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The efficiency of an outdoor pilot-scale raceway pond treating the wastewaters generated by a large-scale piggery farm in Northern Italy was evaluated. The biomass productivity over 208 days of experimentation was 10.7 ± 6.5 g TSS·m−2·d−1, and ammoniacal nitrogen, orthophosphate, and COD average removal efficiencies were 90%, 90%, and 59%, respectively. Results were used to perform a comprehensive techno-economic analysis for integrating algae-based processes in farms of different sizes (100–10000 pigs). The amount of N disposed of on agricultural land could be reduced from 91% to 21%, increasing the fraction returned to the atmosphere from 2.4% to 63%, and the fraction in the biomass from 6.2% to 16%. For intensive farming, the release of 110 t N·ha−1·y−1 contained in the digestate could be avoided by including algae-bacteria processes. The biomass production cost was as low as 1.9 €·kg−1, while the cost for nitrogen removal was 4.3 €·kg N−1.

This study aims at evaluating an innovative biotechnological process for the concomitant bioremediation and valorization of wastewater from textile digital printing technology based on a microalgae/bacteria consortium. Nutrient and colour removal were assessed in lab-scale batch and continuous experiments and the produced algae/bacteria biomass was characterized for pigment content and biomethane potential. Microbial community analysis provided insight of the complex community structure responsible for the bioremediation action. Specifically, a community dominated by Scenedesmus spp. and xenobiotic and dye degrading bacteria was naturally selected in continuous photobioreactors. Data confirm the ability of the microalgae/bacteria consortium to grow in textile wastewater while reducing the nutrient content and colour. Improvement strategies were eventually identified to foster biomass growth and process performances. The experimental findings pose the basis of the integration of a microalgal-based process into the textile sector in a circular economy perspective.

This study aims at evaluating the process efficiency of an outdoor pilot-scale microalgae-based wastewater treatment system. Experimental results from two monitoring campaigns were analysed, showing that the system removed on average 85.1 % and 36.2 % of the influent ammoniacal nitrogen and orthophosphate, respectively, with an associated algal productivity of 9.5 g TSS·m−2·d-1. Based on pilot-scale results, a comprehensive techno-economic assessment was performed, allowing to calculate a biomass production cost of 4.3 €·kg TSS-1 and a wastewater treatment cost of 2.7 €·m−3 (corresponding to a nitrogen removal cost of 12.5 €·kg N−1). These costs turned out to be comparable with conventional wastewater treatment processes, thus recognizing the potential of microalgae cultivation on wastewaters as feasible alternative to conventional energy-demanding bioremediation systems and to expensive algal cultivation processes. A sensitivity and scenario analysis indicated that, under the most optimistic condition (20 % increase in the productivity, and 20 % OPEX and CAPEX reduction), biomass production and nitrogen removal costs could be further reduced of approximately 44 %.

The treatability of seven wastewater samples generated by a textile digital printing industry was evaluated by employing 1) anammox-based processes for nitrogen removal 2) microalgae (Chlorella vulgaris) for nutrient uptake and biomass production 3) white-rot fungi (Pleurotus ostreatus and Phanerochaete chrysosporium) for decolorization and laccase activity. The biodegradative potential of each type of organism was determined in batch tests and correlated with the main characteristics of the textile wastewaters through statistical analyses. The maximum specific anammox activity ranged between 0.1 and 0.2 g N g VSS-1 d-1 depending on the sample of wastewater; the photosynthetic efficiency of the microalgae decreased up to 50% during the first 24 hours of contact with the textile wastewaters, but it improved from then on; Pleurotus ostreatus synthetized laccases and removed between 20-62% of the colour after 14 days, while the enzymatic activity of Phanerochaete chrysosporium was inhibited. Overall, the findings suggest that all microbes have great potential for the treatment and valorisation of textile wastewater after tailored adaptation phases. Yet, the depurative efficiency can be probably enhanced by combining the different processes in sequence.

