How can the wastewater treatment sector contribute for the sustainability of the agro-food industries?

Over the last decades, the agro-food industry has largely intensified its production to cover the growing needs of society. The economic model based on the take-make-dispose paradigm is no longer viable due to its unsustainability. In this context, the agro-food industry has been paying attention to cross-cutting technologies to incorporate sustainability into its processes. The water footprint is a key issue for the agro-food industry. Huge amounts of water are needed, and consequently huge amounts of wastewater are produced. Wastewater treatment processes are necessary for the preservation of water and its environmental quality. Nowadays, the implementation of greener wastewater treatment technologies, that allow for the reduction, reuse and recovery of materials is an asset. The granular sludge technology is an example of a such innovative process, robust to deal with fluctuations in wastewater composition and able to offer opportunities for more value-added processes. In this presentation, recent data and results will be shown to illustrate how the granular sludge technology can help in the transition to achieve sustainilibity in the agro-food industry, especially related to its water footprint.info:eu-repo/semantics/publishedVersio

Nutrient removal in an aerobic granular sludge system facing events of saltwater intrusion

The presence of saltwater in wastewater treatment plants (WWTP) can have diverse origins, for instance from the discharge of industrial saline effluents or the saltwater use for toilet flushing. However, in coastal regions, especially during high tide level, saltwater intrusion occurs changing the wastewater composition, posing a challenge for the nearby WWTPs. The impact of the variable salinity levels of the wastewater over a day can affect the biological removal processes, a topic scarcely studied for granular systems. Aerobic granular sludge (AGS) is one of the most promising biotechnologies for wastewater treatment, mainly due to AGS extraordinary properties, such as the simultaneous nutrient removal capability, good settling properties, and the simplicity of operation. In this study, the nutrients removal performance of an AGS system treating domestic wastewater with variable saltwater concentrations was evaluated. First, the reactor was operated for 4 months stepwise increasing the saltwater concentration (up to 15 g L-1). Then, the saltwater concentration of the wastewater was variable during each day, fluctuating from basal (7.5 g L-1) to maximum salinity (22.5 g L-1) levels to mimic flood tide events. During the first stage of operation, the AGS capacity for carbon, ammonium and phosphate removal increased over time, with most of the carbon and nutrients being removed. In the second stage, the saltwater daily intrusion variation due to tidal cycles did not affect neither the granular structure nor the reactor removal performance, as the granulation processes continued to occur and the biomass was able to efficiently treat the wastewater. The AGS system capacity to deal with saltwater intrusion during high tides showed that this technology is promising to use by utilities situated along the coast with saltwater intrusion events.info:eu-repo/semantics/publishedVersio

Microalgae attachment to aerobic granular sludge for the treatment of freshwater aquaculture effluents

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Exopolysaccharides production by aerobic granular sludge upon exposure to dual anthropogenic stresses

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Performance of microalgae-bacteria granular sludge for nutrient removal of freshwater aquaculture wastewater

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Targeting aerobic granular sludge microbiome salt adaptation

Saline wastewaters can result from different economical activities, such as food and chemical industries. The need to overcome water shortage is also producing more saline wastewater, especially in coastal cities where seawater is used for cleaning processes. This is leading to the need of biological wastewater treatment technologies able to tolerate high salt concentrations. Aerobic granular sludge (AGS) has been appointed as the best aerobic treatment process for saline wastewater, mainly due to the high bacterial aggregation and self-protection level that granules offer. Due to the existence of different microbial metabolic layers within the granules, AGS technology is used for removing organic carbon as well as nitrogen and phosphorous from wastewater. In this study, AGS biomass was acclimated to saline wastewater, by performing a stepwise salt addition over a period of 250 days, from 0 to 14 g NaCl L-1. A high bacterial diversity existed while treating wastewater up to 3 g NaCl L-1. However, the salinity increase up to 6 g NaCl L-1 led to a relevant microbial diversity reduction. Salt increase led to the dominance of Proteobacteria, namely of Lysobacter and Rhodocyclus bacterial genera, both associated to carbon-nitrogen removal and EPS production in AGS processes, respectively. Despite this bacterial selection, carbon and nutrients removal processes were kept stable, even when salinity was increased to 14 g NaCl L-1, which was corroborated by the identification of bacteria responsible for such processes (e.g., PAO, AOB and NOB) throughout reactor operation. Hence, the AGS process was able to adapt to salt by preserving the metabolic diversity required for performing different biological removal processes, showing the microbial selection and plasticity occurring in AGS processes, an issue of great relevance for upgrading wastewater treatment.info:eu-repo/semantics/publishedVersio

Activity of nitrifying bacteria in aerobic granular sludge treating food industry wastewater

Aerobic Granular Sludge (AGS) is an innovative wastewater biological treatment, which uses less energy and space compared to other technological solutions. AGS presents a diverse microbial community responsible for the simultaneous removal of carbon and nutrients. These communities are protected by extracellular polymeric substances (EPS), which provide a compact structure to the granules. As a result, bacteria present in the aerobic granules are more resistant to variable wastewater composition, as commonly produced in food industry. In this study, carbon and NH4+ removal from a fish canning plant wastewater was evaluated using an AGS-SBR (sequential batch reactor), operated during 90 days. Chemical oxygen demand (COD) at the outlet was below the discharge limit of 125 mg O2 L-1 throughout the operation. Nitrification occurred during the first 23 days of operation. Between days 24 and 60, nitrification was completely inhibited, without ammonium removal from the wastewater. Nitrifying bacteria recovered their activity right after a decrease in the wastewater organic load, showing that the inhibition of the nitrification process was reversible. This study will contribute to our knowledge on the application of the AGS process to food industry wastewater treatment.N/

