Enhancement of Oxidation Processes of Cellular Microbial Substrate, Using UV Radiation in Resonant Elliptic Cavity

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Enhancement of Oxidation Processes of Cellular Microbial
Substrate, Using UV Radiation in Resonant Elliptic Cavity HAROLD E. BRAUSTEIN 1 *, IGOR CRETESCU 1 , CONSTANTIN ANTOHI 2 , MARIANA DIACONU 1 , MATEI MACOVEANU 1  "Gh.Asachi" Technical University of Iasi,Faculty of Chemical Engineering, Department of Environmental Engineering and Management, 71A Mangeron Blvd., 700050, Iasi, Romania "Gh.Asachi" Technical University of Iasi, Faculty of Hydrotechnics, Department of Hydrotechnical Structure and Environmental Protection, 71A Mangeron Blvd., 700050, Iasi, Romania The improvement of disinfection efficiency for different contaminated fluid fluxes is related to the enhancement of oxidation processes at cellular level, developing original disinfection equipment.The construction of developed equipment is based on the amplification and focalization of UV germicide and bactericide radiation (wavelength λ = 253.65 nm), using an elliptic cylinder shaped reflector and building up a resonant cavity for these radiations.Some theoretical considerations concerning the experimental device construction are described in the paper.The resonant elliptic cavity is used in LASER technique, as the "optic pumping" and this idea was involved in the developing of our equipment.Two TUV-60 lamps made by Philips Company were placed in the focal points of the elliptic cylinder (made by anodized aluminium) and a central quartz tube (symmetrical disposed between these lamps) was used as plug-andflow photo-chemical reactor, through the fluid fluxes were passed.In these conditions the syntheses of chemical species with high oxidation capacity (hydroxyl radicals, ozone, etc.) can contribute to the advanced oxidation process of cellular microbian substrate.Distillated water and respectively an air flux contaminated with four types of pathogenic microorganisms (E.coli, Streptococcus sp., Salmonella sp., Pseudomonas aeruginosa) were used in all experiments.The best results were recorded in the case of gas flux due to synchrony of UV/Ozone effects when all pathogenic microorganisms were destroyed.In case of water flux were obtained the similar results, for E.coli and Pseudomonas aeruginosa.Salmonella sp. and Streptococcus, were still found in water after desinfection, as refractar pathogens in 34.3 % and respectivly 7.8 % in raport with initial CFU (10 4 colony formatting unities/mL) .
Pathogens commonly found in wastewater effluents are E.coli, Streptococcus sp., Salmonella sp., Pseudomonas aeruginosa and enteroviruses.All of these microorganisms can make people sick [1,2].
E. coli is a common microorganism, which is present everywhere in the environment.E coli is the head of the large bacterial family, Enterobacteriaceae.These enteric bacteria, which are faculatively anaerobic Gram-negative rods, can live in the intestinal tracts of health and ill animals [3].
The Salmonella germ is actually a group of bacteria that can cause diarrheas illness in humans, known as pathogen for over 100 years.There are many different kinds of Salmonella bacteria; Salmonella serotype Typhimurium and Salmonella serotype are most known species from Salmonella family [1,2].
Streptococcus sp. is a Gram-positive, nonmotile, nonsporeforming coccus that occurs in chains or in pairs of cells.Individual cells are round-to-ovoid cocci, 0.6-1.0micrometer in diameter.Streptococci divide in one plane and thus occur in pairs or (especially in liquid media) in chains of varying lengths.The metabolism of Streptococcus sp. is fermentative; the organism is a catalase-negative aerotolerant anaerobe (facultative anaerobe), and requires enriched medium to grow [1,2].
Psudomonas aeruginosa is a Gram negative rod measuring 0.5 to 0.8 µm by 1.5 to 3.0 µm.Almost all strains are motile by means of a single polar flagellum.The bacterium is ubiquitous in soil and water, and in contact with soil or water.Psudomonas aeruginosa has very simple nutritional requirements.It is often observed "growing in distilled water" that evidences its minimal nutritional needs [1,2].
In order to avoid waterborne infections diseases, the disinfection is the most important step in water treatment, removing or inactivating the microorganisms traditionally present in wastewater [1].Similar requirements are imposed for air disinfections from hospitals, laboratories of microbiology and other contaminated places.

