Ignazio Marcello Mancini

Application of fuzzy logic and sensitivity analysis for soil contamination hazard classification.

The present article is aimed at illustrating a methodology for a rapid and effective assessment of pollution hazard connected with the presence of uncontrolled landfills. In particular, by means of a fuzzy approach, the criterion adopted allowed a comparison of the results obtained from a cross analysis of some intrinsic characteristics of the single landfills and the territory where they are located. Their identification shows the most relevant environmental problem. Therefore, we have classified each site within a hazard scale enabling us to understand which one requires to be checked more urgently, to do instrumental surveys and, if needed, to do restoration and reclamation. Moreover, the sensitivity analysis we carried out allowed us to identify which is the best membership function belonging and which is the best defuzzification method. That is, in particular, the trapezoidal function and the centroid method. The proposed fuzzy approach, supported by the sensitivity analysis, has revealed to be an important tool for supporting decisions, in order to optimise technical and economic resources.

Validation of an analytical method for simultaneous high-precision measurements of greenhouse gas emissions from wastewater treatment plants using a gas chromatography-barrier discharge detector system.

Wastewater treatment plants (WWTPs) emit CO2 and N2O, which may lead to climate change and global warming. Over the last few years, awareness of greenhouse gas (GHG) emissions from WWTPs has increased. Moreover, the development of valid, reliable, and high-throughput analytical methods for simultaneous gas analysis is an essential requirement for environmental applications. In the present study, an analytical method based on a gas chromatograph (GC) equipped with a barrier ionization discharge (BID) detector was developed for the first time. This new method simultaneously analyses CO2 and N2O and has a precision, measured in terms of relative standard of variation RSD%, equal to or less than 6.6% and 5.1%, respectively. The methods detection limits are 5.3ppmv for CO2 and 62.0ppbv for N2O. The methods selectivity, linearity, accuracy, repeatability, intermediate precision, limit of detection and limit of quantification were good at trace concentration levels. After validation, the method was applied to a real case of N2O and CO2 emissions from a WWTP, confirming its suitability as a standard procedure for simultaneous GHG analysis in environmental samples containing CO2 levels less than 12,000mg/L.

Monitoring the aeration efficiency and carbon footprint of a medium-sized WWTP: experimental results on oxidation tank and aerobic digester

ABSTRACT The efficiency of aeration systems should be monitored to guarantee suitable biological processes. Among the available tools for evaluating the aeration efficiency, the off-gas method is one of the most useful. Increasing interest towards reducing greenhouse gas (GHG) emissions from biological processes has resulted in researchers using this method to quantify N2O and CO2 concentrations in the off-gas. Experimental measurements of direct GHG emissions from aerobic digesters (AeDs) are not available in literature yet. In this study, the floating hood technique was used for the first time to monitor AeDs. The floating hood technique was used to evaluate oxygen transfer rates in an activated sludge (AS) tank of a medium-sized municipal wastewater treatment plant located in Italy. Very low values of oxygen transfer efficiency were found, confirming that small-to-medium-sized plants are often scarcely monitored and wrongly managed. Average CO2 and N2O emissions from the AS tank were 0.14 kgCO2/kgbCOD and 0.007 kgCO2,eq/kgbCOD, respectively. For an AeD, 3 × 10−10 kgCO2/kgbCOD direct CO2 emissions were measured, while CO2,eq emissions from N2O were 4 × 10−9 kgCO2,eq/kgbCOD. The results for the AS tank and the AeD were used to estimate the net carbon and energy footprint of the entire plant.

Methane oxidation in a biofilter (Part 1): Development of a mathematical model for designing and optimization.

The aim of this work is the evaluation of the efficiency of such a biofilter, through the application of a mathematical model which describes the biological oxidation process. This mathematical model is able to predict the efficiency of the system under varying operating conditions. Literature data have been used in order to build the model. The factors that mostly affect the process and which actually regulate the entire process have been highlighted in this work. Specifically, it was found that temperature, flow and methane concentration are the most important parameters that influence the system. The results obtained from the mathematical model showed also that the biofilter system is simple to implement and manage and allows the achievement of high efficiency of methane oxidation. In the optimal conditions for temperature (between 20–30°C), residence time (between 0.7–0.8 h) and methane molar fraction (between 20–25%) the efficiency of methane oxidation could be around 50%.

Sustainable mechanical biological treatment of solid waste in urbanized areas with low recycling rates

Landfill is still the main technological facility used to treat and dispose municipal solid waste (MSW) worldwide. In developing countries, final dumping is applied without environmental monitoring and soil protection since solid waste is mostly sent to open dump sites while, in Europe, landfilling is considered as the last option since reverse logistic approaches or energy recovery are generally encouraged. However, many regions within the European Union continue to dispose of MSW to landfill, since modern facilities have not been introduced owing to unreliable regulations or financial sustainability. In this paper, final disposal activities and pre-treatment operations in an area in southern Italy are discussed, where final disposal is still the main option for treating MSW and the recycling rate is still low. Mechanical biological treatment (MBT) facilities are examined in order to evaluate the organic stabilization practices applied for MSW and the efficiencies in refuse derived fuel production, organic waste stabilization and mass reduction. Implementing MBT before landfilling the environmental impact and waste mass are reduced, up to 30%, since organic fractions are stabilized resulting an oxygen uptake rate less than 1600 mgO2 h-1 kg-1VS, and inorganic materials are exploited. Based on experimental data, this work examines MBT application in contexts where recycling and recovery activities have not been fully developed. The evidence of this study led to state that the introduction of MBT facilities is recommended for developing regions with high putrescible waste production in order to decrease environmental pollution and enhance human healthy.

