Multispark discharge excited in water is described, and its useful physical and chemical properties are discussed in the light of some environmental issues. Discharge of such a type generates hot and dense plasmoids producing intense biologically active UV radiation and chemically active radicals, atoms, and molecules. Simultaneously, discharge creates strong hydrodynamic perturbations and cavitation bubbles. Particular attention is given to factors influencing on water purity with special reference to discharge application for effective sterilization of water and its cleaning of harmful chemicals. The gas discharges of this type show considerable promise as a means for solving some actual plasma-chemical problems. The above-mentioned discharge properties have been demonstrated in a series of laboratory experiments, which proved the efficiency of disinfection of potable and waste water, water cleaning of pesticide (herbicide) contaminations, and conversion (recovery) of natural methane. 1. Introduction High voltage electric discharge in water [1, 2] has been considered as a potential method of water treatment to kill microorganisms and to clean it of harmful contaminations negating the use of chemicals that leads to by-products which may additionally compromise human health [3–5]. Factors favoring their use include the generation of UV radiation, acoustic, shock waves, chemically active substances, cavitation processes, pyrolysis, and hydrolysis. There are also possible synergetic effects following physical and chemical reactions. Among the different means of in-liquid electric discharge, a novel method involves multielectrode (multispark) slipping (gliding) discharges (SSDs)  which may have some advantages over the two-electrode systems generally used at present [1, 7]. The present work describes the construction of a multispark discharger and discusses results of experimental investigation of SSD-based methods of water disinfection and their application in plasma-chemical technology for solving some of environmental problems, such as conversion (recovery) of methane (as well as other natural hydrocarbons), and water cleaning of pesticide (herbicide) contamination. 2. Treatment System The apparatus used to treat liquids is shown schematically in Figures 1 and 2. The basic components were a chamber filled with water, a multielectrode system for exciting of slipping surface discharge, and high voltage power supply (Figure 1). The multielectrode discharge system (Figure 2) was similar in design to that previously described in [6, 8, 9]. The discharger
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