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Valorization of excess sludge through the recovery of high-value products, such as biopolymers, could be a crucial step to implement circular economy principles in wastewater treatment plant (WWTP). In this frame, the present study was aimed at evaluating the simultaneous production of polyhydroxyalkanoates (PHA) and extracellular polymeric substances (EPS), obtainable from the treatment of an agro-industrial wastewater. Two biological systems, one implementing aerobic granular sludge (AGS) and the other a conventional activated sludge operating as a sequencing batch reactor (SBR) were operated for 204 and 186 days, respectively. Both the systems involved a three-stage process for mixed microbial culture enrichment and biopolymers accumulation. The maximum biopolymers accumulation capacity was close to 0.60 mg gVSS-1 in the AGS when the enrichment reactor was operated at 3 kgCODm-3d-1, whereas in the SBR it was slightly more than half (0.35 mg gVSS-1). Biopolymers extracted from the AGS were mainly constituted by EPS (>70%), which percentage increased with the organic loading rate applied in the enrichment reactor up to 95%. In contrast, SBR enabled to obtain a higher PHA production (50% of the biopolymers). Results suggested that organic carbon was mainly channeled toward metabolic pathways for extracellular storing in AGS, likely as a consequence of metabolic stressors (e.g., hydraulic selection pressure, shear forces) applied for promoting aerobic granulation.

Gli idrocarburi (HC) sono uno dei principali inquinanti ambientali. Una tecnologia promettente per il trattamento di siti contaminati si basa sulla biodegradazione degli inquinanti da parte di popolazioni microbiche capaci di utilizzare HC come fonte di carbonio ed energia (Biorisanamento). La necessità di risanare siti contaminati richiede da una parte la caratterizzazione delle comunità microbiche coinvolte nella biodegradazione, dall’altra lo sviluppo di interventi volti a migliorare il potenziale metabolico dei microrganismi degradatori. La nostra attività di ricerca ha avuto come obiettivo quello di caratterizzare e analizzare la biodiversità di comunità microbiche di un suolo contaminato da HC, verificarne il potenziale di biorisanamento, e valutare in microcosmo l’efficacia di un trattamento di biorisanamento. La comunità microbica di un suolo proveniente dal centro Italia contaminato da idrocarburi (HC) è stata caratterizzata mediante tecniche colturali e molecolari. La stima della contaminazione da n-alcani (C10-C40) è stata effettuata mediante analisi GC-FID. Batteri idrocarburo-ossidanti sono stati isolati su C16 e identificati mediante sequenziamento del gene 16SrRNA. L’intera comunità microbica è stata identificata tramite sequenziamento Illumina Miseq. Le potenzialità degradative delle comunità sono state valutate mediante amplificazione del gene alkB. Il suolo contaminato è stato sottoposto ad un trattamento di biorisanamento in microcosmo per 120 giorni, tramite biostimulation con C, N, P (10:10:1). Contestualmente i microcosmi sono stati areati con due sistemi differenti: landfarming o bioventing. L’efficacia è stata valutata tramite analisi degli HC residui (GC-FID) e identificazione delle comunità batteriche (sequenziamento Illumina) al termine dell’incubazione. Il suolo presenta elevati livelli di HC (4532,722 mg/ Kg). 26 ceppi batteri capaci di crescere su HC sono stati isolati, l’identificazione tassonomica di 18 ceppi mostra una predominanza di Proteobatteri, seguiti da Actinobacteria. Gli isolati appartengono a generi degradatori di idrocarburi policiclici aromatici (IPA) o alifatici (Pseudomonas, Nocardia, Hydrogenophaga, Stenotrophomonas, Delftia, Rhodococcus). L’analisi metagenomica mostra una comunità microbica HC-degradante piuttosto ricca e diversificata. I phyla più rappresentati sono costituiti da Acidobacteria, Actinobactera e Alphaproteobacteria; a livello di genere i più abbondanti degradatori di alcani sono Parvibaculum, Flavobacterium, Pseudoxantamonas, e Solimonas; i più abbondanti degradatori di IPA appartengono al genere Streptomyces e Ralstonia. La presenza del gene alkB conferma il catabolismo degli alcani alifatici nel suolo. Gli esperimenti di biorisanamento in microcosmo mostrano non solo un abbattimento del 30-35% di HC ma anche uno shift nella struttura e composizione delle comunità microbiche rispetto al suolo non trattato. Si osserva un aumento dell’abbondanza di batteri del Phylum dei Actinobacteria e Proteobacteria; questi ultimi diventano la componente predominante nel microcosmo sottoposto a bioventing. A livello di genere si osserva una maggiore diversità di batteri idrocarburo ossidanti, noti per degradare soprattutto IPA, rispetto al suolo non trattato. In termini di composizione e abbondanza le comunità microbiche dei microcosmi appaiono distinte tra loro. Nel microcosmo sottoposto a landfirming si osserva la predominanza del genere Enhydrobacter, Propionibacterium, Staphylococcus, Methylobacterium, mentre nel microcosmo sottoposto a bioventing si osserva la predominanza di Phenylobacterium, Gordonia, Ralstonia, Pseudoxanthomonas, Sphingobium. I risultati ottenuti mostrano che il suolo analizzato presenta un potenziale intrinseco di biorisanamento, dato dalla presenza di batteri idrocarburo-ossidanti altamente efficienti. I trattamenti di biorisanamento basati sulla tecnologia del landfarming e bioventing risultano efficaci per la rimozione degli HC da suolo e hanno un effetto sulla biodiversità delle comunità batteriche idrocarburo-ossidanti. L’abbattimento di HC osservato è da attribuire alla comunità microbica che cambia composizione e struttura quando il suolo è sottoposto a biorisanamento; favorendo i membri della comunità con metabolismo più attivo nelle condizioni testate, e portando alla formazione di un microbiota altamente specializzato nella degradazione di HC e adatto a crescere, prosperare e degradare in quelle condizioni ambientali.

