Potential of endogenous PHA as electron donor for denitrification

The use of wastewater streams to obtain polyhydroxyalkanoates (PHA) as high added-value products is widely studied. However, nitrogen removal is not well integrated into this process. In this study, the optimal conditions to track the specific endogenous denitrifying activity (SEDA) driven by PHA as carbon source were selected as: sludge concentration of 0.5–2 g VSS/L, CODPHA/N ratio higher than 5.4 g/g and between 40 and 60 mg NO3−-N/L. The seeding biomass used to perform the activity tests was collected from two sequencing batch reactors and was able to store up to 69% wt/wt of PHA. SEDA values of 0.26–0.39 g N2-N/(g VSSact d) were achieved, which proved the potential of PHA-accumulating mixed microbial cultures to be used in nitrogen removal processes. The results indicated that there is not a preference in the consumption of hydroxybutyrate over hydroxyvalerate and that PHA concentrations lower than 5% wt/wt do not allow the obtainment of the maximum SEDA value. Finally, N2O gas production was not detected in the SEDA experimentsThe authors would like to thank the Spanish Government (AEI) for funding in the frame of the projects TREASURE (CTQ2017-83225-C2-1-R) and AQUAVAL (PCIN-2017-047), this last also funded by EU in the frame of the collaborative international Consortium AQUAVAL financed under the ERA-NET WaterWorks2015 Cofunded Call. This ERA-NET is an integral part of the 2016 Joint Activities developed by the Water Challenges for a Changing World Joint Programme Initiative (Water JPI). The authors belong to the Galician Competitive Research Group (GRC-ED431C 2017-29) and to the CRETUS Strategic Partnership (ED431E 2018/01), co-funded by FEDER (UE). Angeles Val del Rio is a Xunta de Galicia fellow (ED418B 2017/075)S

Volatile fatty acid production from saline cooked mussel processing wastewater at low pH

The production of VFA using as substrate the wastewater produced in a cooked mussel processing factory, containing large COD (13.7 ± 3.2 g COD/L), salt concentrations (21.8 ± 2.8 g NaCl/L) and characterized by low pH (4.6 ± 0.6) was evaluated. This wastewater was fed to a 5-L completely stirred tank reactor operated in continuous mode. The conversion efficiency of its COD content into volatile fatty acids (VFA) was evaluated. The maximum acidification of 43% (total VFA on soluble COD basis) was obtained when an organic loading rate of 2.5 ± 0.4 g COD/(L·d) was applied to the reactor and corresponded to a VFA volumetric productivity of 0.72 ± 0.07 g CODVFA/(L·d). Under steady-state conditions, the obtained mixture of VFA was composed by 80:18:2 as acetic:propionic:butyric acids (percentage of VFA on soluble COD basis). Carbohydrates were degraded up to 96% while protein fermentation did not take place, probably due to the low pH value, limiting the maximum acidification of the wastewater. Batch experiments showed that the increase of the pH from 4.2 to 4.9 by the addition of NaHCO3 resulted in the improvement of the acidification and changed the VFA mixture composition. Thus, this study demonstrates the opportunity of using complex substrates, as cooked mussel processing wastewater, to produce rich-VFA streams under unfavourable operational conditions, such as high salinity and low pHThis research was supported by the Spanish Government (AEI) through the FISHPOL (CTQ2014-55021-R) and TREASURE (CTQ2017-83225-C2-1-R) projects. The authors belong to the Galician Competitive Research Group GRC ED431C 2017/29 and to the CRETUS Strategic Partnership (ED431E 2018/01). All these programs are co-funded by the FEDER (EU). Special thanks to Dr. Thelmo A. Lú-Chau for his contribution to the statistical analysis of data.S

Optimization of an enriched mixed culture to increase PHA accumulation using industrial saline complex wastewater as a substrate

