RESUMEN

The removal of polychlorinated biphenyls (PCBs) and PCB biosorption was investigated in anaerobic batch reactors with non-adapted sludge fed with 1.5 mg L-1 of six PCB congener (PCB 10, 28, 52, 153, 138 and 180), mineral medium and co-substrates. PCBs were analyzed by gas chromatography using headspace solid-phase microextraction (HS-SPME). In the methanogenic reactor the methane production, COD (Carbon Organic Demand) removal (90% of initial 2292.60 mg L-1) and consumption of volatile organic acids were verified. Nevertheless, anaerobic activity was not observed in the reactor with inactivated biomass and biosorption range of 38% to 89% was measured for distinct PCB congeners in this reactor. The PCB removal was calculated from the PCB bioavailable (not biosorbed) and reached 76% of total PCBs. The selection of some representatives of the Thermotogaceae family, Sedimentibacter and Pseudomonas at 101 days of operation in the methanogenic reactor was correlated with PCB degradation. In addition, the various removal rates for each PCB congener indicate that the removal depends on bioavailability. The selection of the former non-adapted microbiota in the methanogenic reactor combined with PCB degradation occurred at 101 days. These results allow to assert that it is possible to simultaneously couple PCB degradation and community selection, without the previous adaptation step, which is a time-consuming stage.

Asunto(s)

RESUMEN

An expanded granular sludge bed reactor was evaluated for the anaerobic digestion of commercial laundry wastewater and domestic sewage focused on the removal of linear alkylbenzene sulfonate (LAS). The reactor was operated in three stages, all under mesophilic conditions and with a hydraulic retention time of 36 h. At stage I, the laundry wastewater was diluted with tap water (influent: 15.3 ± 4.9 mg LAS/L); at stage II, 50% of the feed volume was domestic sewage and 50% was a mixture of tap water and laundry wastewater (influent: 15.8 ± 4.9 mg LAS/L); and at stage III, only domestic sewage was used as a diluent of the laundry wastewater (influent: 24.1 ± 4.1 mg LAS/L). Due to the addition of domestic sewage the organic compounds content and LAS in the influent increased. Under such conditions, it was observed that LAS removal rate decreased from 77.2 ± 14.9% (stage I) to 55.3 ± 18.4% (stage III). Statistical tests indicated that the decrease of the LAS removal rate was significant and indicated a correlation between the removal of LAS and specific organic loading rate. The analysis of 16S rRNA gene sequencing revealed genera similar to Geobacter, Desulfovibrio, Syntrophomonas, Syntrophus, Desulfobulbus, Desulfomonile, and Desulfomicrobium, which were related to the degradation of LAS.

Asunto(s)

RESUMEN

In this study, two versions of a triple chamber biosystem, coupling anaerobic digestion, nitrification and mixotrophic endogenous denitrification (ADNMED), were evaluated and compared. They were designed to maximize the use of endogenous electron donors produced by anaerobic digestion (residual organic matter and sulfide) to abate a portion of the influent nitrogen contained in domestic sewage while removing the inconvenience of effluent sulfide. The first version was able to abate 40% of the influent nitrogen but presented operational and hydrodynamic problems, which resulted in sulfide emissions. A modified second version was proposed, improving the first approach and achieving a nitrogen abatement of more than 60% and a sulfide-free effluent, complying with local emission standards. The results demonstrated that endogenous electron donors produced by anaerobic digestion should not be neglected, and a significant cost reduction in nitrogen removal from domestic sewage could be achieved by exploiting their potential with novel reactor configurations.

Asunto(s)

RESUMEN

Linear alkylbenzene sulfonate (LAS) is widely used in the formulation of domestic and industrial cleaning products, the most synthetic surfactants used worldwide. These products can reach water bodies through the discharge of untreated sewage or non-effective treatments. This study evaluates the ability of the microorganisms found in the Tiete river sediment to degrade this synthetic surfactant. The experiment was conducted in a bioreactor, operated in batch sequences under denitrifying conditions, with cycles of 24 hours and stirring at 150rpm, using 430 mL of sediments and 1 070mL of a synthetic substrate consisting of yeast extract, soluble starch, sodium bicarbonate and sucrose. LAS was added at different concentrations of l5mg/L and 30mg/L. The reactor operation was divided into the biomass adaptation to the synthetic substrate without LAS and three experimental conditions: a) addition of l5mg/L of LAS; b) 50% reduction the co-substrate concentration and 15 mg/L of LAS, and c) addition of 30mg/L of LAS and 100% co-substrate concentration. The results showed that the degradation efficiency of LAS was directly related to the addition of co-substrates and the population of denitrifying bacteria. The removal of LAS and nitrate can be achieved simultaneously in wastewater with low organic loads. The reduction in the co-substrates concentration was directly influenced by the number of denitrifying bacteria (2.2x10(13) to 1.0 x 10(8) MPN/gTVS), and consequently, LAS degradation (60.1 to 55.4%). The sediment microorganisms in the Tiete river can be used as an alternative inoculum in the treatment of wastewater with nitrate and LAS contamination.

Asunto(s)

RESUMEN

The objective of this study was to evaluate the degradation of Linear Alkylbenzene Sulfonate (LAS) in anaerobic sequencing batch reactor (ASBR) under denitrifying conditions using swine sludge as inoculum. The reactor was operated for 104 days with synthetic substrate containing nitrate, and LAS was added later (22 mg/L). Considering the added mass of the LAS, the adsorbed mass in the sludge and discarded along with the effluent, degradation of the surfactant at the end of operation was 87%, removal of chemical oxygen demand was 86% and nitrate was 98%. The bacterial community was evaluated by cutting the bands and sequencing of polymerase chain reaction (PCR) fragments and denaturing gradient gel electrophoresis (DGGE). The sequences obtained were related to the phylum Proteobacteria and the alpha-and beta-proteobacteria classes, these bacteria were probably involved in the degradation of LAS. The efficiently degraded LAS in the reactor was operated in batch sequences in denitrifying conditions.

RESUMEN

Four anaerobic fluidized bed reactors filled with activated carbon (R1), expanded clay (R2), glass beads (R3) and sand (R4) were tested for anaerobic degradation of LAS. All reactors were inoculated with sludge from a UASB reactor treating swine wastewater and were fed with a synthetic substrate supplemented with approximately 20 mg l(-1) of LAS, on average. To 560 mg l(-1) COD influent, the maximum COD and LAS removal efficiencies were mean values of 97+/-2% and 99+/-2%, respectively, to all reactors demonstrating the potential applicability of this reactor configuration for treating LAS. The reactors were kept at 30 degrees C and operated with a hydraulic retention time (HRT) of 18h. The use of glass beads and sand appear attractive because they favor the development of biofilms capable of supporting LAS degradation. Subsequent 16S rRNA gene sequencing and phylogenetic analysis of samples from reactors R3 and R4 revealed that these reactors gave rise to broad microbial diversity, with microorganisms belonging to the phyla Bacteroidetes, Firmicutes, Actinobacteria and Proteobacteria, indicating the role of microbial consortia in degrading the surfactant LAS.

Asunto(s)