Citrus wastewaters (CWWs) are by-products of the citrus fruit transformation process. Currently, more than 700 million of m³ of CWWs per year are produced worldwide. Until nowadays, the management of CWWs is based on a take-make-use-dispose model. Indeed, after being produced within a citrus processing industry, CWWs are subjected to treatment and then discharged into the environment. Now, the European Union is pushing towards a take-make-use-reuse management model, which suggests to provide for the minimization of residual pollutants simultaneously with their exploitation through a biorefinery concept. Indeed, the recovery of energy nutrients and other value-added products held by CWWs may promote environmental sustainability and close the nutrient cycles in line with the circular bio-economy perspective. Unfortunately, knowledge about the benefits and disadvantages of available technologies for the management and valorisation of CWWs are very fragmentary, thus not providing to the scientific community and stakeholders an appropriate approach. Moreover, available studies focus on a specific treatment/valorisation pathway of CWWs and an overall vision is still missing. This review aims to provide an integrated approach for the sustainable management of CWWs to be proposed to company managers and other stakeholders within the legislative boundaries and in line with the circular bio-economy perspective. To this aim, firstly, a concise analysis of citrus wastewater characteristics and the main current regulations on CWWs are reported and discussed. Then, the main technologies with a general comparison of their pros and cons, and alternative pathways for CWWs utilization are presented and discussed. Finally, a focus was paid to the economic feasibility of the solutions proposed to date relating to the recovery of the CWWs for the production of both value-added compounds and agricultural reuse. Based on literature analysis an integrated approach for a sustainable CWWs management is proposed. Such an approach suggests that after chemicals recovery by biorefinery, wastewaters should be directly used for crop irrigation if allowed by regulations or addressed to treatment plant. The latter way should be preferred when CWWs cannot be directly applied to soil due to lack of concomitance between CWWs production and crop needs. In such a way, treated wastewater should be reused after tertiary treatments for crop irrigation, whereas produced sludges should be undergone to dewatering treatment before being reused as organic amendment to improve soil fertility. Finally, this review invite European institutions and each Member State to promote common and specific legislations to overcome the fragmentation of the regulatory framework regarding CWWs reuse.

The aim of this study was to evaluate the effect of the inoculum to substrate ratio (ISR) and the mixture ratio between organic fraction of municipal solid waste (OFMSW) and sewage sludge (SS) on the methane production potential achievable from anaerobic co-digestion (AcoD). Biochemical Methane Potential (BMP) assays at mesophilic temperature were used to determine the best AcoD configuration for maximizing methane yield and production rate, as well as to address possible synergistic effects. The maximum methane yield was observed at ISR of 1 and 60% OFMSW: 40% SS as co-digestion mixture, whereas the highest methane production rate was achieved at ISR of 2 with the same mixture ratio (207 mL/gVS/d). Synergistic effects were highlighted in the mixtures having OFMSW below 60%, determining an increase of approximately 40% in methane production than the OFMSW and SS digestion as a sole substrate. The experimental data demonstrated that co-digestion of OFMSW and SS resulted in an increase in the productivity of methane than anaerobic digestion using the sole substrates, producing higher yields or production rates while depending on the ISR and the mixture ratio.

Bioremediation is a promising technology for the treatment of hydrocarbon (HC) contaminated soils that is based on the biodegradation capacities of native or introduced microbial populations. Biotractability tests are essential for choosing the optimal bioremediation treatment. For this purpose, multiple microcosm tests, based on biostimulation by landfarming or bioventing and addition of nutrients, were conducted for 120 days on a soil contaminated by diesel, after assessing its intrinsic catabolic potential. An additional bioaugmentation treatment was performed for further 60 days by inoculating selected HC degrading bacteria. HC (C10-C40) concentration was monitored by GC-FID analysis and the bacterial community evolution was analyzed by Illumina-MiSeq sequencing. The contaminated soil was dominated by Acidobacteria, Actinobacteria, Alphaproteobacteria and contained high diversity of potential HC degrading genera. The bacterial communities in microcosms after 120 days of biostimulation respond to bioremediation treatment with a shift on the composition. The main changes observed were an increase of Actinobacteria, Betaproteobacteria and Alphaproteobacteria in bioventing microcosms, while TM7 and Gammaproteobacteria increased in landfarming treatment. Higher abundance of HC degrading genera was detected in both microcosm types in respect to the untreated soil, mainly in landfarming. Approximately 40% of HC was removed after 180 days of sequential bioremediation applications. Longer incubation and finer tuning of nutrients could bring to a more effective reduction of pollutants, encouraging the HC degrading bacteria and increasing the biodegradation efficiency.

Nella nota sono riportati i risultati di una sperimentazione condotta mediante la messa in esercizio di un reattore bioslurry per il trattamento di sedimenti marini contaminati da idrocarburi. Sono state valutate le performance di processo in termini di rimozione di TPH (86% con velocità di rimozione massima di 36 mgTPH kg-1 d-1) congiuntamente ad altre tipologie di indagini volte ad ottenere maggiori informazioni sulla natura dei processi che si sono sviluppati nel reattore. Nello specifico, è stato utilizzato un approccio di tipo microbiologico mediante l’adozione di una tecnica di sequenziamento di nuova generazione (NGS - Next Generation Sequencing). Dall’analisi dei dati biologici è stato quindi possibile identificare i taxa maggiormente coinvolti nella degradazione degli idrocarburi. In particolare, il trattamento ha comportato uno shift nella composizione della comunità batterica a favore di particolari ceppi batterici che riescono ad adattarsi alle condizioni di processo (Hydrogenophaga, Sphingorhabdus, Phaeodactylibacter), presentando un elevato incremento in termini di crescita rispetto al sedimento originario. Inoltre, l’analisi delle emissioni gassose dal sistema ha permesso di quantificare la componente idrocarburica volatilizzata e, conseguentemente, di ottenere una stima più accurata della rimozione per via biologica. Infine, test di fitotossicità su campioni di sedimento hanno evidenziato un miglioramento dello stato di qualità della matrice trattata rispetto allo stato originario; tale aspetto risulta rilevante nell’ipotesi di possibile riutilizzo della matrice decontaminata come alternativa allo smaltimento.