Polyhydroxyalkanoates (PHA) appear as good candidates to substitute conventional petroleum-based plastics since they have similar properties but with the advantage of being biodegradable. Wastewater streams with high organic content are feasible substrates for PHA production resulting in an opportunity for waste recovery. One of the main challenges is the optimization of the selection of microorganisms with high PHA storage capacity. This microbial selection is performed in sequencing batch reactors (SBR) operated under an aerobic feast/famine (F/F) regime. In the present study, a settling stage was added at the end of the feast phase of the enrichment cycle of a SBR fed with pre-acidified cooked mussel processing wastewater (containing up to 12 g NaCl/L). Settling and subsequent supernatant discharge favoured the wash-out of non-accumulating microorganisms as well as the removal of substances that enhanced their undesired development (proteins and carbohydrates). Microbial analysis performed by fluorescence in situ hybridization (FISH) technique showed shifts in the microbial community; the presence of genus Paracoccus increased whereas genera Comamonas decreased. Moreover, the process efficiency was improved with the increase of the PHA production yield (YPHA) and the maximum PHA storage capacity (max. PHA) from 0.48 to 0.72 CmmolPHA/CmmolVFA and from 40 to 60 wt%, respectively. The polymer composition also changed, its HB:HV ratio varied from 83:17 to 70:30. Results obtained in the present study showed that settling after the feast phase promoted the removal of carbon sources that did not contribute to PHA production and the washout of non-storing bacteria, which favoured the culture enrichmentThis research was supported by the Spanish Government (AEI) through the TREASURE project [CTQ2017-83225-C2-1-R]. Lucía Argiz is a Xunta de Galicia fellow (2019), Axudas de Apoio á Etapa Predoutoral (ED481A-2019/083), grant cofunded by the operative program FSE Galicia 2014–2020. Moreover, authors would like to thank the EU and the AEI for funding, in the frame of the collaborative international Consortium AquaVal project, [PCIN-2017-047], financed under the ERA-NET WaterWorks2015 Cofunded Call. This ERA-NET is an integral part of the 2016 Joint Activities developed by the Water Challenges for a Changing World Joint Programme Initiative (Water JPI). The authors belong to CRETUS Strategic Partnership (ED4331e 2018/01) and the Galician Competitive Research Group (GRC ED431C 2017/29). All these programs are co-funded by the FEDER: Fondo Europeo de Desarrollo Regional - EU (European Union)S

Feasible microbial accumulation of triacylglycerides from crude glycerol

This is the peer-reviewed version of the following article: Fra-Vázquez, A. , Pedrouso, A. , Palmeiro-Sánchez, T. , Moralejo-Gárate, H. and Mosquera-Corral, A. (2018), Feasible microbial accumulation of triacylglycerides from crude glycerol. J. Chem. Technol. Biotechnol, 93: 2644-2651, which has been published in final form at https://doi.org/10.1002/jctb.5618. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsBACKGROUND: 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 performedwith crude glycerol, synthetic glycerol and synthetic methanol showed the feasibility of theMMCto producedifferent biopolymers. Triacylglyceride (TAG) accumulation up to 46wt% in yeast cellswas promoted by the presence of residual lipids in crude glycerol. However, bacteria fromclass Betaproteobacteria used glycerol mainly to accumulate 28wt% of polyglucose (PG) andmethanol as carbon source for cell growth. CONCLUSIONS: Aswaste 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 processThis research was supported by the Spanish Government (AEI) through FISHPOL (CTQ2014–55021-R) and GRANDSEA (CTM2014–55397-JIN) projects. The authors belong to the Galician Competitive Research Group GRC ED431C 2017/29 and to the CRETUS Strategic Partnership (AGRUP2015/02). All of these programmes are co-funded by the FEDER (EU)S

Effects of short- and long-term exposures of humic acid on the Anammox activity and microbial community

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.This research work is financially supported by the Tunisian Ministry of Higher Education, Scientific Research and TechnologyS

Bacterial community dynamics in long‐term operation of a pilot plant using aerobic granular sludge to treat pig slurry

This is a Post-print version of the articleAerobic 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 processThis work has been financed by FISHPOL (CTQ2014-55021-R) and GRANDSEA (CTM2014-55397-JIN) projects from the Spanish Government and co-funded by FEDER. The authors belong to the Galician Competitive Research Group GRC 2013-032, programme co-funded by FEDER, and CRETUS (AGRUP2015/02)S

Assessment of a fast method to predict the biochemical methane potential based on biodegradable COD obtained by fractionation respirometric tests

