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The present study used bench scale columns filled with biochar for phosphorous (P) recovery from real ultrafiltered wastewater. No studies are available about the potentiality of biochar using ultrafiltered real wastewater. Therefore, this study aimed to assess phosphate (PO4 3-) recovery by biochar-packed columns employing real treated wastewater from an ultrafiltration process. Three flow rates were tested, specifically 0.7, 1.7 and 2.3 L h-1, to gain insights into the optimal working conditions. Results revealed that the maximum amount of PO4 3- recovery (namely, 3.43 mg g-1 biochar) can be achieved after 7 h by employing the highest tested flow rate. Furthermore, the phosphorus exchange capacity (PEC) was inversely correlated with the feeding flow rate (FFR), with PEC values equal to 35, 25 and 9 % for FFR of 0.67, 1.7 and 2.3 L h-1, respectively. The pseudo-first order model best approximated the adsorption kinetics, thus suggesting that the adsorption of phosphate by biochar depends on its concentrations (i.e. physiosorption mechanism).
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A pilot plant with a conventional activated sludge (CAS) system with intermittent aeration (IA) was monitored. The system was configured as an Oxic Settling Anaerobic (OSA) process with the insertion of one anaerobic side-stream reactor (ASSR). The pilot plant was fed with real wastewater and an intensive experimental campaign was carried out including sludge minimization, nitrogen and carbon removal, GHG emissions and biokinetic parameters. The experimental campaign was divided into periods: Period I, II, and III. In Periods I and II, the ASSR reactor was operated with two different hydraulic retention times (HRT), 4 and 6 h, with an aeration/non-aeration ratio of 30 min/30 min. In Period III, the HRT in the anaerobic reactor was the same as in Period II. In contrast, the biological reactor's aerated/non-aerated ratio was increased to 40 min/20 min. Results demonstrated that combining IA and OSA might be effective in the reduction of excess sludge production. The yield coefficient decreased from Period I to Period II (Yobs from 0.41 to 0.25 gTSS gCOD-1, in Period I and II, respectively). Nevertheless, the HRT increase in the ASSR compromised the system performance regarding nitrification and greenhouse gas emissions and worsened the sludge settleability. However, the increase in the aeration duration was beneficial in restoring the system's nitrification and denitrification ability and carbon footprint. The lowest carbon footprint was obtained during Period III (6.8 kgCO2/d).
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This paper presents a study on reducing sewage sludge by an oxic-settling-anaerobic (OSA) pilot plant compared to the conventional activated sludge (CAS) process in view of resource recovery and moving towards plant carbon neutrality. The OSA plant was supplied with real wastewater and the anaerobic reactor was operated under two hydraulic retention times (HRT) (4 and 6 h). Greenhouse gas (GHG) emissions were monitored for the first time to determine the OSA process's production mechanism. The results highlighted that under the lowest HRT (4 h), the removal efficiencies of COD and PO4-P, increased from 75 to 89% and from 39 to 50% for CAS and OSA configurations, respectively. The observed yield coefficient was reduced from 0.58 gTSS gCOD-1 (CAS period) to 0.31 gTSS gCOD-1 (OSA period). A remarkable deterioration of nitrification efficiency under OSA configuration was obtained from 79% (CAS) to 27% (OSA with HRT of 6 h). The huge deterioration of nitrification significantly affected the GHG emissions, with the N2O-N fraction increasing from 1% (CAS) to 1.55% (OSA 4 h HRT) and 3.54% (OSA 6 h HRT) of the overall effluent nitrogen, thus suggesting a relevant environmental implication due to the high global warming potential (GWP) of N2O.
