THE MANY USES OF PLASMA
From 2000-2010, Dr. Manolache conducted research studies on the application of plasma for removal of various organic chemicals from water. These studies were conducted while previously employed at the University of Wisconsin, Center for Plasma-aided Manufacturing (CPAM). The contaminants covered the major classes of organic compounds (hydrocarbons, alcohols, ketone, ethers, esters, halogenated hydrocarbons).
Mixtures of contaminants typically have a complex chemical mechanism and response to experimental parameters. However, this is actually a huge advantage for decontamination processes using plasma over conventional water treatment methods. This is due to the fact that active plasma species (e.g., free radicals, ions, very reactive molecular compounds) generated by plasma act as a reagent for other chemical compounds that are normally not so reactive.
Pellucid Water uses the synergistic effects of plasma applied to a matrix of chemical contaminants to facilitate the processes of agglomeration, particle formation and flocculation.
Disinfection - primary
In addition to plasma providing chemical decontamination, it is also a strong disinfectant. This was demonstrated in a 2001 study by Dr. Manolache et. al while at CPAM -- refer to publication Dense Medium Plasma Environments: A New Approach for the Disinfection of Water, S. Manolache, E. B. Somers, A. C. L. Wong, V. Shamamian and F. Denes, Environmental Science and Technology 18, 3780 – 3785, 2001.
The study was conducted using water samples containing 16 environmental Gram positive and Gram negative bacterial isolates, including species from Bacillus, Corynebacterium, Enterobacter, Klebsiella, Micrococcus, Proteus, Pseudomonas, Shigella, and Staphylococcus, to ensure that the plasma treatment is effective against a broad spectrum of bacteria. After 20s of Ar/plasma treatment, 91% of the bacteria were killed. Increasing the treatment time to 60s increased the inactivation rate to over 98%. Treatment with O2/plasma showed similar results, with about 99% bacteria inactivated after 20–120s. No reduction in bacterial counts was observed in controls.
Unpublished studies by Dr. Manolache also indicated the effectiveness of plasma treatment for destruction of viruses. The mechanism for destruction of bacteria and viruses using plasma is in attacking the outer membrane.
Current methods of disinfection result in the formation of disinfectant bi-products (DBP). Plasma has not been shown to produce DBPs, because plasma agglomerates the dissolved chemistry into particles. Unlike current methods of disinfection, plasma also removes the micro-organisms from the water through the agglomeration process.
Disinfection - secondary
Currently, chlorinated compounds are primarily used for secondary disinfection, due to their sustained disinfection properties during transmission of treated water from the municipal water treatment facility through the distribution system. There is antidotal evidence to suggest that plasma may be able to provide secondary as well as primary disinfection. This is based on observations after the application of plasma to natural fibers – see discussion below on Manufacturing: Modification of Natural and Synthetic Fiber.
The residual effect of the application of plasma to the surface of cellulose is prolonged protection against microbial decomposition. Natural Organic Matter (NOM) is present in small quantities in treated municipal water. NOM is a food source for micro-organisms that may survive primary disinfection treatment. If plasma renders the surface of NOM unavailable to micro-organisms (i.e., through sterilization) in the same way as cellulose, then residual micro-organisms present would not be able to grow. Thus, secondary disinfection is provided indirectly through plasma treatment of NOM.
Pellucid Water is interested in conducting research to substantiate whether potential exists for plasma as an alternative secondary water treatment method. However, funding to support this study has not been secured.
Organic Compounds and Inorganic Ions
Pellucid Water conducted numerous field studies on effectiveness of the application of plasma for removal of organic compounds and inorganic ions present in various chemical matrixes.
Paper Mill Effluent
Field Samples, from left:
Vial 1: Untreated, from tail end
of treatment facility.
Vial 2: Vial 1 after treatment with
plasma -- note precipitate.
Vial 3: Untreated, from head end
of treatment facility.
Vial 4: Vial 3 after treatment wit
plasma -- note precipitate.
Field samples were obtained from a municipal wastewater treatment facility. The sample to the left was from the head end of the facility, before conventional treatment processes; the sample to the right was from the tail end of the facility, after conventional treatment processes. The vials were then treated with Pellucid Water plasma, resulting in particle formation and flocculation. The concentration of Phosphorus in the clear liquid was reduced in both samples to approximately 0.04 PPM.
Chlorides are present in sea water, brackish water and many industrial effluents. They are also present in municipal sewage as a result of the use of road salt (in northern climates during winter) and use of household water softeners.
Pellucid Water conducted an experiment to validate the capability of plasma to remove chlorides through agglomeration and particle formation. A sample of sea water was treated with plasma. The photograph to the right shows the sample after treatment. Particle formation was initiated by plasma and a flocculent formed. The net reduction in chlorides was approximately 30%.
Manufacturing: Modification of Natural and Synthetic Fiber
Plasma can be applied to modify the surface chemistry of natural and synthetic materials that are used in the manufacture of commercial and industrial products. Such modifications can enhance the properties of the materials
An unpublished experiment was conducted on a sample of cellulosic fiber. The initial objective was to determine the effectiveness in the application of plasma for sterilization. A sample of cellulose treated with plasma and an untreated sample (Control) were placed in separate containers and then stored at room temperature for a period of three months. The treated cellulose remained unaltered from its initial state, while the Control became discolored within a week (due to the growth of micro-organisms. Pellucid Water theorizes that plasma alters the surface chemistry -- possibly the physical structure -- of the cellulosic fibers. This renders it biologically unavailable as a food source for micro-organisms.
In a related experiment, fiber treated with plasma was pressed into a sheet that was used to make a flower pot. [Note: A binder was added to provide strength to the fibers.] A plant was grown for a period of one year without any evidence of decay due to micro-organisms.