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This mini-review is intended to explore the innovative applications of nanoparticles (NPs) in biogas upgrading, emphasizing their capacity to enhance biogas quality. Numerous studies underscore how NPs, when applied during anaerobic digestion, can boost not only the quantity but also the quality of the produced biogas, leading to reduce significantly the concentration of hydrogen sulphide or even to remove it completely. Moreover, NPs are proving to be excellent alternatives as adsorbent materials, achieving up to 400 mgH2S g−1 NPs. In addition, new studies are exploring the application of NPs to increase the efficiency of biological treatments thanks to their unique features. This review also emphasizes the potential benefits and addresses the challenges that need to be overcome for these technologies to reach their full potential, ultimately contributing to the development of a sustainable and environmentally friendly energy landscape.

This study evaluates the effectiveness of microalgal-based carbon-encapsulated iron nanoparticles (ME-nFe) in the removal of pharmaceutical compounds (PhACs) from water solutions and real municipal effluent at a laboratory scale. The investigated PhACs were chosen to represent different classes of synthetic drugs: antibiotics, anti-inflammatory drugs, antihypertensives, antiepileptics, neuroprotectors, and antidepressants. The adsorbent material was produced through hydrothermal carbonization (225 °C for 3 h), using microalgae grown on wastewater as the carbon source. ME-nFe showed heterogeneity in terms of porosity (with both abundance of macro and mesopores), a total pore volume of 0.65 mL g−1, a specific surface area of 117 m2 g−1 and a total iron content of 40%. Laboratory scale adsorption tests (1 g L−1 of nanoparticles with 2 min contact time) showed high removal for the most hydrophobic compounds. Removal efficiencies were high (over 98%) for Irbesartan, Ofloxacin and Diclofenac, promising (over 65–80%) for Clarithromycin, Fluoxetine, Lamotrigine and Metoprolol, but low for Gabapentin-Lactam and Propyphenazone (<20%). Electrostatic interactions between the drugs and the surface of the nanoparticles may account for the observed data, although additional removal mechanisms cannot be ruled out.

This study evaluates the effectiveness of a pilot-scale high-rate algae-bacteria pond (HRAP) to remove pharmaceutical compounds (PhACs) from municipal centrate. The studied PhACs belonged to different classes of synthetic active compounds: antihypertensives, antiepileptics, antidepressants, neuroprotectors, and anti-inflammatory drugs. The HRAP, growing a mixed microalgal consortium made of Chlorella spp. and Scenedesmus spp., was operated in continuous mode (6 days hydraulic retention time) from May to November 2021. Removal efficiencies were high (>85 %) for Sulfamethoxazole and Lamotrigine, promising (65–70 %) for Metoprolol, Fluoxetine, and Diclofenac but low (30–40 %) for Amisulpride, Ofloxacin, Carbamazepine, and Clarithromycin. Propyphenazone and Irbesartan were not removed, and their concentrations increased after the treatment. The combination of abiotic and biotic drivers (mostly global radiation and the synergy between microalgae and bacteria metabolisms) fostered photo and biodegradation processes. Overall, results suggest that microalgae-based systems can be a valuable solution to remove PhACs from wastewater.

Periphyton is the dominant primary producer in mountain streams and sustains the higher trophic levels. While certain periphyton groups, particularly diatoms, have received extensive study, the comprehensive characterization of the entire community has been largely neglected. This study aims to investigate the temporal pattern of biofilm in mountain streams characterized by different water thermal regimes. A one-year quantitative campaign, involving monthly samplings, was conducted in five subalpine streams in Northern Italy’s Orobic Alps to collect epilithic biofilm from a wide surface area. The total biomass was quantified and the periphyton was analyzed both for composition (diatoms, green algae, cyanobacteria, and red algae) and for pigments. Disturbance, water temperature, physico-chemical conditions, nutrients, substrate diversity, and light availability were assessed concurrently with biofilm samplings. Results show sharp biofilm variations over months. In all sites, the disturbance was the primary factor reducing biomass and pigment content. Annually, all sites experienced similar turnover in periphyton composition mainly associated with light and water temperature. Overall, the study indicates that frequent quantitative investigations of biofilm help understand intra-annual variations and identify key drivers. Such information is useful to understand the ecosystem processes and the food web dynamics.