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Óxido Nitroso , Fósforo , Aguas del Alcantarillado , Eliminación de Residuos Líquidos , Aguas del Alcantarillado/química , Eliminación de Residuos Líquidos/métodos , Anaerobiosis , Reactores Biológicos , Aguas Residuales/químicaRESUMEN
The reuse of treated wastewater (TWW) in agriculture for crop irrigation is desirable. Crop responses to irrigation with TWW depend on the characteristics of TWW and on intrinsic and extrinsic soil properties. The aim of this study was to assess the response of tomato (Solanum lycopersicum L.) cultivated in five different soils to irrigation with TWW, compared to tap water (TAP) and an inorganic NPK solution (IFW). In addition, since soil microbiota play many important roles in plant growth, a metataxonomic analysis was performed to reveal the prokaryotic community structures of TAP, TWW and IFW treated soil, respectively. A 56-days pot experiment was carried out. Plant biometric parameters, and chemical, biochemical and microbiological properties of different soils were investigated. Shoot and root dry and fresh weights, as well as plant height, were the highest in plants irrigated with IFW followed by those irrigated with TWW, and finally with TAP water. Plant biometric parameters were positively affected by soil total organic carbon (TOC) and nitrogen (TN). Electrical conductivity was increased by TWW and IFW, being such an increase proportional to clay and TOC. Soil available P was not affected by TWW, whereas mineral N increased following their application. Total microbial biomass, as well as, main microbial groups were positively affected by TOC and TN, and increased according to the following order: IFW > TWW > TAP. However, the fungi-to-bacteria ratio was lowered in soil irrigated with TWW because of its adverse effect on fungi. The germicidal effect of sodium hypochlorite on soil microorganisms was affected by soil pH. Nutrients supplied by TWW are not sufficient to meet the whole nutrients requirement of tomato, thus integration by fertilization is required. Bacteria were more stimulated than fungi by TWW, thus leading to a lower fungi-to-bacteria ratio. Interestingly, IFW and TWW treatment led to an increased abundance of Proteobacteria and Acidobacteria phyla and Balneimonas, Rubrobacter, and Steroidobacter genera. This soil microbiota structure modulation paralleled a general decrement of fungi versus bacteria abundance ratio, the increment of electrical conductivity and nitrogen content of soil and an improvement of tomato growth. Finally, the potential adverse effect of TWW added with sodium chloride on soil microorganisms depends on soil pH.
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Riego Agrícola , Microbiota , Microbiología del Suelo , Suelo , Solanum lycopersicum , Eliminación de Residuos Líquidos , Aguas Residuales , Suelo/química , Riego Agrícola/métodos , Eliminación de Residuos Líquidos/métodos , Nitrógeno/análisis , Agricultura/métodosRESUMEN
The paper reports the results of an experimental study aimed at comparing two configurations of a full-scale wastewater treatment plant (WWTP): conventional activated sludge (CAS) and oxic-settling-anaerobic process (OSA) with intermittent aeration (IA). A comprehensive monitoring campaign was carried out to assess multiple parameters for comparing the two configurations: carbon and nutrient removal, greenhouse gas emissions, respirometric analysis, and sludge production. A holistic approach has been adopted in the study with the novelty of including the carbon footprint (CF) contribution (as direct, indirect and derivative emissions) in comparing the two configurations. Results showed that the OSA-IA configuration performed better in total chemical oxygen demand (TCOD) and ortho-phosphate (PO4-P) removal. CAS performed better for Total Suspended Solids (TSS) removal showing a worsening of settling properties for OSA-IA. The heterotrophic yield coefficient and maximum growth rate decreased, suggesting a shift to sludge reduction metabolism in the OSA-IA configuration. Autotrophic biomass showed a reduced yield coefficient and maximum growth yield due to the negative effects of the sludge holding tank in the OSA-IA configuration on nitrification. The OSA-IA configuration had higher indirect emissions (30.5 % vs 21.3 % in CAS) from additional energy consumption due to additional mixers and sludge recirculation pumps. The CF value was lower for OSA-IA than for CAS configuration (0.36 kgCO2/m3 vs 0.39 kgCO2/m3 in CAS).
