PLANT OPTIMIZATION AT NORTH TABLE MOUNTAIN WATER AND

SANITATION DISTRICT

Presented By:

Rick Jeschke P.E.

District Engineer/Manager

NTMW&SD Background

District formed in November 1958 Publicly owned Run by an elected 5 member Board 3200 service connections Serves a population > 10,000

NTMW&SD Water Plant

Originally constructed in 1962 Major upgrades

• 1985 pump station• 1986 new filters• 1997 Actiflo ballasted floc system• 1999 MIOX chlorination system• 2001 new filters

NTMW&SD Water Plant

Surface water plant Plant rated at 15 MGD Yearly output 650 to 700 MG Actiflo ballasted floc treatment MIOX on-site chlorination system 8 multi media filters

Stage 1 D/DBP Requirements

Prompted by the EPA December 1998 TTHM MCL was set at 0.080 mg/L HAA5 MCL was set at 0.060 mg/L Chlorite MCL was set at 1.0 mg/L Bromate MCL was set at 0.010 mg/L Systems with a population over 10,000 had

to be in compliance by January 1, 2004

NTMW&SD DBP

In 1997 NTMW&SD average DBP were• TTHM 0.063 mg/L• HAA5’s 0.0404 mg/L• Chlorite and Bromate were below DL

The District felt that these values were to close to the MCL so plant upgrades were proposed

DBP Treatment Methods

Oxidation• Ozone• Chlorine dioxide• UV

Aeration Activated carbon Synthetic resins Remove precursors

Actiflo Ballasted Floc Process

Coagulated with alum Microsand and polymer are added next Destabilized suspended solids bind to the

microsand through polymer bridges Maturation to form micro sand ballasted

floc Sludge/microsand sent to hydrocyclones to

separate the microsand from the sludge

Actiflo Flow Schematic

NTMW&SD Actiflo Plant

Construction started Sept. 1997 Online May 1998 Two 7.5 MGD trains Each train 19 feet by 48 feet Total max detention time 21 minutes Total max settling time 10 minutes Designed for 24 GPM/ft squared

Actiflo TTHM Reduction

Pre Actiflo TTHM levels 0.063 mg/L Post Actiflo TTHM levels 0.041 mg/L TTHM levels reduced by 35%

Actiflo HAA5 Reduction

Pre Actiflo HAA5 levels 0.040 mg/L Post Actiflo HAA5 levels 0.028 mg/L HAA5’s levels reduced by 31%

Actiflo Microscopic Particulate Analysis (MPA) Reduction

Pre Actiflo 3 to 4 log removal Post Actiflo 4 to 5.5 log removal before

filtration Post Actiflo 6 to 6.7 log removal after

filtration

Clarified Turbidity

June

July

Aug

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Dec Ja

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yMONTH

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NTU

CONVENTIONAL

ACTIFLO

CLARIFIED NTU

Filtered Turbidity

JuneJuly

AugSept

OctNov

DecJan

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AprilMay

MONTH

0.04

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NTU

CONVENTIONAL

ACTIFLO

FILTERED NTU

Standard Plate Count (SPC)

Raw water SPC are 5/mL to 200/mL Clarified SPC are 2/mL to 16/mL Recycling sand not contributing to SPC

Sand Carryover

During initial startup some sand carry over was observed

After three days no sand carry over was observed

Sand carryover filtered out easily

Sand Consumption

Hydrocyclones are not 100% efficient Sand loss is approximately 4 pounds per

million gallons produced Equates to $0.40/MG Sand purchased 12 tons at a time Sand costs $0.10/pound delivered

Sand Abrasion

Online since May 1998 Six years of operation No wear on SS pipe No wear on hydrocyclones After six years lead pump liners were

replaced

MIOX at NTMW&SD

Before MIOX the District used chlorine gas Safety was the main factor in the decision to

go to on-site generation. On-site generation eliminated the storage

space for bleach On-site generation meant that the chlorine

would only be made when needed (with the system fully automated)

MIOX On-Site Chlorine Production Electrolysis of salt water to

generate chlorine practiced commercially for > 100 years

Chlorine produced at large chlor-alkali plants, packaged, and sold Chlorine gas cylinders Sodium hypochlorite drums Calcium hypochlorite tablets

Within past 30 years, developed smaller equipment to generate sodium hypochlorite on-site by same process

