In the research and development project GINOP-2.1.1-15-2016-01087, based on the operation of natural ecosystems (filtering of mussels), the development of a complex mobile water treatment system with minimal energy use is designed to clean surface water in large equipment placed on floating concrete platforms in a cheap and energy neutral way in large equipment placed on floating concrete platforms. An innovative and low-cost technical solution is provided by the “Clam Island”. The aim of the technology to be introduced is to install a floating plant that aims, among other functions, to further improve water quality. We breed bivalve molluscs with filter lifestyles in special carrier equipment in the contact-space below the float. The design of the equipment is such that, due to their large specific surface area, they are suitable for the living space of up to several tonnes of shellfish. Shellfish, as filtering animals, are able to filter through 0.3-0.7 litres of water per hour and to clean any suspended pollution with a particle size greater than 1 µm. This allows a significant proportion of suspended organic matter, plant nutrients and other contaminants to be eliminated from water with high efficiency. By regularly harvesting shellfish and removing their faeces, the ecological status of the watercourse or lake will be further improved by reducing pollutants (nitrogen and phosphorous forms). The system to be set up will be approximately equivalent to the hydraulic performance of a medium-sized waste water treatment plant. The water purification function is almost entirely below the waterline, so the surfaces of the floating platform above the surface are also suitable for a number of functions linked to different water uses (recreational, nautical, etc.) The mollusc mass formed is an organic product with a high protein content and may, after being tested, be suitable for processing as a product of animal protein origin and then for sale as a product of animal protein origin. In addition, the formation and separately collected mussel faeces, pseudofaeces, due to their high organic matter and plant nutrient content, are directly applicable for soil warming purposes. At present, such a water purification system is not in operation in the world, so the technical novelty of the implementation is significant. It can be pointed out that while managing an ecosystem service connected to a natural system (scallop plant) in a regulated way, it implements near-energy neutral water purification with the addition of other functions. Such intended functions include the use of shellfish island as a biological monitoring system, the ecological demonstration function (training path) and the provision of other community services (birds, training venues). Another main function of the project is the creation of a water quality monitoring station, which is suitable for early warning. Utility companies or industrial water users using coastal filtration water typically do not have a monitoring system capable of detecting potential hazards in a timely manner. Conventional chemical monitoring stations are not capable of detecting all toxic, carcinogenic, teratogenic, bioaccumulative substances potentially present in surface water. Therefore, the development and deployment of reliable and low-noise BEWS (Biological Early Warning Systems) systems would significantly reduce the risks of abstraction, in particular the supply of drinking water. Surface waters may be early warnings for high-sensitivity bivalve molluscs. The life/behaviour of bivalve molluscs, which is associated with the presence of contaminants in surface waters, can be tested in the cages with flow-through cages raised under controlled conditions. Based on these principles, we also develop a biological monitoring system using bivalve molluscs: Intended functions of the floating platform “Clams Island”: 1. Water purification; 2. Early warning system (biological monitoring) 3. Logistical base for havária, disaster management and law enforcement; 4. Provision of other infrastructure services (visitor centre, educational centre, etc.) The project proposes the development of the prototype of an environmentally friendly water treatment process based on ecological processes and its testing and fine-tuning. The environmental boundary conditions (water velocity, water temperature, harvesting cycles, etc.) and the specific removal costs of each pollutant will be clearly identified during the work. Following the successful demonstration phase, the new types of floating plants can be gradually spread out as a framework for the shaping of the Danube Regional Strategy, in which both the protection of water quality and the improvement of the ecological status of the environment fit into the framework.