Occurrence and levels of indicators and selected pathogens in different sludges and biosolids.
OBJECTIVE
Determine the occurrence and levels of pathogens and indicators in raw and treated sludges and compare their persistence after two different treatments.


RESULTS
Helminth ova, Cryptosporidium spp., Salmonella spp., enteroviruses, and bacterial and viral indicators were determined in raw sludges and biosolids produced after mesophilic and thermophilic treatments. Except Salmonella, all of the parameters were quantified. Helminth ova were found at very low concentrations even in raw sludges. Viable Cryptosporidium oocysts were still present in most samples of treated sludges. Faecal coliforms, spores of sulphite-reducing clostridia (SSRC), and somatic coliphages were the only indicators with values above their detection limits in most of the samples.


CONCLUSIONS
Pathogens were still detected in some treated sludge samples. SSRC were the most resistant micro-organisms to treatments and hence may be an indicator for the reduction of protozoan oocysts. Somatic coliphages constitute an alternative as viral indicators due to their detection in sludges before and after treatment.


CONCLUSIONS
Because of the persistence of some pathogens after sludge treatments, additional indicators are needed. SSRC and somatic coliphages are good candidates. Easy and inexpensive methods for the determination of these indicators are feasible both in industrialized and developing countries.
Guzmán
C
C
Department of Microbiology, Biology Faculty, University of Barcelona, Barcelona, Spain.
Jofre
J
J
Montemayor
M
M
Lucena
F
F
D000818:Animals; D001435:Bacteriophages / Q000302:isolation & purification; D003013:Clostridium / Q000302:isolation & purification; D015169:Colony Count, Microbial; D003458:Cryptosporidium / Q000302:isolation & purification; D004770:Enterovirus / Q000302:isolation & purification; D004784:Environmental Monitoring / Q000379:methods*; D005243:Feces / Q000382:microbiology; D006376:Helminths / Q000302:isolation & purification; D006801:Humans; D033661:Oocysts; D010270:Parasite Egg Count; D012475:Salmonella / Q000302:isolation & purification; D012722:Sewage / Q000382:microbiology*; D010948:Viral Plaque Assay; D014865:Waste Disposal, Fluid / Q000379:methods; D014876:Water Pollution
D012722:Sewage