The role of P content on the treatment and valorization of the liquid fraction of digestate, namely centrate, through microalgae-based technologies was evaluated in this study. The performance of four column photobioreactors, which were fed on diluted centrate with corrected (10 mg N/ mg P) and not modified (129 mg N/ mg P) N:P ratio, were monitored and compared. The results demonstrated that P shortage in the centrate affected neither the total nitrogen and COD removal rate nor the volumetric biomass productivity, suggesting that expensive addition of P salts is not necessary to maximize the efficiency of the process. On the contrary, the addition of P to the centrate promoted the ammonia oxidation process as higher nitrite production was observed in the photobioreactors with adjusted N:P ratio than in the ones fed with the non-adjusted N:P ratio. These findings were confirmed by fluorescence in-situ hybridization and quantitative PCR assays, which revealed a higher number of ammonia-oxidizing bacteria in the microalgal suspensions cultivated on centrate with P addition. In conclusion, the N:P ratio in the centrate seems to have a role in controlling the nitrification process rather than in the overall nutrient removal rate and biomass productivity of the microalgae-based system.

The use of phototrophic organisms in wastewater treatment is gaining increasing interest, due to the possibility of exploiting photosynthetic oxygenation, thus lowering treatment costs and environmental impacts. Mixed consortia of phototrophic organisms and aerobic bacteria rapidly develop in photobioreactors receiving wastewaters; in this case, the complex mutualistic interactions among microorganisms cannot be easily described, making difficult to forecast removal efficiencies and biomass productivities. Respirometric methods are applied for evaluating bacterial activity in activated sludge (conventional respirometry) or photosynthetic activity in phototrophic organisms (photorespirometry). Photo-respirometric methods can be also exploited for monitoring algae-bacteria systems and for calibrating mathematical models, allowing for a better comprehension of the interactions involved and a more accurate prediction of system efficiencies. A general protocol and a series of guidelines for conducting photorespirometric tests on algal-bacterial suspensions are here proposed, based on the review of experimental protocols applied to evaluate the effects of several parameters on these systems.

Genetic engineering of plants has turned out to be an attractive approach to produce various secondary metabolites. Here, we attempted to produce kynurenine, a health-promoting metabolite, in plants of Nicotiana tabacum (tobacco) transformed by Agrobacterium tumefaciens with the gene, coding for human indoleamine 2,3-dioxygenase 1 (IDO1), an enzyme responsible for the kynurenine production because of tryptophan degradation. The presence of IDO1 gene in transgenic plants was confirmed by PCR, but the protein failed to be detected. To confer higher stability to the heterologous human IDO1 protein and to provide a more sensitive method to detect the protein of interest, we cloned a gene construct coding for IDO1-GFP. Analysis of transiently transfected tobacco protoplasts demonstrated that the IDO1-GFP gene led to the expression of a detectable protein and to the production of kynurenine in the protoplast medium. Interestingly, the intracellular localisation of human IDO1 in plant cells is similar to that found in mammal cells, mainly in cytosol, but in early endosomes as well. To the best of our knowledge, this is the first report on the expression of human IDO1 enzyme capable of secreting kynurenines in plant cells.

Milk whey processing wastewaters (MWPWs) are characterized by high COD and organic nitrogen content; the concentrations of phosphorus are also relevant. A microalgal-based process was tested at lab scale in order to assess the feasibility of treating MWPW without any dilution or pre-treatment. Different microalgal strains and populations were tested. Based on the obtained results, Scenedesmus acuminatus (SA) and a mixed population (PM) chiefly made of Chlorella, Scenedesmus, and Chlamydomonas spp. were grown in duplicate for 70 days in Plexiglas column photobioreactors (PBRs), fed continuously (2.5 L culture volume, 7 days hydraulic retention time). Nutrient removal, microalgae growth, photosynthetic efficiency, and the composition of microalgal populations in the columns were monitored. At steady state, the microalgal growth was similar for SA and PM. The average removal efficiencies for the main pollutants were: 93% (SA), 94% (PM) for COD; 88% (SA) and 90% (PM) for total N; and 69% (SA) and 73% (PM) for total P. The residual pollution levels in the effluent from the PBRs were low enough to allow their discharge into surface waters; such good results were achieved thanks to the synergy between the microalgae and bacteria in the CO2 and oxygen production/consumption and in the nitrogen mineralization.

