The pollution effect on the denitrifying capacity of methanogenic sludges.

The denitrification process has been studied for biodegradation of some emerging contaminants (ECs). For this, anaerobic sludges from different Wastewater Treatment Plants (WTP) have been used; however, the biodegradation capacity can differ due to the contact they have had with various pollutants, given their origin. This work aims to evaluate the kinetic and metabolic capacity of two denitrifying sludges from different WTPs to biodegrade CH3COO--C and NO3--N. Denitrifying tests were carried out in batches with CH3COO--C (30 mg L-1) in a CN-1 relationship of 1.8 with sludge from a WTP of an educational center (WTP-A) and CH3COO--C (50 mg L-1) to a CN-1 of 1.4 with another from the WTP of Atotonilco de Tula, Hidalgo, México (WTP-B). The results showed that the biodegradation rate of CH3COO--C and NO3--N with the WTP-B sludge was 35 and 75% greater, respectively, compared to the WTP-A sludge. Therefore, we suggest that the consumption difference of substrate is attributable to the sludges of WTP, which have been exposed to a high concentration of a great variety of pollutants.

Biotransformation of 17ß-Estradiol through a Denitrifying Sludge.

17ß-estradiol (E2) is the natural estrogen with the most significant potential for endocrine disruption in the biota of aquatic ecosystems at trace concentrations. It is, therefore, essential to study treatments for water polluted with E2 that would guarantee its complete elimination and mineralization. Denitrification is a biological process shown to have the capacity to completely biodegrade drugs, such as ampicillin. This work is aimed to evaluate the biotransformation of 17ß-estradiol by employing a denitrifying sludge. The assays performed were: (I) abiotic with 3.5 mg E2-C L-1 and (II) denitrifying with 10 mg CH3COO--C L-1 as the reference, 10 mg E2-C L-1 as the sole electron donor, and a mixture of (mg L-1) 10 E2-C with 10 CH3COO--C at C N-1 of 1.1. The E2-C and NO3--N consumption efficiencies were greater than 99%, and HCO3--C and N2 production yields were close to 1 in all assays. The denitrifying sludge could biodegrade up to 10 mg E2-C L-1 as the sole electron donor and when mixed with 10 mg CH3COO--C L-1. No intermediate metabolites were generated from the process.