Roma-Montelibretti Head Office
C. Braguglia
D. Marani
G. Mininni
M.C. Tomei
Bari Section
V. Lotito
G. Mascolo
V. Uricchio

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Intro Sludge and solid waste management

The recent Directive 2008/98 sets new objectives and opens new perspectives in waste management, in particular as regards the production of secondary raw materials (that finish to be waste) and the standards required for energy recovery. Research may actively provide solutions in important topics as waste recovery and the valorisation of their content. As far as the waste characterization is concerned, research plays the lead role of suggesting solutions for the age-old problem of waste classification and the related attribution of the risk codes, for which the Directive has defined new approaches.
Regarding processes and treatment technologies, the research has also the role of supporting the enterprises to assess new solutions assuring the minimization of landfill disposal after the complete recovery of the economically available resources. The complexity and the difficulty of a correct management and the consequent temptation of illegal, offhanded and gainful disposals impose development and application of waste traceability procedures deterring illegal actions.

Paragraph 1 Resource recovery from waste and biomasses

Recovery and disposal are the two important sectors as regards waste management. In fact, according to the new directive 08/98 the following priority list should be respected: prevention, preparing for re-use, recycling, other recovery (e.g. energy recovery), and the last option should be the disposal. The research activity should be therefore addressed to reliable and cost-effective techniques for recovering both material and energy from wastes. IRSA is engaged in activities on biogas maximization during anaerobic digestion of biological sludge and biomasses with specific regard to olive residues. Considering that the performances of these processes are generally scarce, improvement may be achieved by means of mechanical, biological or thermal pre-treatments, using ultrasounds, enzymes or high temperature processes, which allow hydrolysing organic particulate matter thus accelerating the anaerobic process.

Paragraph 2 Preparation for re-use or disposal

Sewage sludge and generally speaking the biodegradable wastes although present a negligible content of persistent and bio-accumulating pollutants, pose serious problems in their management as regards the emission of unpleasant odours, and the production of biogas and very polluted leachate in landfill.
IRSA is engaged in improving the use of anaerobic digestion by lowering the convenience level towards smaller treatments plants, and contemporaneously by upgrading the employ of sludge digesters for the combined digestion with other biodegradable wastes derived from the separate waste collection. Moreover, another research objective is to delve into the process study and to understand the degradation pathways of the single components. This may be useful to verify which processes may be suitable to guarantee a good sludge quality appropriate for the use in agriculture precluding the presence of compounds that may present ecotoxic and specifically phytotoxic effects.

Paragraph 3 Advanced diagnosis of thermal processes

The assessment of the treatability of a waste for the thermal treatment at high temperature is often required, i.e. it is useful to predict destruction efficiency of principal organic hazardous constituents (POHCs) and the whole spectrum of organic emissions of products of incomplete combustion (PICs). IRSA has a long expertise in this field and set up with the University of Dayton (U.S.A.) an equipment with the name of System for Thermal Diagnostic Studies (STDS). This instrument allows carrying out experiments under controlled conditions regarding temperature, residence time and atmosphere (over or under stoichiometric oxygen). The gaseous compounds produced in the above conditions are cryofocused and then analyzed separately by GC-MS without any requirement of time consuming sampling which often can be responsible for producing artefacts. Moreover, IRSA developed an algorithm for the evaluation of a process including thermal drying, incineration, thermal recovery, condensation of the exhaust vapours from the dryer, which well suits with sewage sludge. This algorithm is able to assess the optimal conditions for the operation of an incineration plant to minimize the capital (design of different operating units) and operating costs (fuel consumption and exhaust gas production).

Paragraph 4 Optimization of waste management

Waste classification into hazardous or non-hazardous is absolutely necessary for an accurate waste management. The normative is of controversial interpretation as it is required ascertaining whether hazardous substances are present in concentration exceeding limit values depending on the class of hazard. Unfortunately, no precise indication is included on the specific substances to be analyzed. It is therefore quite usual that the producer does not know the proper classification of his own waste. Considering that it is impossible to determine the presence of all the hazardous substances, the role of the researcher is to list the substances according to the productive process and to the substances used during the process. Moreover, the wastes have to be properly characterized in view of their recovery and/or disposal.
The activity of IRSA is predominantly addressed to the assessment of support protocols for SME for the correct waste classification and management. Moreover, many research studies are also conducted for optimal management of sewage sludge at district level and for applying the best available technologies in the waste branch.
Research activities are mainly the following:

  • Pre-treatment procedures to homogenize wastes without any modification of the original characteristics;
  • development of standardized analytical methods for hard-to-detect parameters;
  • individuation of critical points of the productive process and development of solution proposals.

Paragrafo 5 Waste traceability

The need of wastes traceability derives from economics and potential impacts on the human health and on environment. Referring to the conventional methodologies, it is possible to consider: the formulary of identification (FIR), the loading-downloading register, the single form for declaration (MUD), the traceability of knots included in any material handling, the optical system for bar code reader, up to the new data transmission register. The above instruments are very useful to carry out specific control activities. Nevertheless they base their efficiency on the probity of the involved key persons. Specifically, the technological devices can be addressed to matter traceability, to vectors traceability or to the interactions between waste and transport. An operating laboratory was implemented for experimenting approaches and innovative methodologies to contrast illegal traffics, thus reducing health and environmental hazards. In this contest, a specific software called Perimsiti was implemented and successfully used by police force and local authorities in Southern Italy.