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Golden mussel
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The golden mussel is a small-sized (3 to 4cm) freshwater mollusk originating in Southeast Asia and accidentally coming to South America in the mid-1990s. Brought by the ballast waters of cargo ships after the Rio de la Plata watershed occupation, it has upwardly spread through the Paraguay and Paraná rivers watersheds and got to Itaipu by 2001.
 
Due to its sessile (fixing to rigid structures) and gregarious (forming a population) features and its great proliferation capacity, the golden mussel stands out as an invasive species by being potentially able to cause pipe and/or equipment obstruction in hydroelectric and supply facilities.
 
Soon after the species was detected and it started to spread along Itaipu reservoir, the areas susceptible to possible impacts in generating energy were mapped starting by systematically monitoring the species in the areas considered as vulnerable. In the following years, several species control measures tests (physical and chemical) were carried out on an experimental scale in order to assess their efficiency and feasibility in the Hydroelectric Center during emergency situations.
 
Some cooling system's filters and pipes of the Generating Units were adjusted simultaneously to the tests in order to decrease mollusk incrustation and equipment obstruction caused by dead organisms. The heat exchangers flow was increased wherever possible and necessary by reaching speeds close to 1.8 meters per second for inhibiting the mussel’s development and not causing equipment impairment.
 
None of the experimental measures tested has been required since the emergence of the species to the present day thanks to some hydraulic features of the Itaipu Hydroelectric Center. The previously mentioned adjustments and the periodic mechanical cleaning of the systems have been enough to avoid the species to impair energy generation. 
 
Mussel monitoring carried out in the raw water collected for the cooling systems and floodgates in the last 17 years has shown a stabilized population with decreased individuals abundance after the first years of infestation and also a well-marked influence of the temperature as a limiting factor for the species reproduction in winter.
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