A knowledge discovery framework to predict the N2O emissions in the wastewater sector.

Data Analytics is being deployed to predict the dissolved nitrous oxide (N2O) concentration in a full-scale sidestream sequence batch reactor (SBR) treating the anaerobic supernatant. On average, the N2O emissions are equal to 7.6% of the NH4-N load and can contribute up to 97% to the operational carbon footprint of the studied nitritation-denitritation and via-nitrite enhanced biological phosphorus removal process (SCENA). The analysis showed that average aerobic dissolved N2O concentration could significantly vary under similar influent loads, dissolved oxygen (DO), pH and removal efficiencies. A combination of density-based clustering, support vector machine (SVM), and support vector regression (SVR) models were deployed to estimate the dissolved N2O concentration and behaviour in the different phases of the SBR system. The results of the study reveal that the aerobic dissolved N2O concentration is correlated with the drop of average aerobic conductivity rate (spearman correlation coefficient equal to 0.7), the DO (spearman correlation coefficient equal to -0.7) and the changes of conductivity between sequential cycles. Additionally, operational conditions resulting in low aerobic N2O accumulation (<0.6 mg/L) were identified; step-feeding, control of initial NH4+ concentrations and aeration duration can mitigate the N2O peaks observed in the system. The N2O emissions during aeration shows correlation with the stripping of accumulated N2O from the previous anoxic cycle. The analysis shows that N2O is always consumed after the depletion of NO2- during denitritation (after the "nitrite knee"). Based on these findings SVM classifiers were constructed to predict whether dissolved N2O will be consumed during the anoxic and anaerobic phases and SVR models were trained to predict the N2O concentration at the end of the anaerobic phase and the average dissolved N2O concentration during aeration. The proposed approach accurately predicts the N2O emissions as a latent parameter from other low-cost sensors that are traditionally deployed in biological batch processes.

Pilot-scale multi-stage reverse osmosis (DT-RO) for water recovery from landfill leachate.

Recovery of high quality water from municipal landfill leachate was studied by three-stage disc tube reverse osmosis optimized in pilot-scale. Following UF-membrane-assisted activated sludge plant, overall 46.5 tons of leachate were post-treated in real environment and analyzed for conventional contaminants and hazardous compounds (e.g. heavy metals, boron, selenium) throughout operation of membrane system. Operating pressure ranged from 21 to 76 bar, while permeate flux varied in the range 7.1-32.5 L m-2 h-1. Rejection factors of specific ions were related to the pressure and global removals were assessed for each stage (e.g. E%COD = 92.4-99.2%, E%NH4 = 46.2-95.8%, E%NOx = 84.8-97.9%; E%TDS = 88-95.5%). Boron removal was assessed in the range 34-48%, so as to require the third stage to reach standard for discharge or reuse. Two stages were sufficient to reach water recovery higher than 91%. Long-term operation and mathematical modeling demonstrated how the Δπ/ΔP ratio can support the decisions for membrane cleaning and predictive maintenance: permeability decline was associated to the ratio increase from 0.72 to 0.73 to 1.13-1.21.

Nutrients recovery from anaerobic digestate of agro-waste: Techno-economic assessment of full scale applications.

The sustainable production of fertilizers, especially those based on phosphorus, will be one of the challenges of this century. Organic wastes produced by the agriculture, urban and industrial sectors are rich in nutrients which can be conveniently recovered and used as fertilizers. In this study five full scale systems for the recovery of nutrients from anaerobic digestate produced in farm-scale plants were studied. Monitored technologies were: drying with acidic recovery, stripping with acidic recovery and membrane separation. Results showed good performances in terms of nutrients recovery with average yields always over 50% for both nitrogen and phosphorus. The techno-economic assessment showed how the specificity of the monitored systems played a major role: in particular, membranes were able to produce a stream of virtually pure water (up to 50% of the treated digestate) reducing the digestate volume, while drying, because of the limitation on recoverable heat, could treat only a limited portion (lower than 50%) of produced digestate while stripping suffered some problems because of the presence of suspended solids in the liquid fraction treated. Specific capital and operational costs for the three systems were comparable ranging between 5.40 and 6.97 € per m3 of digestate treated and followed the order stripping > drying > membranes. Costs determined in this study were similar to those observed in other European experiences reported in literature.

