This study explores sustainable methods for Sardine Processing Waste (SPW) valorization. Two approaches were investigated: (a) SPW microbial pretreatment adding Saccharomyces cerevisiae or Bacillus sp. in a two-stage anaerobic digestion (AD) for enzyme and biomethane production and (b) a single-stage AD without SPW pretreatment. Both S. cerevisiae and Bacillus sp. secreted proteases (0.66 and 0.58 U mL−1, respectively) and lipases (3.8 and 4.3 U mL−1, respectively) during hydrolysis, thus reducing viscosity (2.8 and 2.9 cP, respectively) compared with the untreated SPW (4.1 cP). Biomethane production was higher in the single-stage AD (1174 mL CH4 g−1 VS−1) when compared with the two-stage AD (821.5 and 260 mL CH4 g−1 VS−1 with S. cerevisiae and Bacillus sp., respectively). S. cerevisiae addition enhanced SPW degradation as implied by VS and sCOD values (70 and 84%, respectively), but this also resulted in a higher toxicity due to a three-fold increment in NH4-N content, reducing methanogen activity. This research demonstrates the innovative application of S. cerevisiae, a common bread-making yeast, in the biotechnological enhancement of SPW hydrolysis. Non-genetically engineered S. cerevisiae not only co-produced proteases and lipases but also significantly improved solubilization, degradation, and viscosity reduction, thereby rendering the yeast a key player in solid fish waste valorization, beyond its traditional applications.
During the COVID-19 pandemic, wastewater-based epidemiology (WBE) has been engaged to complement medical surveillance and in some cases to also act as an early diagnosis indicator of viral spreading in the community. Most efforts worldwide by the scientific community and commercial companies focus on the formulation of protocols for SARS-CoV-2 analysis in wastewater and approaches addressing the quantitative relationship between WBE and medical surveillance are lacking. In the present study, a mathematical model is developed which uses as input the number of daily positive medical tests together with the highly non-linear shedding rate curve of individuals to estimate the evolution of global virus shedding rate in wastewater along calendar days. A comprehensive parametric study by the model using as input actual medical surveillance and WBE data for the city of Thessaloniki (~700,000 inhabitants, North Greece) during the outbreak of November 2020 reveals the conditions under which WBE can be used as an early warning tool for predicting pandemic outbreaks. It is shown that early warning capacity is different along the days of an outbreak and depends strongly on the number of days apart between the day of maximum shedding rate of infected individuals in their disease cycle and the day of their medical testing. The present data indicate for Thessaloniki an average early warning capacity of around 2 days. Moreover, the data imply that there exists a proportion between unreported cases (asymptomatic persons with mild symptoms that do not seek medical advice) and reported cases. The proportion increases with the number of reported cases. The early detection capacity of WBE improves substantially in the presence of an increasing number of unreported cases. For Thessaloniki at the peak of the pandemic in mid-November 2020, the number of unreported cases reached a maximum around 4 times the number of reported cases.
Detection of SARS-CoV-2 in sewage has been employed by several researchers as an alternative early warning indicator of virus spreading in communities, covering both symptomatic and asymptomatic cases. A factor that can seriously mislead the quantitative measurement of viral copies in sewage is the adsorption of virus fragments onto the highly porous solids suspended in wastewater, making them inaccessible. This depends not only on the available amount of suspended solids, but also on the amount of other dissolved chemicals which may influence the capacity of adsorption. On this account, the present work develops a mathematical framework, at various degrees of spatial complexity, of a physicochemical model that rationalizes the quantitative measurements of total virus fragments in sewage as regards the adsorption of virus onto suspended solids and the effect of dissolved chemicals on it. The city of Thessaloniki in Greece is employed as a convenient case study to determine the values of model variables. The present data indicate the ratio of the specific absorption (UV
Epidemic spread models are useful tools to study the spread and the effectiveness of the interventions at a population level, to an epidemic. The workhorse of spatially homogeneous class models is the SIR-type ones comprising ordinary differential equations for the unknown state variables. The transition between different states is expressed through rate functions. Inspired by -but not restricted to- features of the COVID-19 pandemic, a new framework for modeling a disease spread is proposed. The main concept refers to the assignment of properties to each individual person as regards his response to the disease. A multidimensional distribution of these properties represents the whole population. The temporal evolution of this distribution is the only dependent variable of the problem. All other variables can be extracted by post-processing of this distribution. It is noteworthy that the new concept allows an improved consideration of vaccination modeling because it recognizes vaccination as a modifier of individuals response to the disease and not as a means for individuals to totally defeat the disease. At the heart of the new approach is an infection age model engaging a sharp cut-off. This model is analyzed in detail, and it is shown to admit self-similar solutions. A hierarchy of models based on the new approach, from a generalized one to a specific one with three dominant properties, is derived. The latter is implemented as an example and indicative results are presented and discussed. It appears that the new framework is general and versatile enough to simulate disease spread processes and to predict the evolution of several variables of the population during this spread.
The physicochemical and toxic properties of fly ash samples obtained from various coal combustion power plants were evaluated in this work using an integrated approach including chemical analyses and bioassays. Physicochemical analyses showed that Al, Ca, Fe, Mg and Si were the elements presented in high concentrations in all solid samples. The results of the chemical analysis of eluates deduced by the application of standard leaching tests according to EN 12457-2 and TCLP methods indicated that the compounds contained in the fly ash samples presented a potential to be transferred to the liquid phase depending upon the leaching method used. The pH values of the EN eluates were in most cases in the high alkaline range, ranging from 9.5 up to 12.7, while the pH value of TCLP eluates varied between 3.9 and 7.5. The leachability of the compounds was higher in TCLP leaching test, indicating that the initial pH value of the leaching medium affected significantly the transfer of these elements to the liquid phase. The photobacterium Vibrio fischeri (Microtox test), the crustaceans Daphnia magna and the rotifers Brachionus calysiflorus were used for the toxicity measurement of the eluates obtained by the EN leaching test, suggesting that the toxicity of the eluate samples depended on the test organism used. The toxicity of the fly ash samples and the corresponding solid filter residuals that were remained after the EN and TCLP leaching tests was also measured using the Microtox Basic Solid Phase Test.
