AUTOTROPHIC DENITRIFICATION OF LANDFILL LEACHATE USING ELEMENTAL SULFUR

One of the most economical means of nitrogen removal from leachate is biological treatment by nitrification, followed by heterotrophic denit rification. An alternative biological denitrification process is autot rophic denitrification using Thiobacillus denitrificans. This autotrop hic bacteria oxidizes elemental sulphur to sulphate while reducing nit rate to elemental nitrogen gas, thereby eliminating the need for addit ion of organic carbon compounds. For this study, pilot-scale elemental sulphur packed bed columns with fixed-film denitrification have been selected as the most suitable treatment process. The effect of hydraul ic retention time as well as the effect of concentration and loading r ate of nitrate on nitrate removal efficiency as a function of sulphur particle size were determined. The results indicate that (i) autotroph ic denitrification can effectively remove nitrate from synthetic and a ctual nitrified leachate at concentrations much higher than hitherto r eported; (ii) the minimum hydraulic retention time necessary for compl ete denitrification depends on sulphur particle size; (iii) the maximu m area loading rate, in g NO3.-N/m(2) . d, appears to be the process l imiting factor and is practically independent of sulphur particle size ; and (iv) the observed stoichiometric relationships compare well with those previously reported. Copyright (C) 1996 IAWQ.