TEJO, C. P; TEJO, Cristina Di Pace.
Résumé:
This work aimed the study of physico-chemical and microbiological
fluctuations in a pond system treating domestic sewage and its evaluation.
The Guarabira treatment sewage plant has two series of ponds in parallel, each
with an anaerobic followed by a facultative. The system was designed to operate in two
stages (from 1987 to 1996 and from 1997 to 2006) and aims to attend 33,000 inhabitants at
the end of the plan. During november 1990 to October 1991 only one series was monitored
since not all residential connections were completed.
Research methodology consisted by the sampling of raw sewage and anaerobic
and facultative pond effluents and analysing them for pH, temperature, dissolved oxygen,
BOD5, COD, nitric and ammoniacal nitrogen, total phosphorous, soluble orthophosphate,
suspended solids, streptococus and faecal coliforms. Algae identification and biomass
quantification were only performed in the facultative pond effluent.
Monitoring results showed no significant variations in the physico-chemical
and microbiological parameters. Chlorophyll a content showed an average of 223 jug/L with
the predominance of non-motile green algae.
The series of ponds removed 94% of the BOD5, 80% of suspended solids, 99.8
and 99.7% of faecal coliforms and streptococus.
Results of diurnal studies showed significant fluctuations in the physicochemical
and microbiological parameters indicating that grab samples were not necessarilly
representative of the system.
