| 1. |
- Crisafi, F., et al.
(author)
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From Organic Wastes and Hydrocarbons Pollutants to Polyhydroxyalkanoates: Bioconversion by Terrestrial and Marine Bacteria
- 2022
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In: Sustainability. - : MDPI AG. - 2071-1050. ; 14:14
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Journal article (peer-reviewed)abstract
- The use of fossil-based plastics has become unsustainable because of the polluting production processes, difficulties for waste management sectors, and high environmental impact. Polyhydroxyalkanoates (PHA) are bio-based biodegradable polymers derived from renewable resources and synthesized by bacteria as intracellular energy and carbon storage materials under nutrients or oxygen limitation and through the optimization of cultivation conditions with both pure and mixed culture systems. The PHA properties are affected by the same principles of oil-derived polyolefins, with a broad range of compositions, due to the incorporation of different monomers into the polymer matrix. As a consequence, the properties of such materials are represented by a broad range depending on tunable PHA composition. Producing waste-derived PHA is technically feasible with mixed microbial cultures (MMC), since no sterilization is required; this technology may represent a solution for waste treatment and valorization, and it has recently been developed at the pilot scale level with different process configurations where aerobic microorganisms are usually subjected to a dynamic feeding regime for their selection and to a high organic load for the intracellular accumulation of PHA. In this review, we report on studies on terrestrial and marine bacteria PHA-producers. The available knowledge on PHA production from the use of different kinds of organic wastes, and otherwise, petroleum-polluted natural matrices coupling bioremediation treatment has been explored. The advancements in these areas have been significant; they generally concern the terrestrial environment, where pilot and industrial processes are already established. Recently, marine bacteria have also offered interesting perspectives due to their advantageous effects on production practices, which they can relieve several constraints. Studies on the use of hydrocarbons as carbon sources offer evidence for the feasibility of the bioconversion of fossil-derived plastics into bioplastics.
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| 2. |
- Micolucci, Federico, 1984, et al.
(author)
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Candidatus Scalindua, a Biological Solution to Treat Saline Recirculating Aquaculture System Wastewater
- 2023
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In: Processes. - : MDPI AG. - 2227-9717. ; 11:3
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Journal article (peer-reviewed)abstract
- Recirculating aquaculture systems (RAS) are promising candidates for the sustainable development of the aquaculture industry. A current limitation of RAS is the production and potential accumulation of nitrogenous wastes, ammonium (NH4+), nitrite (NO2-) and nitrate (NO3-), which could affect fish health and welfare. In a previous experiment, we have demonstrated that the marine anammox bacteria Candidatus Scalindua was a promising candidate to treat the wastewater (WW) of marine, cold-water RAS. However, the activity of the bacteria was negatively impacted after a direct exposure to RAS WW. In the current study, we have further investigated the potential of Ca. Scalindua to treat marine RAS WW in a three-phase experiment. In the first phase (control, 83 days), Ca. Scalindua was fed a synthetic feed, enriched in NH4+, NO2- and trace element (TE) mix. Removal rates of 98.9% and 99.6% for NH4+ and NO2-, respectively, were achieved. In the second phase (116 days), we gradually increased the exposure of Ca. Scalindua to nitrogen-enriched RAS WW over a period of about 80 days. In the last phase (79 days), we investigated the needs of TE supplementation for the Ca. Scalindua after they were fully acclimated to 100% RAS WW. Our results show that the gradual exposure of Ca. Scalindua resulted in a successful acclimation to 100% RAS WW, with maintained high removal rates of both NH4+ and NO2- throughout the experiment. Despite a slight decrease in relative abundance (from 21.4% to 16.7%), Ca. Scalindua remained the dominant species in the granules throughout the whole experiment. We conclude that Ca. Scalindua can be successfully used to treat marine RAS WW, without the addition of TE, once given enough time to acclimate to its new substrate. Future studies need to determine the specific needs for optimal RAS WW treatment by Ca. Scalindua at pilot scale.
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| 3. |
- Roques, Jonathan, 1985, et al.
