One liter of water and sludge were taken in April 2012, in glass
bottles previously sterilized and stored at 4 C until analysis in the
laboratory (Eaton et al., 2005). Bacteriological tests were
conducted within 6 h from sample collection. In addition, an
aliquot of sludge samples (S11, S12 and S13) was preserved in SAF
solution (sodium acetate formalin) for parasite analysis until they
were observed by microscopy. Biofilm samples were taken with a
cotton swab and stored in a 1.5 ml eppendorf tube with 1ml of
sterile saline solution (0.9% NaCl) at room temperature.