A total of 174 actinomycete cultures were isolated from a constructed biological water treatment system (BIOWATSYST)established at Abu Attwa station in Ismailia city, Egypt and funded by the European Commission Grant No.IC18-CT97-0163. The isolates were identified to belong to eight genera; Nocardia, Streptomyces, Intrasporangium, Micromonospora, Nocardioides, Actinomadura, Nocardiopsis, and Thermomonospora.  They were screened for their antibacterial, antifungal and cytotoxic activities against certain human and plant pathogens. Antimicrobial activities were determined by measuring bacterial and fungal growth inhibitions while cytotoxic activity was studied by using the Artemia salina bioassay. Thirty two percent of isolated cultures displayed antibacterial activity, 15% displayed antifungal activity and 9% displayed cytotoxic activity. Members of genus Streptomyces has recorded as the most frequent active isolates against tested bacteria (42%) and fungi (49%). However, the most cytotoxic activity was found with members of genus Nocardia (46%).  Results evaluated the fact that actinomycetes isolated from such systems could be considered as promising source for antimicrobial and cytotoxic bioactive agents.