The upgrading of conventional activated sludge processes with thermophilic aerobic membrane reactor: Alternative solutions for sludge reduction.

Sludge recovery/disposal represents one of the most crucial aspects related to the management of wastewater treatment plants. The most widely diffused technology for the treatment of industrial and municipal wastewaters is the conventional activated sludge (CAS) process, which is characterized by a relatively high excess sludge production. Different technical solutions are proposed in the literature for sludge minimization and they can be applied either on wastewater line (WL) or sludge line (SL). This work is focused on different approaches based on the use of Thermophilic Aerobic Membrane Reactor (TAMR): this can be added to a CAS plant, and integrated to WL or SL, yielding a significant sludge reduction. The process performance was analysed in terms of volatile solids (VS) reduction and specific sludge production. The TAMR was tested both at full-scale and pilot-scale with different feeding substrates: industrial wastewater for the full-scale plant; industrial wastewater, sludge and a mix of these for the pilot-scale plants. The results obtained are: (i) good solids removal (38-90% and 40-50% in terms of VS for sludge and mix of industrial wastewater and sludge, respectively), (ii) low specific sludge production (0.01-0.09 kgVSS produced kgCOD removed-1 for industrial wastewater and 0.014-0.069 kgVSS produced kgCOD removed-1 for mix of industrial wastewater and sludge) and (iii) a significant reduction of sludge when CAS is improved with the TAMR technology.

Valorization of agro-industry residues in the building and environmental sector: A review.

Environmental pollution has become a relevant issue as the population rises and resources decrease. Reuse and recycling still have the greatest potential as they turn the waste into a new resource, representing the 'closed-loop' step of a circular economy (CE). Looking for new applications for agro-industry waste represents both an environmental issue, as its incorrect disposal is a cause of pollution, and a chance to exploit zero-cost natural wastes. The present review, with around 200 articles examined, focuses on possible reuses of these residues in (a) building construction, as additives to produce thermal and acoustic insulation panels, and (b) in water treatments, exploited for removal of pollutants. The selected materials (coconut, coffee, corn, cotton and rice) have industry production wastes with suitable applications in both sectors and huge worldwide availability; their reuse may thus represent a new resource, with an impact based on the production rate and the possible replacement of current inorganic materials. Along with possible implementation of the selected materials in the building industry and environmental engineering, a brief description of the production and supply chain are provided.

Treatments for color removal from wastewater: State of the art.

It is evident from many recent papers that release of colored wastewater into the environment is source of pollution and this is a problem that particularly affect textile, dyeing and food industries. The review: (i) presents an analysis of various mechanisms involved in the different processes for color removal; (ii) describes conveniences and disadvantages that may exist in adopting one type of treatment in spite of another; (iii) reports the results of approximately 180 experimental tests. Both examples of treatments already widely applied to the real scale and still in the experimental phase are reported. This work focuses on different types of chemical/physical, chemical, electrochemical and biological processes applied in the field of color removal from industrial wastewater. Common chemical/physical treatments such as coagulation/flocculation, adsorption and membrane filtration as well as chemical-type processes are discussed, both those that exploit the traditional oxidizing chemical agents such as Ozone, H2O2 and reactive based on chlorine and those based on the principle of advanced chemical oxidation. In particular, both Hydroxyl radical based Advanced Oxidation Processes (AOPs) and Sulfate radical based AOPs are reported. The most commonly used Electrochemical processes for the removal of color are also presented as well as biological treatments. Based on more than 200 papers, this review provides important information on the use, effectiveness, advantages and downsides of the various treatments aimed at removing the color from the wastewater with a look at the technologies still under development.

Process auditing and performance improvement in a mixed wastewater-aqueous waste treatment plant.

The wastewater treatment process is based on complex chemical, physical and biological mechanisms that are closely interconnected. The efficiency of the system (which depends on compliance with national regulations on wastewater quality) can be achieved through the use of tools such as monitoring, that is the detection of parameters that allow the continuous interpretation of the current situation, and experimental tests, which allow the measurement of real performance (of a sector, a single treatment or equipment) and comparison with the following ones. Experimental tests have a particular relevance in the case of municipal wastewater treatment plants fed with a strong industrial component and especially in the case of plants authorized to treat aqueous waste. In this paper a case study is presented where the application of management tools such as careful monitoring and experimental tests led to the technical and economic optimization of the plant: the main results obtained were the reduction of sludge production (from 4,000 t/year w.w. (wet weight) to about 2,200 t/year w.w.) and operating costs (e.g. from 600,000 €/year down to about 350,000 €/year for reagents), the increase of resource recovery and the improvement of the overall process performance.

