Anode Modification with Fe2O3 Affects the Anode Microbiome and Improves Energy Generation in Microbial Fuel Cells Powered by Wastewater.

This study investigated how anode electrode modification with iron affects the microbiome and electricity generation of microbial fuel cells (MFCs) fed with municipal wastewater. Doses of 0.0 (control), 0.05, 0.1, 0.2, and 0.4 g Fe2O3 per the total anode electrode area were tested. Fe2O3 doses from 0.05 to 0.2 g improved electricity generation; with a dose of 0.10 g Fe2O3, the cell power was highest (1.39 mW/m2), and the internal resistance was lowest (184.9 Ω). Although acetate was the main source of organics in the municipal wastewater, propionic and valeric acids predominated in the outflows from all MFCs. In addition, Fe-modification stimulated the growth of the extracellular polymer producers Zoogloea sp. and Acidovorax sp., which favored biofilm formation. Electrogenic Geobacter sp. had the highest percent abundance in the anode of the control MFC, which generated the least electricity. However, with 0.05 and 0.10 g Fe2O3 doses, Pseudomonas sp., Oscillochloris sp., and Rhizobium sp. predominated in the anode microbiomes, and with 0.2 and 0.4 g doses, the electrogens Dechloromonas sp. and Desulfobacter sp. predominated. This is the first study to holistically examine how different amounts of Fe on the anode affect electricity generation, the microbiome, and metabolic products in the outflow of MFCs fed with synthetic municipal wastewater.

Chemical and microbiological changes on the surface of microplastic after long term exposition to different concentrations of ammonium in the environment.

The increasing production of plastic in the world has resulted in the widespread pollution of the environment with microplastics (MP). MP enter facilities such as wastewater treatment plants or landfills characterized by various ammonium concentrations. The aim of this study was to determine the structure of the microbial community on MP surfaces at various concentrations of ammonium nitrogen, and in particular, to identify microorganisms capable of polyethylene terephthalate (PET) degradation. Moreover, changes in the chemical characteristics of the MP surface resulting from microbial activity were also investigated, and the potential of MP to serve as a vector for pollutants was determined. The tests were carried out in a reactor filled with PET for a period of 260 days. The experiment was carried out in 3 phases: in I and III phase, the concentration of N-NH4 was about 70 mg/L, while in II phase, it was about 430 mg/L. On the MP surface, biofilm-forming microorganisms from the genera Rhodococcus, Pseudomonas and Xantomonas were identified at the lower ammonium concentration. At this concentration, MP-degraders belonging to genera Acidovorax, Gordonia, Pseudomonas, Sphingomonas, and Sphingopyxis were identified in the biofilm. At the higher N-NH4 concentration, the biomass was enriched with bacteria from genera Nitrosospira, Nitrosomonas and Terrimonas, and the number of microorganisms with the potential to degrade MP decreased. Analysis of the MP surface during the experiment has showed the loss of carbonyl groups and formation of carboxyl and hydroxyl groups, which indicated the degradation of MP. Independent of the ammonium concentration in the environment, MP was a carrier of pathogenic microorganisms from the genera Mycobacterium, Enterobacter and Brevundimonas.

Biological release of phosphorus is more efficient from activated than from aerobic granular sludge.

Sewage sludge is a rich source of phosphorus. The kinetics of orthophosphate release and the efficiency of phosphorus recovery from aerobic granular sludge (GS) and activated sludge (AS) were compared at external organics (F) to biomass (M) ratios that ranged from 0 to 0.10. Changes in the F/M ratio affected orthophosphates release from AS to a greater extent than their release from GS. On average, increasing the F/M ratio by 0.02 increased the rate of phosphorus release from AS and GS by 2.12 and 1.75 mg P/(L h), respectively. Phosphorus release was highest at an F/M ratio of 0.04 (114.03 and 60.71 mg P/L from AS and GS, respectively). The efficiency of phosphorus recovery from AS ranged from 51.3 to 56.1%; the efficiency of its recovery from GS ranged from 32.8 to 37.5%. From GS, mostly inorganic phosphorus was released (about 8.5 mg/g MLSS), most of which was NAIP, i.e. phosphorus bound to Fe, Mn and Al. At a stoichiometric dose of MgO to PO43-, the precipitation efficiency was 30.13% ± 4.51 with uncontrolled pH and reached 81.73% ± 0.17 at a controlled pH of 10.