Phosphorus recovery by struvite (MgNH
4PO
4·6H
2O) crystallization is one of the most widely recommended technologies for treating sludge digester liquors especially in wastewater treatments plants ...(WWTP) with enhanced biological phosphorus removal (EBPR). In this paper, phosphorus recovery by struvite crystallization is assessed using the rejected liquors resulting from four different operational strategies of the sludge treatment line. Phosphorus precipitation and recovery efficiencies of between 80–90% and 70–85%, respectively, were achieved in the four experiments. The precipitates formed were mainly struvite, followed by amorphous calcium phosphate and, in some experiments, by calcite. The highest global phosphorus recovery taking into account both the sludge line and the crystallizer was achieved when mixed thickening and high elutriation were carried out (8.4 gP/kg treated sludge). However, low struvite content was obtained in the crystallizer with this operation scheme due to the high calcium content in the elutriation stream. Therefore, if the final purpose is to obtain struvite, the reduction of the elutriation flowrate is widely recommended in the case of high water hardness.
► SAnMBR represents a sustainable approach for urban wastewater treatment. ► The biogas-assisted mixing avoids super-saturation of methane at the effluent. ► The methane recovery efficiency obtained ...at 20°C was slightly lower than at 33°C. ► A temperature drop reduced the treatments efficiency and increased gases solubility. ► The methane recovery efficiency was mainly affected by the influent COD/S-SO4 ratio.
The present paper presents a submerged anaerobic membrane bioreactor (SAnMBR) as a sustainable approach for urban wastewater treatment at 33 and 20°C, since greenhouse gas emissions are reduced and energy recovery is enhanced. Compared to other anaerobic systems, such as UASB reactors, the membrane technology allows the use of biogas-assisted mixing which enhances the methane stripping from the liquid phase bulk. The methane saturation index obtained for the whole period (1.00±0.04) evidenced that the equilibrium condition was reached and the methane loss with the effluent was reduced. The methane recovery efficiency obtained at 20°C (53.6%) was slightly lower than at 33°C (57.4%) due to a reduction of the treatment efficiency, as evidenced by the lower methane production and the higher waste sludge per litre of treated wastewater. For both operational temperatures, the methane recovery efficiency was strongly affected by the high sulphate concentration in the influent wastewater.
Current wastewater treatment plants (WWTPs) paradigm is moving towards the so-called water resource recovery facilities in which sewage is considered a source of valuable resources. In particular, ...urban WWTPs are crucial systems to enhance phosphorus (P) recycling. This paper evaluates the implementation of a P-recovery system in Calahorra WWTP combining the operation of a new sludge line configuration coupled to a struvite crystallisation reactor at demonstration-scale. This new configuration consisted in the elutriation in the gravity thickener of the mixed sludge contained in the mixing chamber in order to reduce the phosphate load to the anaerobic digestion. The results indicated that the P available in the primary sludge overflow was nearly five times more than the obtained for the conventional configuration (1.88 vs. 0.39 gP/kg sludge treated), and the uncontrolled P precipitation inside the anaerobic digester was reduced by 43%. Regarding the total P entering the WWTP, 19% of the total P could be recovered with the new configuration proposed in comparison with 9% in the previous conventional configuration. The average recovery efficiency in the crystallisation plant was 86.9 ± 0.4%, yielding a struvite recovery of 8.0 ± 0.6 kg/d (0.67 ± 0.04 kg/m3 fed to the crystalliser). The potential struvite production with the new configuration would be around 41 kg/d (15 t/y) crystallising the thickener supernatant which could be increased up to around 103 kg/d (38 t/y) treating all the P-enriched streams (thickener supernatant and centrate streams). The paper demonstrates that WWTPs can contribute to reduce P scarcity, resulting in environmental and economic benefits.