The aim of this study was to acclimate anaerobic prokaryotes to saline microalgae biomass. Semi-continuous experiments were conducted using two 1.5 L mesophilic reactors for 10 weeks, (hydraulic retention time of 21 days). The first reactor was solely fed with sewage sludge (control), while the second received a mixture of sewage sludge and microalgal biomass (80/20 %w/w) cultivated at 70 g·L-1 salinity. The in-reactor salinity reached after the acclimation phase was 14 g·L-1. Biomethane production was comparable between the control and acclimated reactors (205 ± 29 NmLMethane·gVolatileSolids-1). Salinity tolerance assessment of methanogenic archaea revealed that salinity causing 50% inhibition of methane production increased from 10 to 27 g·L-1 after acclimation. Microbial diversity analyses revealed notable changes in methanogenic archaea populations during co-digestion of saline microalgae biomass, particularly methylotrophic (+27%) and acetotrophic (-26%) methanogens. This study has highlighted the possibility of treating efficiently saline microalgae in co-digestion with sewage sludge in future industrial biogas plants.

Large amounts of produced water are extracted by the Oil and Gas energy sector since the industrial revolution. This available water, often salty, can be used to dilute liquid digestate from the anaerobic digestion process, a promising source of nutrients for microalgae cultivation. The study investigates the growth of halotolerant microalgae and their associated bacteria in column photobioreactors (PBRs) and open raceway pond (RWP), to treat industrial wastewaters while producing biomass for energy valorisation. Microalgae were cultured in mixtures of saline artificial produced water (7–44 %v/v), liquid digestate (5 %v/v using PBRs, 29–63 %v/v using RWP) and seawater. Nannochloropsis oceanica and Tetraselmis suecica strains were firstly cultivated in 70 L PBRs in indoor conditions for 3 months and later in 1.1 m3 RWP operated in outdoor conditions for 5 months in spring-summer period. In PBRs, average productivity was 9.0 ± 4.2 gVSS·m−2·d−1 (102–153 mgVSS·L−1·d−1), with daily removal efficiencies for chemical oxygen demand, nitrogen and phosphorous up to 61.8, 31.6 and 97.2 %, respectively. In RWP, strong changes in the microalgae populations were observed. Productivity was 6.7 ± 5.2 gVSS·m−2·d−1 (30 ± 23 mgVSS·L−1·d−1), with daily removal efficiencies for chemical oxygen demand, nitrogen and phosphorous up to 48.4, 44.4 and 88.1 %, respectively. In parallel with the production of microalgae, a nitrifying microbial population grew in the RWP despite the high salinity (70 g L−1). Over these periods of several months, microalgae production was maintained using a culture medium containing high salt concentration, metals and harmful aromatic compounds.

The study explores the use of microalgal-based carbon-encapsulated iron nanoparticles to enhance the anaerobic digestion process. These nanoparticles are synthesized through hydrothermal carbonization (225°C, 3h) by combining iron nitrate with algal biomass grown on urban wastewater (Mantovani et al., 2022; Peng et al., 2014). The nanoparticles have been characterized through ICP-OES, TEM, SEM-EDX, and XRD to understand their morphology, properties, presence and abundance of oxides, and crystalline phases. They were integrated into semi-continuous lab-scale reactors fed with municipal sludges, where different concentrations of nanoparticles (100 mg/L and 500 mg/L) were tested. The results indicated that nanoparticles at 100 mg/L significantly increase methane production by 24% to 180 ± 50 NmL/gVS and biogas production by 30% to 248 ± 58 NmL/gVS compared to the control. Additionally, the presence of nanoparticles improved organic matter degradation and volatile fatty acid conversion. These findings suggest that microalgal-based iron nanoparticles enhance microbial metabolic efficiency, leading to improved biogas yields and a reduction in undesired compounds such as hydrogen sulfide by 54%. It is hypothesized that the inclusion of iron nanoparticles will improve microbial metabolism efficiency, leading to increased methane production while concurrently reducing undesired compounds such as hydrogen sulfide, which will be eliminated via precipitation (Feng et al., 2014).

