Development and validation of a sampling and analysis method to determine biogenic sulfur in a desulfurization bioreactor by gas chromatography coupled with a pulsed flame photometric detector (GC-PFPD).

Suspended biomass bioreactors can be operated to remove H2S from biogas under anoxic conditions and produce elemental sulfur, the commercial value of which has been demonstrated. In the present paper, a novel methodology comprising the optimization of a determination method performed in a gas chromatograph equipped with a pulsed flame photometric detector (GC-PFPD), combined with a simple preparation based on filtration and extraction with toluene, is proposed. The injector temperature and carrier gas flow rate (QHe) values were optimized using a response surface methodology based on a face-centred composite central design. This optimization revealed that the optimum conditions were an injector temperature and carrier gas flow rate of 222 °C and 7 mL min-1, respectively. The chromatographic method shows an analysis time of 48 min, a detection limit of more than 5.9 mg L-1, a relative standard deviation of less than 3.71%, and a sulfur recovery percentage of more than 98%. These values provide excellent linearity and a reasonable concentration range (10-200 mg L-1). Finally, a measurement error of 4.45% was obtained when using the present method in a selectivity test.

Effect of two different intermediate landfill leachates on the ammonium oxidation rate of non-adapted and adapted nitrifying biomass.

A widely employed approach to minimize the detrimental effect of landfill leachates (LL) on nitrifying biomass is to adapt it to these contaminated effluents prior to use. In the study reported here the impact of different intermediate landfill leachates (intermediate 1 (ILL1) and intermediate 2 (ILL2)) and synthetic medium (SM) on the nitritation rates of non-adapted and adapted nitrifying biomass were evaluated and modeled. The models, based on previously reported models (Haldane, Edwards and Aiba), considered the effect of three different heavy metals (Cu, Ni and Zn) present in both landfill leachates. The proposed models fitted well with the different biomasses. The highest specific substrate oxidation rate (qS) of the present study (41.85 ± 1.09 mg N-NH4+ g TSS-1 h-1) was obtained by the non-adapted biomass using SM. The non-adapted biomass was characterized by ~5- and ~28-fold higher nitritation rates on using the different ammonium sources tested (SM, ILL1 and ILL2) when compared to the other biomasses adapted to ILL1 (~9 mg N-NH4+ g TSS-1 h-1) and ILL2 (~1.3 mg N-NH4+ g TSS-1 h-1), respectively. The calculated inhibition constants indicate that the inhibitory effect of the heavy metals followed the order Ni>Zn>Cu. The results reported here bring into question the commonly accepted idea that an adaptation period of the biomass is required to treat landfill leachate.