Lagoon systems are a common and effective method to purify communal sewage in rural areas. Low costs and high purification rates are some of their advantages. But mostly algae blooms in the lagoon cause a secondary pollution of the following stream. In order to tackle this problem, several tests have been carried out combining both lagoon and filtering system. This paper describes a 3 year study on the combination of a lagoon and a planted filter dam in one basin. This system has shown a high and continuous retention rate of algae, pH buffering and a further reduction of general sewage parameters. Furthermore, the effects of varying weather conditions (dry, wet) and seasonal aspects on this combined system will be presented.