SILVA, O. L. C.; http://lattes.cnpq.br/5693142763073866; SILVA, Ofélia de Lira Carneiro.
Abstract:
An investigation on the sulphur cycle was carried out in two, pilot-scale, 2.3 mdeep
primary facultative ponds treating municipal wastewater at EXTRABES - UFPB
( Experimental Station for the Research on Biological Treatment of Sewage - Federal
University of Paraiba), Campina Grande City ( 7° 13' 11" S, 35° 52' 11" W, 550 m above
m.s.l), Paraiba state, northeast Brazil. Both ponds were operated under a mean surface
organic loading of 330 kg BOD5/ha.d and a hydraulic retention time of 15 days, being one
of them provided with longitudinal round - the - corner baffles and the other, without
baffles, maintained as a control reactor.
Effluent concentrations of total sulphide, hydrogen sulphide and sulphate measured
in both ponds during a routine monitoring, between 15th October 1997 and 14* December
1998, were respectively compared, being found that no significant difference was
observed, demonstrating that from the sulphur cycle point of view baffling has not
influenced the facultative pond performance.
Between September and November 1998, sulphur transformations were studied
within the baffled pond water bulk. The main diurnal transformations were observed in
the 5 cm-top layer which showed a typical anaerobic/aerobic daily cycle that determined
the predominance of either reduced or oxidized sulphur species. From a general point of
view, however, it was found that about 80 percent of the water bulk was predominantly
anaerobic and total sulphide concentrations were kept high. Both toxicity and odour
nuisance possibly may occur in these circumstances.