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This study presents the effects on carbon and nutrient removal, membrane fouling and greenhouse gas (GHG) emissions of an Oxic-Settling-Anaerobic (OSA) - Membrane Bioreactor (MBR) pilot plant fed with real wastewater. The influence of three sludge return internal ratios (IR) was investigated by testing 45, 75 and 100%. The results showed that with the increase of IR, the biological sludge production substantially decreased by 85.8% due to the combination of cell lysis and endogenous metabolism. However, a worsening of ammonia removal efficiencies occurred (from 94.5 % to 84.7 with an IR value of 45 and 100%, respectively) mostly due to the ammonia release caused by cell lysis under anaerobic conditions. The N2O emission factor increased with the rise of IR (namely, from 2.17% to 2.54% of the total influent nitrogen). In addition, a variation of carbon footprint (CF) (0.78, 0.62 and 0.75 kgCO2eq m-3 with 45, 75 and 100% IR, respectively) occurred with IR mainly due to the different energy consumption and carbon oxidation during the three periods. The study's relevance is to address the optimal operating conditions in view of reducing sludge production. In this light, the need to identify a trade-off between the advantages of reducing sludge production and the disadvantages of increasing membrane fouling and GHG emissions must be identified in the future.
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Gases de Efecto Invernadero , Aguas del Alcantarillado , Eliminación de Residuos Líquidos/métodos , Biosólidos , Carbono , Amoníaco , Nutrientes , Reactores BiológicosRESUMEN
Volatile fatty acids (VFA) from sewage sludge represent an excellent recovered resource from wastewater treatment. This study investigated four sludge pre-treatments (namely, potassium permanganate - KMnO4, initial pH = 10, initial pH = 2.5 and low-temperature thermal hydrolysis) by operating batch reactors under acidogenic fermentation conditions. Results revealed that 0.1 g KMnO4/g of total suspended solids represents the best pre-treatment obtaining up to 2713 mgCOD L-1 and 452 mgCOD/g of volatile suspended solids. These results also paralleled metataxonomic analysis highlighting changes in prokaryotic microbial structures of sewage sludge of the batch fermentations subjected to the different pre-treatments.
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Reactores Biológicos , Aguas del Alcantarillado , Fermentación , Aguas del Alcantarillado/química , Ácidos Grasos Volátiles , Hidrólisis , Concentración de Iones de HidrógenoRESUMEN
Recovering resources from wastewater treatment is vital for the transition from a linear to a circular economy model in the water sector. Volatile Fatty Acids (VFAs) are valuable products among the possible recovered resources. This study investigates the influence of potassium permanganate (KMnO4) addition during acidogenic fermentation of waste activated sludge for enhancing VFAs production. Specifically, different fermentation batch tests with and without KMnO4 addition were carried out using two distinctive sewage sludges as feedstocks. Results showed that KMnO4 addition increased the VFAs yield up to 144 and 196 mgCOD/g VSS for the two sludges. When KMnO4 was used as pre-treatment, 55 % of sCOD were VFAs. This latter result was mainly debited to the recalcitrant organics' disruption promoted by the oxidative permanganate ability.
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This paper presents a comprehensive study on polyhydroxyalkanoate (PHA) production from sewage sludge. Greenhouse gas (GHG) emissions were monitored for the first time to assess the impact of climate change and environmental sustainability. The pilot plant was composed of a fermenter with a membrane and two biological reactors (namely, selection and accumulation). Results showed that despite a low organic loading rate (namely, 0.06 kg BOD kg SS-1 day-1), a good PHA yield was obtained (namely, 0.37 g PHA/g volatile fatty acids), confirming that sewage sludge can be a suitable feedstock. GHG emissions were 3.85E-04 g CO2eq/g and 32.40 g CO2eq/g, direct and indirect, respectively. Results provided valuable insights in view of finding a trade-off between PHA production and GHG emissions to prove the PHA production process as an effective solution for biosolids disposal at a low carbon footprint.
