Banca de DEFESA: VANESSA GOMES GONÇALVES

STUDY OF THE OCCURRENCE OF BIODETERIORATION ON FACADES BY RED BIOFILMS IN THE CITY OF SALVADOR-BA

Biodeterioration. Red biofilm. Red stains. Facades. Logistic regression
model.

Biodeterioration on facades due to red biofilm is a type of damage characterized by
the action of microorganisms that affect the integrity of the paint film applied to the
coating, consequently impacting its aesthetics. The red stains originating from this type
of biofilm can lead to a commercial devaluation of the developments. Because of this,
facade maintenance services may occur even before the estimated period. The red
biofilm is a scarcely explored subject in the literature, but visible in buildings from
various countries such as Mexico, Portugal, Spain, Ireland, France, etc. Thus, there is
a recognized need for studies to comprehend this topic. Therefore, the present
research aims to infer about the influence of extrinsic and intrinsic factors on the facade
surfaces in the emergence of red biofilm, considering a sample from the population of
buildings in Salvador, Bahia, Brazil. Additionally, the research aims to identify the
microorganism causing this biofilm. The methodological procedure was divided into
three phases: the first was dedicated to statistical analysis using a sample of 66
buildings, applying a logistic regression model (LRM) to infer the variables influencing
the emergence of red biofilm. The second phase involved a microbiological analysis,
in which five samples of red biofilm were collected from one of the studied facades,
aiming to verify if the identified microorganism coincides with the one depicted in the
literature. Lastly, the third phase encompassed the development of an experimental
model, involving the cleaning of a facade affected by red stains and subsequently
creating six panels with different treatments and roughness to assess the recurrence
time of the damage. The obtained LRM showed that variables such as years since the
last painting, number of floors, and altitude significantly influence the emergence of red
biofilm. The older the paint, the higher the number of floors, and the greater the altitude,
the higher the chances of the studied damage occurring. Through the morphological
analysis of the collected material, it was determined that the microorganism
responsible for the red stains is an algae of the Trentepohlia sp. genus from the
Trentepohliaceae family, which coincides with what is addressed in the literature.
However, the experimental model did not allow the observation of stain development
on the treated panels during the one-year period.