Microbial Persistence in the Presence of Triclosan: Evaluation of Green Roof Substrates Irrigated with Artificial Greywater

Open Access
Author:
Bloss, Heather C
Graduate Program:
Environmental Pollution Control
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 01, 2015
Committee Members:
  • Katherine H Baker, Thesis Advisor
  • Shirley Elizabeth Clark, Thesis Advisor
  • Daniel M Borsch, Thesis Advisor
Keywords:
  • Triclosan
  • Antibiotic Resistance
  • Antimicrobial Resistance
  • Green Roof
  • Greywater
  • Greywater Reuse
Abstract:
The installation of green roofs is an increasing trend to reduce the urban heat index, control stormwater runoff, and provide wildlife habitat. Lightweight soil substrate can reduce the modifications required for existing structures to support a green roof. Recycled crumb rubber offers an alternative to conventional green roof medium that both reduces the weight of a green roof and repurposes tires entering the waste stream. Vegetation can be maintained on such roofs through the reuse of household greywater, significantly reducing freshwater demand. Analysis of the microbial quality of conventional and recycled soil irrigated with artificial greywater was evaluated via culturable heterotrophs and most probable number assays for coliforms. Samples from both soil types irrigated with greywater supplemented with triclosan contained organisms resistant to triclosan. Triclosan resistant Escherichia coli were detected on two occasions in commercial media but did not persist. At no point were resistant E. coli detected in recycled substrate. The presence of triclosan caused fluctuations in the concentration of total coliforms present in commercial soil. Replicate plating further underscored the effect low-level, consistent biocide exposure has on the ability of microorganisms to develop resistance.