The integration of microalgae cultivation in anaerobic digestion (AD) plants can take advantage of relevant nutrients (ammonium and ortho-phosphate) and CO2 loads. The proposed scheme of microalgae integration in existing biogas plants aims at producing approximately 250 ty(-1) of microalgal biomass, targeting the biostimulants market that is currently under rapid expansion. A full-scale biorefinery was designed to treat 50 kty(-1) of raw liquid digestate from AD and 0.45 kty(-1) of CO2 from biogas upgrading, and 0.40 kty(-1) of sugar-rich solid by-products from a local confectionery industry. An innovative three-stage cultivation process was designed, modelled, and verified, including: i) microalgae inoculation in tubular PBRs to select the desired algal strains, ii) microalgae cultivation in raceway ponds under greenhouses, and iii) heterotrophic microalgae cultivation in fermenters. A detailed economic assessment of the proposed biorefinery allowed to compute a biomass production cost of 2.8 +/- 0.3 kg DW-1, that is compatible with current downstream process costs to produce biostimulants, suggesting that the proposed nutrient recovery route is feasible from the technical and economic perspective. Based on the case study analysis, a discussion of process, bioproducts and policy barriers that currently hinder the development of microalgae-based biorefineries is presented.

The growth of the polyextremophile red microalga Galdieria sulphuraria ACUF 064 was evaluated under mixotrophy and heterotrophy in a 13-L lab-scale stirred photobioreactor, using buttermilk as a carbon source. Beforehand, G. sulphuraria ACUF 064 growth on glucose, galactose and lactose was evaluated. No significant differences were observed in terms of growth when lactose, glucose or galactose was used as a carbon source. Overall, the biomass yield on carbon was 70% higher in mixotrophy than heterotrophy for galactose (2.0 gx gC−1) and lactose (2.0 gx gC−1), while it was similar for glucose (1.5 gx gC−1). At the same time, the yield of biomass on nitrogen for cultures grown in lactose was the lowest in comparison to all the other tested substrates. This was also supported by a higher C-phycocyanin content, with 5.9% wC-PC/wx as the highest value in mixotrophy. A preliminary experiment in flasks under mixotrophic conditions with different buttermilk dilutions revealed that a dilution ratio of 40% v/v of buttermilk (corresponding to 2.0 gC L−1) was optimal for biomass production. Finally, G. sulphuraria ACUF 064 was grown in the optimal buttermilk dilution ratio in a 13 L photobioreactor. The highest biomass productivity was also obtained in mixotrophy (0.55 gx L−1 d−1), corresponding to a carbon removal of 61%. Overall, lactose-containing substrates such as buttermilk hold promise as a substrate for the growth of G. sulphuraria while revalorizing an industrial effluent.

The results of a first campaign of sampling and analyses of emerging micropollutants in the influent (municipal centrate) and effluent of a pilot MBP raceway are reported. The algal population was chiefly made of Chlorella spp. and the pilot worked satisfactorily for the removal of nitrogen. 14 emerging micropollutants were analysed. Average removal efficiencies exceeding 80 % were observed for diclofenac, lamotrigine, ketoprofene, clarithromycin. For such compounds the variability of removal efficiency was also reduced, with respect to the other tested molecules, and was particularly low for diclofenac and lamotrigine. Removal efficiencies over 50 % were measured for azithromycin, metoprolol and irbesartan but with strong variability. Lower removal efficiencies were observed for amisulpride and 5-methylbenzotriazole, while for the remaining compounds the concentrations in the effluent were higher than in the influent.

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.

Research data produced within the CARIPLO IMAP and Perform Water 2030 projects were processed using the SimaPro software to carry out the Life Cycle Assessment according to ISO 14040-44 of an innovative process of treated effluents' polishing. The study aims to evaluate the integration of a microalgae culture as a side-stream process into the baseline layout of a wastewater treatment plant to remove nitrogen from the supernatant of sludge centrifugation from an environmental perspective. In particular, the investigated system focuses on using the algal biomass produced as an organic matrix for encapsulating zero-valent iron nanoparticles to be used for the final refinement of the effluent. Zero-valent iron (ZVI) is a reactive metal and an effective reducing agent. It can be used to remove organic and inorganic pollutants (e.g., chlorinated organics, pharmaceuticals, metals, textile dyestuffs). The encapsulation of ZVI by hydrothermal carbonization (HTC) in a carbonaceous matrix allows for overcoming the problems related to its lack of stability, easy aggregation, and difficulty in separating the ZVI nanoparticles from the treated solution. The case study refers to Bresso wastewater treatment plant (Milan province, Northern Italy). The environmental performances of the study were assessed following the Life Cycle Impact Assessment methods IMPACT 2002+. According to the results, the new process integration does not affect the environmental performance of the WWTP, still implying a significant improvement in the removal of metals and micropollutants. In fact, due to the ability of ZVI nanoparticles to remove organic and inorganic pollutants, the outflowing load will be significantly reduced, which will improve the environmental performance of the entire Bresso wastewater treatment plant.

