Giulio Zanaroli

In situ groundwater and sediment bioremediation: barriers and perspectives at European contaminated sites

This paper contains a critical examination of the current application of environmental biotechnologies in the field of bioremediation of contaminated groundwater and sediments. Based on analysis of conventional technologies applied in several European Countries and in the US, scientific, technical and administrative barriers and constraints which still need to be overcome for an improved exploitation of bioremediation are discussed. From this general survey, it is evident that in situ bioremediation is a highly promising and cost-effective technology for remediation of contaminated soil, groundwater and sediments. The wide metabolic diversity of microorganisms makes it applicable to an ever-increasing number of contaminants and contamination scenarios. On the other hand, in situ bioremediation is highly knowledge-intensive and its application requires a thorough understanding of the geochemistry, hydrogeology, microbiology and ecology of contaminated soils, groundwater and sediments, under both natural and engineered conditions. Hence, its potential still remains partially unexploited, largely because of a lack of general consensus and public concerns regarding the lack of effectiveness and control, poor reliability, and possible occurrence of side effects, for example accumulation of toxic metabolites and pathogens. Basic, applied and pre-normative research are all needed to overcome these barriers and make in situ bioremediation more reliable, robust and acceptable to the public, as well as economically more competitive. Research efforts should not be restricted to a deeper understanding of relevant microbial reactions, but also include their interactions with the large array of other relevant phenomena, as a function of the truly variable site-specific conditions. There is a need for a further development and application of advanced biomolecular tools for site investigation, as well as of advanced metabolic and kinetic modelling tools. These would allow a quicker evaluation of the bioremediation potential of a site, and in turn a preliminary assessment of the technical feasibility of the chosen bioprocess which could replace or at least reduce the need for time-consuming and expensive field tests. At the same time, field tests will probably remain unavoidable for a detailed design of full scale remedial actions and the above reported tools will in any event be useful for a better design and a more reliable operation.

In situ aerobic cometabolism of chlorinated solvents: a review.

The possible approaches for in situ aerobic cometabolism of aquifers and vadose zones contaminated by chlorinated solvents are critically evaluated. Bioaugmentation of resting-cells previously grown in a fermenter and in-well addition of oxygen and growth substrate appear to be the most promising approaches for aquifer bioremediation. Other solutions involving the sparging of air lead to satisfactory pollutant removals, but must be integrated by the extraction and subsequent treatment of vapors to avoid the dispersion of volatile chlorinated solvents in the atmosphere. Cometabolic bioventing is the only possible approach for the aerobic cometabolic bioremediation of the vadose zone. The examined studies indicate that in situ aerobic cometabolism leads to the biodegradation of a wide range of chlorinated solvents within remediation times that vary between 1 and 17 months. Numerous studies include a simulation of the experimental field data. The modeling of the process attained a high reliability, and represents a crucial tool for the elaboration of field data obtained in pilot tests and for the design of the full-scale systems. Further research is needed to attain higher concentrations of chlorinated solvent degrading microbes and more reliable cost estimates. Lastly, a procedure for the design of full-scale in situ aerobic cometabolic bioremediation processes is proposed.

New advances in the integrated management of food processing by-products in Europe: sustainable exploitation of fruit and cereal processing by-products with the production of new food products (NAMASTE EU)

By-products generated every year by the European fruit and cereal processing industry currently exceed several million tons. They are disposed of mainly through landfills and thus are largely unexploited sources of several valuable biobased compounds potentially profitable in the formulation of novel food products. The opportunity to design novel strategies to turn them into added value products and food ingredients via novel and sustainable processes is the main target of recently EC-funded FP7 project NAMASTE-EU. NAMASTE-EU aims at developing new laboratory-scale protocols and processes for the exploitation of citrus processing by-products and wheat bran surpluses via the production of ingredients useful for the formulation of new beverage and food products. Among the main results achieved in the first two years of the project, there are the development and assessment of procedures for the selection, stabilization and the physical/biological treatment of citrus and wheat processing by-products, the obtainment and recovery of some bioactive molecules and ingredients and the development of procedures for assessing the quality of the obtained ingredients and for their exploitation in the preparation of new food products.