•The new sludge line configuration in WWTP reduces P precipitation in digesters by 43%.•About 103 kg/d (38 t/y) of struvite will be produced with the P-recovery system implemented.•19% of the total P entering the WWTP could be recovered, contributing to reduce P scarcity.•The revenue of the recovery system implemented is about 4.74€/kg of P recovered.•The struvite obtained would fulfil the requirements for its use as fertiliser.
The influence of ultrasound and conventional heating under different processing conditions on the inactivation and potential subsequent growth of micro-organisms in orange juice was investigated. ...Although a limited level of microbial inactivation (⩽1.08 log CFU ml
−1) was obtained by selected batch ultrasonic treatment: 500
kHz/240
W for 15
min, microbial growth was observed in the substrate following 14
days of storage at both refrigeration (5
°C) and mild abusive (12
°C) temperatures. The presence of pulp in the juice increased the resistance of micro-organisms to ultrasound. After continuous ultrasonic treatments at flow rates of 3000
L
h
−1 negligible reductions of microbial counts were obtained. No ultrasound-related detrimental effects on the quality attributes of juice (limonin content, brown pigments and colour) were found. Therefore, to prevent the development of food-borne pathogens in orange juice it will be necessary to combine ultrasound with other processing methods with greater antimicrobial potency, as well as to achieve a very low initial concentration of bacteria, yeast and moulds in the juice. Such combinations will require further exploration of important synergistic effects that are relevant for industrial use. In this regard, the use of ultrasound in combination with mild heating for industrial use is discussed.
This research work proposes an innovative water resource recovery facility (WRRF) for the recovery of energy, nutrients and reclaimed water from sewage, which represents a promising approach towards ...enhanced circular economy scenarios. To this aim, anaerobic technology, microalgae cultivation, and membrane technology were combined in a dedicated platform. The proposed platform produces a high-quality solid- and coliform-free effluent that can be directly discharged to receiving water bodies identified as sensitive areas. Specifically, the content of organic matter, nitrogen and phosphorus in the effluent was 45 mg COD·L
, 14.9 mg N·L
and 0.5 mg P·L
, respectively. Harvested solar energy and carbon dioxide biofixation in the form of microalgae biomass allowed remarkable methane yields (399 STP L CH
·kg
COD
) to be achieved, equivalent to theoretical electricity productions of around 0.52 kWh per m
of wastewater entering the WRRF. Furthermore, 26.6% of total nitrogen influent load was recovered as ammonium sulphate, while nitrogen and phosphorus were recovered in the biosolids produced (650 ± 77 mg N·L
and 121.0 ± 7.2 mg P·L
).
This study compares the operation of mesophilic and thermophilic anaerobic digestion of sewage sludge and their effects in uncontrolled phosphorus precipitation. The research has been carried out ...using a pilot plant consisting of two digesters of 1.6 m
3
working volume, treating the mixed sludge of Alzira WWTP (Valencia, Spain). The digesters were operated in parallel, at different conditions: mesophilic (38 ± 2.0°C) and thermophilic (55 ± 2.5°C) temperatures and organic loading rates (OLR) ranging from 1.1 to 1.7 kg volatile solids (VS) m
−3
d
−1
and different hydraulic retention times (HRT) 20, 15 and 12 days. Uncontrolled precipitation was evaluated through P, Mg and Ca mass balances in both digesters. The results revealed that up to 82% of the available P and 81% of the available Mg precipitated in the mesophilic digester at HRT = 20 days which suggests the possible formation of struvite in both digesters. At lower HRT (HRT = 12 days) Mg and Ca precipitation was negligible and P fixation has been attributed to the possible formation of iron phosphates or adsorption processes on solid surfaces.
Carotenoids from persimmon juice processing Gea-Botella, S.; Agulló, L.; Martí, N. ...
