Andrea Fra-Vázquez

Humic acid has a controversial effect on the biological treatment processes. Here, we have investigated humic acid effects on the Anammox activity by studying the nitrogen removal efficiencies in batch and continuous conditions and analyzing the microbial community using Fluorescence in situ hybridization (FISH) technique. The results showed that the Anammox activity was affected by the presence of humic acid at a concentration higher than 70 mg/L. In fact, in the presence of humic acid concentration of 200 mg/L, the Anammox activity decreased to 57% in batch and under continuous condition, the ammonium removal efficiencies of the reactor decreased from 78 to 41%. This reduction of Anammox activity after humic acid addition was highlighted by FISH analysis which revealed a considerable reduction of the abundance of Anammox bacteria and the bacteria living in symbiosis with them. Furthermore, a total inhibition of Candidatus Brocadia fulgida was observed. However, humic acid has promoted heterotrophic denitrifying bacteria which became dominant in the reactor. In fact, the evolution of the organic matter in the reactor showed that the added humic acid was used as carbon source by heterotrophic bacteria which explained the shift of metabolism to the favor of heterotrophic denitrifying bacteria. Accordingly, humic acid should be controlled in the influent to avoid Anammox activity inhibition.

BACKGROUND: Crude glycerol, a by‐product of the biodiesel production industry, was used to produce intracellular storage polymers for waste valorization. The enrichment of a mixed microbial culture (MMC) in microorganisms with the ability to accumulate intracellular polymers was performed in a sequencing batch reactor (SBR) submitted to feast–famine conditions. The effect of different carbon sources in the accumulation of biopolymers was investigated.RESULTS: A MMC enriched in yeast and bacteria was obtained using crude glycerol as feedstock. Accumulation experiments performed with crude glycerol, synthetic glycerol and synthetic methanol showed the feasibility of the MMC to produce different biopolymers. Triacylglyceride (TAG) accumulation up to 46 wt% in yeast cells was promoted by the presence of residual lipids in crude glycerol. However, bacteria from class Betaproteobacteria used glycerol mainly to accumulate 28 wt% of polyglucose (PG) and methanol as carbon source for cell growth.CONCLUSIONS: As waste valorization, a possible advantage which comes out of the present study is the use of open, non‐sterile and non‐defined systems to produce TAGs. These TAGs can potentially re‐enter the biodiesel production process helping on the maximisation of the feedstock used in this process. © 2018 Society of Chemical Industry

The study of biogeochemical cycles is important to understand the circulation of elements through aquatic, aerial and terrestrial ecosystems. Among others, N and P are considered as the limiting nutrients that determine the productivity of organisms. Since human activity is increasing its influence over these cycles at a global scale, it is important to analyze the implications of anthropogenic variations in order to detect the sources and try to prevent or reduce their impact. Moreover, not only the increasing or diminished concentration of nitrogen and phosphorus in nature by human resource exploitations is needed to account today. As metals play a crucial role in the dynamics of these essential elements, their presence in the environment also requires a significant attention.

Aerobic granular sludge represents an interesting approach for simultaneous organic matter and nitrogen removal in wastewater treatment plants. However, the information about microbial communities in aerobic granular systems dealing with industrial wastewater like pig slurry is limited. Herein, bacterial diversity and dynamics were assessed in a pilot scale plant using aerobic granular sludge for organic matter and nitrogen elimination from swine slurry during more than 300 days. Results indicated that bacterial composition evolved throughout the operational period from flocculent activated sludge, used as inoculum, to mature aerobic granules. Bacterial diversity increased at the beginning of the granulation process and then declined due to the application of transient organic matter and nitrogen loads. The operational conditions of the pilot plant and the degree of granulation determined the microbial community of the aerobic granules. Brachymonas, Zoogloea and Thauera were attributed with structural function as they are able to produce extracellular polymeric substances to maintain the granular structure. Nitrogen removal was justified by partial nitrification (Nitrosomonas) and denitrification (Thauera and Zoogloea), while Comamonas was identified as the main organic matter oxidizing bacteria. Overall, clear links between bacterial dynamics and composition with process performance were found and will help to predict their biological functions in wastewater ecosystems improving the future control of the process. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1212–1221, 2016