This study investigated the treatment of a shipboard slop containing commercial gasoline in a pilot plant scale consisting of a membrane biological reactor (MBR) and photocatalytic reactor (PCR) acting in series. The MBR contributed for approximately 70% to the overall slop purification. More precisely, the biological process was able to remove approximately 40%, on average, of the organic pollution in the slop. Nevertheless, the membrane was capable to retain a large amount of organic molecules within the system, amounting for a further 30% of the influent total organic content removal. However, this affected the membrane fouling, thus resulting in the increase of the pore blocking mechanism that accounted for approximately 20% to the total resistance to filtration (2.85∙10 13 m −1 ), even if a significant restoration of the original membrane permeability was obtained after chemical cleanings. On the other hand, the biological treatment produced a clear solution for the photocatalytic system, thereby optimizing the light penetration and generation of highly oxidizing active oxygen species that enabled the degradation of bio-recalcitrant compounds. Indeed, low total organic carbon (TOC) values (

The production of polyhydroxyalkanoates (PHA) using industrial wastewaters as feedstocks is a current and challenging topic. This study investigated the production of biopolymers by a mixed microbial culture under different OLRs equal to 1 kgCOD m-3d-1 (Period 1), 2 kgCOD m-3d-1 (Period 2) and 3 kgCOD m-3d-1 (Period 3). The maximum PHA content was achieved in Period 2 (0.38 gPHA gTSS-1), whereas lower values were obtained in Period 1 (0.13 gPHA gTSS-1) and Period 3 (0.26 gPHA gTSS-1). Overall, the maximum PHA productivity resulted equal to 0.08 gPHA L-1h-1 (P2), 0.05 gPHA L-1h-1 (P1) and 0.04 gPHA L-1h-1 (P3), respectively. The molecular weight of the PHA increased from Period 1 (250 kDa) to Period 2 (417 KDa) and Period 3 (463 KDa), although resulting in a slight decrease of crystallinity degree. Microbial community analysis, revealed a reduction in bacterial diversity and a progressive shift of the microbial community with the increasing OLR. Alpha-diversity indexes based on Operational Taxonomic Units (OTUs) at 99% identity revealed higher species richness (Taxa (S) 280) and diversity (Shannon (H) 4,06) in Period 1, whereas Period 3 was characterized by reduced richness and diversity and higher dominance (Taxa (S) 133, Shannon (H) 2,40). Based on the results obtained, it was pointed out that the OLR variation determined significant effects on the process performances, as well as on the productivity and quality of the biopolymers. This means that OLR is a key control parameter to maximize the PHA production and control the physical-chemical characteristics of the polymers.

The paper reports the main results of an experiment carried out on a membrane bioreactor (MBR) plant designed for the treatment of shipboard slops. With a view of a co-treatment process of the slop with other wastewaters, sodium acetate, as external co-substrate, was supplied (high dosage – Period 1, low dosage – Period 2) to evaluate its effects on hydrocarbons removal. The MBR pilot plant enabled approximately 99% of total petroleum hydrocarbon (TPH) removal during the entire experiment, confirming the robustness of the MBR technology for the treatment of slops. The chromatography/mass spectrometry analysis showed that the removal efficiency for each alkane was close to the value observed for total mixture removal (>99%) and the hydrocarbons removal was mostly due to the microorganism-mediated biodegradation. The biological contribution to TPH removal increased from approximately 85% to 98% when the co-substrate was decreased. Biomass kinetics revealed that a lower co-substrate dosage enhanced the growth of bacterial groups able to use hydrocarbons as primary substrate. A clear predominance of Microthrix Parvicella under low co-substrate dosage was observed. However, the lower co-substrate addition caused a significant worsening in the physical properties of the activated sludge, which resulted enriched in soluble exopolymers (>70%), more hydrophobic (>90%) and with small and dispersed flocs (

Citrus wastewater is a sugar-rich waste stream suitable for the recovery of energy of material from its treatment. In this study, fermentation of citrus wastewater was carried out to assess the optimal conditions to maximize the bioconversion of the organic substrate into acetate. Unbalanced nutrient (C: N: P 200:0.1:0.1) enabled the highest acetate production. The presence of the particulate organic fraction enabled to obtain a higher acetate concentration regardless the initial COD concentration. Initial pH values higher than 5 did not cause substantial differences on the maximum bioconversion of COD into acetate in Trial 3, whereas pH lower than 5 hindered the hydrolysis process. Lastly, the bioconversion rate of the organic substrate into acetate decreased from a maximum of 23% to a minimum of 8% related to the initial COD. The achieved results demonstrated that the characteristics of citrus wastewater enable its valorisation without the need to apply energy-consuming processes.

The integration of one anaerobic reactor in the mainstream (AMSR) of a pre-denitritication-MBR was evaluated with the aim to achieve simultaneous sludge minimization and phosphorous removal. The excess sludge production was reduced by 64% when the AMSR was operated under 8 h of hydraulic retention time (HRT). The highest nutrients removal performances referred to organic carbon (98%), nitrogen (90%) and phosphorous (97%) were obtained under 8 h of HRT. In contrast, prolonged anaerobic-endogenous conditions were found to be detrimental for all nutrients removal performances. Similarly, the lowest membrane fouling tendency (FR = 0.65∙1011 m−1 d−1) was achieved under 8 h of HRT, whereas it significantly increased under higher HRT. The highest polyphosphate accumulating organisms kinetics were achieved under HRT of 8 h, showing very high exogenous P-release (46.67 mgPO4-P gVSS−1 h−1) and P-uptake rates (48.6 mgPO4-P gVSS−1 h−1), as well as a not negligible P-release rate under endogenous conditions at low COD/P ratio (≈1).

