Guido Del Moro

A chemically enhanced biological process for lowering operative costs and solid residues of industrial recalcitrant wastewater treatment

An innovative process based on ozone-enhanced biological degradation, carried out in an aerobic granular biomass system (SBBGR--Sequencing Batch Biofilter Granular Reactor), was tested at pilot scale for tannery wastewater treatment chosen as representative of industrial recalcitrant wastewater. The results have shown that the process was able to meet the current discharge limits when the biologically treated wastewater was recirculated through an adjacent reactor where a specific ozone dose of 120 mg O3/L(influent) was used. The benefits produced by using ozone were appreciable even visually since the final effluent of the process looked like tap water. In comparison with the conventional treatment, the proposed process was able to reduce the sludge production by 25-30 times and to save 60% of operating costs. Molecular in situ detection methods were employed in combination with the traditional measurements (oxygen uptake rate, total protein content, extracellular polymeric substances and hydrophobicity) to evaluate microbial activity and composition, and the structure of the biomass. A stable presence of active bacterial populations was observed in the biomass with the simultaneous occurrence of distinctive functional microbial groups involved in carbon, nitrogen and sulphate removal under different reaction environments established within the large microbial aggregates. The structure and activity of the biomass were not affected by the use of ozone.

Antibiotic resistance genes fate and removal by a technological treatment solution for water reuse in agriculture

In order to mitigate the potential effects on the human health which are associated to the use of treated wastewater in agriculture, antibiotic resistance genes (ARGs) are required to be carefully monitored in wastewater reuse processes and their spread should be prevented by the development of efficient treatment technologies. Objective of this study was the assessment of ARGs reduction efficiencies of a novel technological treatment solution for agricultural reuse of municipal wastewaters. The proposed solution comprises an advanced biological treatment (Sequencing Batch Biofilter Granular Reactor, SBBGR), analysed both al laboratory and pilot scale, followed by sand filtration and two different disinfection final stages: ultraviolet light (UV) radiation and peracetic acid (PAA) treatments. By Polymerase Chain Reaction (PCR), the presence of 9 ARGs (ampC, mecA, ermB, sul1, sul2, tetA, tetO, tetW, vanA) were analysed and by quantitative PCR (qPCR) their removal was determined. The obtained results were compared to the reduction of total bacteria (16S rDNA gene) and of a faecal contamination indicator (Escherichia coli uidA gene). Only four of the analysed genes (ermB, sul1, sul2, tetA) were detected in raw wastewater and their abundance was estimated to be 3.4±0.7 x10(4) - 9.6±0.5 x10(9) and 1.0±0.3 x10(3) to 3.0±0.1 x10(7) gene copies/mL in raw and treated wastewaters, respectively. The results show that SBBGR technology is promising for the reduction of ARGs, achieving stable removal performance ranging from 1.0±0.4 to 2.8±0.7 log units, which is comparable to or higher than that reported for conventional activated sludge treatments. No reduction of the ARGs amount normalized to the total bacteria content (16S rDNA), was instead obtained, indicating that these genes are removed together with total bacteria and not specifically eliminated. Enhanced ARGs removal was obtained by sand filtration, while no reduction was achieved by both UV and PAA disinfection treatments tested in our study.

Integration of an innovative biological treatment with physical or chemical disinfection for wastewater reuse

In the present paper, the effectiveness of a Sequencing Batch Biofilter Granular Reactor (SBBGR) and its integration with different disinfection strategies (UV irradiation, peracetic acid) for producing an effluent suitable for agricultural use was evaluated. The plant treated raw domestic sewage, and its performances were evaluated in terms of the removal efficiency of a wide group of physical, chemical and microbiological parameters. The SBBGR resulted really efficient in removing suspended solids, COD and nitrogen with an average effluent concentration of 5, 32 and 10 mg/L, respectively. Lower removal efficiency was observed for phosphorus with an average concentration in the effluent of 3 mg/L. Plant effluent was also characterized by an average electrical conductivity and sodium adsorption ratio of 680 μS/cm and 2.9, respectively. Therefore, according to these gross parameters, the SBBGR effluent was conformed to the national standards required in Italy for agricultural reuse. Moreover, disinfection performances of the SBBGR was higher than that of conventional municipal wastewater treatment plants and met the quality criteria suggested by WHO (Escherichia coli<1000 CFU/100 mL) for agricultural reuse. In particular, the biological treatment by SBBGR removed 3.8±0.4 log units of Giardia lamblia, 2.8±0.8 log units of E. coli, 2.5±0.7 log units of total coliforms, 2.0±0.3 log units of Clostridium perfringens, 2.0±0.4 log units of Cryptosporidium parvum and 1.7±0.7 log units of Somatic coliphages. The investigated disinfection processes (UV and peracetic acid) resulted very effective for total coliforms, E. coli and somatic coliphages. In particular, a UV radiation and peracetic acid doses of 40 mJ/cm(2) and 1 mg/L respectively reduced E. coli content in the effluent below the limit for agricultural reuse in Italy (10 CFU/100 mL). Conversely, they were both ineffective on C.perfringens spores.

The essential role of filling material in aerobic granular biomass generation in a periodic submerged biofilter

The paper reports the results of a laboratory-scale investigation aimed at evaluating the influence of the filling material of a Sequencing Submerged Biofilter Reactor (SSBR) on granular biomass generation. The results showed that aerobic granular biomass generation was obtained only in the reactor filled with kmt-k1 carrier, since the features of this filling media are such that they generate a bed characterised by rather uniform internal and external small-sized pore volumes able to retain the released biofilm particles. Finally, the aerobic granule formation improved the biomass retention efficiency and reduced the excess sludge production.