Food research international,
March 2021, 2021-Mar, 2021-03-00, 20210301, Letnik:
141
Journal Article
Recenzirano
Odprti dostop
Display omitted
•Revalorization of by-products derived from industrialization of persimmon juice was approached.•By-product B resulting from an enzymatic treatment was especially suitable for ...recovery carotenoids.•Acetone extract from by-product B showed the largest amount of these pigments.•β-cryptoxanthin and β-carotene represented 49.2% and 13.2% of total carotenoid content in the acetone extract.•Total carotenoid content contributed greatly to antioxidant activity of persimmon by-product extract.
The aim of this study was the use and revalorization of two persimmon by-products A and B generated in the juice production process. The by-product B resulting from a pectinase enzymatic treatment of peels and pulp to optimize juice extraction was especially suitable for recovery of valuable bioactive carotenoids. The extraction solvents and solvent combinations used were: ethanol, acetone, ethanol/acetone (50:50 v/v) and ethanol/acetone/hexane (25:25:50 v/v/v). HPLC-DAD analysis detected and identified a total of nine individual carotenoids namely violaxanthin, neoxanthin, antheraxanthin, lutein, zeaxanthin, β-cryptoxanthin 5,6-epoxide, β-cryptoxanthin, α-carotene, and β-carotene. β-cryptoxanthin and β-carotene represented 49.2% and 13.2% of the total carotenoid content (TCC) in the acetone extract from by-product B. TCC contributed greatly to antioxidant activity of acetone extract derived from this by-product. Pectinase enzymatic treatment of persimmon peels and pulp followed by absolute acetone extraction of carotenoids could be an efficient method to obtain a rich extract in these compounds that could be used as nutraceutical ingredient.
The objective of this study was to evaluate the effect of seasonal temperature variations on the anaerobic treatment of urban wastewater in membrane bioreactors (MBRs). To this aim, sludge ...production, energy recovery potential, chemical oxygen demand (COD) removal and membrane permeability were evaluated in a submerged anaerobic MBR fitted with industrial-scale membrane units. The plant was operated for 172 days, between summer and winter seasons. Sludge production increased and energy recovery potential decreased when temperature decreased. COD removal and membrane permeability remained nearby stable throughout the whole experimental period.
Anaerobic membrane bioreactors (AnMBRs) can achieve maximum energy recovery from urban wastewater (UWW) by converting influent COD into methane. The aim of this study was to assess the anaerobic ...biodegradability limits of urban wastewater with AnMBR technology by studying the possible degradation of the organic matter considered as non-biodegradable as observed in aerobic membrane bioreactors operated at very high sludge retention times. For this, the results obtained in an AnMBR pilot plant operated at very high SRT (140 days) treating sulfate-rich urban wastewater were compared with those previously obtained with the system operating at lower SRT (29 to 70 days). At 140 days SRT the organic matter biodegraded by the AnMBR system accounted for 64.4% of the influent COD (45.9% was removed by sulfate reducing bacteria (SRB), and only 18.5% was converted into methane, highlighting the strong competition between SRB and methanogenic archaea (MA) when treating sulfate-rich wastewater). Almost half of the methane produced (46%) was dissolved in the permeate and most of it was recovered by a degassing membrane. The organic matter biodegraded by the AnMBR system was similar to the influent anaerobic biodegradability determined by wastewater characterization assays (68.5% of the influent COD), indicating that nearly all the influent's biodegradable organic matter had been removed. This percentage of degraded COD was similar to that obtained in previous studies working at 70 days SRT, showing that the limit of anaerobic biodegradability was already reached in this SRT. The organic matter considered as non-biodegradable according to wastewater characterization assays therefore was not seen to degrade in the AnMBR pilot plant, even at very high SRT. Once the biodegraded COD is close to the influent's anaerobic biodegradability, increasing the SRT is not justified as it only leads to higher operational costs for the same biogas production. These findings support the use of mathematical models for AnMBR design since they accurately represent the behaviour of these systems in a wide range of operating conditions.
Anaerobic membrane bioreactors (AnMBRs) can achieve maximum energy recovery from urban wastewater (UWW) by converting influent COD into methane.
PDF