This chapter reviews the state of the art regarding the use of membrane bioreactor (MBR) systems for saline wastewater treatment. In particular, a comprehensive review is presented discussing the most adopted MBR configurations for the treatment of saline wastewater. Further, the chapter discusses the main effects of salinity on the biological performance, kinetic parameters, fouling development, sludge rheological features, and greenhouse gas (GHG) production. Literature results show that there is a significant effect of the salinity (and/or salinity variations) on the biological performance and membrane filtration. Specifically, it was found that a gradual salinity increase, carried out at moderate steps, might be a good strategy for limiting the negative effects of saline wastewater by enhancing the acclimation of the bacterial consortium to the saline environment.

The biodegradability and treatability of a young (3 years old) municipal landfill leachate was evaluated by means of chemical oxygen demand (COD) fractionation tests, based on respirometric techniques. The tests were performed using two different biomasses: one cultivated from the raw leachate (autochthonous biomass) and the other collected from a conventional municipal wastewater treatment plant after its acclimation to leachate (allochthonous biomass). The long term performances of the two biomasses were also studied. The results demonstrated that the amount of biodegradable COD in the leachate was strictly dependent on the biomass that was used to perform the fractionation tests. Using the autochthonous biomass, the amount of biodegradable organic substrate resulted in approximately 75% of the total COD, whereas it was close to 40% in the case of the allochthonous biomass, indicating the capacity of the autochthonous biomass to degrade a higher amount of organic compounds present in the leachate. The autochthonous biomass was characterized by higher biological activity and heterotrophic active fraction (14% vs 7%), whereas the activity of the allochthonous biomass was significantly affected by inhibitory compounds in the leachate, resulting in a lower respiration rate (SOUR = 13 mg O2 gVSS−1 h-1 vs 37 mg O2 gVSS−1 h−1). The long-term performance of the autochthonous and allochthonous biomasses indicated that the former was more suitable for the treatment of raw landfill leachate, ensuring higher removal performance towards the organic pollutants.

Contaminated marine sediments represent a critical threat towards human health and ecosystems, since they constitute a potential reservoir of toxic compounds release. In the present study, a bioslurry reactor was studied for the treatment of real marine sediments contaminated by petroleum hydrocarbons. The experimental campaign was divided in two periods: in the first period, microcosm trials were carried out to achieve useful indicators for biological hydrocarbon removal from sediments. The microcosm trials highlighted that the inoculum of halotolerant allochthonous bacteria provided the highest performance followed by autochthonous biomass. Based on the achieved results, in the second experimental period a bioslurry reactor was started up, based on a semisolid stirred tank reactor (STR) operated in batch mode. The process performances have been evaluated in terms of total petroleum hydrocarbon (TPH) removal, coupled with the characterization of microbial community through a Next Generation Sequencing (NGS) and phytotoxicity tests through the Germination Index (GI) with Lepidium Sativum seeds. The achieved results showed good hydrocarbons removal, equal to 40%, with a maximum removal rate of 220 mgTPH kg-1 d-1, but highlighting that high contaminant concentrations might affect negatively the overall removal performance. In general, the observed results were encouraging towards the feasibility of biological treatment of marine sediments contaminated by hydrocarbons. The microbiological analysis allowed the identification of taxa most involved in the degradation of TPH, highlighting after the treatment a shift in the microbial community from that of the raw sediment.

An integrated membrane bioreactor (MBR) model was previously proposed and tested. The model provides a comprehensive and detailed description of the nitrogen biological removal processes with respect to up-to-date literature. This paper presents a sensitivity and uncertainty analysis aimed at identifying the key factors affecting the variability of the model predictions. The Standardized Regression Coefficients (SRC) method was adopted for the sensitivity analysis. The uncertainty analysis was employed by running Monte Carlo simulations by varying only the value of the key factors affecting the model outputs. The sensitivity analysis combined with the uncertainty analysis applied here enabled to gain useful insights about the robustness of the model. By means of the SRC method 45 model factors (of 122) were selected as important. The results obtained here allowed to investigate the advantage of a detailed description of the nitrogen transformation bioprocesses (nitrification/denitrification) in terms of model accuracy and uncertainty bandwidth. The model allows to simulate the intermediate product during nitrification/denitrification, thus providing the possibility to control the nitrogen compounds that favour the formation of nitrous oxide.

In this study the occurrence and the behavior of illicit drugs and their metabolites have been investigated for two wastewater treatment plants (WWTPs) (namely, WWTP-1 and WWTP-2) located in Sicily (island of Italy). Samples were analyzed for methamphetamine, cocaine (COC), 3,4-methylenedioxymethamphetamine (MDMA), methadone (METH), 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), 3,4-methylenedioxy amphetamine (MDA); 3,4-methylenedioxy ethylamphetamine (MDEA), 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH) and Benzoylecgonine (BEG). The BEG, COC, MOR and THC-COOH were found at the highest concentration in both WWTPs. The Wastewater-based epidemiology calculation for BEG, COC, cannabinoids and THC-COOH was performed. On average, for both plants, population consumes 1.6 and 23.4 dose 1000 inh−1day−1of cocaine and cannabis, respectively. For WWTP-1 negative removals of illicit drugs were observed. For WWTP-2 the following average removal efficiencies were obtained: BEG (77.85%), COC (92.34%), CODEINE (64.75%), MOR (90.16%) and THC-COOH (68.64%).