(author)
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Effects of Recirculating Aquaculture System Wastewater on Anammox Performance and Community Structure
- 2021
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In: Processes. - : MDPI AG. - 2227-9717. ; 9:7
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Journal article (peer-reviewed)abstract
- Recirculating aquaculture systems (RAS) are good candidates for the sustainable development of the aquaculture sector. A current limitation of RAS is the production and accumulation of nitrogenous waste, which could affect fish health. We investigated the potential of the anaerobic ammonia oxidation (anammox) process to treat marine wastewater from a cold-water RAS. We show that the marine anammox bacteria Candidatus Scalindua is a promising candidate. However, its activity was affected by unknown compounds in the RAS wastewater and/or the sub-optimum of essential trace elements (TEs). Anammox activity dropped to 2% and 13% in NH4+ and NO2- removal, respectively, when nitrate-rich RAS wastewater was used as a medium in the absence of TE supplementation. A TE supplementation was added to the RAS wastewater in a subsequent phase, and a recovery in anammox activity was shown (25% and 24% in NH4+ and NO2- removal, respectively). Future studies need to identify the unknown factor and determine the specific needs regarding TE for optimal RAS wastewater treatment by Candidatus Scalindua
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| 4. |
- Tayou, L. N., et al.
(author)
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Acidogenic fermentation of food waste and sewage sludge mixture: Effect of operating parameters on process performance and safety aspects
- 2022
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In: Process Safety and Environmental Protection. - : Elsevier BV. - 0957-5820. ; 163, s. 158-166
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Journal article (peer-reviewed)abstract
- The production of added-value bio-products and energy from waste streams while minimizing environmental impacts is a crucial aspect within the circular economy's principles. The biorefinery can be an exit to the constant increasing of organic food waste and sewage sludge to solve the issues of waste disposal. This work deals with the production of volatile fatty acids (VFA) as added-value products from food waste and sewage sludge mixture in a pilot scale acidogenic fermentation process. Moreover, due to the lack of information about safety aspects in the literature, the explosive risk of the fermenter has been assessed by means of the quantification of lower flammability limit (LFL) of the generated flammable gases. Different temperature and feedstock's composition were tested, as well as the effect of thermal hydrolysis. Mesophilic fermentation (37 degrees C) on thermally hydrolysed feedstock (48 h at 72 degrees C) ensured stability in terms of VFA production at high concentration (30 +/- 2 gCOD(VFA)/L) and CODVFA/CODSOL ratio (0.86 +/- 0.09). Such condition also showed high LFL (28.9%), corresponding to a less hazardous condition compared to the other investigated, especially the thermophilic ones where LFL changed between 18% and 26%. (C) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
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| 5. |
- Valentino, F., et al.
(author)
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Valuable Routes for Sewage Sludge Utilization: Effect of Temperature and Hydraulic Retention Time in the Acidogenic Fermentation Process
- 2022
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In: Chemical Engineering Transactions. - 2283-9216. ; 93, s. 193-198
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Journal article (peer-reviewed)abstract
- The disposal of sewage sludge potentially reaches the 50-60% of WWTP’s total operation cost. Such stream can be considered a renewable carbon source to produce added-value products. Different pre-treatment methods have been applied on thickened sewage sludge (SS) coming from the domestic wastewater treatment plant (WWTP) of Treviso (northeast Italy) to favour its acidogenic fermentability. Alkaline (pH 9-11) and thermal (50-70°C) hydrolysis were applied separately and in combination The following fermentation process was addressed to the recovery of volatile fatty acids (VFA) as valuable building blocks substances. Batch fermentation tests were conducted at lab-scale under controlled temperature (T): 20, 37, 55 and 70°C by using an available mixed fermentative consortium as inoculum. Thermophilic T (55°C) was chosen in the following semi-continuous fermentation process (fill and draw), carried out with three different hydraulic retention time (HRT; 4-5-6 days). In terms of organic matter solubilisation, the thermal hydrolysis (70°C) allowed to obtain a soluble chemical oxygen demand (CODSOL) concentration around 10.0 g/L, with no additional benefits from the combined alkaline treatment. The batch acidogenic fermentation tests highlighted the T effect on acidification performances; thermophilic trials (55°C) showed the highest CODVFA/CODSOL ratio (0.81). The three semi-continuous tests (HRT 4-5-6 days) were followed for 45 days (roughly), under the chosen thermophilic condition (55°C). The highest fermentation rate was obtained at 4.0 d as HRT (22 mgCODVFA/gVS d); on the contrary, the highest fermentation yield (0.30 gCODVFA/gVS) and CODVFA/CODSOL ratio (0.73) were obtained at 6.0 d as HRT. In practice, low HRT selected for a mixed consortium with high fermentation rate, but less efficient in the conversion of the organic matter into VFA. No HRT’s effect was instead observed in the VFA composition, always rich in acetic (29-31% COD basis) and butyric acid (31-32%), and poorer in propionic (14-15%), valeric (12-13%) and caproic acid (11-12%). Copyright © 2022, Aidic Servizi S.R.L.
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