Background Contaminated waste water represents a significant strain for the natural environment. Such waste water is produced in significant quantities by large numbers of industries, municipal landfill sites and dumps, and the public at large. To avoid releasing this water straight into the environment, complex and technical systems of water treatment have been developed. However, these processes themselves produce their own waste and use up significant amounts of energy. ‘Ultrasonic Resonance Cleaning’ (ultrasonic based oxidation) offers the possibility for dramatic efficiency gains in the process of treating waste water, reducing the energy needs of the process whilst simultaneously exceeding the performance of all traditional procedures. Objectives The project “Ultraschallreinigung” intended to develop and test three prototypes for Ultrasonic Resonance Cleaning processes. These would be specifically designed for use in different EU countries and fields of application. The technology should prove to be reliable and superior to the treatment technologies currently in use. These processes would significantly reduce the organic contaminant load of the waste water to the point where the water could be drained into a body of natural water without causing environmental damage or be used as process water. This would be achieved at reduced levels of energy consumption. The know-how generated during the project should lead to the optimisation of the system and broad market entry in a variety of water treatment industries. Results The project successfully developed and tested an innovative Ultrasonic Plasma Resonator (UPR) in three applications. It uses ultrasound technology to improve the efficiency of wastewater treatment processes, to expel dissolved solids and eliminate strong odours from excreta products. The project managed to outperform alternative processes whilst at the same time reducing costs and energy requirements – an important positive step for the environment. The process reduced chemical oxygen demand (COD) and total organic carbon (TOC) in the leakage water of a waste dump by 50%. In the pre-treatment of waste water, it reduced ammonia by 50% with 50-70% less strip air consumption. In disinfecting communal waste water it was able to achieve a decrease of bacteria from factor 100 (log 2) to 1000 (log 3). Further advantages are the complete elimination from the microbiological load of elements such as fungi and bacteria, and a drastic reduction of the nitrogen load. As a result of the ultrasound treatment, chemical reactions bring the substances more quickly into a liquid phase (sono-chemical reactions). Pollutant charges for which a traditional biological purification plant would require six weeks are now treated within ten minutes. The process also requires less space. Biological plants with a comparable capacity of 5 m3/h require about 1.6 hectare; the UPR, in contrast, requires only 120m2 - indoors or outside, including all peripheral devices. The unit itself measures only 2x2x3 metres. The pilot plant's throughput of around 5m³ of water per hour was raised to 8-15m³/h. The more controlled input of power sources and oxygen in the process, the reduced space requirements and the absence of need for additional pumps or expensive expendables mean that the UPR energy requirements are significantly lower than those of conventional technologies. Similarly, the UPR is an inexpensive device, both in terms of initial outlay and operating costs. The beneficiary estimates that cost savings of 50% can be made in the field of ammonia reduction and treatment of contaminated waste water. The process is transferable to a wide range of water treatment processes, including the treatment of leachates from landfills and the purification of drinking water. It could even be used in industries such as fish farms and hatcheries where gas also needs to be transferred to liquids. Three companies have already declared their interest in applying or distributing the technology. This project has been selected as one of the 22 "Best" LIFE Environment projects in 2006-2007