Marcello Civilini

Composting Management: a New Process Control Through O2 Feedback

A new strategy for composting has been developed, based on O2 feedback control. Experiments were carried out on composting the biodegradable fraction of municipal solid waste in a closed bioreactor, aerated by pressure ventilation. Ventilation was controlled in order to maintain the O2 level in the internal atmosphere of the composting mass between 15 and 20%. The new strategy seems to give satisfactory results in terms of process control, quality of end-product, low energy consumption, and hygienization of compost. These results were supported by analyses of: (1) the variation of the main microbial groups during composting; (2) the balance of material; (3) the gas present in the internal atmosphere (O2, NH3, CO2, H 2S); (4) phytotoxicity; and (5) pathogenic and indicator micro-organisms. The importance of carrying out these analyses to guarantee the quality of the end-product and to control the process is discussed. Finally, the new system for controlling composting is compared with the existing strategies (Beltsville and Rutgers systems).

Yard Waste Composting with Heat Recovery

▪ The feasibility of yard waste composting in a closed continuous reactor with heat recovery has been investigated. Results obtained in this research are reported and discussed. In the system, the recovered energy (heat) can be transformed by a heat pump in hot water both for domestic and for residential heating. The organic fertilizer produced can be used in horticulture.

High Rate Composting with Innovative Process Control

Despite the variety of composting plants present on the market, the design and operation of composting systems to improve the rate of the process and quality of end products are still an objective that has not been achieved. The composting process evolves through a thermophilic phase followed by a mesophilic one. The metabolism of microorganisms involved in the process is deeply disturbed by environmental changes like temperature, oxygen level and moisture. The aim of this study was to carry out a composting process in two separate reactors: the first, only in the thermophilic phase, with the purpose of pathogen destruction and decomposition by selected thermophilic microorganisms; the second, only in the mesophilic phase, to perform the main microbial transformations with a higher rate of volatile solids destruction. The results confirmed that maintaining constant the main parameters which affect the process, the microbial activity is enhanced. In the two-phase process, the evolution of parameters like moisture, organic carbon, humified organic matter, organic N, C/N and germination index (phytotoxicity) is more rapid relative to the single phase process. Also pathogen destruction is improved with the complete elimination of Faecal coliforms and Enterobacteriaceae and with a stronger reduction of Faecal streptococci.

Monoclonal antibody detection of naphthalene dioxygenase from Pseudomonas aeruginosa 2NR

A monoclonal antibody, designated mAbα(CT), was generated against a peptide of the ISPNAPα‐subunit of the naphthalene dioxygenase (NDO) enzyme of Pseudomonas aeruginosa. Since NDO expression is induced by aromatic hydrocarbons, its detection is important as a tool for environmental biomonitoring. This antibody is highly specific and works well both in an indirect ELISA assay and Western Blot analysis, allowing the detection of Pseudomonas spp. expressing the NDO inducible enzyme. The detection threshold for the ELISA assay developed in this work was 104 colony forming units (cfu) per ml. Thus, this mAb could represent a powerful tool to test for pollutants in soil, groundwater, and other natural environments.

Composting and Selected Microorganisms for Bioremediation of Contaminated Materials

Environmental contaminants such as the monocyclic aromatic group and polycyclic aromatic hydrocarbon (PAH) group can be found in practically all industrial areas. Pollution by these compounds are primarily associated with the processing, combustion, and disposal of fossil fuels. Industrial effluents from coal gasification and liquification processes, waste incineration, coke, carbon black, coal tar, and other petroleum-derived products are all major sources of contamination.

Biological wastewater treatments for metallurgical industries

Variable contents of nitrite (NO2−)- and nitrate (NO3−)-nitrogen are present in wastewater of metallurgical cylinder-producing industries after treatment in a physical-chemical plant. Biological denitrification and oxidation treatments to reduce the oxidized nitrogen forms to within legal limits were evaluated. Wastewater streams were characterized and quantified in order to build a pilot plant, improve strategies to reduce environmental impact and increase water recycling. Initial sedimentation of raw mixed streams reduced iron and zinc contents by 87% and 71%, respectively. The resulting COD was refractory to be used in biological phases and an added carbon source was necessary to optimise the denitrification process. The biological treatment gave good results even without subsequent physical-chemical treatments, lowering NO2− and NO3− values to below the 0.6 and 20 mg L−1 limits respectively.