The effects of salinity fluctuations on the activity of autochthonous halophilic bacteria in aerobic granular sludge (AGS) and flocculent activated sludge (FAS) reactors were investigated. The response of nitrifiers and denitrifiers activity to drastic and moderate salinity shocks in the short-term (ST) and long-term (LT) was examined. The BOD5removal efficiency decreased only in the reactors subjected to the drastic LT salinity increase. Nevertheless, stable performances were achieved 18 days after the shock in the AGS-R1 (90%), whereas after 27 days in the FAS-R1 (82%). The loss in nitritation efficiency was higher in the FAS reactors and was proportional to the shock intensity. Nitritation activity collapsed from approximately 3.8 mgNH4-N gVSS−1h−1to 0.73 mgNH4-N gVSS−1h−1and from 4.5 mgNH4-N gVSS−1h−1to 0.24 mgNH4-N gVSS−1h−1in the AGS-R1 and FAS-R1, respectively, even if the ammonium oxidation capacity did not completely disappeared. Denitritation activity decreased from 11.44 mgNO2-N gVSS−1h−1to 3.93 mgNO2-N gVSS−1h−1in the AGS-R1 at steady state, whereas in the FAS-R1, it decreased from 12.53 mgNO2-N gVSS−1h−1to 2.09 mgNO2-N gVSS−1h−1. Nitritation and denitritation were completely restored 5 days after ST shock. No significant effects were observed after the moderate shock. The changes in the total EPS content were lower than 10%, therefore, it was considered negligible. Only drastic shocks caused significant changes in the EPS structure, with an increase of the loosely-bound by 45% in the AGS and 55% in the FAS.

Bio-trenches are a sustainable option for treating nitrate contamination in groundwater. However, a possible side effect of this technology is the production of nitrous oxide, a greenhouse gas that can be found both dissolved in the liquid effluent as well as emitted as off gas. The aim of this study was to analyze NO3 − removal and N2O production in lab-scale column trials. The column contained olive nut as organic carbon media. The experimental study was divided into three phases (I, II and III) each characterized by different inlet NO3 − concentrations (30, 50, 75 mg NO3-N L−1 respectively). Sampling ports deployed along the length of the column allowed to observe the denitrification process as well as the formation and consumption of intermediate products, such as nitrite (NO2 −) and nitrous oxide (N2O). In particular, it was observed that N2O production represent only a small fraction of removed NO3 − during Phase I and II, both for dissolved (0.007%) and emitted (0.003%) phase, and it was recorded a high denitrification efficiency, over 99%. Nevertheless, significantly higher values were recorded for Phase 3 concerning emitted phase (0.018%). This fact is due to increased inlet concentration which resulted in a carbon limitation and in a consequent decrease in denitrification efficiency (76%).

The paper presents the sensitivity and uncertainty analysis of an integrated urban drainage model which includes micropollutants. Specifically, a bespoke integrated model developed in previous studies has been modified in order to include the micropollutant assessment (namely, sulfamethoxazole – SMX). The model takes into account also the interactions between the three components of the system: sewer system (SS), wastewater treatment plant (WWTP) and receiving water body (RWB). The analysis has been applied to an experimental catchment nearby Palermo (Italy): the Nocella catchment. Overall, five scenarios, each characterized by different uncertainty combinations of sub-systems (i.e., SS, WWTP and RWB), have been considered applying, for the sensitivity analysis, the Extended-FAST method in order to select the key factors affecting the RWB quality and to design a reliable/useful experimental campaign. Results have demonstrated that sensitivity analysis is a powerful tool for increasing operator confidence in the modelling results. The approach adopted here can be used for blocking some non-identifiable factors, thus wisely modifying the structure of the model and reducing the related uncertainty. The model factors related to the SS have been found to be the most relevant factors affecting the SMX modeling in the RWB when all model factors (scenario 1) or model factors of SS (scenarios 2 and 3) are varied. If the only factors related to the WWTP are changed (scenarios 4 and 5), the SMX concentration in the RWB is mainly influenced (till to 95% influence of the total variance for S SMX,max ) by the aerobic sorption coefficient. A progressive uncertainty reduction from the upstream to downstream was found for the soluble fraction of SMX in the RWB.

The paper focused on the evolution and the comparison of the extracellular polymeric substances (EPSs) content during the granulation process in two Granular Sequencing Batch Airlift Reactors (GSBAR) (3,5 L) fed with synthetic (R1) and industrial wastewater (R2). The results showed that in both the reactors the EPSs, in particular proteins (PN), were mainly produced during the feast phase because of the high substrate availability, especially under conditions of metabolic stress. Then, the EPSs content reduced during the famine period, because of biodegradation by bacteria. More in detail, during the granulation process, a greater polysaccharides (PS) consumption occurred in both reactors, whereas the PN content reduced significantly only in R2. As a result, the PN/PS ratio increased significantly during the granules formation, confirming the key role of proteins on the granulation process. In R2, the granules produced a greater amount of PN on average, and this resulted in a more rapid granulation. Nevertheless, due to the several consumption of PN during the famine period, the granules in R2 resulted weaker and less dense compared with the granules in R1. For this reason, the granules in R2 were more susceptible to breakage. Overall, although the industrial wastewater favored a more rapid granulation, the excessive consumption of the EPSs, led to the structural weakening of the granules.

The paper reports the main results of an experimental campaign carried out on two bench scale pilot plants for the treatment of synthetic shipboard slops. In particular, two membrane bioreactors (MBRs) with submerged configuration were analyzed. One MBR pilot plant (namely, Line A) was fed with synthetic shipboard slop and was subjected to a gradual increase of salinity. Conversely, the second MBR pilot plant (namely, Line B) was fed with the same synthetic shipboard slop but without salt addition, therefore operating as a “control” unit. Organic carbon, hydrocarbons and ammonium removal, kinetic constants, extracellular polymeric substances (EPSs) production and membranes fouling rates have been assessed. The observed results highlighted a stress effect exerted by salinity on the biological performances, with lower removal efficiencies in the Line A compared to Line B. Significant releases of soluble EPS in Line A promoted an increase of the resistance related to particle deposition into membrane pores (pore fouling tendency), likely due to a worsening of the mixed liquor features. Such a condition enhanced the reduction of the “pre-filter” effect of the cake layer.