Quantification of CO2 and N2O Emissions from a Pilot-Scale Aerobic Digester, Towards the Validation and Calibration of the First Activated Sludge Model for Aerobic Digestion (AeDM1)

In this study, a pilot aerobic digester was developed and operated to monitor N2O and CO2 emissions using the off-gas technique. A 30-days monitoring campaign was carried out to evaluate the impact of aerobic digestion (AeD) in Greenhouse Gas (GHG) estimation. After the achievement of the equilibrium conditions for a conventional AeD, a monitoring campaign was performed assuming 20 days as sludge retention time. The N2O gas flux was found equal to 71.7 mgN2O m−2min−1 against 16914 mgCO2 m−2min−1 calculated for CO2, demonstrating that strong aerobic oxidation processes occur inside the digester. In terms of equivalent CO2, N2O covers the 55% of the total CO2,eq emissions and CO2 the 45%. The experimental campaigns were coupled with the development of a mathematical model for AeD, named Aerobic Digestion Model No. 1 (AeDM1). The Morris Method allowed us to carry out a sensitivity analysis on the main kinetic parameters, resulting that the maximum specific growth rate of heterotrophs is the more sensitive parameter. After the model calibration, the experimental results on the pilot digester were used to validate the model, inserting the data collected during the experimental tests as model inputs.

Methane oxidation in a biofilter (Part 2): A lab-scale experiment for model calibration

In this study an experimental study on a biological methane oxidation column presented with the aim to calibrate a mathematical model developed in an earlier study. The column was designed to reproduce at lab-scale a real biofilter trying to consider the more probable landfill boundary conditions. Although the methane oxidation efficiency in the column was lower than the expected (around 35%), an appropriate model implementation showed an acceptable agreement between the outcomes data of the model simulation and the experimental data (with Theils Inequality Coefficient value of 0.08). A calibrated model allows a better management of the biofilter performance in terms of methane oxidation.

Fuzzy Logic and Neuro-Fuzzy Networks for Environmental Hazard Assessment

Pollution and management of the environment are serious problems which concern the entire planet; the main responsibility should be attributed to human activities that contribute significantly to damage the environment, leading to an imbalance of natural ecosystems. In recent years, numerous studies focused on the three environmental compartments: soil, water and air. The pollution of groundwater is a widespread problem. The causes of pollution are often linked to human activities, including waste disposal.

CO2 and N2O from water resource recovery facilities: Evaluation of emissions from biological treatment, settling, disinfection, and receiving water body

Water resource recovery facilities (WRRFs) contribute to climate change and air pollution, as they are anthropogenic potential sources of direct and indirect emission of greenhouse gases (GHGs). Studies concerning the monitoring and accounting for GHG emissions from WRRFs are of increasing interest. In this study, the floating hood technique for gas collection was coupled with the off-gas method to monitor and apportion nitrous oxide (N2O) and carbon dioxide (CO2) emissions from both aerated and non-aerated tanks in a municipal water resource recovery facility, in order to investigate its carbon footprint (CFP). To our knowledge, this is the first time that the chamber technique was applied to evaluate gas fluxes from the settler, where an emission factor (EF) of 4.71 ∗ 10-5 kgCO2,eq kgbCOD-1 was found. Interesting results were found in the disinfection unit, which was the major contributor to direct N2O emissions (with a specific emission factor of 0.008 kgCO2,eq kgbCOD-1), due to the chemical interaction between hydroxylamine and the disinfectant agent (hypochlorite). The specific emission factor of the biological aerated tank was 0.00112 kgCO2,eq kgbCOD-1. The average direct CO2 emission was equal to 0.068 kgCO2 kgbCOD-1 from the activated sludge tank and to 0.00017 kgCO2 kgbCOD-1 from the secondary clarifier. Therefore, taking into account the contribution of both direct N2O and CO2 emissions, values of 0.069 kgCO2,eq kgbCOD-1, 0.008 kgCO2,eq kgbCOD-1 and 0.00022 kgCO2,eq kgbCOD-1, were found for the net CFP of the aerated compartment, the disinfection unit and the clarifier, respectively. The plant energy Footprint (eFP) was also evaluated, confirming that the aeration system is the major contributor to energy consumption, as well as to indirect CO2 emission, with a specific eFP of 1.49 kWh kgbCOD-1.

Environmental factors influencing landfill gas biofiltration: Lab scale study on methanotrophic bacteria growth

ABSTRACT The post-management of landfills represents an important challenge for landfill gas treatment. Traditional systems (energy recovery, flares, etc.) present technical problems in treating flow with low methane (CH4) concentrations. The objective of this study was to isolate methanotrophic bacteria from a field-scale biofilter in order to study the bacteria in laboratories and evaluate the environmental factors that mostly influence Microbial Aerobic Methane Oxidation (MAMO). The soil considered was sampled from the biofilter located in the landfill of Venosa (Basilicata Region, Italy) and it was mainly composed of wood chips and compost. The results showed that methanotrophic microorganisms are mainly characterized by a slow growth and a significant sensitivity to CH4 levels. Temperature and nitrogen (N) also have a very important role on their development. On the basis of the results, biofilters for biological CH4 oxidation can be considered a viable alternative to mitigate CH4 emissions from landfills.