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Gases de Efecto Invernadero , Polihidroxialcanoatos , Humanos , Aguas del Alcantarillado , Fermentación , Polihidroxialcanoatos/metabolismo , Universidades , ItaliaRESUMEN
A trade-off between greenhouse emissions (direct and indirect) and operational costs in the water treatment sector is of great importance, although only few literature studies exist. The paper presents a comprehensive experimental study on a Membrane Bioreactor (MBR) pilot plant at the Water Resource Recovery Facility of Palermo University (Italy). The MBR pilot plant was aimed at reducing carbon footprint while producing water suitable for water reuse in agriculture. Multiple scenarios were assessed to unveil the best operational variables including the assessment of the reclaimed water quality index for water reuse. Results showed the lowest operational costs for the MBR of 5.05 cent/m3 with Class B according to 741/2020 European legislation. Results revealed optimised values, in terms of airflow rate and backwash frequency, of 0.8 m3/m2/h and 12 times/h, respectively. The highest N2O emission was measured in correspondence of scenario S5 (airflow rate of 1.6 m3/m2/h) with 0.40 mg N2O-N/m2/h in agreement with previous literature studies. The obtained results could effectively address the operators to find a trade-off between operational costs and water quality.
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Gases de Efecto Invernadero , Humanos , Eliminación de Residuos Líquidos , Unión Europea , Agricultura , ItaliaRESUMEN
Greenhouse gas (GHG) emissions from wastewater treatment plants (WWTPs) can affect climate change and must be measured and reduced. Mathematical modelling is an attractive solution to get a tool for GHG mitigation. However, although many efforts have been made to create reliable tools that can simulate "sustainable" full-scale WWTP operation, these studies are not considered complete enough to include GHG emissions and energy consumption of biological processes under long-term dynamic conditions. In this study, activated sludge model no. 1 (ASM1) was modified to model nitrous oxide (N2O) emissions with a plant-wide modelling approach. The model is novel compared to the state of the art since it includes three steps denitrification, all N2O production pathways and its stripping in an ASM1. The model has been calibrated and validated through long-term water quality and short-term N2O emissions data collected from Corleone (Italy) WWTP. Different dissolved oxygen (DO) concentrations and return sludge (RAS) ratios were tested with dynamic simulations to optimise the full-scale WWTP. The scenarios have been compared synergistically with effluent quality, direct GHG emissions, and energy footprint by the water-energycarbon coupling index (WECCI). This modelling study is novel as it fully covers long-term calibration/validation of the model with N2O measurements and tests the dynamic optimisation. Decision-makers and operators can use this new model to optimise GHG emissions and treatment costs.
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Gases de Efecto Invernadero , Purificación del Agua , Aguas Residuales , Aguas del Alcantarillado , Modelos Teóricos , Óxido Nitroso/análisisRESUMEN
A mathematical correlation between biomass kinetic and membrane fouling can improve the understanding and spread of Membrane Bioreactor (MBR) technology, especially in solving the membrane fouling issues. On this behalf, this paper, produced by the International Water Association (IWA) Task Group on Membrane modelling and control, reviews the current state-of-the-art regarding the modelling of kinetic processes of biomass, focusing on modelling production and utilization of soluble microbial products (SMP) and extracellular polymeric substances (EPS). The key findings of this work show that the new conceptual approaches focus on the role of different bacterial groups in the formation and degradation of SMP/EPS. Even though several studies have been published regarding SMP modelling, there still needs to be more information due to the highly complicated SMP nature to facilitate the accurate modelling of membrane fouling. The EPS group has seldom been addressed in the literature, probably due to the knowledge deficiency concerning the triggers for production and degradation pathways in MBR systems, which require further efforts. Finally, the successful model applications showed that proper estimation of SMP and EPS by modelling approaches could optimise membrane fouling, which can influence the MBR energy consumption, operating costs, and greenhouse gas emissions.
