Fast inactivation of microbes and degradation of organic compounds dissolved in water by thermal plasma

The multifunctionality and the advantages of thermal plasma for the fast inactivation of viable cells and degradation of organic compounds dissolved in waste water are presented.A complete bacterial inactivation process was observed and studied using a thermal plasma treatment source with very short application times,in particular for Staphylococcus aureus bundle spore survival.The survival curves and analyses of the experimental data of the initial and final densities of S.aureus bacteria show a dramatic inhibitory effect of the plasma discharge on the residual bacteria survival ratio.As the exposure time increased,the inactivation process rate increased for direct exposure more than it did for indirect exposure.The evaluation of direct and indirect exposure was based on the analysis of the ultraviolet spectrum from the absorbance spectra of the organic compound dye called benzene sulfonate(C_(16)H_(11)N_2Na O_4S)and of viable cells called S.aureus.Organic compounds were degraded and viable cells were killed in a short time by thermal plasma.Moreover,analyses of total carbon,total organic carbon,and total inorganic carbon showed a fast decrease in organically bound carbon,however,this was not as fast as the absorbance spectra revealed by the exposure time increasing more for direct exposure than indirect exposure.After 100 s of exposure to the organic compound dye the removal had a maximun of 40%for samples with indirect exposure to the plasma and a maximum of 90%for samples with the direct exposure.For both samples,where some organic contaminants still remained in treated water,four electrolytes(KCl,Na Cl,Na_2SO_4,and CH_3COONa)were added to be effective for complete sterilization,reaching a purity of 100%.A proposal is made for an optimized thermal plasma water purification system(TPWPS)to improve fast inactivation of microbes and the degradation of organic compounds dissolved in water(especially for direct exposure rather than indirect exposure)using a hybrid plasma torch with an electrical power of 125 kW(500 V–250 A)producing a high-temperature(10 000 K–19 000 K)plasma jet with a maximum gas consumption of 28 mg s^(-1).

Environmental and economic vision of plasma treatment of waste in Makkah

An environmental and economic assessment of the development of a plasma-chemical reactor equipped with plasma torches for the environmentally friendly treatment of waste streams by plasma is outlined with a view to the chemical and energetic valorization of the sustainability in the Kingdom of Saudi Arabia(KSA). This is especially applicable in the pilgrimage season in the city of Makkah, which is a major challenge since the amount of waste was estimated at about 750 thousand tons through Arabic Year 1435 H(2015), and is growing at a rate of 3%–5% annually. According to statistics, the value of waste in Saudi Arabia ranges between 8 and 9 billion EUR. The Plasma-Treatment Project(PTP) encompasses the direct plasma treatment of all types of waste(from source and landfill), as well as an environmental vision and economic evaluation of the use of the gas produced for fuel and electricity production in KSA, especially in the pilgrimage season in the holy city Makkah. The electrical power required for the plasmatreatment process is estimated at 5000 kW(2000 kW used for the operation of the system and 3000 kW sold), taking into account the fact that:(1) the processing capacity of solid waste is 100 tons per day(2) and the sale of electricity amounts to 23.8 MW at 0.18 EUR per kWh.(3) The profit from the sale of electricity per year is estimated at 3.27 million EUR and the estimated profit of solid-waste treatment amounts to 6 million EUR per year and(4) the gross profit per ton of solid waste totals 8 million EUR per year. The present article introduces the first stage of the PTP, in Makkah in the pilgrimage season, which consists of five stages:(1) study and treatment of waste streams,(2) slaughterhouse waste treatment,(3) treatment of refuse-derived fuel,(4)treatment of car tires and(5) treatment of slag(the fifth stage associated with each stage from the four previous stages).

Disinfection of Microbes by Magnetized DC Plasma

A different combined effects for helium gas discharge such as: magnetic field strength, breakdown voltage, applied power, applied pressure, cathode fall thickness, edge effect, distribution of the electron temperature and density, and finally exposure time for Staphylococcus aureus substrate over slides at the cathode edge, are discussed under the influence of cold, nonthermal plasmas, ultra low pressure, and presence of the magnetic field for disinfection of bacteria for short exposure times, compatible to International Commission on Non-Ionizing Radiation Protection, Health Phys (ICNIRP) for healing applications. Furthermore, analyses of the experimental data of initial and final densities of cells alive, using survival curves, showed an impressive inhibitory effect of plasma discharge to the remaining survival of bacterial ratio under the influence of the magnetic field.