Both reservoirs and run of river power plants affect the thermal regime of rivers but despite the higher number of the latter few studies have focused on their effect. In this study, we investigated the water thermal regime of Serio River (Northern Italy), a subalpine river regulated by a reservoir and characterized by a cascade system of run of river power plants. Water temperature has been monitored continuously for more than 4 years at the extremes of 4 stretches subjected to water diversion and thermal alterations have been quantified. Our results show that hydroelectric power plants act locally causing a considerable thermal alteration that increases with the distance from the diversion weir. Indeed, within the by-passed stretch, the rate of warming doubles the natural gradient (0.47 degrees C/km vs. 0.19 degrees C/km annually) with peaks in summer (0.73-0.90 degrees C/km on average). By contrast, the run of river power plants keep the water temperature almost constant in the diversion channels. Thus, a cascade system of run of river plants shifts the overall riverine thermal regime from a continuous to a "stepped" longitudinal profile. Results highlight that the thermal effects of run of rivers plants are not negligible and should be considered and monitored continuously. Since there are thousands of hydropower plants powered by flowing waters it is time to consider their thermal impacts in environmental flow policies and bioassessment programs.

The integration of microalgae-bacteria consortia within existing wastewater treatment plants as alternative biological treatment could be an interesting option to improve the sustainability of these facilities. However, the fate of the produced biomass is decisive to make that option economically attractive. The present study aimed to valorize the microalgae grown at a pilot scale and used for the treatment of the centrate from municipal sewage sludge, producing microalgal-based iron nanoparticles (ME-nFe), by hydrothermal carbonization. The final product had high carbon content, strong sorbent power, and reducing properties, due to the presence of zerovalent iron. Different synthesis conditions were tested, comparing iron (III) nitrate nonahydrate (Fe (NO3)(3)center dot 9H(2)O) and ammonium iron (III) sulfate dodecahydrate (NH4 Fe (SO4)(2)center dot 12 H2O) as iron sources, four different Fe/C molar ratios (0.02, 0.05, 0.1, 0.2), and three process temperatures (180, 200, 225 degrees C). Based on the characterization of all the prototypes, the best one (having a specific area of 110 m(2)g(-1)) was chosen and tested for the removal of selected heavy metals by Jar tests. The removal of copper, zinc, cadmium, and nickel from the treated effluent from the wastewater treatment plant was 99.6%, 97.8%, 96.4%, and 80.3%, respectively, also for very low starting concentrations (1 mg L-1). The removal of total chromium, on the contrary, was only 12.4%. Thanks to the magnetic properties, the same batch of ME-nFe was recovered and used effectively for three consecutive Jar tests.

Water temperature is one of the main abiotic factors affecting the structure and functioning of aquatic ecosystems and its alteration can have important effects on biological communities. Macroinvertebrates are excellent bio-indicators and have been used for decades to assess the status of aquatic ecosystems as a result of environmental stresses; however, their responses to temperature are poorly documented and have not been systematically evaluated. The aims of this review are: (i) to collate and summarize responses of freshwater macroinvertebrates to different temperature conditions, comparing the results of experimental and theoretical studies; (ii) to understand how the focus of research on the effects of temperature on macroinvertebrates has changed during the last 51 years; and (iii) to identify research gaps regarding temperature responses, ecosystem types, organism groups, spatiotemporal scales, and geographical regions to suggest possible research directions. We performed a comparative assessment of 223 publications that specifically consider freshwater macroinvertebrates and address the effects of temperature. Short-term studies performed in the laboratory and focusing on insects exposed to a range of temperatures dominated. Field studies were carried out mainly in Europe, at catchment scale and almost exclusively in rivers; they mainly investigated responses to water thermal regime at the community scale. The most frequent biological responses tested were growth rate, fecundity and the time and length of emergence, whereas ecological responses mainly involved composition, richness, and distribution. Thermal research on freshwater macroinvertebrates has undergone a shift since the 2000s when studies involving extended spatiotemporal scales and investigating the effects of global warming first appeared. In addition, recent studies have considered the effects of temperature at genetic and evolutionary scales. Our review revealed that the effects of temperatu

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 %.