This study aims at demonstrating the feasibility of using microalgae-bacteria consortia for the treatment of the sidestream flow of the supernatant from blackwater dewatering (centrate) in an urban wastewater treatment plant in Northern Italy. A 1200 L raceway reactor was used for the outdoor cultivation of a diverse community of Chlorella spp., Scenedesmus spp. and Chlamydomonas spp. in continuous operation mode with 10 days hydraulic retention time. During the trial, an average daily areal productivity of 5.5 ± 7.4 g TSS m−2 day−1 was achieved while average nutrient removal efficiencies were 86% ± 7% and 71% ± 10% for NH4-N and PO4-P, respectively. The microalgal nitrogen assimilation accounted for 10% of the nitrogen in the centrate while 34% was oxidized to nitrite and nitrate. The oxygen produced by microalgae fully covert the oxygen demand for nitrification. This suggests that the proposed process would reduce the aeration demand for nitrification in the water line of the plant, while producing algal biomass to be further valorized for energy or material recovery.

BACKGROUND: Secondary effluent wastewaters still contain resources including water and nutrients that must be safely reused and recovered. In this study, the combined role of microalgae as disinfectant and nutrient removal agent was evaluated for the potential application of a microalgae-based process as a cost-effective tertiary treatment. Nutrient removal, biomass productivity and disinfection performances were monitored in laboratory-scale photobioreactors (batch and continuous) fed on a secondary effluent mixed with a 10% on influent collected at a large municipal wastewater treatment plant where tertiary disinfection is performed by UV treatment. RESULTS: In microalgae-based batch disinfection tests, Escherichia coli counts (0.5 ± 0.7 log CFU 100 mL−1) were comparable to those after traditional UV process (0.7 ± 0.84 log CFU 100 mL−1) and lower than in tests where light was applied without microalgae. In the following continuous test, E. coli counts were reduced by one order of magnitude and the pathogenic strain of E. coli O157:H7/H−, Salmonella spp. and indicators such as Bacteroides spp. and Enterococcus spp. were never detectable in the effluents by molecular tools. Total nitrogen and phosphorus removals reached 93 and 100%, respectively, while the algal biomass productivity of the system averaged 50 ± 30 mg TSS L−1 day−1. CONCLUSIONS: The effluents of the photobioreactors reached quality standards appropriate for water reuse. Moreover, nutrients could be recovered through the generation of algal biomass suitable for further valorization. © 2019 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

BACKGROUND: Microalgae–bacteria-based processes are among the most promising low-cost technologies to treat livestock wastewaters. The current literature reports the need for pretreatment or dilution of piggery wastewater for adequate microalgal growth. The aim of this study is to optimize the potential of microalgal–bacterial communities to treat undiluted and untreated piggery wastewater by investigating the influence of some operational parameters such as phosphorus and CO 2 availability and hydraulic retention time on the nitrogen removal efficiency and biomass productivity. RESULTS: The microalgal community (dominated by Chlorella spp.) developed quickly and remained quite stable. The rates of biomass production and NH 4 -N removal were 55 ± 30 mg TSS L −1 day −1 and 13 ± 3 mg NH 4 -N L −1 day −1 respectively. CO 2 adjustment had a positive effect on microalgal growth and NH 4 -N removal. CONCLUSION: Data confirm the ability of the microalgal–bacterial consortium to grow on undiluted and untreated piggery wastewater under semi-continuous conditions. Synergy between algae and bacteria seems positive since photosynthesis produces the oxygen needed for ammonia oxidation

