Portinho added that given the "urgency of the matter and its fundamental role in the event, it is of great importance that the funds be released in order to allow construction (on the two RTUs) to begin in the second half of 2014."
Reached by telephone, Marisa Bastos, a spokeswoman for Rio's environment agency, confirmed the authenticity of the letter. She said it was a copy of an earlier letter sent to the Ministry of Cities.
In the letter, Portinho wrote that even if authorities were to tackle the bigger problem of a lack of basic sanitation by expanding the sewage network, it would prove are too little, too late for the Olympics.
"Even if the necessary resources to implement sanitation systems in the waterways mentioned were released . it would not be possible to plan and implement all the projects within a timeframe that would make a significant difference in the water quality in Guanabara Bay by the 2016 Olympics," the letter stated.
It added that several state agencies "have been studying the issue and concluded that the beneficial effects on the waters of Guanabara Bay will only occur in at least a decade, if the current levels of spending on sewage collection and treatment are maintained."
Authorities here have consistently maintained that Rio was on track to meeting its Olympic commitments.
Several Olympic sports federations raised fears that Rio's polluted waters could prove harmful to athletes' health. Exposure to fecal matter can cause Hepatitis A, dysentery, cholera other diseases.
AP writer Jenny Barchfield: https://twitter.com/JennyBarchfield