Metal-based flocculants are commonly used for biomass harvesting in microalgae-based bio-refineries. Besides the high separation efficiency, additional aspects should be considered, related to the toxicity of metals for the algal biomass. Partitioning tests for commonly used flocculants (i.e., FeCl3 and Al2(SO4)3) showed that metals were mostly transferred to the solid phase with more than 95% of dosed metal ending up into the biomass, and low metal concentrations in the liquid effluent (lower than 0.4 mg L−1 for both metals), thus allowing for water reuse. Photosynthesis inhibition was tested on microalgae and microalgae-bacteria cultures, using a standardized photo-respirometry protocol in which typical concentrations used during coagulation-flocculation were assessed. Modelling dose-response curves, concentrations corresponding to 50% inhibition (IC50) were obtained, describing short-term effects. The obtained IC50 ranged from 13.7 to 28.3 mg Al L−1 for Al, and from 127.9 to 195.8 mg Fe L−1 for Fe, showing a higher toxicity for the Al-based flocculant. The recovery of photosynthesis inhibition was also quantified, to evaluate the possibility of reusing/recycling the harvested biomass. The results highlighted that the residual photosynthetic activities, evaluated after 1 h and 24 h of exposure to metals were partially recovered, especially for Al, passing from 67.3% to 94.6% activity, respectively, while long-term Fe effects were stronger (passing from 64.9% to 77.6% activity). A non-toxic flocculant (cationic starch) was finally tested, excluding potential effects due to biomass aggregation, as the reduction of photosynthetic activity only reached 3.4%, compared to control. Relevant modifications to the light availability and the optical properties of algal suspensions were assessed, identifying a strong effect of iron which caused an increase of the light absorbance up to approximately 40% at high Fe concentrations. Possible implications of dosing metallic flocc

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.

This study investigates the environmental improvements associated to the integration of a microalgae unit as a side-stream process within an existing municipal wastewater treatment facility in northern Italy. Microalgae are fed on the centrate from sludge dewatering, rich in nutrients, and on the CO2 in the flue-gas of the combined heat and power unit. The produced biomass is recirculated upflow the water line where it settles and undergoes anaerobic digestion generating extra biogas. A life cycle assessment was performed collecting primary data from an algal pilot-scale plant installed at the facility. Fifteen environmental indicators were evaluated. Compared to the baseline wastewater treatment, the new algal configuration allows an improvement for 7 out of 15 indicators mainly thanks to the electricity savings in the facility. Some recommendations are provided to improve the performance of the algal system in the scaling up.

Activated carbon pre-treatment was applied to anaerobic digestion effluent in order to reduce the optical density. Up to 78% reduction of OD was achieved suggesting activated carbon pre-treatment a promising tool to increase the light transmission of agricultural digestate. The pre-treated digestate was applied for microalgae cultivation as a source of nutrients and compared to the untreated diluted digestate. Microalgae growth was similar at the first period of cultivation in pre-treated and diluted untreated digestate. However, at the other part of the cultivation higher growth rate and biomass accumulation in untreated digestate was observed. We discuss the possibility of too high nutrient load in pre-treated digestate that may have limited the microalgae growth. PAM measurements showed no stress from the substrate highlighting that activated carbon pre-treated digestate is a suitable medium for microalgae growth. Moreover, vitality of cultures in pre-treated PBRs dropped at the end of the cultivation suggesting some inhibitory effect may be present. Results of current study demonstrate that activated carbon holds a great potential for agricultural digestate pre-treatment to decrease the optical density.