Integrating the selection of PHA storing biomass and nitrogen removal via nitrite in the main wastewater treatment line.

A novel scheme was developed for the treatment of municipal wastewater integrating nitritation/denitritation with the selection of polyhydroxyalkanoates (PHA) storing biomass under an aerobic/anoxic, feast/famine regime. The process took place in a sequencing batch reactor (SBR) and the subsequent PHA accumulation in a batch reactor. The carbon source added during the selection and accumulation steps consisted of fermentation liquid from the organic fraction of municipal solids waste (OFMSW FL) (Period I) and OFMSW and primary sludge fermentation liquid (Period II). Selection of PHA storing biomass was successful and denitritation was driven by internally stored PHA during the famine phase. Under optimum conditions of SBR operation ammonia removal was 93%, reaching a maximum nitrite removal of 98%. The treated effluent met the nitrogen limits, while PHA-storing biomass was successfully selected. The maximum accumulation of PHA was 10.6% (wt.) since the nutrients present in the carbon source promoted bacterial growth.

Recovery of volatile fatty acids from fermentation of sewage sludge in municipal wastewater treatment plants.

This work investigated the pilot scale production of short chain fatty acids (SCFAs) from sewage sludge through alkaline fermentation and the subsequent membrane filtration. Furthermore, the impact of the fermentation liquid on nutrient bioremoval was examined. The addition of wollastonite in the fermenter to buffer the pH affected the composition of the carbon source produced during fermentation, resulting in higher COD/NH4-N and COD/PO4-P ratios in the liquid phase and higher content of propionic acid. The addition of wollastonite decreased the capillary suction time (CST) and the time to filter (TTF), resulting in favorable dewatering characteristics. The sludge dewatering characteristics and the separation process were adversely affected from the use of caustic soda. When wollastonite was added, the permeate flux increased by 32%, compared to the use of caustic soda. When fermentation liquid was added as carbon source for nutrient removal, higher removal rates were obtained compared to the use of acetic acid.

Coupling the treatment of low strength anaerobic effluent with fermented biowaste for nutrient removal via nitrite.

Nutrient removal via nitrite was investigated in a sequencing batch reactor (SBR) treating low strength effluent produced from an upflow anaerobic sludge blanket (UASB). Domestic organic waste (DOW) and vegetable and fruit waste (VFW) were fermented and applied as external carbon source to the SBR. Nutrient removal via nitrite was much higher when DOW fermentation liquid (FL) was applied rather than VFW FL and acetic acid. The DOW FL contained propionic acid and butyric acid in significant proportions, favouring the nutrient removal via nitrite, while the VFW FL contained mainly acetic acid, which was associated with lower nutrient via nitrite activity. The application of high volumetric nitrogen loading rate (vNLR = 0.19-0.21 kgN m(-3) d(-1)) in combination with low dissolved oxygen (DO) concentration during the aerobic phase, resulted in high and stable nitrite accumulation (NO2-N/NOx-N >97%). These conditions favoured the phosphorus uptake via nitrite, which reached high rates (5.95 ± 2.21 mgP (gVSS h)(-1)), while the aerobic phosphorus removal was much lower. Through mass balances, it was demonstrated that the application of the UASB-SBR process with nutrient removal via nitrite at a decentralized level is a sustainable solution for effective co-treatment of domestic sewage and biowaste.

Life cycle assessment of nutrient removal technologies for the treatment of anaerobic digestion supernatant and its integration in a wastewater treatment plant.