Profuse efforts have been committed to develop efficient tools to measure the ecological status of the receiving water body quality state. The recurrence to mathematical models as support tools for the receiving water body quality assessment can be an optimal choice. Indeed, mathematical models can allow to build-up the cause effect relationship between polluting sources and receiving water quality. Regarding the river water quality modelling, two different kinds of river can be single out: large and small rivers. In the modelling approach, the main differences between the two types of river are reflected in the model kinetic constants. Indeed, the main quality processes which control and govern the quality state (i.e. de-oxygenation and re-oxygenation process) play a differ rule. As a results, the application of model approaches as well as kinetic constants derived for large river, can lead to wide biases thus misevaluating the river quality state. The paper presents a study where a multiregression analysis was carried out for assessing relationships to be employed for the evaluation of the kinetics constants for small rivers. To accomplish such a goal, the kinetic constants derived by a previous application of a river water quality model applied to a real case study (Oreto river) were used. Such kinetics constants were employed for deriving new multiregression equations for the assessment of the kinetics constants for small rivers.

In this study, the treatment of citrus wastewater with membrane bioreactors (MBRs) under different configurations was investigated for water reuse. In particular, one MBR and one aerobic granular sludge MBR (AGS + MBR) bench scale plants were operated for 60 days. The experimental campaign was divided into two periods. In Phase I, a conventional hollow fiber MBR was employed for the treatment of the raw high strength wastewater, whereas in Phase II a combination of in-series reactors (AGS + MBR) was adopted for the treatment of the high strength citrus wastewater The results demonstrated that both plant configurations enabled very high COD removal, with average values close to 99%. Respirometric batch tests revealed a considerable high metabolic activity of the biomass in both plant configurations, with higher values in the AGS + MBR. It was speculated that the MBR reactor was enriched in active biomass deriving from the erosion of the external granule layers in the upstream reactor. In terms of fouling tendency, higher resistance to filtration was observed in the AGS + MBR plant, also characterized by higher irremovable resistance increase compared to the MBR plant, that might severely affect the membrane service life.

Natural water resources are becoming increasingly limited due to global-scale climate change and water availability issues have become so severe that they must be addressed. Given these issues, reuse of wastewater and rainwater provides a promising way to cope with water shortages. This paper describes an investigation into the efficiency of rainwater usage systems. A conceptual model was built to assess the behaviour of rainwater tanks and their effectiveness in coping with water shortages. The study is based on a long-term simulation (12 years) of different rainwater reuse tank schemes. The associated reductions in residential freshwater demand (water reuse efficiency) and wet-weather runoff delivered to the sewer system (sewer discharge efficiency) were surveyed. The results clearly show that rainwater usage systems can significantly reduce drinking water consumption. The specific volumes required for the reuse of rainwater are high; however, for local scale application, the specific volumes necessary are comparable to the reservoir volumes already used to store freshwater resources during potable water shortage.

Partial nitrification (PN) is a technically and economically effective solution for the treatment of wastewater featuring low C/N ratio, allowing to achieve approximately 25% energy saving and 40% carbon source for denitrification. This study investigated the effect of different carbon to nitrogen ratio (C/N) and ammonia loading rate (ALR) on PN performances in a sequencing batch reactor (SBR) treating landfill leachate with municipal wastewater. The aim was to find an optimum range for C/N and ALR to maximize PN performances. Results demonstrated that a proper balancing between ALR and C/N is crucial to achieve high PN efficiency. The results highlighted the existence of an optimum range for ALR and C/N of approximately 0.30–0.50 kg NH4-N m−3d−1 and 2–4, respectively. Although complete suppression of NOB was not achieved at these values, a predominance of nitrite (125 mg L−1) to nitrate (50 mg L−1) was observed. The results demonstrated the achievement of PN even at high C/N (4) but, on the other hand, C/N higher than 6 were not favorable to autotrophic growth. C/N significantly lower than 4 caused a stress condition for the biomass, leading to an excess in SMP production. Therefore, the operational parameters as well as the co-treatment ratio should be adjusted in order to operate the system under specific ALR (0.30–0.50 kg NH4-N m−3 d−1) and C/N (2–4).

The paper reports the main results of an experimental campaign performed on a membrane bioreactor pilot plant designed to treat synthetic shipboard slops. The experimental campaign was divided into two phases: salinity acclimation up to 20 g NaCl L −1 (Phase I) and hydrocarbon (diesel fuel) dosing (Phase II). The observed results show that the carbon removal was not severely affected by the wastewater features. Conversely, respirometric tests showed that nitrification was strongly affected by the salinity (33% of nitrification efficiency at 20 g NaCl L −1 – Phase I) as a result of the salinity in the autotrophic biomass. Moreover, the sludge viscosity increased during Phase II due to the wastewater composition, leading to an increase in the membrane resistance, and severe degradation of the sludge dewaterability was also observed. Indeed, the capillary suction time increased by a factor of 3 times compared with that of Phase I.

This study investigated the chance to couple the conventional Oxic Settling Anaerobic (OSA) process with a thermic treatment at moderate temperature (35 °C). The maximum excess sludge reduction rate (80%) was achieved when the plant was operated under 3 h of hydraulic retention time (HRT). Compared with the conventional OSA system, the thermic treatment enabled a further improvement in excess sludge minimization of 35%. The observed yield coefficient decreased from 0.25 gTSS gCOD−1 to 0.10 gTSS gCOD−1 when the temperature in the anaerobic reactor was increased to 35 °C, despite the lower HRT (3 h vs 6 h). Moreover, the thermic treatment enabled the decrease of filamentous bacteria, thereby improving the sludge settling properties. The thermic treatment enhanced the destruction of extracellular polymeric substances and the increase of endogenous decay rate (from 0.64 d−1 to 1.16 d−1) that reduced the biomass active fraction (from 22% to 4%).