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Matriz Extracelular de Sustancias Poliméricas , Membranas Artificiales , Reactores Biológicos/microbiología , Bacterias , Biomasa , Aguas del Alcantarillado/microbiologíaRESUMEN
Purpose of Review: Annually, huge amounts of microplastics (MPs) are added to farmlands through sewage sludge (SS)/biosolid applications as a fertilizer. Most research emphasizes the enormity of the problem and demonstrates the fate, impacts, and toxicity of MPs during SS treatment processes and land applications. None has addressed the management strategies. To address the gaps, the current review evaluates the performance analysis of conventional and advanced sludge treatment methods in eliminating MPs from sludge. Recent Findings: The review uncovers that the occurrence and characteristics of MPs in SS are highly governed by factors such as population density, speed and level of urbanization, citizens' daily habits, and treatment units in wastewater treatment plants (WWTPs). Furthermore, conventional sludge treatment processes are ineffective in eliminating MPs from SS and are accountable for the increased small-sized MPs or micro(nano)plastics (MNPs) along with altered surface morphology facilitating more co-contaminant adsorption. Simultaneously, MPs can influence the operation of these treatment processes depending on their size, type, shape, and concentration. The review reveals that research to develop advanced technology to remove MPs efficiently from SS is still at a nascent stage. Summary: This review provides a comprehensive analysis of MPs in the SS, by corroborating state-of-the-knowledge, on different aspects, including the global occurrence of MPs in WWTP sludge, impacts of different conventional sludge treatment processes on MPs and vice versa, and efficiency of advanced sludge treatment and upcycling technologies to eliminate MPs, which will facilitate the development of mitigation measures from the systematic and holistic level.
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Anammox is a widely adopted process for energy-efficient removal of nitrogen from wastewater, but challenges with NOB suppression and NO3- accumulation have led to a deeper investigation of this process. To address these issues, the synergy of partial denitrification and anammox (PD-anammox) has emerged as a promising solution for sustainable nitrogen removal in wastewater. This paper presents a comprehensive review of recent developments in the PD-anammox system, including stable performance outcomes, operational parameters, and mathematical models. The review categorizes start-up and recovery strategies for PD-anammox and examines its contributions to sustainable development goals, such as reducing N2O emissions and saving energy. Furthermore, it suggests future trends and perspectives for improving the efficiency and integration of PD-anammox into full-scale wastewater treatment system. Overall, this review provides valuable insights into optimizing PD-anammox in wastewater treatment, highlighting the potential of simultaneous processes and the importance of improving efficiency and integration into full-scale systems.
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Desnitrificación , Aguas Residuales , Aguas del Alcantarillado , Nitrógeno , Oxidación Anaeróbica del Amoníaco , Reactores Biológicos , Oxidación-ReducciónRESUMEN
The aim of this work was to study the effect of organic loading rate on the production of Polyhydroxyalkanoates (PHA) from sewage sludge. Synthesis of PHA using sewage sludge as platform was achieved in this work. Three pilot-scale selection-sequencing batch reactors (S-SBR) were used for obtaining a culture able to accumulate PHA following a strategy of aerobic dynamic feeding (ADF) at different volumetric organic-loading-rate (vOLR): 1.3, 1.8 and 0.8 g COD L-1 d-1 for S-SBR 1, S-SBR 2 and S-SBR 3, respectively. Decreasing the vOLR enhanced the general performance of the process as for organic matter removal (from 99.2% ± 0.3% in S-SBR-3 to 92 ± 2 in S-SBR-2) while the opposite trend was recorded for PHA production (6.0 PHA % w/w in S-SBR-3 vs 13.7 PHA % w/w in S-SBR-2 at the end of the feast phase). Furthermore, indirect and direct emissions, as N2O, were evaluated during the process for the first time. Finally, three accumulation tests were performed achieving 24% w/w.