Treatment of high strength aqueous wastes in a thermophilic aerobic membrane reactor (TAMR): performance and resilience.

In the present work, the thermophilic aerobic membrane reactor technology was studied for the treatment of high strength aqueous wastes mainly containing dyes, surfactants and solvents. The thermophilic biomass resilience and the process stability under critical conditions (such as rapid rise of the mixed liquor pH, oxygen supply interruption, etc.) were also evaluated. The experimental work was carried out with the use of a pilot plant at semi-industrial scale, which was managed throughout for 14 months; the operation temperature was 49 °C and the organic loading rate was increased from 3 to 12 kgCOD m-3 d-1. Critical conditions, especially the interruption of oxygen supply, affected the pilot plant performance but did not cause a complete system break down. After the temporary reduction of process performance, also proven by the decrease in the oxygen consumption, the normal working conditions were restored. Moreover, the longer non-aerated phase involved a significant reduction (40%) of volatile suspended solids concentration in the biological reactor and the increase of 30% in foaming power; nevertheless, once the oxygen supply was reactivated, optimal conditions were rapidly restored. Therefore, the study showed the high resilience of the thermophilic biomass, which was able to recover full functionality after critical events.

Leaching behaviour of municipal solid waste incineration bottom ash: From granular material to monolithic concrete.

The aim of this work was to assess the leaching behaviour of the bottom ash derived from municipal solid waste incineration (MSWI) used in concrete production. In particular, the release of pollutants was evaluated by the application of different leaching tests, both on granular materials and monolithic samples (concrete mixtures cast with bottom ash). The results confirmed that, according to Italian regulations, unwashed bottom ashes present critical issues for the use as alternative aggregates in the construction sector due to the excessive release of pollutants; instead, the leachate from washed bottom ashes was similar to natural aggregates. The concentration of pollutants in the leachate from concrete mixtures was lower than regulation limits for reuse. The crushing process significantly influenced the release of pollutants: this behaviour was due both to the increase in surface area and the release of contaminants from cement. Moreover, the increase in contact time (up to 64 days) involved more heavy metals to be released.

Treatment of sewage sludge in a thermophilic membrane reactor (TMR) with alternate aeration cycles.

The management of sewage sludge is becoming a more and more important issue, both at national and international level, in particular due to the uncertain recovery/disposal future options. Therefore, it is clear that the development of new technologies that can mitigate the problem at the source by reducing sludge production is necessary, such as the European Directive 2008/98/EC prescribes. This work shows the results obtained with a thermophilic membrane reactor, for processing a biological sludge derived from a wastewater treatment plant (WWTP) that treats urban and industrial wastewater. Sewage sludge was treated in a thermophilic membrane reactor (TMR), at pilot-scale (1 m(3) volume), with alternate aeration cycles. The experimentation was divided into two phases: a "startup phase" during which, starting with a psychrophilic/mesophilic biomass, thermophilic conditions were progressively reached, while feeding a highly biodegradable substrate; the obtained thermophilic biomass was then used, in the "regime phase", to digest biological sludge which was fed to the plant. Good removal yields were observed: 64% and 57% for volatile solids (VS) and total COD (CODtot), respectively, with an average hydraulic retention time (HRT) equal to 20 d, an organic loading rate (OLR) of about 1.4-1.8 kg COD m(-3) d(-1) and aeration/non aeration cycles alternated every 4 h.

Methodological approach for the optimization of drinking water treatment plants' operation: a case study.

Critical barriers to safe and secure drinking water may include sources (e.g. groundwater contamination), treatments (e.g. treatment plants not properly operating) and/or contamination within the distribution system (infrastructure not properly maintained). The performance assessment of these systems, based on monitoring, process parameter control and experimental tests, is a viable tool for the process optimization and water quality control. The aim of this study was to define a procedure for evaluating the performance of full-scale drinking water treatment plants (DWTPs) and for defining optimal solutions for plant upgrading in order to optimize operation. The protocol is composed of four main phases (routine and intensive monitoring programmes - Phases 1 and 2; experimental studies - Phase 3; plant upgrade and optimization - Phase 4). The protocol suggested in this study was tested in a full-scale DWTP placed in the North of Italy (Mortara, Pavia). The results outline some critical aspects of the plant operation and permit the identification of feasible solutions for the DWTP upgrading in order to optimize water treatment operation.

Why use a thermophilic aerobic membrane reactor for the treatment of industrial wastewater/liquid waste?