This study was carried out to assess the efficiency of a pilot-scale bubble-column reactor to remove nitrogen in centrate from the biosolid dewatering of a municipal wastewater treatment plant whilst producing biomass for agricultural purposes. The column was inoculated with a mixed community of Scenedesmus and Chlorella spp. and operated outdoor in batch for 55 days and in continuous for further 130 days. In continuous, the average daily biomass productivity was 40 ± 62 mg TSS L −1 d−1 and the average NH4+-N removal was 20 ± 10 mg L −1 d−1. Nitrification was fostered by photo‐oxygenation leading to the oxidation of 34 ± 27% of the incoming ammonia nitrogen. Microalgal and bacterial activity inside the column was analyzed by the Generalized Linear Models in order to understand the main factors affecting the process performances. Microalgal growth was affected positively by the NH4+-N content in the influent and negatively by the amount of TSS entering the system, probably due to the competition between microalgae and bacteria for phosphorus and other nutrients. The removal rate of NH4+-N was positively affected by NH4+-Nin (influent concentration) and by pH, whose increase fosters stripping, and decreased for increasing NH3-N concentrations, responsible for inhibiting nitrifying bacteria. NH4+-N oxidation was the result of complex interactions between algae and bacteria and was also affected by flow and solar radiation. No other specific limiting factors have been highlighted. The possibility of improving the process performance by controlling pH, by supplying off-gas as CO2 additional source, appears as an interesting option. In view of a scale-up, the most relevant expected result would be the energy saving due to the decrease in the oxygen demand for nitrification in the water line. The microalgal biomass grown on centrate was suitable for agricultural use due to its low contamination by heavy metals.

This paper addresses the efficiency of a microalgae-based agricultural digestate treatment at pilot-scale in an outdoor raceway pond (880 L, pH-dependent CO2 dosage) and in a bubble column (74.5 L, air-bubbling). Specifically, nitrogen removal, evolution of the algae-bacteria consortium, and the actual process applicability in the Po Valley climate are discussed. The performance of the two reactors varied seasonally. The average algal productivity in the raceway was 32.4 ± 33.1 mg TSS·L−1·d−1 (8.2 ± 8.5 g TSS·m−2·d−1) while in the PBR it was 25.6 ± 26.8 mg TSS·L−1·d−1; the average nitrogen removal was 20 ± 29% (maximum 78%) and 22 ± 29% (maximum 71%) in the raceway and in the column, respectively. Nevertheless, nitrification had a key role as 61 ± 24% and 52 ± 32% of the nitrogen load was oxidized in the raceway and in the column, respectively.

This work concerns the possibility of using phycoremediation of piggery wastewater (PW) in order to remove nitrogen and to send the produced algal biomass to anaerobic digestion. A semi-continuous culturing test was performed in 150 mL glass test tubes (4.5 cm diameter, 20 cm high), in four replicates, and run for 90 days. Light was provided artificially, with 12 h dark/light periods, mixing was allowed by air bubbling and temperature was 20±2°C. Algae developed quickly with values over 1 g TSS L-1after one week and maximum concentrations between 2.4 and 2.7 g TSS L-1, and the community was made by Chlorella and Scenedesmus spp., in similar proportion all over the test. The average productivity was 0.26 to 0.40 g L-1day-1. In the absence of pH control, the intense photosynthesis raised pH, whose value was proportional to the TSS concentration. The pH raise caused the production and stripping of NH3-N (26% of the inflow N), while the algal assimilation of N accounted for 45% and the oxidation for 25%. The overall % removal was about 96% for NH4-N, 85% for P and 74% for COD. The maximum methane production was 267 NmL CH4g VS-1(mean of the two replicates), higher than reported for pig and cow manure.

Respirometric techniques are useful tools to evaluate bacterial activities in activated sludge processes due to their fast execution and the possibility to obtain several kinetic parameters from a single test. Using such techniques in microalgae-bacteria consortia treating wastewater could allow a better understanding of mutual interactions between the microbial populations as a function of environmental parameters. This work aims at developing and testing a novel experimental respirometric protocol to determine oxygen uptake rates and oxygen production rates by a microalgae-bacteria consortium. The defined protocol is characterized by alternating light/dark regimes and by dosing substrates/inhibitors to selectively activate/inactivate microalgal and bacterial metabolisms. The protocol was then applied on microalgal and bacterial consortia, which were grown on the liquid fraction of black water from biogas plants fed on agricultural and municipal waste sludge. Results elucidate the presence and activity of microalgae and nitrifying bacteria in the tested systems, suggesting that the respirometric tests could be included into monitoring procedures of photobioreactors/algal ponds.

Recensione del film di Alain Gsponer