Experimental part
The experiments involving the UV irradiation were carried out into a laboratory plug-and-flow photo-chemical reactor, placed into a resonant elliptic cavity, whose schematic diagram is illustrated in figure 1.
Two TUV-60 lamps made by Philips Company were placed in the focal points of the elliptic cylinder and a central quartz tube with small diameter (symmetrical disposed between these lamps) was used as plug-and-flow photo-chemical reactor, through the fluid fluxes were passed.
The installation was operated in two modes, correlated with the processing of an infested water flux, respectively, an infested air flux.First operating mode was related to the passing of distilled water infested with microorganisms through the installation shown above and respectively the second mode was related to the passing of contaminated air.This air flux was obtained splashing compressed air through a trap vessel containing the same microorganisms in distilled water (suspension).
The water flux (Flow rate of 1 mL/min) was passed through the irradiation area in thin film in order to increase the UV radiation effect, minimizing the absorption phenomena.
Four types of microorganisms (Ecoli, Salmonella sp., Streptococcus sp., Pseudomonas aeruginosa) were involved in order to perform the disinfection tests using the "developed" equipment.All of these are provided by Microbiology Laborator y from our Environmental Engineering Department.The microorganisms were grown on elective Agar mediums specific for each microorganism in order to obtain fresh cultures in exponential growing phase.The microorganisms were inoculated using the seriated dilution procedure to establish the initial values of CFU (colony formatting unities) / mL.
The culture mediums inoculated with suspensions diluted of microorganisms have been thermostated for 48 hours at 37°C.The cultures developed on the medium surface divided in Petri plates were counted.After counting, the cultures were suspended in distilled water in order to estimate the efficiency of disinfection installation.
After passing through installation, the contaminated fluxes of water and respectively of air were passed through another trap vessel, in order to determine the number of valid microorganisms, corresponding to the final moment of each disinfection test.
For each microorganism was chosen the dilution of 10 4 in order to count the grown cultures.The water samples, respectively the solutions from the air trap vessel (input and output) were inoculated on solid mediums.

Theoretical considerations for experimental device construction
Disinfection is based on the advanced oxidation processes at cellular level, leading to the destruction of pathogenic microorganisms.The enhancement of the disinfection and respectively of oxidation processes for different contaminated fluid fluxes is related to the development of original equipment, in order to amplify the intensity of UV germicide radiation, improving the focalization on the irradiation area [1,4].
It is well known the germicide and bactericide effect of UV-C radiation, with a wavelength λ = 253.65 nm, due to high penetration and partial ionization capacity.The ionizing radiation consists of high-energy waves that are able to penetrate cells and can cause ionization in different parts of the cell.The ionization leads to the development of a positive charge in a molecule that is normally neutral from electrical point of view.So, during the irradiation process will be issued chemical species with high oxidation capacity, which will determine the destructive effect toward cellular organic substrate of microorganisms.The target molecules are especially the deoxyribonucleic acid, which serves as the carrier for the genetic information inside every living cell, and respectively ribonucleic acids.
In order to achieve the above mentioned objectives, an elliptic cylinder shaped reflector, made by anodised aluminium, was used.Further are presented few considerations concerning the selection of the construction material and shape of reflector.
The simplest equation of ellipse (canonic equation) is obtained if it is considered the OX axis as the line connecting the two focal points, F 1 , F2 (focal axis), while the mediator of the focal segment is considered OY axis (fig.2).The mathematical equation of the ellipse is [5]: (1) where: b 2 = a 2 -c 2 are constants characteristic for ellipse considered.
Takeing a generic point M(x,y) on the ellipse circumference, the geometrical segments obtained F 1 M and MF 2 are called focal radii of the considered ellipse and are denominated as r 1 and r 2 .Consequently, these could be expressed according to the basis of geometry: Introducing ec.(3) in ec (4) , r 1 and respectively r 2 could be expressed as function of ellipse characteristics and variable x.
The value c/a is written as "e" and represents the "ellipse eccentricity".As result r 1 = a + e .x (5') and respectively r 2 = a -e .x (6') and therefore: (7) According to the equation ( 7) the constant ratio of distance r 1 and respectively the distance from the focal point F1 (-c; 0) to the line defined as x + a/e= 0, is equal with "ellipse eccentricity".This means that from the point of view of optical geometry, the ellipse can be used as focusing reflector for the radiations emitted from a source light, located in one of its focal points [4,6].
According to figure 2, any light ray departing from the focal point F2, after reflection on the interior edge of the ellipse, compulsory will pass through the focal point F1.Therefore, in the focal point F1 will appear a concentration of the light energy emitted by the source, still energy loss is minimal, due to the partial reflection.A similar resonant elliptic cavity, used in LASER technique, as the "optic pumping" is achieved by means of an impulse lightning lamp positioned in one focal point, while the other one accommodates the ruby bar (ruby LASER), allowing thus the population inversion between energy levels [6].Unfolding the ellipse along the symmetric axis OZ is obtained an elliptical cylinder, whose length depends on the length of the germicide lamp.Anodized aluminium tube (lightpipe from Monodraught Ltd), due to interior shining reflection surface with high reflectance (more than 0.98) was used to build up the resonant cavity.Increasing interest in lightpipe technology has led to competition to find the most reflective material, suitable for the best optical performance.A sunpipe consists of a super-reflective aluminium tube, with an internal mirror finish, that intensifies and reflects natural daylight.Monodraught Ltd, launched the Super Silver SunPipe, an aluminium tube impregnated with pure silver and stabilized by physical vapor deposition, with high reflectance, about 0.996 [7,8].The last above mentioned treated aluminium will be tested in the next study.