Excess sludge minimization was studied in a MBR with pre-denitrification scheme. Sludge minimization, nitrogen removal performance and membrane fouling tendency were investigated in two configurations, characterized by a different position of the sludge retention reactor (SRR). In particular, the SRR was placed: i) in the return activated sludge line (Anaerobic Side-Stream Reactor – ASSR configuration) and ii) in the mainstream between the anoxic and aerobic reactor (Anaerobic Main-Stream Reactor – AMSR configuration). The achieved results demonstrated that the ASSR enabled a higher excess sludge reduction (74% vs 32%), while achieving lower biological nitrogen removal (BNR) (TN = 63% vs 78%) and membrane fouling tendency (FR = 2.1 · 1012 m−1 d−1 vs 4.0 · 1011 m−1 d−1) than the AMSR. It was found that metabolism uncoupling, destruction of EPS and endogenous decay simultaneously occurred in the ASSR. Conversely, selective enrichment of bacteria population with low biomass yield was found the main mechanism affecting sludge minimization in the AMSR.

A University of Cape Town Integrated Fixed-Film Activated Sludge Membrane Bioreactor (UCT-IFAS-MBR) pilot plant was operated at different values of the sludge retention time (SRT). Three SRTs were investigated at different durations: indefinitely, 30 and 15 days. The organic carbon, nitrogen and phosphorus removal, kinetic/stoichiometric parameters, membrane fouling tendency and sludge filtration properties were assessed. The findings showed that by decreasing the SRT, the pilot plant could maintain excellent carbon removal efficiencies throughout the experiments. In contrast, the biological carbon removal showed a slight nitrification and was slightly affected by the decrease of the SRT, showing high performance (approximately 91%, on average). Thus, the biofilm might have helped sustain the nitrification throughout the experiments. The average phosphorus removal performance increased slightly with a decrease in SRT, achieving the maximum efficiency (61.5%) at a SRT of 15 days. After a 30-day SRT, an increase in resistance due to pore blocking and a general worsening of the membrane filtration properties occurred.

The work focuses on the feasibility of treating slop with aerobic granular sludge. For this purpose, a 3.5 L granular sequencing batch reactor was activated and it was monitored for 156 days. The experimental campaign was divided into two periods, named Period I (100 days) and Period II (56 days). Total Petroleum Hydrocarbon (TPH) concentration in the slop was, on average, equal to 6.8 ± 1.5 mg L−1 and 13 ± 1.5 mg L−1 in Period I and Period II respectively. The obtained results during the first experimental period indicated that about 80 days were required to reach steady state with mature granules, when TPHs removal efficiency was approximately 90%. The results indicated that both adsorption and biodegradation phenomena occurred. Subsequently, due to the increase in the TPH concentration in Period II, a temporary degranulation was observed, leading to the deterioration of effluent quality. When the granulation was recovered, the TPHs removal efficiencies were gradually recovered. Based on the results, the granular sludge appears able to remove hydrocarbons, in compliance the discharge limits, even if a significant deterioration in granular sludge structure was observed with the increase in TPH concentration.

Autochthonous halophilic biomass was cultivated in a sequencing batch reactor (SBR) aimed at analyzing the potential use of autochthonous halophilic activated sludge in treating saline industrial wastewater. Despite the high salt concentration (30 g NaCl L −1 ), biological oxygen demand (BOD) and total suspended solids (TSS), removal efficiencies were higher than 90%. More than 95% of the nitrogen was removed via a shortcut nitrification-denitrification process. Both the autotrophic and heterotrophic biomass samples exhibited high biological activity. The use of autochthonous halophilic biomass led to high-quality effluent and helped to manage the issues related to nitrogen removal in saline wastewater treatment.

The paper presents a mathematical model for the simulation of the ecology of a wastewater stabilization reservoir (WSR). WSRs are hypertrophic aquatic systems devoted to water storage in warm countries where shortage conditions are often encountered. Several factors that affect the stabilization reservoir’s effluent quality were taken into account: hydraulics and hydrology, solar radiation, reaeration, algae, zooplankton, organic matter, pathogens, and sediment-water interactions. The model quantifies the specific influence of each factor on effluent quality, and evaluating the correlation between the different factors. State variables included in the model were: algae, dissolved oxygen, organic matter, zooplankton and indicator bacteria. The model was applied to an Italian stabilization reservoir located in the south part of Sardinia: Simbirizzi lake. The model generated satisfactory results and can be employed as a useful tool for environmental water quality management of stabilization reservoirs.

Municipal solid waste (MSW) landfills now represent one of the most important issues related to the waste management cycle. Knowledge of biogas production is a key aspect for the proper exploitation of this energy source, even in the post-closure period. In the present study, a simple mathematical model was proposed for the simulation of biogas production. The model is based on first-order biodegradation kinetics and also takes into account the temperature variation in time and depth as well as landfill settlement. The model was applied to an operating landfill located in Sicily, in Italy, and the first results obtained are promising. Indeed, the results showed a good fit between measured and simulated data. Based on these promising results, the model can also be considered a useful tool for landfill operators for a reliable estimate of the duration of the post-closure period.

The objective of this paper is to evaluate the potential impact of in-sewer processes (COD components transformation and hydrogen sulphide production) on the design of sewer systems. The tool used for such analysis is a mathematical model derived from the WATS model (Wastewater Aerobic/anaerobic Transformation in Sewers) able to describe the processes occurring in the sewer system both under aerobic and anaerobic conditions. The model is applied to three synthetic catchments with, respectively, 10,000, 50,000 and 250,000 inhabitants connected to gravity sewer systems different in terms of type (separate or combined), slope, length, travel time, wastewater temperature. The simulation results enable to assess the effect of the in sewer transformations in terms of hydrogen sulphide formation and transformation of the biodegradable organic matter that is necessary for biological nutrients removal at the WWTP.