The biochemical methane potential test (BMP) is the most common analytical technique to predict the performance of anaerobic digesters. However, this assay is time-consuming (from 20 to over than 100 days) and consequently impractical when it is necessary to obtain a quick result. Several methods are available for faster BMP prediction but, unfortunately, there is still a lack of a clear alternative. Current aerobic tests underestimate the BMP of substrates since they only detect the easily biodegradable COD. In this context, the potential of COD fractionation respirometric assays, which allow the determination of the particulate slowly biodegradable fraction, was evaluated here as an alternative to early predict the BMP of substrates. Seven different origin waste streams were tested and the anaerobically biodegraded organic matter (CODmet) was compared with the different COD fractions. When considering adapted microorganisms, the appropriate operational conditions and the required biodegradation time, the differences between the CODmet, determined through BMP tests, and the biodegradable COD (CODb) obtained by respirometry, were not significant (CODmet (57.8026 ± 21.2875) and CODb (55.6491 ± 21.3417), t (5) = 0.189, p = 0.853). Therefore, results suggest that the BMP of a substrate might be early predicted from its CODb in only few hours. This methodology was validated by the performance of an inter-laboratory studyconsidering four additional substratesThis research was supported by the Spanish Government (AEI) through the TREASURE project [CTQ 2017-83225-C2-1-R]. Moreover, authors would like to thank the EU and the AEI for funding, in the frame of the collaborative international Consortium AquaVal project, [PCIN-2017-047], financed under the ERA-NET WaterWorks2015 Co-funded Call. This ERA-NET is an integral part of the 2016 Joint Activities developed by the Water Challenges for a Changing World Joint Programme Initiative (Water JPI). Authors from the USC belong to the Galician Competitive Research Group GRC ED431C 2017/29. All these programs are co-funded by the FEDER (EU). Lucia Argiz is a Xunta de Galicia Fellow, Axudas de Apoio á Etapa Predoutoral (ED481A-2019/083), grant cofounded by the operative program FSE Galicia 2014–2020. In addition, this work was funded by the Chilean Government through the projects FONDECYT 1180650 and ANID/FONDAP/15130015. Marisol Belmonte belongs to LABMAI-Facultad de Ingeniería, HUB-Ambiental UPLA and UPLAguas Research GroupS

Performance and microbial features of the partial nitritation-anammox process treating fish canning wastewater with variable salt concentrations

The partial nitritation-anammox (PN-AMX) process applied to wastewaters with high NaCl concentration was studied until now using simulated media, without considering the effect of organic matter concentration and the shift in microbial populations. This research work presents results on the application of this process to the treatment of saline industrial wastewater. Obtained results indicated that the PN-AMX process has the capability to recover its initial activity after a sudden/acute salt inhibition event (up to 16 g NaCl/L). With a progressive salt concentration increase for 150 days, the PN-AMX process was able to remove the 80% of the nitrogen at 7–9 g NaCl/L. The microbiological data indicated that NaCl and ammonia concentrations and temperature are important factors shaping PN-AMX communities. Thus, the NOB abundance (Nitrospira) decreases with the increase of the salt concentration, while heterotrophic denitrifiers are able to outcompete anammox after a peak of organic matter in the feedingThis work was supported by the Spanish Government through GRANDSEA (CTM2014-55397-JIN) and FISHPOL (CTQ2014-55021-R) projects co-funded by FEDER, and the Chilean Government (CONICYT/FONDAP/15130015). The authors from the USC belong to CRETUS (AGRUP2015/02) and the Galician Competitive Research Group (GRC 2013-032), programs co-funded by FEDERS

Recovery of Polyhydroxyalkanoates from Cooked Mussel Processing Wastewater at High Salinity and Acidic Conditions

Polyhydroxyalkanoates (PHA) are biodegradable polymers that can be intracellularly produced by microorganisms valorizing organic-rich wastes. In the present study, a PHA production system was fed with mussel cooker wastewater after acidogenic fermentation. Besides low pH (4.0 ± 0.3) and high salt (21.7 ± 2.9 g NaCl/L) concentrations, this wastewater also contained nitrogen concentrations (0.8 ± 0.1 g N/L), which were previously reported to be a challenge to the PHA accumulating bacteria enrichment. Bacteria with a PHA storage capacity were selected in an enrichment sequencing batch reactor (SBR) after 60 days of operation. The enriched mixed microbial culture (MMC) was mainly formed by microorganisms from phylum Bacteroidetes, and genera Azoarcus, Comamonas and Thauera from phylum Proteobacteria. The MMC was able to accumulate up to 25 wt% of PHA that was mainly limited by the wastewater nitrogen content, which promoted biomass growth instead of PHA accumulation. Indeed, when the presence of nutrient was limited, PHA stored in the accumulation reactor increased to up to 40.9 wt%. This work demonstrated the feasibility of the enrichment of a MMC with a PHA storage ability valorizing the fish-canning industrial wastewater at low pH, which is generally difficult to treat in wastewater treatment plantsThis research was funded by the Spanish Government (AEI) through the FISHPOL (CTQ2014-55021-R) and TREASURE (CTQ2017-83225-C2-1-R) projects. The authors belong to the Galician Competitive Research Group GRC ED431C 2017/29 and to the CRETUS Strategic Partnership (ED431E 2018/01). All these programs are co-funded by the FEDER (EU)S