Visit us at: www.ci.englewood.co.us\wwtp\default.htm

K. I. S. S.K. I. S. S.

KKChemical IInjection

SSystem

SSimplified

Presented by

• Kirk PetrikKirk Petrik - Project Manager, Brown and Caldwell

• Darwin BarrieDarwin Barrie - Maintenance Supervisor, Littleton / Englewood WWTP

• Greg FarmerGreg Farmer - Operations Supervisor, Littleton / Englewood WWTP

• James WidnerJames Widner - Brown and Caldwell

HistoryHistory

• 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 TeamL / E WWTP Action Team

• RecordsRecords– Operations log entries – Maintenance work orders

• www.wef.orgwww.wef.org– Discussion forums

• MeetingsMeetings– Staff interviews

• BrainstormingBrainstorming– Develop action plan

ResearchResearch

Chemical Supplier Experience• Tank penetrations / Rigid connectionsTank penetrations / Rigid connections

– Minimal below liquid level

• Connections / valves / fittingsConnections / valves / fittings– Each connection a leak source

• System replacementSystem replacement– Tank selection critical– Every 5 years

• Off gassingOff gassing– 50% decomposition to gas every 100 days @ 21C

Original Liquid SystemOriginal Liquid System

• Chemical isolated in valves and piping

• Repairs require additional piping, fittings

• Specialized electronic repair on-site

Manifold & Fixed Pump ConceptManifold & Fixed Pump Concept

LeakageLeakageResult of NaOCl isolation in piping-chemical decomposition

Specialized electronic repairSpecialized electronic repair

Complex PipingComplex Piping

How many valves can you count?

Complex Control SystemComplex Control System

L/E WWTP System ConceptL/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 OverviewL/E WWTP System Overview

Containment areas

Simplified LayoutSimplified Layout

Simplified PipingSimplified Piping

Sodium bisulfite pumps

110 V outlet

Speed indicator / totalizer

Simplified ControlSimplified Control

Simplified Pump ControlsSimplified Pump Controls

Hand - Off - Auto Switch

Manual speed control dial

4 - 20 mA input

110 V connection

Plug and Play

Temporary SystemTemporary System

Chemical Transfer / Emergency ResponseChemical Transfer / Emergency Response

Containment drain valve

Transfer pump

Transfer pump connection

Off - GassingOff - Gassing

Chlorine gas trapped in line

Pressure relieved

Pumps & PipingPumps & Piping

Before After

PumpsPumps

AfterBefore

Pump ControlsPump Controls

Before After

System Operation & ControlSystem Operation & Control

Pump MaintenancePump Maintenance

1

2

3

4

Change pump tube as indicated by totalizer:

Hypochlorite -every 2 months

Bisulfite -every 3 weeks

Dosage Control MethodsDosage Control Methods

• Wet chemistry residual analyzer– Unreliable

• Hach DPD method– Interference

• Oxidation Reduction Potential

OxidationOxidation ReductionReduction PotentialPotential • 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 LocationsORP Probe Locations

Effluent ORP

Influent ORP

ORP Controller

ORP Controller & ProbeORP Controller & ProbeInfluent ORP

Effluent ORP

Programming access

ChlorinationChlorination SetpointSetpoint

• Select a setpoint that gives the desired fecal kill

• The setpoint is dependant on the chlorine residual species

DechlorinationDechlorination SetpointSetpoint

• Start with a low setpoint to assure compliance

• Gradually increase setpoint if chemical savings is desired

ORP MaintenanceORP Maintenance

• Autowash cycle once/dayAutowash 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/weekManual cleaning twice/week– Pull the probe and clean with a toothbrush

Auto wash reservoir

Manual Probe CleaningManual Probe Cleaning

Acid cleaning solution

Toothbrush

ORP PerformanceORP Performance

Fecal Coliform 3330 /100ml*

Since ORP Installation - 300 / 100 ml

Effluent Chlorine Residual 0.003 mg/lSince ORP Installation - 0 Violations

* 30 day geometric mean

Alternate Control ModesAlternate Control Modes

• Flow paced modeFlow paced mode– The pump speed is paced by the flow meter

• Manual modeManual mode– The Pump speed is manually adjusted to maintain the

desired ORP mV

ORP / Flow Paced ControlORP / Flow Paced Control

Choose flow paced or ORP paced pump speed

Operational SummaryOperational Summary

• More is not always better

• Simplicity in design = Simplicity in operation and maintenance

• Simplicity can increase versatility

• Chlorination / dechlorination automation can provide reliability

Alternative Capital Annual O & M Present Worth

SodiumHypochlorite $ 383,000 $ 424,000 $ 4,546,000

Low PressureUV

(200 FC/100 ml)

$ 6,230,000 $ 212,000 $ 8,311,000

MediumPressure UV(200 FC/100 ml)

$ 5,093,000 $ 300,000 $ 8,038,000

Disinfection Alternative CostsDisinfection Alternative Costs

The EndThe End