This paper describes the advantages of thermophilic aerobic membrane reactor (TAMR) for the treatment of high strength wastewaters. The results were obtained from the monitoring of an industrial and a pilot scale plant. The average chemical oxygen demand (COD) removal yield was equal to 78% with an organic loading rate (OLR) up to 8-10 kgCOD m(-3) d(-1) despite significant scattering of the influent wastewater composition. Total phosphorus (TP) was removed with a rate of 90%, the most important removal mechanism being chemical precipitation (as hydroxyapatite, especially), which is improved by the continuous aeration that promotes phosphorus crystallization. Moreover, surfactants were removed with efficiency between 93% and 97%. Finally, the experimental work showed that thermophilic processes (TPPs) are complementary with respect to mesophilic treatments.

Reducing the chlorine dioxide demand in final disinfection of drinking water treatment plants using activated carbon.

Chlorine dioxide is one of the most widely employed chemicals in the disinfection process of a drinking water treatment plant (DWTP). The aim of this work was to evaluate the influence of the adsorption process with granular activated carbon (GAC) on the chlorine dioxide consumption in final oxidation/disinfection. A first series of tests was performed at the laboratory scale employing water samples collected at the outlet of the DWTP sand filter of Cremona (Italy). The adsorption process in batch conditions with seven different types of GAC was studied. A second series of tests was performed on water samples collected at the outlet of four GAC columns installed at the outlet of the DWTP sand filter. The results showed that the best chlorine dioxide demand (ClO2-D) reduction yields are equal to 60-80% and are achieved in the first 30 min after ClO2 addition, during the first 16 days of the column operation using a mineral, coal-based, mesoporous GAC. Therefore, this carbon removes organic compounds that are more rapidly reactive with ClO2. Moreover, a good correlation was found between the ClO2-D and UV absorbance at wavelength 254 nm using mineral carbons; therefore, the use of a mineral mesoporous GAC is an effective solution to control the high ClO2-D in the disinfection stage of a DWTP.

How can sludge dewatering devices be assessed? Development of a new DSS and its application to real case studies.

A key issue in biological Waste Water Treatment Plants (WWTPs) operation is represented by the sludge management. Mechanical dewatering is a crucial stage for sludge volume reduction; though, being a costly operation, its optimization is required. We developed an original experimental methodology to evaluate the technical (dewatering efficiency) and financial (total treatment costs) performance of dewatering devices, which might be used as a DSS (Decision Support System) for WWTP managers. This tool was then applied to two real case studies for comparing, respectively, three industrial size centrifuges, and two different operation modes of the same machine (fixed installation vs. outsourcing service). In both the cases, the best option was identified, based jointly on economic and (site-specific) technical evaluations.

Reduction of pathogens in greywater with biological and sustainable treatments selected through a multicriteria approach.

Non-potable reuse of greywater (GW) can represent a valid alternative to freshwater consumption, satisfying the Sustainable Development Goals promoted by United Nations. The Multi-Criteria Analysis (MCA) was applied to select the most suitable processes for the reduction of microbiological contamination in GW. A pilot plant, including horizontal flow constructed wetland (CW) and anaerobic filtration (AF) in parallel, best treatment options according to MCA results, was built to treat GW collected from a Venezuelan family. (i) The removal efficiency of microbiological parameters, and (ii) the turbidity as possible microbiological contamination indicator and possible influence factor of disinfection treatment, were investigated. Except for Escherichia coli (4.1 ± 0.9 log reduction with AF), CW achieved the best reductions yields for total coliforms, faecal coliforms, and Salmonella, respectively equal to 3.1 ± 0.5 log, 4.3 ± 0.5 log, and 2.9 ± 0.4 log. In accordance with Venezuelan legislation and WHO guidelines, GW treated with CW was found to be suitable for irrigation reuse for non-edible crops. However, the reduction of pathogens by CW should be considered as a preliminary and not complete disinfection treatment. To reuse GW, especially in the irrigation of edible crops, stronger disinfection treatment should be considered as a complement to the preliminary disinfection performed by CW, to avoid any kind of risk. No significant correlation was found for turbidity either as a possible predictor of microbiological contamination or as an influence on biological disinfection.

Discussion about the Latest Findings on the Possible Relation between Air Particulate Matter and COVID-19.