This study aimed at evaluating the effects of different environmental conditions (irradiance, temperature, pH and dissolved oxygen) on a microalgae-bacteria consortium cultivated in a pilot-scale open pond and fed on the liquid fraction of anaerobic digestate. A standardized photo-respirometry protocol was followed to evaluate the activity of microalgae under different conditions. Two datasets (specific photosynthetic oxygen production rates and respiratory oxygen consumption rates) were obtained for each environmental parameter, throughout the entire range of conditions found in the outdoor cultivation system. Different kinetic models available in literature were fitted to experimental data and the resulting outputs were compared through model selection estimators, in order to select the most appropriate equations. The proposed set of equations constitute a modelling tool for the prediction of algal growth rates in algae-bacteria systems, as a function of environmental conditions.

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.

Metropolitana Milanese (MM Spa), the water authority of the city of Milan, has carried out, on both water and sewage networks, installation of new pipelines and rehabilitation of the already existing ones using no-dig technologies, i.e. techniques alternative to open cut excavations. To spread such techniques, having evident advantages with respect to the traditional ones, a procedure to assess its sustainability in different cases was developed based on SAT analysis (Technology Sustainable Assessment), a procedure adopted to support the decision-making process, including a set of indicators that take into account the technological, environmental, economic and social aspects. To take into account the most relevant aspects in the specific case the SAT procedure was modified: the environmental impacts were calculated by LCA, the economic costs as direct costs and the social ones as indirect costs (including logistic aspects) and risks for the exposed population (workers and general population). To setup the methodology, two significant case studies of the city of Milan in order to disclose and assess the environmental, social and economic impacts which should be used for decision making.

The integration of microalgae in the municipal wastewater treatment scheme could certainly be an interesting option to reduce the carbon footprint of the process. The obtained microalgae could be valorized through hydrothermal carbonization (HTC), producing a sorbent material to be used as an alternative to activated carbon. However, HTC of microalgae does produce potentially harmful byproducts. The present work aims to investigate the possibility of using the effluent derived from the hydrothermal carbonization of microalgae (HTC-LF), performed to produce microalgal-based carbon encapsulated iron nanoparticles (ME-nFe), as a growth medium for the microalgae. Since this raw effluent was proved to be toxic for Allivibrio fisheri (EC50 = 1.8 %), the microalgal activity was studied also for detoxification. A 20 % dilution of the HTC-LF, using municipal centrate as the diluent, was proved to be suitable for microalgal growth without affecting the photochemical efficiency. In a continuous test, a community made of Chlorella spp. and Euglena gracilis was able to grow with and without CO2 addition, with average productivity of 62 +/- 5 and 43 +/- 8 mg L-1 d(-1), respectively. The treatment led to a 60 % COD removal, suggesting that the HTC-LF was not harmful to the microalgae-bacteria consortia, which was also able to decrease its toxicity. Environmental implications: The liquid byproduct of the hydrothermal carbonization (HTC-LF) is a known toxic for the water compartment. The possibility to exploit its nutrient content for microalgal growth was already proved by different studies using strong dilution with synthetic medium to perform batch cultivations. Here, the HTC-LF was diluted with the blackwater from biosolid dewatering, without adding any microelements or main nutrients to perform a continuous cultivation. A microalgal community was grown, consuming nutrients and the COD, lowering the toxicity. The obtained biomass was used to produce second-generation nano -parti

Alpine and pre-alpine lotic ecosystems are often remote and not affected by humans, which makes them some of the world’s most pristine ecosystems. However, their status is often altered by the presence of reservoirs that are built to fulfil agricultural needs and hydroelectric demands. These reservoirs also disrupt stream continuity and alter the magnitude, timing, and frequency of natural flows. The present work assessed how high altitude reservoirs affect the riverine ecosystems focusing on: i) the macroinvertebrate communities; ii) the breakdown of organic matter; iii) the thermal regime. Stretches altered by high altitude reservoirs had the best conditions for most macroinvertebrate families due to a more stable flow conditions. The breakdown rate of coarse particulate organic matter was not affected by high altitude reservoirs but its availability was higher in altered compared to pristine stretches. The presence of hydroelectric power plants modified the stream thermal regime. Reservoirs mitigate the atmospheric influence on stream water temperature while run of the river plants strengthen it in the diverted stretches. Where both these alterations were present the thermal regime of the stream was more similar to the natural ones compared to stretches subjected to only one kind of alteration. This research showed how river impoundment alters the structure of macroinvertebrate communities and the function of the downstream lotic ecosystems and can provide the basis to correctly guide management strategies for lotic ecosystems affected by hydrological alterations.