Feed frequency in a Sequencing Batch Reactor strongly affects the production of polyhydroxyalkanoates (PHAs) from volatile fatty acids

The production of polyhydroxyalkanoates (PHAs) by activated sludge selected in a sequencing batch reactor (SBR) has been investigated. Several SBR runs were performed at the same applied organic load rate (OLR), hydraulic retention time (HRT) and feed concentration (8.5 g COD L(-1) of volatile fatty acids, VFAs) under aerobic conditions. The effect of the feeding time was only evaluated with a cycle length of 8h; for this particular cycle length, an increase in the storage response was observed by increasing the rate at which the substrate was fed into the reactor (at a fixed feeding frequency). Furthermore, a significantly stronger effect was observed by decreasing the cycle length from 8h to 6h and then to 2h, changing the feed frequency or changing the organic load given per cycle (all of the other conditions remained the same): the length of the feast phase decreased from 26 to 20.0 and then to 19.7% of the overall cycle length, respectively, due to an increase in the substrate removal rate. This removal rate was high and similar for the runs with cycle lengths of 2h and 6h in the SBR. This result was due to an increase in the selective pressure and the specific storage properties of the selected biomass. The highest polymer productivity after long-term accumulation batch tests was 1.7 g PHA L(-1)d(-1), with PHA content in the biomass of approximately 50% on a COD basis under nitrogen limitation. The DGGE profiles showed that the good storage performance correlated to the development of Lampropedia hyalina, which was only observed in the SBR runs characterized by a shorter cycle length.

Development of an attached-growth process for the on-site bioremediation of an aquifer polluted by chlorinated solvents

A procedure for the design of an aerobic cometabolic process for the on-site degradation of chlorinated solvents in a packed bed reactor was developed using groundwater from an aquifer contaminated by trichloroethylene (TCE) and 1,1,2,2-tetrachloroethane (TeCA). The work led to the selection of butane among five tested growth substrates, and to the development and characterization from the site’s indigenous biomass of a suspended-cell consortium capable to degrade TCE (first order constant: 96xa0Lxa0gprotein–1xa0day–1 at 30xa0°C and 4.3xa0Lxa0gprotein–1xa0day–1 at 15xa0°C) with a 90xa0% mineralization of the organic chlorine. The consortium immobilization had strong effects on the butane and TCE degradation rates. The microbial community structure was slightly changed by a temperature shift from 30 to 15xa0°C, but remarkably affected by biomass adhesion. Given the higher TCE normalized degradation rate (0.59xa0day–1 at 15xa0°C) and attached biomass concentration (0.13xa0gproteinxa0Lbioreactor–1 at 15xa0°C) attained, the porous ceramic carrier Biomax was selected as the best option for the packed bed reactor process. The low TeCA degradation rate exhibited by the developed consortium suggested the inclusion of a chemical pre-treatment based on the TeCA to TCE conversion via β-elimination, a very fast reaction at alkaline pH. To the best of the authors’ knowledge, this represents the first attempt to develop a procedure for the development of a packed bed reactor process for the aerobic cometabolism of chlorinated solvents.

Electrochemical stimulation of microbial cis-dichloroethene (cis-DCE) oxidation by an ethene-assimilating culture

This study investigated the feasibility of using a polarized graphite electrode as direct or indirect (via electrolytic oxygen generation) electron acceptor to stimulate the microbial oxidation of cis-dichloroethene (cis-DCE) in contaminated groundwater. A microbial culture was enriched in the anode chamber of a bioelectrochemical cell using a mixture of cis-DCE and ethene as substrates. The bioelectrochemical cell was operated by controlling the anode potential at +1.0 V or +1.5 V versus the standard hydrogen electrode (SHE). Enhanced cometabolic removal of cis-DCE, with ethene serving as the growth substrate, was observed in batch tests with the anode polarized at +1.5 V versus SHE. At this potential, (chloro)ethenes removal was probably sustained by molecular oxygen generated at the anode from water oxidation. Conversely, negligible anaerobic degradation was observed at +1.0 V versus SHE (a potential which does not allow oxygen generation), hence suggesting that molecular oxygen is needed to initiate (chloro)ethene degradation. PCR-DGGE analysis of the microbial culture followed by band sequencing and phylogenetic analysis evidenced the selective enrichment of a Bacillus species, providing a strong indication that this microorganism was responsible for cis-DCE and ethene degradation.

The role of environmental biotechnology in exploring, exploiting, monitoring, preserving, protecting and decontaminating the marine environment

In light of the Marine Strategy Framework Directive (MSFD) and the EU Thematic Strategy on the Sustainable Use of Natural Resources, environmental biotechnology could make significant contributions in the exploitation of marine resources and addressing key marine environmental problems. In this paper 14 propositions are presented focusing on (i) the contamination of the marine environment, and more particularly how to optimize the use of biotechnology-related tools and strategies for predicting and monitoring contamination and developing mitigation measures; (ii) the exploitation of the marine biological and genetic resources to progress with the sustainable, eco-compatible use of the maritime space (issues are very diversified and include, for example, waste treatment and recycling, anti-biofouling agents; bio-plastics); (iii) environmental/marine biotechnology as a driver for a sustainable economic growth.