The supernatant resulting from the anaerobic digestion of sludge generated by wastewater treatment plants (WWTP) is an attractive flow for technologies such as partial nitritation-anammox (CANON), nitrite shortcut (NSC) and struvite crystallization processes (SCP). The high concentration of N and P and its low flow rate facilitate the removal of nutrients under more favorable conditions than in the main water line. Despite their operational and economic benefits, the environmental burdens of these technologies also need to be assessed to prove their feasibility under a more holistic perspective. The potential environmental implications of these technologies were assessed using life cycle assessment, first at pilot plant scale, later integrating them in a modeled full WWTP. Pilot plant results reported a much lower environmental impact for N removal technologies than SCP. Full-scale modeling, however, highlighted that the differences between technologies were not relevant once they are integrated in a WWTP. The impacts associated with the WWTP are slightly reduced in all categories except for eutrophication, where a substantial reduction was achieved using NSC, SCP, and especially when CANON and SCP were combined. This study emphasizes the need for assessing wastewater treatment technologies as part of a WWTP rather than as individual processes and the utility of modeling tools for doing so.

Start-up of the completely autotrophic nitrogen removal process using low activity anammox inoculum to treat low strength UASB effluent.

The start-up of the completely autotrophic nitrogen removal process was examined in a sequencing batch reactor (SBR) using low activity anoxic ammonium oxidation (anammox) inoculum. The SBR received effluent from an upflow anaerobic sludge blanket (UASB) that treated low strength wastewater. The volumetric nitrogen loading rate (vNLR) was first 0.24 ± 0.11 kg Nm(-3)d(-1) and then reduced to 0.10 ± 0.02 kg Nm(-3)d(-1). The average specific anammox activity was 2.27 ± 1.31 mg N (gVSS h)(-1), at 30°C representing an increase of 161% compared to the inoculum. The decrease in vNLR did not significantly affect anammox activity, but resulted in a decrease of denitrifying heterotrophic activity to very low levels after the first 30 days owing to the decrease of organic loading rate (OLR). Fluorescence in situ hybridization (FISH) analysis confirmed the stable presence of anammox bacteria in biomass. Numerous filamentous microorganisms were present, several of which were in a state of endogenous respiration.

Glycofection: facilitated gene transfer by cationic glycopolymers.

Mammalian cells express several types of lectins involved in intracellular trafficking, including endocytosis, interorganelle routing and putatively nuclear import. In order to enhance the gene transfer efficiency, glycosylated cationic polymers have been used as nonviral vectors. We developed a simple method to convert reducing saccharides into glycosynthons. Glycosynthons are used to synthesize cationic glycopolymers, called Glycofectins. Glycofectins interact with a plasmid to give a glycoplex, a compacted form of a polymer/DNA complex. The high glycoplex efficiency depends on the sugar involved in the uptake and in the intracellular trafficking of glycoplexes. The present paper deals with glycoplexes, with gene transfer into cystic fibrosis airway epithelial and gland serous cells, and with some of the problems that have to be solved before clinical trials.

Uptake of dimannoside clusters and oligomannosides by human dendritic cells.

Knowing that human blood monocyte-derived dendritic cells express cell-surface mannose-specific lectins, we prepared various mannoses containing glycoconjugates with the aim of developing highly specific synthetic carriers of oligonucleotides and genes. Conjugates were prepared from oligosaccharides obtained by hydrazinolysis of Saccharomyces cerevisiae invertase glycopeptides. The reducing saccharides were converted into glycosynthons, i.e., into glyco-amino acids. Fluorescein derivatives were obtained by coupling the free carboxyl group of oligosaccharyl-pyroglutamate to the alpha-amino group of epsilon-fluoresceinyl-thiocarbamyl lysine methyl ester. It has been shown by others that glycosylated linear oligolysines containing up to six alpha-D-mannopyranosylphenylthiocarbamyl units have a high affinity for the human mannose receptor. In order to obtain fully biodegradable clusters and to improve both the specificity and the selectivity, disaccharides transformed into glycosynthons were coupled to pentalysine carriers (Lys5-Ala-Cys-NH2). Glycosylated pentalysyl cysteine conjugates were made fluorescent upon substitution of the cysteine thiol group with fluorescein iodoacetamide. As shown by flow cytofluorimetry, both the dimannoside clusters and yeast oligomannosides were very efficiently taken up by DC, conversely lactoside clusters were not.