Results and discussion
The UV irradiation mechanism, presented as simple as possible, could be taken into consideration the following two cases: the case of resonant-cavity absence, when the the action of UV radiations generated by the sources placed in F1 and F2 focal points lied over the lateral walls of central quarts-tube (reactor plug-and-flow) according to figure 3; On the basis of the data shown in table 1 it can be noted that the best results were recorded in the case of gas flux due to synchrony of UV/Ozone effects, when all pathogenic microorganisms were destroyed.In case of water flux were obtained the similar results, for E.coli and Pseudomonas aeruginosa.
Salmonella sp. and Streptococcus, were still found in water after desinfection, as refractar pathogens in 34.3 % and respectivly 7.8 % in raport with initial CFU (10 4 colony formatting unities/mL) .
This amplification of UV radiation can be ascribed to the stimulated emission due to the geometry of the reflector, and the characteristics of the radiation emitted by UV Germicidal Philips lamps TUV60 (λ = 253.65 nm).The spectral line of Hg corresponds to 253.652 nm, having a relative intensity I of 15 000, and a transition probability A ki = 8 .10 6 s -1 [9].The corresponding lifetime τ is quite long: The long lifetime, together with high intensity I could lead to the stimulated emission, corresponding to the possible non-linear effect in the central area of the ellipse (marked zone).
In these conditions the water radiolysis could generate the free radicals: Also, the oxygen presence could lead to the syntheses of ozone, which also contributes to the additional enhancement of the oxidation process [10].
The generated hydroxyl radicals have a higher oxidative potential (E 0 = 2.80V) than other oxidants such as atomic oxygen (E 0 = 2.42 V) and ozone (E 0 = 2.07V), but the oxidative power of mixed chemical species will depend on the ratio between concentration of water vapours and oxygen into the photo-chemical reactor (keeping constant the characteristic of UV radiation).
The water and oxygen traces are present both in water and air fluxes.The dissolved oxygen from water and the remaining oxygen in the free space over the water film also could be taken into account.
In the presence of UV radiations, the ozone molecule is decomposite, leading to other free radicals, with high oxidation capacity [11]: the case of resonant cavity presence, when the same UV radiations act over the central tube as in figure 3.At these radiations are added other radiations reflected due to the presence of resonant cavity, as it was demonstrated previously.Another amplifying and focusing phenomenon for these radiations, which have to be mentioned, takes place in the area of N 1 N 2 plane, at a distance as near as possible, versus the F 1 F 2 axis.This is pointed out in figure 4, by the emphasized zone determined by intersection between the two triangles MM'F 1 and NN'F 2 .In the presence of water the above mentioned interactions are stronger and the higher oxidative power is obtained: The obtained results concerning the disinfection efficiency toward tested microorganisms are presented in table 1.

Conclusions
Disinfection is based on the advanced oxidation processes of cellular organic substrate, leading to the destruction of pathogenic microorganisms.The improvement of disinfection efficiency for different contaminated fluid fluxes is related to the enhancement of advances oxidation processes by UV germicide radiation, using an elliptic resonant cavity.Thus, the new equipment with high efficiency for water and air disinfection was developed.
Using the achieved equipment, the best results were recorded in the case of gas flux due to synchrony of UV/ Ozone effects, when all pathogenic microorganisms were destroyed.In case of water flux some refractar pathogens as Salmonella sp. and Streptococcus, were still found in water after desinfection, that demonstrate the important role played by UV radiation, whose effects are diminished.

Fig. 3 .
Fig. 3. Details concerning the UV irradiation mechanism in the absence of resonant cavity

Fig. 4 .
Fig. 4. Details concerning the UV irradiation mechanism in the presence of resonant cavity

Table 1
DISINFECTION EFFICIENCY TOWARD TESTED MICROORGANISMS