Since SARS-CoV-2 was identified, the scientific community has tried to understand the variables that can influence its spread. Several studies have already highlighted a possible link between particulate matter (PM) and COVID-19. This work is a brief discussion about the latest findings on this topic, highlighting the gaps in the current results and possible tips for future studies. Based on the literature outcomes, PM is suspected to play a double role in COVID-19: a chronic and an acute one. The chronic role is related to the possible influence of long-term and short-term exposure to high concentrations of PM in developing severe forms of COVID-19, including death. The acute role is linked to the possible carrier function of PM in SARS-CoV-2. The scientific community seems sure that the inflammatory effect on the respiratory system of short-term exposure to a high concentration of PM, and other additional negative effects on human health in cases of longer exposure, increases the risk of developing a more severe form of COVID-19 in cases of contagion. On the contrary, the results regarding PM acting as a carrier of SARS-CoV-2 are more conflicting, especially regarding the possible inactivation of the virus in the environment, and no final explanation on the possible acute role of PM in the spread of COVID-19 can be inferred.

Thermophilic biological fluidized bed reactor in sludge line reduces greenhouse gas emissions in wastewater treatment system.

Greenhouse gas (GHG) emissions represent one of the main drawbacks of wastewater (WW) treatment. However, results of a detailed estimation of the emissions can be a valid tool to define optimal solutions for minimizing impact of WW treatment system on the environment. Thermophilic biological fluidized bed reactor (TBFBR) has been recently proposed as an alternative solution for biological sludge minimization in wastewater treatment plant (WWTPs). In this work, 5 diverse scenarios of sludge line composition were studied and combined with 5 diverse sludge disposal options. GHG emissions in 25 combinations were fully investigated to define optimal sludge treatment and disposal option. Results suggested that TBFBR help to reduce net emitted GHGs with respect to scenario with conventional stabilization treatment in sludge line (anaerobic digestion) (-32.3 ± 3.55 %) thanks to (i) the reuse in water line of the aqueous residue of TBFBR as alternative carbon source, (ii) the significant minimization of sludge production, and (iii) the contained impact of gross GHG emissions due to the energy consumption of this process. The strong minimization of sludge also led to a decisive reduction in GHG emissions in the subsequent phases of transport, additional treatments, and final disposal making the choice of the disposal option indifferent on the overall GHG emission estimation. Moreover, the coupling of processes for the simultaneous and preventive maximization of energy recovery (TCH, and AnaD) before sludge minimization in TBFBR determined a limited reduction of GHG emission compared to scenario with TBFBR alone (-3.71 ± 1.47 %).

The performance evaluation of wastewater service: a protocol based on performance indicators applied to sewer systems and wastewater treatment plants.

This research aimed to identify a tool to objectively analyse the performance and the environmental contextualisation of sewer systems (SwSs) and wastewater treatment plants (WWTPs). This procedure performs assessment by calculating performance indices which could be subsequently applied to SwSs and WWTPs with different characteristics. The proposed tool can be applied conveniently over the years by managers of integrated urban water management systems for the analysis of different realities also allowing the evaluation of the effects of upgrades carried out during the management phases. The proposed analysis allows the optimisation of SwSs and can profitably guide the choice and the priority among possible interventions for the sewerage infrastructure and WWTPs providing a verification and evaluation protocol as well as a financial planning tool.

How to Produce an Alternative Carbon Source for Denitrification by Treating and Drastically Reducing Biological Sewage Sludge.

Minimizing the biological sewage sludge (BSS) produced by wastewater treatment plants (WWTPs) represents an increasingly difficult challenge. With this goal, tests on a semi-full scale Thermophilic Alternate Membrane Biological Reactor (ThAlMBR) were carried out for 12 months. ThAlMBR was applied both on thickened (TBSS) and digested biological sewage sludge (DBSS) with alternating aeration conditions, and emerged: (i) high COD removal yields (up to 90%), (ii) a low specific sludge production (0.02-0.05 kgVS produced/kgCODremoved), (iii) the possibility of recovery the aqueous carbon residue (permeate) in denitrification processes, replacing purchased external carbon sources. Based on the respirometric tests, an excellent biological treatability of the permeate by the mesophilic biomass was observed and the denitrification kinetics reached with the diluted permeate ((4.0 mgN-NO3-/(gVSS h)) were found comparable to those of methanol (4.4 mgN-NO3-/(gVSS h)). Moreover, thanks to the similar results obtained on TBSS and DBSS, ThAlMBR proved to be compatible with diverse sludge line points, ensuring in both cases an important sludge minimization.

Applications of Up-Flow Anaerobic Sludge Blanket (UASB) and Characteristics of Its Microbial Community: A Review of Bibliometric Trend and Recent Findings.

