Grantee Research Project Results

Final Report: Singlet Oxygen Disinfection of Drinking Water

EPA Contract Number: 68D99049
Title: Singlet Oxygen Disinfection of Drinking Water
Investigators: Thomas, Rhys N.
Small Business: Fayette Environmental Services Inc.
EPA Contact:
Phase: I
Project Period: September 1, 1999 through March 1, 2000
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (1999) RFA Text |  Recipients Lists
Research Category: SBIR - Water and Wastewater , Watersheds , Small Business Innovation Research (SBIR)

Description:

This Phase I research demonstrated the disinfection and dehalogenation functions of a polymeric coating that has immediate application to drinking water treatment. Upon exposure to low intensity visible light, the coating photoinitiates singlet oxygen from the dissolved oxygen in water or air. Singlet oxygen is a potent disinfectant, known to disable a wide range of bacteria and viruses without promoting resistant strains. The use of this coating would eliminate the need for other disinfectants, although post chlorination would still be needed for water distribution systems. The polymeric coating on baffles or on the interior of containers or tubing, continuously disinfects in the presence of low intensity visible light and dissolved oxygen without by-products or residuals. As a side benefit, the same catalyst may be cast on an electrically grounded substrate to catalyze the dehalogenation of organohalides such as Atrazine. Without the grounded substrate, the dehalogenation function is deactivated.

Summary/Accomplishments (Outputs/Outcomes):

Two photoinitiating polymers have been developed for drinking water treatment. One, based on polyvinylchloride, effects 100% disinfection of water spiked with E. coli. The other, based on polyvinylcarbazole, decomposes Atrazine and other chlorinated hydrocarbons in a flow-through system at a rate proportional to the surface area of the filter and the flow. No components of the coating were detectable in the water.

The disinfecting coating was applied to sheets of commercial polyvinyl chloride and exposed to water spiked with 1000 CFU/mL E. coli. The coating was applied at four concentrations of the active ingredient. A monolayer of the polymeric coating was found to be both functional and durable. Across five iterations, each containing three replicates of each of three depths of coating, complete disinfection was obtained quickly and maintained for three days. Rinsing with warm water was the only physical cleaning between iterations. No biofilm was observed. Efficacy was not reduced with repetition.

Chlorinated hydrocarbons were removed from water in a flow-through filter system with varying results based on the reactivity of the target analyte, as compiled in Table 1. Smaller, polychlorinated molecules were not removed significantly. Atrazine was removed quite well. The initial concentrations varied from 1 ppm to 1 ppb with no significant difference in removal percentage.

Name	Contaminant Rate (mL/min/m2)	Residence Time (min/mL)	Removal %
Chlorodecane	14.5	0.61	65
Atrazine	18.5	0.48	57
Chlorobenzene	15.6	0.57	36
Bromoform	16.4	0.54	22
Trichloroethene	42.7	0.41	10
4-Chloro-2-methylphenol	16.4	0.54	8
Nitrophenol	16.4	0.54	7
Pentachlorophenol	16.4	0.54	4

Table 1. Removal of hydrocarbons from water.

Conclusions:

The coatings developed in this research have immediate application to drinking water systems for disinfection and pesticide removal. The synthesis is straightforward and scalable. No components of the coating are released into the water. The range of types of polymeric substrates and the coating solvent system will be addressed in future research.

Supplemental Keywords:

Publicly Owned Treatment Works., RFA, Scientific Discipline, Water, Engineering, Chemistry, Engineering, Chemistry, & Physics, Wastewater, Drinking Water, municipal wastewater treatment, treatment, viruses, organohalides, microbial risk management, exposure, water treatment, drinking water treatment, wastewater treatment, water utilities, municipal water, bacteria, municipal wastewater, dehalogenation