On-site generation uses only salt, water, and electricity Eliminates hazardous chemicals Heart of technology is the electrolytic cell

How the Cell Works Brine -- NaCl dissolved in H2O Positive ions are drawn to the

cathode; negative ions are drawn to the anode

Apply power Possible electrolytic reactions

Anode:

2 Cl- ==> Cl2 + 2e-

HOCl + H2O ==> ClO2 + 3H+ + 3e-

2H2O ==> O2 + 4H+ + 4e-

O2 + H2O ==> O3 + 2H+ + 2e-

Cathode:

2H2O + 2e- ==> H2 + 2OH-

Hydrolysis in Bulk:

Cl2 + H2O ==> HOCl + Cl- + H+

MIOX On-Site Chlorine Generation System

DC POWER SUPPLY

On-Site Chlorine Generation Advantages

Safety• No hazardous chemicals used, generated

stored, or transported• Chlorine concentration approx. 0.37-0.40%• No potential for chlorine leak• No possibility of forming chlorine gas

cloud by mixing with water• No combustible combinations

On-Site Generation Advantages (continued)

Regulatory Ease• No RMP• No HAZMAT training• No SCBA equipment• No “two man rule” for changing out cylinders• No chlorine scrubber, as required by Uniform

Fire Code• No DOT trucking requirements• No corrosion due to chlorine off-gassing

On-Site Generation Advantages (continued)

Cost Savings• Operating costs depend on cost of salt and

power• Cost of power offset by not purchasing chlorine• Lower than bleach or calcium hypochlorite

• Lower than ozone, UV, or ClO2

• Lower liability

On-Site Generation Advantages (continued)

Freshness and Consistency of Solution• Generated on-site as need• Shelf-life is a non-issue• No need to change dilution or mixing ratios• No degradation to chlorite or chlorate on shelf

MIOX at NTMW&SD

Three 50 pound per day cells One 100 pound per day cell Bulk salt storage Storage capacity of up to 600 gallons of

MIOX solution

MIOX TTHM Reduction

With the Actiflo system reducing the TTHM by 35%, no further improvement was expected using MIOX

Pre-MIOX TTHM levels 0.041 mg/L Post-MIOX TTHM levels 0.023 mg/L TTHM levels reduced by 44%

MIOX HAA5’s Reduction

With the Actiflo system reducing the HAA5’s by 35%, no further improvement was expected using MIOX

Pre-MIOX HAA5 levels 0.028 mg/L Post-MIOX HAA5 levels 0.016 mg/L HAA5’s levels reduced by 43%

NTMW&SD Chlorine Dosage

District policy is to maintain a minimum 0.4 mg/L residual in the distribution system

Pre-MIOX residual leaving the plant was 1.1 mg/L

Post-MIOX residual leaving the plant 0.8 mg/L

Chlorine dosage reduced by 27%

NTMW&SD Lime Dosage

MIOX is near pH neutral Chlorine gas has a low pH Post-MIOX the lime dosage reduced by

50%

MIOX System Maintenance

Amps and volts checked daily Pressure at cell checked daily Combined chlorine concentration checked

daily Individual MIOX cell concentration

checked monthly Hardness checked weekly

MIOX System Maintenance (continued)

Orifices are checked for blockages weekly Flows through the cells are checked twice

per month Cartridges Filters are changed out twice per

year

Control Panel

MIOX Cell Acid Cleaning

MIOX cells are acid cleaned twice per year Cleaned with a 50/50 HCl solution Allowed to sit for 15 minutes Rinsed with softened water Entire process takes approximately 1 hour

Miscellaneous MIOX Information

Important to buy highest quality salt Salt received in 25 ton bulk shipments 25 tons of salt costs $1,600 including

delivery MIOX provided a list of recommended

spare parts

Total TTHM Reduction

Pre-Actiflo and pre-MIOX TTHM levels 0.063 mg/L

Post-Actiflo and post-MIOX TTHM levels 0.023 mg/L

TTHM levels reduced by 63% in total

Total HAA5 Reduction

Pre-Actiflo and pre-MIOX HAA5 levels 0.040 mg/L

Post-Actiflo and post-MIOX HAA5 levels 0.016 mg/L

HAA5 levels reduced by 60% in total

THANK YOU!!

ANY QUESTIONS?