Bacterial diversity shifts in AGS reactor treating food industry wastewater

Aerobic granular sludge (AGS) is a promising technology for treating industrial wastewater, possessing higher biomass retention and tolerance to toxic substrates than conventional activated sludge systems. AGS presents a diverse microbial community responsible for the simultaneous removal of carbon and nutrients. These communities are protected by extracellular polymeric substances (EPS) that allow for the compact structure of the granules. As a result, bacteria present in the aerobic granules are more resistant to variable wastewater composition, as commonly produced in food industry. The main objective of this work is to study the microbial community dynamics of an AGS reactor treating wastewater from a fish canning plant. The reactor was monitored during 220 days, divided into eight operational phases. COD, NH4+ and PO43- removal were assessed and biomass samples were collected throughout time for microbiome profiling. The reactor presented good COD, PO43- and NH4+ removal during phases I, II and III, but decreased performance during phase IV, when a higher organic load was applied. The removal processes recovered after phase IV until the end of operation. Proteobacteria were dominant in the inoculum (relative abundance of 64.8 %) and dominated almost all reactor phases. Bacteroidetes were second dominant in the inoculum (17.5 %) as well in most reactor phases, being present with higher relative abundance (55.5 %) than Proteobacteria (38.4 %) during phase IV. Within Proteobacteria, Gammaproteobacteria were initially more abundant but Betaproteobacteria predominated after phase IV. For Bacteroidetes, the community dynamics has also changed from phase IV onwards, with Flavobacteriia losing its high relative abundance to Saprospiria and Cytophagia. Several bacterial genera were detected throughout reactor operation, such as Phenylobacterium and Flavobacterium, while other were detected with higher abundance before (Methylocaldum and Plasticicumulans) or after phase IV (Thauera and Paracoccus). The relationship between bacterial community shifts and process performance was assessed. This study increases our knowledge on AGS technology application in real wastewater treatment.info:eu-repo/semantics/publishedVersio

Aerobic granular sludge has EPS-producing bacteria able to tolerate salt

The aerobic granular sludge (AGS) process is a promising biotechnology which relies on the formation of compact biomass granules. Granulation occurs due to the overproduction of extracellular polymeric substances (EPS) by some microbes in response to stress conditions. EPS protect bacteria from the effect of toxic or inhibiting compounds present in the wastewater, such as salts. One of the current challenges is to use the AGS process to treat high salinity wastewater, commonly produced by agro-food and chemical industries. The main objective of this study was to screen for EPS-producing bacteria bacteria in an AGS reactor treating synthetic saline wastewater contaminated with a toxic compound. Several bacterial isolates were obtained from the reactor biomass. Genomic DNA was extracted and isolates (30) were grouped according to species similarity, based on RAPD profiles. Isolates displaying unique profiles (15) were subsequently identified by 16S rRNA gene sequencing analysis. Bacteria highly related to Pseudomonas, Aeromonas, Stenotrophomonas, Flavobacterium and Pseudoxanthomonas were obtained. Isolates SG4 (Stenotrophomonas) and FG10 (Flavobacterium) belong to bacterial genera associated to EPS production in granules. These were selected for growth and biofilm formation assays with increasing NaCl concentrations (0 to 35 g L-1). Both isolates were able to grow in the presence of 35 g NaCl L-1, despite at a lower growth rate. Although salt increase affected biofilm production, SG4 was the best biofilm producer. EPS production by SG4 in the presence of 10 and 20 g L-1 of NaCl was compared. EPS was extracted and the content in proteins, humic acids and carbohydrates was quantified. SG4 was able to produce more EPS in the presence of 10 g L-1 (123 mg g-1 VSS) compared to 20 g L-1 of NaCl (77.6 mg g-1 VSS). EPS-producing bacteria with ability to tolerate high salinity were retrieved from an AGS process treating synthetic wastewater. Further research is required to gain more knowledge on these bacteria and their importance for the robustness of a process treating saline wastewater.info:eu-repo/semantics/publishedVersio

Targeting aerobic granular sludge microbiome salt adaptation

Saline wastewaters can result from different economical activities, such as food and chemicals industries. The need to overcome water shortage is also producing more saline wastewater, especially in coastal cities where seawater is used for cleaning processes. This is leading to the need for biological wastewater treatment technologies able to tolerate high salt concentrations. Aerobic granular sludge (AGS) has been appointed as the best aerobic treatment process for saline wastewater, mainly due to the high bacterial aggregation and self-protection level that granules offer. Due to the existence of different microbial metabolic layers within the granules, AGS technology is used for removing organic carbon as well as nitrogen and phosphorous from wastewater. In this study, AGS biomass was acclimated to saline wastewater, by performing a stepwise salt addition over a period of 250 days, from 0 to 14 g NaCl L-1. A high bacterial diversity existed while treating wastewater up to 3 g NaCl L-1. However, the salinity increase up to 6 g NaCl L-1 led to a relevant microbial diversity reduction. Salt increase led to the dominance of Proteobacteria, namely of Lysobacter and Rhodocyclus bacterial genera, both associated to carbon-nitrogen removal and EPS production in AGS processes, respectively. Despite this bacterial selection, carbon and nutrients removal processes were kept stable, even when salinity was increased to 14 g NaCl L-1, which was corroborated by the identification of bacteria responsible for such processes (e.g., PAO, AOB and NOB) throughout reactor operation. Hence, the AGS process was able to adapt to salt by preserving the metabolic diversity required for performing different biological removal processes, showing the microbial selection and plasticity occurring in AGS processes, an issue of great relevance for upgrading wastewater treatment.info:eu-repo/semantics/publishedVersio