Ludovico Pontoni

Use of chitosan and chitosan-derivatives to remove arsenic from aqueous solutions--a mini review.

Arsenic removal has become a relevant concern due to the final confirmation of its behaviour as chronic human carcinogen, corresponding to an ever-increasing contamination of water, soil and crops in many parts of the world. Developing easily accessible removal strategies is therefore a primary environmental matter. Chitosan and chitosan derivatives show good adsorption performances against arsenic removal and are considered low cost products, easily obtainable. This review provides a summary of recent advances of the application of these compounds in the area of sorption sciences for arsenate and arsenite removal from water, focusing on equilibrium and kinetic mechanisms.

Effect of the concentration of essential oil on orange peel waste biomethanization: Preliminary batch results.

The cultivation of orange (Citrus×sinensis) and its transformation is a major industry in many countries in the world, it leads to the production of about 25-30Mt of orange peel waste (OPW) per year. Until now many options have been proposed for the management of OPW but although they are technically feasible, in many cases their economic/environmental sustainability is questionable. This paper analyse at lab scale the possibility of using OPW as a substrate for anaerobic digestion. Specific objectives are testing the possible codigestion with municipal biowaste, verifying the effect on methane production of increasingly high concentration of orange essential oil (EO, that is well known to have antioxidant properties that can slower or either inhibit biomass activity) and obtaining information on the behaviour of d-limonene, the main EO component, during anaerobic digestion. The results indicate that OPW can produce up to about 370LnCH4/kgVS in mesophilic conditions and up to about 300LnCH4/kgVS in thermophilic conditions. The presence of increasingly high concentrations of EO temporary inhibits methanogenesis, but according to the results of batch tests, methane production restarts while d-limonene is partially degraded through a pathway that requires its conversion into p-cymene as the main intermediate.

Effect of total solids content on methane and volatile fatty acid production in anaerobic digestion of food waste

This work investigates the role of the moisture content on anaerobic digestion of food waste, as representative of rapidly biodegradable substrates, analysing the role of volatile fatty acid production on process kinetics. A range of total solids from 4.5% to 19.2% is considered in order to compare methane yields and kinetics of reactors operated under wet to dry conditions. The experimental results show a reduction of the specific final methane yield of 4.3% and 40.8% in semi-dry and dry conditions compared with wet conditions. A decreasing trend of the specific initial methane production rate is observed when increasing the total solids concentration. Because of lack of water, volatile fatty acids accumulation occurs during the first step of the process at semi-dry and dry conditions, which is considered to be responsible for the reduction of process kinetic rates. The total volatile fatty acids concentration and speciation are proposed as indicators of process development at different total solids content.

Thermal pretreatment of olive mill wastewater for efficient methane production: control of aromatic substances degradation by monitoring cyclohexane carboxylic acid

Anaerobic digestion is investigated as a sustainable depurative strategy of olive oil mill wastewater (OOMW). The effect of thermal pretreatment on the anaerobic biodegradation of aromatic compounds present in (OMWW) was investigated. The anaerobic degradation of phenolic compounds, well known to be the main concern related to this kind of effluents, was monitored in batch anaerobic tests at a laboratory scale on samples pretreated at mild (80 ± 1 °C), intermediate (90 ± 1 °C) and high temperature (120 ± 1 °C). The obtained results showed an increase of 34% in specific methane production (SMP) for OMWW treated at the lowest temperature and a decrease of 18% for treatment at the highest temperature. These results were related to the different decomposition pathways of the lignocellulosic compounds obtained in the tested conditions. The decomposition pathway was determined by measuring the concentrations of volatile organic acids, phenols, and chemical oxygen demand (COD) versus time. Cyclohexane carboxylic acid (CHCA) production was identified in all the tests with a maximum concentration of around 200 µmol L−1 in accordance with the phenols degradation, suggesting that anaerobic digestion of aromatic compounds follows the benzoyl-CoA pathway. Accurate monitoring of this compound was proposed as the key element to control the process evolution. The total phenols (TP) and total COD removals were, with SMP, the highest (TP 62.7% – COD 63.2%) at 80 °C and lowest (TP 44.9% - COD 32.2%) at 120 °C. In all cases, thermal pretreatment was able to enhance the TP removal ability (up to 42% increase).

