Acute toxicity of the substrates and products in a simultaneous denitrification desulfurization process to Photobacterium

To make clear the effect of substrates and products on process performance in a denitrification-desulfurization reactor,the acute toxicity of the substrates and products to Photobacterium phosphoreum was studied using the 15-min half inhibitory concentration (IC50) at pH=7.50±0.05. The relative luminosity of P. phosphoreum decreased as the concentration of substrate and product increased and there was a good linear correlation between the toxicity of substrate and product and their concentrations. Individual toxicity tests indicated that the IC50 (mg·L-1)of sulfide was 78.1,sulfate 12077.8,sulfite 254.5,nitrate 3852.1 and nitrite 1066.3. Using the equivalent concentration mixing method,the combined toxicity of substrates and products showed that sulfide and sulfate,sulfide and sulfite,sulfide and nitrate were additive,while the combined effect of sulfide and nitrite was synergistic. The combined effects of all substrates and products were also additive.