Aerobic bacterial spores as process indicators for protozoa cysts in water treatment plants.

The possibility of using aerobic spores as indicators (surrogates) of water treatment efficiency for the removal of Giardia cysts and Cryptosporidium oocysts was evaluated in a water treatment plant that supplies the Barcelona area of Spain. The water treatment consists of pre-chlorination, flocculation-sedimentation, double filtration (sand and granular activated carbon, GAC) with intermediate ozonation and post-chlorination. Aerobic spores significantly increased after GAC filtration, which indicated an active propagation of aerobic spore-formers. However, anaerobic (Clostridium) spores could be a good surrogate for Cryptosporidium oocysts, especially if their detection in samples at low concentrations was improved.

Occurrence and levels of phages proposed as surrogate indicators of enteric viruses in different types of sludges.

A method based on the treatment of sludge with beef extract recovered, with similar efficiency, the three groups of bacteriophages studied from different kinds of sludges. The three groups of bacteriophages were found in high numbers in the different sludge types, the highest value being that of somatic coliphages in primary sludge of a biological treatment plant (1.1 x 10(5) pfu g-1) and the lowest being that of Bacteroides fragilis phages (110 pfu g-1) in de-watered, anaerobically, mesophilically-digested sludge. All phages studied accumulated in the sludges. In primary and activated sludges, all three types accumulated similarly but in lime-treated sludge and de-watered, anaerobically, mesophilically-digested sludge, the relative proportion of F-specific bacteriophages decreased significantly with respect to somatic coliphages and bacteriophages infecting B. fragilis. All phages survived successfully in stored sludge, depending on the temperature, and again, F-specific bacteriophages survived less successfully than the others.