Ricardo Beristain-Cardoso

Effect of initial sulfide concentration on sulfide and phenol oxidation under denitrifying conditions.

The objective of this work was to evaluate the effect of the initial sulfide concentration on the kinetics and metabolism of phenol and sulfide in batch bioassays using nitrate as electron acceptor. Complete oxidation of sulfide (20 mg L(-1) of S(2-)) and phenol (19.6 mg L(-1)) was linked to nitrate reduction when nitrate was supplemented at stoichiometric concentrations. At 32 mg L(-1) of sulfide, oxidation of sulfide and phenol by the organo-lithoautotrophic microbial culture was sequential; first sulfide was rapidly oxidized to elemental sulfur and afterwards to sulfate; phenol oxidation started once sulfate production reached a maximum. When the initial sulfide concentration was increased from 20 to 26 and finally to 32 mg L(-1), sulfide oxidation was inhibited. In contrast phenol consumption by the denitrifying culture was not affected. These results indicated that sulfide affected strongly the sulfide oxidation rate and nitrate reduction.

Simultaneous removal of 2-chlorophenol, phenol, p-cresol and p-hydroxybenzaldehyde under nitrifying conditions: Kinetic study

The kinetic behavior of a stable nitrifying consortium exposed to 2-chlorophenol (2-CP), phenol, p-cresol and p-hydroxybenzaldehyde (p-OHB) was evaluated in batch assays. Phenolic compounds were evaluated either individually or in mixture. In individual assays, 2-CP inhibited stronger the nitrification, diminishing the ammonium consumption efficiency (16%) and the nitrate production rate (at 91%). Nonetheless, the consumption efficiencies for all phenolics were of 100%. On the other hand, in mixture, the inhibitory effect of 2-CP diminished significantly, since ammonium consumption efficiency and nitrate production rate were improved. Consumption efficiencies for most of the phenolic compounds were high. Furthermore, the kinetic of 2-CP oxidation was 2.4-fold-faster than the individual assays. Finally, the experimental results showed the potential of nitrifying consortium for removing 2-CP, phenol, p-cresol and p-OHB. This is the first work showing the simultaneous removal of these pollutants and also this information might be useful for treating wastewaters of chemical complexity.

Simultaneous oxidation of ammonium and p-cresol linked to nitrite reduction by denitrifying sludge.

The metabolic capability of denitrifying sludge to oxidize ammonium and p-cresol was evaluated in batch cultures. Ammonium oxidation was studied in presence of nitrite and/or p-cresol by 55 h. At 50 mg/L NH4+-N and 76 mg/L NO2--N, the substrates were consumed at 100% and 95%, respectively, being N2 the product. At 50 mg/L NH4+-N and 133 mg/L NO2--N, the consumption efficiencies decreased to 96% and 70%, respectively. The increase in nitrite concentration affected the ammonium oxidation rate. Nonetheless, the N2 production rate did not change. In organotrophic denitrification, the p-cresol oxidation rate was slower than ammonium oxidation. In litho-organotrophic cultures, the p-cresol and ammonium oxidation rates were affected at 133 mg/L NO2--N. Nonetheless, at 76 mg/L NO2--N the denitrifying sludge oxidized ammonium and p-cresol, but at different rate. Finally, this is the first work reporting the simultaneous oxidation of ammonium and p-cresol with the production of N2 from denitrifying sludge.

Simultaneous oxidation of ammonium, p-cresol and sulfide using a nitrifying sludge in a multipurpose bioreactor: a novel alternative.

A nitrifying continuous stirred tank reactor was used as multipurpose bioreactor and it was operated for 325 days at 220 mg NH(4)(+)-N/Ld, 89 mg p-cresol-C /Ld and 36-76 mg S(2-)/Ld. The bioreactor was fed in sequential way, firstly with ammonium, achieving a consumption efficiency of 89%, with a nitrate yield of 0.99. Afterward, p-cresol was fed, achieving ammonium and p-cresol consumption efficiencies of 95% and 100%, respectively. The nitrate yield was higher and no aromatic intermediaries from p-cresol were detected. Finally sulfide was fed and the consumption efficiencies for all substrates were of 100%, being nitrate, HCO(3)(-) and sulfate the end products. The kinetic results showed that biological sulfide consumption was 13-fold faster than the chemical oxidation. This is the first time that a nitrifying reactor can be used for multiple purposes and also for the simultaneous removal of ammonium, sulfide and p-cresol in one step.

Biological removal of p-cresol, phenol, p-hydroxybenzoate and ammonium using a nitrifying continuous-flow reactor

Phenolic compounds biodegradation and its effect on the nitrification process were studied. A continuous stirrer tank reactor was operated in four stages, and phenolic compounds were fed as sequential way. In the first stage, at loading rate of 220 mg NH(4)(+)-N/Ld, the consumption efficiency was of 91%, being the product, nitrate. After that, p-cresol was fed at 53 mg C/Ld, reaching removal efficiencies for both substrates higher than 90%. In the third stage, p-hydroxybenzoate was fed at 56 mg C/Ld, and the removal efficiencies for all substrates remained high. In the last stage, the reactor was fed at 54 mg C/Ld of phenol, and it caused a diminishing on the ammonium removal efficiency; however, all phenolic compounds were efficiently removed. Kinetic results showed that the presence of each phenolic compound improved the ammonium oxidizing activity, but the nitrite oxidizing activity was not affected.

Sequential nitrification-denitrification process for nitrogenous, sulfurous and phenolic compounds removal in the same bioreactor.

The kinetic and metabolic behavior of an aerobic granular sludge to nitrify, denitrify and nitrify-denitrify was evaluated in batch cultures. In nitrification control, ammonium, 4-methylphenol and sulfide were consumed efficiently (∼100%) and recovered as NO3(-), CO2, S(0) and SO4(2-), respectively. In denitrification control, S(0) and nitrate were efficiently consumed and recovered as SO4(2-) and N2, respectively. Sequential nitrification-denitrification process was evaluated by applying oxic/anoxic conditions. Ammonium, 4-methylphenol and sulfide were oxidized to nitrate, CO2 and mainly S(0), respectively, under aerobic conditions. After that, anoxic conditions were established where S(0) reduced all nitrate to N2, with molecular nitrogen yield (YN2) of 1.03 ± 0.06 mg/mg NH4(+)-N consumed. This is the first study to show the capability of an aerobic granular sludge in simultaneous removal of ammonium, 4-methylphenol and sulfide by sequential nitrification-denitrification process in the same bioreactor.