Removal of pollutants and pathogens by a simplified treatment scheme for municipal wastewater reuse in agriculture.

The availability of high quality water has become a constraint in several countries. Agriculture represents the main water user, therefore, wastewater reuse in this area could increase water availability for other needs. This research was aimed to provide a simplified scheme for treatment and reuse of municipal and domestic wastewater based on Sequencing Batch Biofilter Granular Reactors (SBBGRs). The activity was conducted at pilot-scale and particular attention was dedicated to the microbiological quality of treated wastewater to evaluate the risk associated to its reuse. The following microorganisms were monitored: Escherichia coli, Salmonella, Clostridium perfringens, somatic coliphages, adenovirus, enterovirus, Giardia lamblia and Cryptosporidium parvum. The possibility of SBBGR enhancement with sand filtration was also evaluated. The SBBGR removed >90% of suspended solids and chemical oxygen demand, and 80% and 60% of total nitrogen and phosphorous, respectively. SBBGR was also effective in removing microbial indicators, from 1 (for C. perfringens) up to 4 (for E. coli) log units of these microorganisms. In particular, the quality of SBBGR effluent was already compatible with the WHO criteria for reuse (E. coli ≤103CFU/100mL). Sand filtration had positive effects on plant effluent quality and the latter could even comply with more restrictive reuse criteria.

Municipal landfill leachate treatment by SBBGR technology.

The paper reports the results of a laboratory-scale investigation aimed at evaluating the performance of a periodic biofilter with granular biomass (SBBGR) for treating leachate coming from a mature municipal landfill. The results show that the SBBGR was able to remove roughly 80% of COD in leachate. The remaining 20% of COD were, therefore, presumably owing to the presence in the leachate of recalcitrant compounds. Ammonia removal efficiency was low because of the presence of high salinity and inhibitory compounds in the investigated leachate. The process was characterised by very low sludge production (lower than 0.02 kg TSS/kg CODremoved).

Iodinated contrast media electro-degradation: Process performance and degradation pathways

The electrochemical degradation of six of the most widely used iodinated contrast media was investigated. Batch experiments were performed under constant current conditions using two DSA® electrodes (titanium coated with a proprietary and patented mixed metal oxide solution of precious metals such as iridium, ruthenium, platinum, rhodium and tantalum). The degradation removal never fell below 85% (at a current density of 64 mA/cm(2) with a reaction time of 150 min) when perchlorate was used as the supporting electrolyte; however, when sulphate was used, the degradation performance was above 80% (at a current density of 64 mA/cm(2) with a reaction time of 150 min) for all of the compounds studied. Three main degradation pathways were identified, namely, the reductive de-iodination of the aromatic ring, the reduction of alkyl aromatic amides to simple amides and the de-acylation of N-aromatic amides to produce aromatic amines. However, as amidotrizoate is an aromatic carboxylate, this is added via the decarboxylation reaction. The investigation did not reveal toxicity except for the lower current density used, which has shown a modest toxicity, most likely for some reaction intermediates that are not further degraded. In order to obtain total removal of the contrast media, it was necessary to employ a current intensity between 118 and 182 mA/cm(2) with energy consumption higher than 370 kWh/m(3). Overall, the electrochemical degradation was revealed to be a reliable process for the treatment of iodinated contrast media that can be found in contaminated waters such as hospital wastewater or pharmaceutical waste-contaminated streams.

Enhanced Biological Wastewater Treatment to Produce Effluents Suitable for Reuse

Enhanced performance of biological processes for xenobiotic removal in municipal and industrial wastewater treatment plants can be achieved by adopting the following general strategies based on different principles of operation: increase of the biomass concentration (i.e., using biofilm, immobilized cell, and granular sludge reactors); dynamic operating conditions able to modify the biocenosis composition and to induce alternative metabolic pathways required by xenobiotic biodegradation; two-phase systems, which optimize the substrate delivery to the microorganisms on the basis of their metabolic demand; and combined treatment processes utilizing synergistic physical/chemical methods.

Fingerprinting Hydrocarbons in a Contaminated Soil from an Italian Natural Reserve and Assessment of the Performance of a Low-Impact Bioremediation Approach

An environmentally friendly procedure suitable to restore a protected area was evaluated at laboratory scale. Soil contaminated by high molecular weight (C > 10) aliphatic hydrocarbons and by chromium was withdrawn from the study site and a qualitative study of soil hydrocarbon components was first performed in order to assess the potential source of contamination. To this aim, a number of characteristic diagnostic ratios of hydrocarbon components were derived by processing chromatographic data, and were used as indicators for distinguishing anthropogenic from natural hydrocarbons. Then, the efficiency of landfarming for soil remediation was tested by comparing the effect of a few selected amendments and by monitoring the fate of chromium. Soil microbial abundance and activity were also evaluated. Results showed that soil hydrocarbons were mainly of anthropogenic origin and land treatment allowed effective degradation by native microbial populations even in the absence of amendments. The investigated procedures had no effect on the mobilisation of chromium that remained in its stable form of Cr(III). Conventional land treatment may therefore be an effective and safe procedure for the removal of hydrocarbons even in the presence of chromium, and may be applied to areas where low-impact procedures are strictly required.