action plan
Chemical Supplier Experience • Tank penetrations / Rigid connections • Minimal below liquid level • Connections / valves / fittings • Each connection a leak source • System replacement • Tank selection critical • Every 5 years • Off gassing • 50% decomposition to gas every 100 days @ 21C
Original Liquid System Manifold & Fixed Pump Concept • Chemical isolated in valves and piping • Repairs require additional piping, fittings • Specialized electronic repair on-site
Leakage Result of NaOCl isolation in piping- chemical decomposition
Complex Piping How many valves can you count?
L/E WWTP System Concept • Keep it Simple • One Tank + One Pump = One System • Easily isolated • Remove and replace pump- no tools required • Minimal piping and valves • Flexibility/Versatility
L/E WWTP System Overview Containmentareas
Simplified Control Speed indicator / totalizer 110 V outlet Sodium bisulfite pumps
Simplified Pump Controls Hand - Off - Auto Switch 110 V connection 4 - 20 mA input Manual speed control dial Plug and Play
Chemical Transfer / Emergency Response Containment drain valve Transfer pump connection Transfer pump
Off - Gassing Chlorine gas trapped in line Pressure relieved
Pumps & Piping Before After
After Pumps Before
Pump Controls Before After
1 2 Pump Maintenance Change pump tube as indicated by totalizer: Hypochlorite -every 2 months Bisulfite -every 3 weeks 3 4
Dosage Control Methods • Wet chemistry residual analyzer • Unreliable • Hach DPD method • Interference • Oxidation Reduction Potential
OxidationReductionPotential • ORP measures the transfer of electrons • Chlorine forms that are toxic to microorganisms are missing one or more electrons and satisfy their need for electrons by stealing them from organics or other donors through an electrical attraction. • This electrical potential is the ORP and is measurable in millivolts (mV) • Higher mV = greater disinfecting capability
ORP Probe Locations ORP Controller Effluent ORP Influent ORP
ORP Controller & Probe Influent ORP Effluent ORP Programming access
ChlorinationSetpoint • Select a setpoint that gives the desired fecal kill • The setpoint is dependant on the chlorine residual species
DechlorinationSetpoint • Start with a low setpoint to assure compliance • Gradually increase setpoint if chemical savings is desired
ORP Maintenance • Autowash cycle once/day • A weak acid solution is pumped to the electrode • A calculated average dosage is maintained while in the wash cycle • Manual cleaning twice/week • Pull the probe and clean with a toothbrush
Manual Probe Cleaning Acid cleaning solution Auto wash reservoir Toothbrush
ORP Performance Fecal Coliform 3330 /100ml* Since ORP Installation - 300 / 100 ml Effluent Chlorine Residual 0.003 mg/l Since ORP Installation - 0 Violations * 30 day geometric mean
Alternate Control Modes • Flow paced mode • The pump speed is paced by the flow meter • Manual mode • The Pump speed is manually adjusted to maintain the desired ORP mV
ORP / Flow Paced Control Choose flow paced or ORP paced pump speed
Operational Summary • More is not always better • Simplicity in design = Simplicity in operation and maintenance • Simplicity can increase versatility • Chlorination / dechlorination automation can provide reliability