For the lakes there are four main methods: mechanical, biological, chemical and purification using ultraviolet radiation.
Mechanical cleaning involves the collection of garbage from water surface with nets or special devices such as nets. Mechanical cleansing of large reservoirs is also possible when using small vessels and work divers. The last time the water began to actively connect and divers.
Purification is carried out in several stages. First, use machinery, excavators, digging drainage ditches and an additional reservoir and pull water from the lake. Then clean the bottom, remove debris, silt, bottom sediments, clear lake shores from excessive vegetation, clear springs. The purified water is carried out using mechanical filtration. This is the most cheap and effective way to purify water from small organics and algae.
Artificial reservoirs, lakes on private land, the owners cleaned it themselves. You can use a regular net, and for deeper cleaning - "underwater vacuum cleaner". The device acts as a conventional vacuum cleaner, sucking up the dirty water with ground silt, algae, organic matter. Various nozzles such mechanisms help to clean the most intricate reliefs in the bottom of artificial reservoirs. All the absorbed waste is collected in a separate reservoir, which must be clean when filled.
In addition to mechanical cleaning can also be done with biological treatment of the lake using bio-filters filled with a porous material conducive to the growth of aerobic and anaerobic bacteria that feed on organic matter retained in these filters.
Chemical cleaning is performed by adding to the water chemicals to restore the chemical composition of water and dissolved oxygen. This water purification can be done only by professionals because it requires precise calculations.
Purification by ultraviolet light is to dive into the lake of lamps with UV light (a wavelength of 180-300 nm). Ultraviolet radiation affects the DNA of small algae and micro-organisms, bacteria and kills them. All devices required for cleaning , are commercially available in specialized stores and organizations.