PathShield-EPA-approved-ClearwaterSolutionsInc

Removal of Waterborne Bacteria from stormwater Runoff Using An Antimicrobial Filter Media ASF Tech Report 13.1 May 2013

A S Filtration is pleased to introduce PathShield™ Antimicrobial Filter Media for the reduction and control of coliform bacteria in municipal waste water and stormwater treatment applications. PathShield™ is registered with the U.S Environmental Protection Agency (EPA ) in accordance with Federal law for its intended antimicrobial uses.View this ADF13.1 Tech Report in PDF
CLEARWATER SOLUTIONS

Technology Description

PathShield™ effectively reduces coliform bacteria without releasing, discharging, or leaching any antimicrobial agents, chemicals or heavy metals. PathShield™ kills coliform bacteria as the organisms physically move over the hostile surface of filter media granules (Figure 1). Efficacy is achieved at high filtration loading rates up to 20 gallons per minute per square foot (gpm/ft²). PathShield™ filter media is not consumed, requires no power source, has no moving parts, is non-corrosive, and is unaffected by seasonal temperature changes.

Laboratory Testing

A number of independent efficacy tests were performed by a NELAP accredited laboratory certified to perform E. coli plate counts. Various influent surface area loading rates and test cartridges simulated over 400,000 gallons of water passing through 24 cubic feet of PathShield™ media on an annual basis.

Laboratory Testing

A number of independent efficacy tests were performed by a NELAP accredited laboratory certified to perform E. coli plate counts. Various influent surface area loading rates and test cartridges simulated over 400,000 gallons of water passing through 24 cubic feet of PathShield™ media on an annual basis.

Table 1

Summarizes the results of the laboratory simulations. E. coli concentrations ranged from 150 to 36,000 colony forming units per 100 milliliters (cfu/100 ml) while loading rates ranged from 9 to 118 gpm/ft². Efficacies of >99.9% or log three reductions, were achieved for these eight simulations.

Additional independent long term laboratory efficacy challenges against E. coli were performed using 15 separate quality control PathShield™ filter media samples.

Table 2

Summarizes testing results using an average target influent E. coli concentration of 16,500 cfu/100 ml and an influent surface area loading rate of 10 gpm/ft² . Over 99.99% removal efficiency, or greater than a log four reduction, was consistently achieved for the long term testing program.

Field Testing

A series of independent filed verification tests were performed by university researchers using PathShield™ filter media within a full scale commercially available stormwater catch basin insert at an ultra urban location in Los Angeles, California.

Table 3

CLEARWATER SOLUTIONS

Summarizes the stormwater influent and effluent concentration of E. coli Enterococci and Total Coliform bacteria. An influent device loading rate of 19 gpm/ft² was measured for the testing events. Influent bacteria concentrations varied from under 2,000 cfu/100ml to very high concentration representative of stressed conditions. While all efficacies exceeded 92%, maximum efficacies of 99.9% were achieved resulting in a three log bacterial reduction.

Toxicity Testing

Comprehensive studies have been confirmed through the PathShield™ EPA registration that the media does not leach any antimicrobial agents, chemicals, or heavy metals and the effluent treated water is non-toxic.

Conclusions and Benefits

PathShield™ Antimicrobial Filter Media demonstrates superior performance for the removal of coliform bacteria in a variety of treatment applications including municipal waste water and stormwater runoff. EPA registration of PathShield™ confirms that coliform bacteria are physically killed as they pass through the media.

Significant operational and environmental benefits can be realized through the use of PathShield™ filter media including:

Conclusion and Benefits of PathShield
  • EPA registered antimicrobial filter media
  • Media does not discharge, release or leach any antimicrobial agents
  • Long term and high level of performance
  • Does not rely on physical trapping
  • No external power source or moving parts
  • Media is non-corrosive and is not consumed
  • Unaffected by seasonal temperature changes
Table 1. Summary of Laboratory Simulations
Influent E. coli (col/100ml) Loading Rate (gpm/ft²) Efficacy ( %)
150 19 >99.9
1,180 30 >99.9
2,120 9 >99.9
2,150 22.5 >99.9
3,000 10 >99.9
3,500 10 >99.9
4,300 18 >99.9
36,000 10 >99.9
Table 2. Long Term Laboratory Efficacy Testing
Influent E. coli (col/100ml) Effluent E. coli (cfu/100 ml) Efficacy ( %)
15,900 0.5 99.997
15,900 0.5 99.997
16,100 0.5 99.997
16,200 0.5 99.997
16,200 0.5 99.997
16,300 0.5 99.997
16,500 0.5 99.997
16,500 0.5 99.997
16,600 0.5 99.997
16,800 0.5 99.997
17,100 0.5 99.997
17,200 0.5 99.997
17,200 0.5 99.997
17,700 0.5 99.997
17,900 0.5 99.997
Table 3. Summary of Field Efficacy Results
Influent (col/100ml) Effluent (col/100ml) ( %)
E. Coli
1,800 <10 99.7
2,300 <10 99.8
7,000 120 98.3
10,000 770 92.3
Enterococci
5,000 <10 99.9
16,000 230 98.6
77,000 50 99.9
170,000 170 99.9
Total Coliform
1,700 <10 99.7
5,800 <10 99.9
9,900 <10 99.9
240,000 <10 99.9