Stricter effluent limits, water shortage conditions, land availability requires today even more the needs of advanced wastewater treatments. Attractive solutions come from membrane bioreactors (MBR), Integrated Fixed Film Activated Sludge (IFAS) or combinations (i.e., IFAS-MBRs). One crucial aspect for the applicability of this overall new technology, compared to the conventional activated sludge systems, is the lack of knowledge for design and manage (e.g., kinetic constants, optimal operative conditions etc.). In view of the above frame, the aim of the present study was to assess the kinetic and stoichiometric parameters of bacterial species in MBRs by means of respirometric techniques. Plant configurations, operational conditions and wastewater features (domestic/industrial) were analysed. Four different MBR plants were investigated: i) sequencing batch MBR subjected to a gradual salinity increase; ii) pre-denitrification MBR treating saline wastewater contaminated by hydrocarbons; iii) University of Cape Town (UCT) MBR treating domestic wastewater subjected to a carbon-to-nitrogen (C/N) ratio variation; iiii) UCT- IFAS -MBR treating domestic wastewater. Results show a significant influence on biomass respiratory activity from both plant configurations and operational conditions. The salinity increase severely affected the activity of autotrophic species, while heterotrophic community was mainly influenced by the C/N variation. Moreover, it was observed a specialization in the IFAS-MBR configuration, with the suspended biomass more affine to organic matter, whilst biofilm in the nitrification process. The respirometric analysis confirmed to be an effective tool for the evaluation of the biomass kinetic and stoichiometric parameters. The results of this study can be useful for the application of mathematical models in the design phase and for the monitoring of biomass viability during plant operations.

Sanitary landfills for municipal solid waste (MSW) represent one of the major anthropogenic source of GHGs emissions and are directly responsible of the climate changes we are facing nowadays. Indeed, the biodegradable organic matter of MSW undergoes anaerobic digestion producing the landfill gas (LFG), whose main components are CH4 and CO2. Therefore, biomethane energy exploitation in MSW landfills will reduce GHGs emission positively affecting the global warming. The aim of the present study was to assess the methane production in a Sicilian landfill by comparing the results from field measurements of methane emission and the estimates achieved by applying different mathematical models. A subsequent energetic/economic analysis was carried out based on the Italian incentive mechanisms. Two different scenarios were simulated for LFG valorization considering either internal combustion engines or micro gas turbines. The evaluation of the economic viability was performed by applying the classic models of the Net Present Value and Internal Rate of Return. The results of the present study showed that the LFG produced in the investigated landfill could be profitably used as energetic source and the economic income due to thermal and electrical energy valorization might positively contribute to the landfill management.

Sensitivity and uncertainty analysis, although can be of primarily importance in mathematical modelling approaches, are scarcely applied in the field of membrane bioreactor (MBR). An integrated mathematical model for MBR is applied with the final aim to pin down sources of uncertainty in MBR modelling. The uncertainty analysis has been performed combining global sensitivity analysis (GSA) with the generalized likelihood uncertainty estimation (GLUE). The model and methodology were applied to a University Cape Town pilot plant. Results show that the complexity of the modelled processes and the propagation effect from the influent to the effluent increase the uncertainty of the model prediction. It was found that the uncertainty of nitrogen and phosphorus model outputs increases from the first reactor-section plant to the last. Results show also that the GSA-GLUE methodology is a valid tool for uncertainty assessment for MBR modelling. Furthermore, the GSA-GLUE allows to identify the most critical processes/plant sections and the key sources of uncertainty where attention should be paid in view of model predictions improvement.

In the present paper, the feasibility of citrus wastewater treatment with aerobic granular sludge sequencing batch reactors (AGSBR) was investigated. Two AGSBRs (named R1 and R2, respectively) were operated for 90 days under different organic loading rates (OLR) and pH in two experimental periods. The OLR ranged approximately between 3.0 kg TCOD m−3d−1 and 7 kg TCOD m−3d−1 during Period I, whereas between 7 kg TCOD m−3d−1 and 15 kg TCOD m−3d−1 during Period II. pH was maintained at 7.0 and 5.5 in R1 and R2, respectively. The results revealed that under high OLR and unbalanced feast/famine regime (Period I), the development of fast-growing microorganisms (fungi and filamentous bacteria) was favoured in both reactors, resulting in granular sludge instability. An extended famine phase and a proper balancing between feast and famine periods (Period II) were favourable for the development of bacteria with low growth rates (0.05 d−1) thus enhancing the granules stability. To the benefit of granular sludge stability and effluent quality, the length of the feast period should not exceed 25% of cycle length. Moreover, under OLR lower than 7 kg TCOD m−3d−1 the removal efficiency of total chemical oxygen demand (TCOD) was approximately 90% in R1 and R2 and no side effects on the organic carbon removal performance related to the pH were observed. In contrast, at higher OLR a significant decrease in the removal efficiency (from 90% to less than 75%) was observed in R2. Results revealed also that under low pH, hydrolysis of proteins occurred and a decrease in the biological kinetic rates proportionally to the applied OLR was observed.

The aim of the present work was to investigate the behavior of a membrane bioreactor (MBR) system for the treatment of oily wastewater. A bench scale MBR was fed with synthetic wastewater containing diesel fuel. Organic carbon, hydrocarbon and ammonium removal, kinetic constants, extracellular polymeric substances production, and membrane fouling rates were monitored. The MBR plant was operated for more than 200 days, and the results highlighted good carbon removal and nitrification, suggesting a sort of biomass adaptation to hydrocarbons. Membrane fouling analysis showed an increase in total resistance, likely due to hydrocarbons, which caused an irreversible fouling (pore blocking) mainly due to oil deposition.