The interest in research on up-flow anaerobic sludge blanket (UASB) reactors is growing. The meta-analysis of bibliometric data highlighted the growing interest in four diverse topics: (i) energy recovery production; (ii) combination with other treatments; (iii) the study of processes for the removal of specific pollutants and, (iv) characterization of microbial community and granular sludge composition. In particular, the papers published in the first 6 months of 2021 on this process were selected and critically reviewed to highlight and discuss the results, the gaps in the literature and possible ideas for future research. Although the state of research on UASB is to be considered advanced, there are still several points that will be developed in future research such as the consolidation of the results obtained on a semi-industrial or real scale, the use of real matrices instead of synthetic ones and a more in-depth study of the effect of substances such as antibiotics on the microbiota and microbiome of UASB granular biomass. To date, few and conflicting data about the environmental footprint of UASB are available and therefore other studies on this topic are strongly suggested.

Photoelectrocatalysis on TiO2 meshes: different applications in the integrated urban water management.

Recently, among AOPs, photoelectrocatalysis (PEC) on TiO2 is gaining interest. In this study, five different real waters sampled in four different points of the integrated urban water management (IUWM) system were tested with PEC and UV alone, for comparison. This work aims to verify the effect of the PEC suggesting the optimal position in IUWM system where the PEC should be located to obtain the best performance. In groundwaters (GWs), PEC effectively removed atrazine-based compounds (> 99%), trichloroethylene, and perchloroethylene (96%), after 15 min of reaction time. However, given the low concentrations of emerging compounds, the synergistic effect of UV radiation with the catalyst and with the polarization of the mesh was not visible, with very few differences compared with the results obtained with UV alone. Pharmaceutical industrial wastewater (IWW) showed a significant increase in biodegradability after 2 h, both if subjected to PEC or UV (200%), despite the absence of COD removal. The PEC applied on IWW from a sewage sludge treatment plant allowed to effectively remove the COD (39.6%) and increase the biodegradability (300%). Good results in terms of COD removal (33.9%) and biodegradability increase (+900%) were also achieved testing PEC on wastewater treatment plant effluent. Except for GWs, PEC allowed significant EEO savings respect to UV alone (76.2-99.1%).

Can particulate matter be identified as the primary cause of the rapid spread of CoViD-19 in some areas of Northern Italy?

Northern Italy was the most affected by CoViD-19 compared to other Italian areas and comprises zones where air pollutants concentration was higher than in the rest of Italy. The aim of the research is to determine if particulate matter (PM) has been the primary cause of the high CoViD-19 spread rapidity in some areas of Northern Italy. Data of PM for all the 41 studied cities were collected from the local environmental protection agencies. To compare air quality data with epidemiological data, a statistical analysis was conducted identifying the correlation matrices of Pearson and Spearman, considering also the possible incubation period of the disease. Moreover, a model for the evaluation of the epidemic risk, already proposed in literature, was used to evaluate a possible influence of PM on CoViD-19 spread rapidity. The results exclude that PM alone was the primary cause of the high CoVid-19 spread rapidity in some areas of Northern Italy. Further developments are necessary for a better comprehension of the influence of atmospheric pollution parameters on the rapidity of spread of the virus SARS-CoV-2, since a synergistic action with other factors (such as meteorological, socio-economic and cultural factors) could not be excluded by the present study.

Analysis of lockdown for CoViD-19 impact on NO2 in London, Milan and Paris: What lesson can be learnt?

Nitrogen dioxide (NO2) can have harmful effects on human health and can act as a precursor for the formation of other air pollutants in urban environment such as secondary PM2.5 and ozone. The lockdown measures for CoViD-19 allowed to simulate on a large scale the massive and prolonged reduction of road traffic (the main source for NO2 in urban environment). This work aims to selectively assess the maximum impact that total traffic blocking measures can have on NO2. For this reason, three megacities (London, Milan and Paris) were chosen which had similar characteristics in terms of climatic conditions, population, policies of urban traffic management and lockdown measures. 52 air quality control units have been used to compare data measured in lockdown and in the same periods of previous years, highlighting a significant decrease in NO2 concentration due to traffic (London: 71.1 % - 80.8 %; Milan: 8.6 % - 42.4 %; Paris: 65.7 % - 79.8 %). In 2020 the contribution of traffic in London, Milan and Paris dropped to 3.3 ± 1.3 µg m-3, 6.1 ± 0.8 µg m-3, and 13.4 ± 1.5 µg m-3, respectively. Despite the significant reduction in the NO2 concentration, in UT stations average NO2 concentrations higher than 40 µg m-3 were registered for several days. In order to reduce the pollution, the limitation of road traffic could be not enough, but a vision also aimed at rethink the vehicles and their polluting effects should be developed.