Dust Plasma Effect on the Etching Process of Si[100] by Ultra Low Frequency RF Plasma

Dust-plasma interactions play vital roles in numerous observed phenomena in the space environment, their scope in the industrial laboratory has grown rapidly in recent times to include such diverse areas as materials processing, microelectronics, lighting and nuclear fusion. The etching processes of Si wafer has been studied using Ultra low frequency RF plasma (ULFP) at (1 KHz) by two different techniques namely: ion etching using inert gas only (e.g., argon gas), and ion chemical etching using an active gas (beside the inert gas) such as oxygen. In the case of large dust particle, the dust might act as a floating body in the plasma collecting equal fluxes of electrons and ions. The velocity of the ions flux out from the mesh (cathode) and cause ion sputtering for the sample (Si-Wafer) measured, moreover the rate coefficient for collection of electrons and ions by dust (K) is calculated here, the presence of dust, however, may itself cause loss process. As the plasma density increases, the etching rate increases and the volumetric rate of loss of electron and ions due to dust particle increases (K). A comparison between the volumetric rate of loss (K) due to ion chemical etching (75% Ar/25% O2) and ion etching (Pure Ar) has been carried out.

Comparison between Theoretical and Experimental Radial Electron Temperature Profiles in a Low Density Weakly Ionized Plasma

Experimental and theoretical studies of the radial distribution function of the electron temperature (RDFT) in a low-density plasma and weakly ionized gas for the abnormal glow region are presented. Experimentally, the electron temperatures and densities are measured by a Langmuir probe moved radially from the center to the edge of the cathode electrode for helium gas at different pressures in the low-pressure glow discharge. The comparison of the final experimental data for the radial distribution of electron temperatures and densities for different low pressures ranging from 0.2 to 1.2 torr, with the final proved equation of RDFT confirms that the electron temperatures decrease with increasing product of radial distance and gas pressures, showing a radial decrement dependence of the electron temperature from the center to the edge of the electrode. This is attributed to the increase of the number of electron-atom collisions at higher gas pressures and consequently of the rate of ionization. For the axial distance (L) from the tip of the probe to cathode electrode and the cathode electrode radius (R), a theoretical and experimental comparison for the two conditions L R and L > R, for both cases the produced plasma temperatures decrease and densities increase. It is concluded that the RDFT accurately shows a dramatic decrease for L R by 60% less than RDFT values for L > R similar as for conditions of magnetized and unmagnetized effect for DC plasma. This means that the rate of plasma loss by diffusion decreased for L R, agrees well with the applied of magnetic field

Nano-Coating Process for Si [1 0 0] Wafer Using Atmospheric Pressure Plasma Jet (APPJ)

Three-electrode plasma jet system consisting of a perforated dielectric tube with two outer and one floating inner electrodes was developed and employed for nano-coating processes of Si [1 0 0] wafer. Lowered gas breakdown voltage, increasing plasma density and increased discharge current were achieved by using the floating inner electrode. The low temperature (Nonthermal) Atmospheric Pressure Plasma protective coating technique using precursor-containing gases (Ar, O2 and OMCTS mixture) which injected into Plasma Jet (APPJ), there are several techniques are introduced here to avoid substrate damage including increasing plasma density without increasing the kinetic energy of the ion bombardment. Furthermore some few precautions are given here to insure good media for silicon wafer prepared for coating.

Gap Mesh Wire Control on Nano-Particles Growth

The influence effect of different holes per inch on the plasma parameters and particle growth has been studied by compression between two different gap Aluminum meshes of 3 mm width, and 8 holes per inch (8 h/in) and 0.3 mm width and 20 holes per inch (20 h/in) at very low pressure. The perforated aluminum mesh with small diameter holes 20 h/in shows a better glow discharge stabilization than mesh with large diameter holes 8 h/in. For both 20 h/in and 8 h/in, sharp axial decrements for electron Temperature (Te), where Te decreased from 5.2 to 3.8 eV for 8 h/in, from 2.75 to 1.8 eV for 20 h/in. In contrast sharp axial increments for electron density (Ne), whereas Ne increased from 0.9 × 109 to 20 × 109 cm-3 for 8 h/in and from 8 × 109 to 42 × 109 cm-3 for 20 h/in. Silicon wafer [100] was exposed directly behind the meshes to realize nano-particle growth in sputtering discharge, where there are two different particles shapes: spherical shape particles produced by 20 h/in, and filamentary-shaped fractal particles formed by 8 h/in. The particle radius growth for 20 h/in was in the range of 4.67 - 301 nm during exposure time 40 - 95 min, and for 8 h/in were in the range of 9.2 - 28.8 nm during exposure time 60 - 95 min.

Numerical Calculations of Some Plasma Parameters of the Capacitively Coupled <i>RF</i>Discharge

Numerical calculations by using a self-consistent model of the collisional sheath for the capacitively coupled RF discharge are our target. The results indicated that, at high pressure, the ohmic heating is usually the dominant heating mechanism in the discharge. The power dissipated in the sheath is calculated and compared with the measured data. Moreover, we indicated that, when the gas pressure is increased, the calculated dissipated power is decreased also while the measured input RF power is increased. Furthermore the sheath thickness of the capacitively coupled discharge is calculated and in the same order of the electron oscillation amplitude in the RF field, while the ionization mean free path is shorter than it.