Persistent pharmaceutical pollutants (PPPs) have been identified as potential endocrine disruptors that mimic growth hormones when consumed at nanogram per litre to microgram per litre concentrations. Their occurrence in potable water remains a great threat to human health. Different conventional technologies developed for their removal from wastewater have failed to achieve complete mineralisation. Advanced oxidation technologies such as dielectric barrier discharges (DBDs) based on free radical mechanisms have been identified to completely decompose PPPs. Due to the existence of pharmaceuticals as mixtures in wastewater and the recalcitrance of their degradation intermediate by-products, no single advanced oxidation technology has been able to eliminate pharmaceutical xenobiotics. This review paper provides an update on the sources, occurrence, and types of pharmaceuticals in wastewater by emphasising different DBD configurations previously and currently utilised for pharmaceuticals degradation under different experimental conditions. The performance of the DBD geometries was evaluated considering various factors including treatment time, initial concentration, half-life time, degradation efficiency and the energy yield (G₅₀) required to degrade half of the pollutant concentration. The review showed that the efficacy of the DBD systems on the removal of pharmaceutical compounds depends not only on these parameters but also on the nature/type of the pollutant.

This paper presents the results of experimental investigations on the generation of supershort avalanche electron beams (SAEB) at nanosecond discharges initiated in gas-filled diodes. In air, at a pressure of 1 atm with a sharply non-uniform electric field, an SAEB is generated from the inter-electrode gap at a solid angle exceeding 2π sr. Reduction of gap d between the cathode and the anode leads to a decrease in the current amplitude of the beam incident on the lateral walls of the gas-filled diode and in an increase in the pulse duration of the beam current both in the axial and radial directions. Pulses of the beam current initiated on the lateral surface of a tube cathode have been recorded. It is shown that to generate electrons with an ‘anomalous’ energy, cathodes with an increased radius of curvature should be used.

The paper provides a review of research data showing the role of runaway electrons in gas breakdowns and diffuse discharges in an inhomogeneous electric field at a pressure of 0.01–1.2 MPa. From the data presented the reader can grasp the idea of how such discharges develop at negative and at positive voltage polarity, what setups and conditions are best suited to detect runaway electron beams, and what factors influence their amplitude, duration, and energy. Also analyzed are the streamer mechanisms of diffuse discharges and the generation of runaway electrons in high-pressure gases in an inhomogeneous electric field. The review is supplemented with respective diagrams and with images captured at high resolution to trace the plasma dynamics of nanosecond gas discharges from early prebreakdown stages till their final diffuse appearance.

The properties of an electron beam (e-beam) formed in air under atmospheric pressure are reported. The nanosecond generators RADAN-303 (two devices) and RADAN-220, producing nanosecond voltage pulses with amplitude of up to 400 kV and subnanosecond rise time were used in the experiments. It was shown for the first time that the duration of e-beam current of gas diode behind the foil does not exceed 0.1 ns. The maximum amplitude of current of a supershort avalanche electron beam (SAEB) behind the foil was ∼400 A. The data on the influence of various parameters on e-beam current amplitude measured behind the foil were obtained. An electron beam with energy less than 60 keV and powerful X-ray radiation were formed in discharge gap simultaneously with SAEB.

Pulsed discharges in high-pressure gases are of considerable interest as sources of nonequilibrium plasma for various technological applications: pollution control, pumping of laser media, plasma-assisted combustion, etc. Recently, attention has been attracted to the use of subnanosecond voltage fronts, producing diffuse discharges with radii of several millimeters. Such plasma structures, similar to pulsed glow discharges, are of special interest for applications due to quasi-uniformity of plasma parameters in relatively large gas volumes. This review presents the results of experimental and computational study of subnanosecond diffuse discharge formation. A description of generators of short high-voltage pulses with subnanosecond fronts and of discharge setups is given. Diagnostic methods for the measurement of various discharge parameters with high temporal and spatial resolution are described. Obtained experimental data on plasma properties for a wide range of governing factors are discussed. A review of various theoretical approaches used for computational study of the dynamics and structure of fast ionization waves is given; the applicability of conventional fluid streamer models for simulation of subnanosecond ionization waves is discussed. Calculated spatial-temporal profiles of plasma parameters during streamer propagation are presented. The efficiency of subnanosecond discharges for the production of reactive species is evaluated. On the basis of the comparison of simulation results and experimental data the effects of various factors (voltage rise time, polarity, etc.) on discharge characteristics are revealed. The major physical phenomena governing the properties of subnanosecond breakdown are analyzed.