Traditionally, anaerobic digestion has been applied to mixed sludge, combining primary sludge (PS) with secondary sludge. However, recent research has unveiled the advantages of dedicated PS digestion due to its higher energy content. Anaerobic digestion (AD) of primary sewage sludge can offer a sustainable solution for managing sewage sludge while generating renewable energy. The present study provides a comprehensive examination of the current state of knowledge regarding the anaerobic digestion of PS. Co-digestion of PS with organic substrates, including food waste and agro-industrial residues, emerges as a promising approach to boost biogas production. Additionally, the utilization of additives such as glucose and clay minerals has shown potential in improving methane yield. Critical factors affecting AD, such as pretreatment methods, carbon-to-nitrogen (C/N) ratio, temperature, pH, volatile fatty acids (VFAs) levels, organic loading rates (OLR), inoculum-to-substrate ratio (ISR), and the role of additives, have been meticulously studied. Finally, this review consolidates existing knowledge to advance our understanding of primary sewage sludge anaerobic digestion, fostering more efficient and sustainable practices in sludge management and renewable energy generation.
Abstract Accounting for SARS-CoV-2 adsorption on solids suspended in wastewater is a necessary step towards the reliable estimation of virus shedding rate in a sewerage system, based on measurements performed at a terminal collection station, i.e., at the entrance of a wastewater treatment plant. This concept is extended herein to include several measurement stations across a city to enable the estimation of spatial distribution of virus shedding rate. This study presents a pioneer general model describing the most relevant physicochemical phenomena with a special effort to reduce the complicated algebra. This is performed both in the topology regime, introducing a discrete-continuous approach, and in the domain of independent variables, introducing a monodisperse moment method to reduce the dimensionality of the resulting population balance equations. The resulting simplified model consists of a large system of ordinary differential equations. A sensitivity analysis is performed with respect to some key parameters for a single pipe topology. Specific numerical techniques are employed for the integration of the model. Finally, a parametric case study for an indicative—yet realistic—sewerage piping system is performed to show how the model is applied to SARS-CoV-2 adsorption on wastewater solids in the presence of other competing species. This is the first model of this kind appearing in scientific literature and a first step towards setting up an inverse problem to assess the spatial distribution of virus shedding rate based on its concentration in wastewater.
<p>Biofilms are bacterial communities embedded in an extracellular matrix, able to adhere to surfaces. A deeper knowledge of the biofilm as a whole will aid the development of efficient methods to control deleterious biofilms (clinical biofilms, biofouling) or to enhance beneficial ones (waste-water treatment, bio-filtration). P. fluorescens has been widely studied, this strain produces bioactive secondary metabolites, and forms biofilms[1]. Several experimental set-ups have been widely used for in vitro biofilm cultivation of P. fluorescens, even if a deep characterization among different culture conditions is still lacking in the literature. This work, based on previous studies[2], is focused on the investigation of growth conditions on biofilm structure and properties. Growth kinetics of P. fluorescens biofilms was characterized in vitro under stagnant and flow-controlled conditions, using a rotating annular bioreactor. Two different supports in borosilicate glass and polycarbonate have been used. Bacterial growth kinetics has been measured through bio-turbidity analysis and TOC/DOC quantification. Biofilm morphology has been quantified through optical microscopy and image analysis by measuring the fraction of support surface covered by biofilm. The wetting properties of the biofilm layers have been investigated by using an innovative device, named Kerberos®, able to control centrifugal and gravitational forces acting on a single droplet placed on a surface[3]. The evolution of the droplet shape and position was measured as function of the imposed stress, to quantify wetting of different biofilm coated samples, following already assessed methodologies[4]. Different chemo-physical environments, investigated by changing growth medium, physical support, and imposed flow stress, induced different growth kinetics, biofilm morphology, and wetting properties. Accurate experimental measurements allowed us to estimate in a quantitative way the influence of investigated parameters on specific morphologic measurements.</p> <div><br /> <div> <p>[1] Brittan S. Scales and others, ‘Microbiology, Genomics, and Clinical Significance of the Pseudomonas Fluorescens Species Complex, an Unappreciated Colonizer of Humans’, Clinical Microbiology Reviews, 27.4 (2014), 927–48 <https://doi.org/10.1128/CMR.00044-14>.</p> </div> <div> <p>[2] Federica Recupido and others, ‘The Role of Flow in Bacterial Biofilm Morphology and Wetting Properties’, Colloids and Surfaces B: Biointerfaces, 2020 <https://doi.org/10.1016/j.colsurfb.2020.111047>.</p> </div> <div> <p>[3] Sotiris P. Evgenidis and others, ‘Kerberos: A Three Camera Headed Centrifugal/Tilting Device for Studying Wetting/Dewetting under the Influence of Controlled Body Forces’, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017 <https://doi.org/10.1016/j.colsurfa.2016.07.079>.</p> </div> <div> <p>[4] Inmaculada Ríos-López and others, ‘Effect of Initial Droplet Shape on the Tangential Force Required for Spreading and Sliding along a Solid Surface’, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2018 <https://doi.org/10.1016/j.colsurfa.2018.04.004>.</p> </div> </div>