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Polihidroxialcanoatos , Aguas del Alcantarillado , Reactores BiológicosRESUMEN
The global energy crisis is approaching due to rapid population growth and overexploitation of fossil fuels. Therefore, the development and use of new and renewable energy sources is already in the extreme urgency. This work developed a novel technology to efficiently produce renewable liquid bioenergy from discarded wastes, by effectively transforming sewage sludge into high-value medium chain fatty acids (MCFA). The maximum MCFA yield in the anaerobic sludge fermentation was revealed to be 10.6 times of control when utilizing sewage sludge with 1.78 mg-N/L free nitrous acid (FNA) pretreatment. The carbon flow from sewage sludge into MCFA in the fermentation system was significantly enhanced with appropriate levels (0.71-1.78 mg-N/L) of FNA pretreatment. Compared to FNA pretreatment, however, its direct addition severely inhibited total products (i.e., carboxylates and complex alcohols) generation because of the toxicity on live cells (decreasing to 8.3 %-13.9 %) in sludge. Kinetic models (one-substrate and two-substrate) were utilized to investigate the mechanism of MCFA promotion by FNA pretreatment on anaerobic sludge fermentation, in which linear relationship analysis between FNA-derived organic release and the fitted parameters were also performed. The results indicated that the conversion of refractory materials into rapidly bioavailable substrates for MCFA production contributed to increasing MCFA production rate and potential. Moreover, the relative abundances of functional microorganisms related to hydrolysis-acidification and chain elongation process increased under FNA pretreatment, further favoring the MCFA production. This study provides a novel and effective technology of sludge energy recovery that can achieve the next-generation sustainable sewage sludge management.
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Ácido Nitroso , Aguas del Alcantarillado , Aguas del Alcantarillado/química , Ácido Nitroso/análisis , Ácidos Grasos Volátiles/análisis , Ácidos Grasos , Fermentación , AnaerobiosisRESUMEN
Volatile fatty acids (VFAs) produced by acidogenic digestion of sewage sludge are very interesting bio-products which can contribute to carbon neutrality of wastewater treatment plants. Studies on the production of VFAs from sewage sludge from fermenters with membrane are limited. In view of above, VFAs from a fermenter pilot plant equipped with a membrane bioreactor and fed with real sewage sludge has been monitored. The effect of headspace volume (HdV) on VFA production was studied for the first time to elucidate the optimal operation conditions. Specifically, three fermenter HdV values (namely, 20, 40 and 60% of the total volume) have been investigated. Results revealed that the HdV of 20% ensured the highest sCOD production (900 mgCOD/L) and VFA/COD ratio (45.4%). High value of HdV (namely, 40 and 60%) strongly decreased the acidogenic fermentation performance in terms of VFA production.
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Carbono , Aguas del Alcantarillado , Fermentación , Reactores Biológicos , Ácidos Grasos Volátiles , Ácidos , Concentración de Iones de HidrógenoRESUMEN
Pharmaceutical and personnel care products (PPCPs) from wastewater are a potential hazard to the human health and wildlife, and their occurrence in wastewater has caught the concern of researchers recently. To deal with PPCPs, various treatment technologies have been evolved such as physical, biological, and chemical methods. Nevertheless, modern and efficient techniques such as advance oxidation processes (AOPs) demand expensive chemicals and energy, which ultimately leads to a high treatment cost. Therefore, integration of chemical techniques with biological processes has been recently suggested to decrease the expenses. Furthermore, combining ozonation with activated carbon (AC) can significantly enhance the removal efficiency. There are some other emerging technologies of lower operational cost like photo-Fenton method and solar radiation-based methods as well as constructed wetland, which are promising. However, feasibility and practicality in pilot-scale have not been estimated for most of these advanced treatment technologies. In this context, the present review work explores the treatment of emerging PPCPs in wastewater, via available conventional, non-conventional, and integrated technologies. Furthermore, this work focused on the state-of-art technologies via an extensive literature search, highlights the limitations and challenges of the prevailing commercial technologies. Finally, this work provides a brief discussion and offers future research directions on technologies needed for treatment of wastewater containing PPCPs, accompanied by techno-economic feasibility assessment.