Methane and VFA production in anaerobic digestion of rice straw under dry, semi-dry and wet conditions during start-up phase

ABSTRACT This work investigates the start-up phase of anaerobic digestion in wet, semi-dry and dry conditions of rice straw analysing the role of volatile fatty acid (VFA) production on process kinetics. Methane production yields and biodegradation kinetics in reactors operated under wet semi-dry and dry conditions were investigated. The experimental results showed a reduction in the specific final methane production yield of 57% and 63% in, respectively, semi-dry (TS = 14.8%) and dry (TS = 23.4%) conditions compared to wet (TS = 4.8%) conditions. The total VFA concentration and speciation are proposed as indicators of process development at different total solids content. High VFA concentrations were found in dry conditions, with a maximum total VFA concentration of 2110 mg/kg in dry conditions, 930 mg/kg in semi-dry conditions and 180 mg/kg in wet conditions.

Effect of Anaerobic Digestion on Rheological Parameters and Dewaterability of Aerobic Sludges from MBR and Conventional Activated Sludge Plants

The paper investigates and compares the characteristics of sludges produced by membrane Bio-Reactor (MBR) and Conventional Activated Sludge (CAS) systems. Stability and dewaterability of full-scale MBR and CAS treatment plants are measured and compared. Obtained results show that specific methane production is higher in CAS sludge compared to MBR sludge because of the higher solid retention time of the MBR. Nonetheless MBR sludge results to be characterized by a non-negligible biometanation potential (BMP). Methane production measured during BMP tests is around 250 NmL/gVS for MBR sludge, equaling 2/3 of methane production obtained, in similar condition, for CAS sludge. Dewaterability is evaluated by Specific Resistance to Filtration (SRF), Capillary Suction Time (CST) and Time To Filter (TTF) tests. Data obtained before and after the anaerobic digestion of the sludges show that the stabilization process affects much more the resistance to filtration of CAS sludge than the resistance to filtration of MBR sludge. The same trend is observed, for the other measured parameters. This is attributed to the variation of the rheological characteristics of the two sludges during the stabilization process, and to the different initial rheological properties of them due to the different selection process of the biomass deriving from the different biomass retention methods of MBR and CAS systems.

Dewaterability of CAS and MBR Sludge: Effect of Biological Stability and EPS Composition

AbstractThe dewaterability of sludge from two conventional activated sludge (CAS) and three membrane bioreactor (MBR)–based wastewater treatment plants is investigated prior to and after anaerobic ...

Optimization of the treatment cycle of pressed-off leachate produced in a facility processing the organic fraction of municipal solid waste

The paper investigates, at a laboratory scale, the applicability of anaerobic digestion for the treatment of pressed-off leachate produced in a biomechanical treatment plant for municipal solid waste. Batch tests show that the anaerobic process proceeds smoothly and produces about 10,000 mL of methane per litre of treated leachate. The process is characterized by a lag phase lasting about 30 days, and is completed in about 2 months. Chemical oxygen demand (COD) and volatile fatty acids monitoring allows studying process kinetics that are modelled through a triple linear expression. Physical and biological treatments are also investigated to reduce the residual organic charge of the produced digestate. The best performances are obtained via aerobic degradation followed by assisted sedimentation. This cycle reduces the residual COD of about 85%, and allows the correct disposal of the final waste stream.

Modified Sample Preparation Approach for the Determination of the Phenolic and Humic-Like Substances in Natural Organic Materials By the Folin Ciocalteu Method

A novel modification of the sample preparation procedure for the Folin-Ciocalteu colorimetric assay for the determination of total phenolic compounds in natural solid and semisolid organic materials (e.g., foods, organic solid waste, soils, plant tissues, agricultural residues, manure) is proposed. In this method, the sample is prepared by adding sodium sulfate as a solid diluting agent before homogenization. The method allows for the determination of total phenols (TP) in samples with high solids contents, and it provides good accuracy and reproducibility. Additionally, this method permits analyses of significant amounts of sample, which reduces problems related to heterogeneity. We applied this method to phenols-rich lignocellulosic and humic-like solids and semisolid samples, including rice straw (RS), peat-rich soil (PS), and food waste (FW). The TP concentrations measured with the solid dilution (SD) preparation were substantially higher (increases of 41.4%, 15.5%, and 59.4% in RS, PS and FW, respectively) than those obtained with the traditional method (solids suspended in water). These results showed that the traditional method underestimates the phenolic contents in the studied solids.