Aqueous DBNPA: A New Spin on an Old Favorite

Liz Sutton Jonathan Howarth

Enviro Tech Chemical Services, Inc.

Outline

•  Efficacy and Persistance

•  Limitations of Existing Liquid Formulations

•  New Form = New Approach

–  Stoke’s Law

•  General Information & Storage Stability

–  Pumping Options & Compatible Materials

•  Field Trial Results

–  **Reactivation of –Br to HOBr**

•  Conclusions

Efficacy & Persistance

Source: Dow Antimicrobial 7287 and Dow Antimicrobial 8536 brochure.

Half Life vs. Temperature & pH

Source: Dow Antimicrobial 7287 and Dow Antimicrobial 8536 brochure.

At normal operating temps, ½ life ≈ 9 hr.s

Stability of DBNPA as a Function of pH

• New product is buffered at the stable pH of 3.7

Source: Dow Antimicrobial 7287 and Dow Antimicrobial 8536 brochure.

Limitations of Existing DBNPA Liquids

•  Low aqueous solubility. •  ≈ 60% polyethylene glycol.

–  Expensive and price fluctuates with oil markets.

•  Contributes both C.O.D. and B.O.D. to receiving waters.

New Formula = New Approach

•  Utilize knowledge of Stoke’s Law to develop aqueous suspension.

•  Replace PEG with H2O – Decrease and stabilize cost. – Eliminate issue of increased BOD & COD. –  Improve environmental profile.

Stoke’s Law

2 9

(ρp- ρf) µ vs = g R2

vs= Settling Velocity

ρp = Mass Density of Particles

ρf = Mass Density of Fluid

µ = Dynamic Viscosity of Fluid

g = Gravitational Force

R = Radius of Particles

Stokes Law Applied

•  Decreased R2 using high speed dispersion homogenizer.

•  Increased ρf by using NaBr brine rather than plain water.

•  Increased µ by using a food grade viscosifier.

•  These variables minimize vs and result in a greater physical stability.

1 Year Storage Photo

Fluid level.

No settling observed after 1 year.

1 Year Storage Stability of DBNPA Active in Non-Climate Controlled Warehouse

Label Information

•  18% active DBNPA – Dosed same rate by volume as 20% liquids

due to difference in density. •  Registered biocide, bactericide, fungicide,

algaecide, and slimicide, for recirculating cooling water, enhanced oil and oilfield systems, RO Membranes, and paper mills

•  EPA Reg. No. 63838-11 •  Optimum performance is achieved by

continuous or intermittent treatment

Features and Benefits Biocidal benefits derived from active DBNPA:

•  Low dosage requirements •  Extremely fast antimicrobial action •  Broad Spectrum efficacy • Compatible with chlorine treatment.

Additional Features and Benefits

•  Stable suspension, easily fed using traditional pumps or eductors.

•  Heavy brine resists freezing. •  Favorable environmental fate profile. •  No VOC’s •  No BOD or COD contribution •  “Green” alternative to other liquid DBNPA

products.

Hydrolysis

•  Aqueous phase composed of brine of 11.8% NaBr and 14.2% NaCl.

•  Presence of bromide ions in aqueous phase suppresses hydrolysis reactions.

Known Hydrolysis Routes

DBNPA decomposes to bromide ions.

Field Test

Tower Parameters:

– Holding Capacity 2600 gallons – Recirculation Rate 300 gpm – pH 8.1 – Delta T 3 degrees – Cycles of concentration 4.25 – HTI (calculated) 6435 hours (~268 days)

Field Test Because of high HTI and long time

necessary to reach equilibrium, DBNPA added at 40 ppm as product.

• 4.8 ppm Br- contributed by NaBr “carrier” • 4.4 ppm Br- contributed by degradation of DBNPA molecule • 9.2 ppm total Br- should be present in the system

•  Cooling tower slug dosed 2X per week •  Tower tested using DPD method and split

sample.

Test Results

Sample Free Cl2 (Glycine Added)

Free Cl2 (No Glycine)

1 0.40 0.44

2 0.53 0.51

3 0.48 0.48

Glycine added – measure only bromine No Glycine - measure chlorine and bromine

Is Br- Ion Available for Activation to HOBr?

•  Br- ion 9 ppm •  Introduced NaOCl bleach (free Cl2) to

recirculating water. •  Avg. of 0.40 ppm as free halogen in

presence of glycine •  Avg. of 0.94 ppm total Cl2

Is Br- Ion Available for Activation to HOBr?

•  Activation reaction is slow - 42% halogen exists as HOBr despite 8.5X excess of Br- ion

•  Confirms work of Kumar and Margerum. - Inorg. Chem. 26 2706 (1987) - HOCl is 1.5 million times faster than OCl-

Pumping Options

•  Eductors operated by solenoids for the drive water. – Larger diameter suction tubes due to viscosity

of neat product. •  Peristaltic Pumps

– Any Cl2 compatible tubing such as Hypalon® or Norprene ®.

•  Normal ball & seat chemical pump valves may tend to lose prime.

Compatible Materials

• At end use concentrations, DBNPA is compatible with all commonly used materials of construction in industrial cooling water systems.

• Neat product is compatible with: – PVC – HDPE & LDPE – Teflon®, Kynar®, Hypalon® – Polypropylene and all fiberglass reinforced plastics.

•  As a neat product, DBNPA is incompatible with: – Copper – Brass – Aluminum – Carbon Steel – Stainless Steel – Galvanized Steel

Conclusions •  New aqueous DBNPA encompasses all of

the positive attributes of existing liquids, while eliminating negatives associated w/ PEG.

•  Displays excellent chemical and physical stability.

•  NaBr brine: – Densifies aqueous phase – Suppresses hydrolysis reaction –  Is available for reactivation – Prevents product from freezing

•  EPA registered and available to members of AWT.