Innovative technologies to remove alkylphenols from wastewater: a review

Environmental Chemistry Letters - Alkylphenols and alkylphenol polyethoxylates are emerging hazardous contaminants due in particular to their endocrine-disrupting properties. These compounds...     

Environmental and biological monitoring of benzene in traffic policemen, police drivers and rural outdoor male workers

To evaluate exposure to benzene in urban and rural areas, an investigation into personal exposure to benzene in traffic policemen, police drivers and rural (roadmen) male outdoor workers was carried out. Personal samples and data acquired using fixed monitoring stations located in different areas of the city were used to measure personal exposure to benzene in 62 non-smoker traffic policemen, 22 police drivers and 57 roadmen. Blood benzene, urinary trans-trans muconic acid (t,t-MA) and S-phenyl-mercapturic acid (S-PMA) were measured at the end of work shift in 62 non-smoker traffic policemen, 22 police drivers and 57 roadmen and 34 smoker traffic policemen, 21 police drivers and 53 roadmen. Exposure to benzene was similar among non-smoker traffic policemen and police drivers and higher among non-smoker urban workers compared to rural workers. Blood benzene, t,t-MA and S-PMA were similar among non-smoker traffic policemen and police drivers; blood benzene and t,t-MA were significantly higher in non-smoker urban workers compared to rural workers. Significant increases in t,t-MA were found in smokers vs. non-smokers. In non-smoker urban workers airborne benzene and blood benzene, and t,t-MA and S-PMA were significantly correlated. This study gives an evaluation of the exposure to benzene in an urban area, comparing people working in the street or in cars, to people working in a rural area. Benzene is a certain carcinogen for humans. The results we showed should lead to more in-depth studies about the effects on health of these categories of workers.     

Exposure to cadmium in male urban and rural workers and effects on FSH,LH and testosterone

ObjectiveThis cross-sectional study was conducted to assess the relationship between exposure to cadmium and circulating reproductive hormone levels in urban and rural male workers.Materials and MethodsUrinary cadmium, blood cadmium, luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone were obtained from 86 non-smoking traffic policemen and 86 subjects working as roadmen in a rural area. All subjects were monitored to evaluate airborne exposure to cadmium.ResultsThe mean value of exposure to cadmium was 1.3 ng m^?3 in traffic policemen, while the mean value was less than 0.5 ng m^?3 in roadmen. The mean concentrations of urinary cadmium (1.4 vs. 0.9 μg g^?1 creatinine; p = 0.001), blood cadmium (1.1 vs. 0.7 μg l^?1; p = 0.000), FSH (2.6 vs. 3.2 μlU ml^?1; p = 0.02) and LH (2.6 vs. 3.1 μlU ml^?1; p = 0.03) were significantly different between traffic policemen and roadmen. No differences were found in the mean values of testosterone between the two groups. Multiple linear regression models showed associations between (a) urinary cadmium, airborne cadmium, working life, job category and consumption of water from water supply (b) blood cadmium, airborne cadmium and job category (c) the values of FSH and age, working life, job category, urinary cadmium and blood cadmium (d) the values of LH and both the age and working life.ConclusionThe above results must be confirmed by further studies, but they indicate the influence of exposure to the cadmium present in urban air on the circulating FSH, even at low doses.     

Soy production and certification: the case of Argentinean soy-based biodiesel

With the rising emphasis on biofuels as a potential solution to climate change, this paper asks whether certification schemes, developed to promote sustainable feedstock production, are able to deliver genuine sustainability benefits. The Round Table on Responsible Soy (RTRS) is a certification scheme that aims to promote responsible soy production through the development of principles and criteria. However, can and does this initiative address the negative impacts associated with the intensive production of soy? Taking the example of soy biodiesel produced in Argentina, this paper asks whether the social and environmental impacts of soybean production can be mitigated by the RTRS. It concludes that at present certification schemes are unlikely to be able to address either the institutional challenges associated with their implementation or the detrimental impacts of the additional demand generated by biofuels.     

Microbial and kinetic characterization of pure and mixed cultures aerobically degrading 4-nitrophenol

The molecular and kinetic characterization of a microorganism able to aerobically degrade 4-nitrophenol (4NP) is presented. The microorganism was isolated from a mixed culture operating in a laboratory-scale sequencing batch reactor with an aerobic anoxic cycle. It was identified as a member of Ralstonia genus within Betaproteobacteria. It is a gram negative coccobacillum (cell length of 2-3 microm) able to aerobically store lipid inclusions when grown aerobically on nitrophenol as the sole carbon source in the range of tested concentrations (80-320 mg l(-1)). Batch kinetic tests were performed with the pure culture, while the kinetics of the mixed biomass was directly investigated in the reactor. For pure cultures exponential growth was observed, with growth rate values in the range of 2-6 d(-1); in experiments with the mixed cultures 4NP concentrations were correlated with growth using the Haldane equation (k(max) = 0.30 mg 4NP mg(-1) VSSh(-1); K(s) = 55 mg 4NPl(-1) and K(I) = 15 mg 4NPl(-1)). Observed pure culture growth rates were higher than those of mixed cultures. This result can be explained by considering that in mixed culture the biomass is evaluated as volatile suspended solids, including both specialized biomass for 4NP removal and denitrifying bacteria.     

Biodegradation of phenolic mixtures in a sequencing batch reactor

GOAL, SCOPE AND BACKGROUND: In this study, attention was focused on substituted phenols because of their widespread presence in industrial effluents originating from many different sources: they are major constituents of wastewater from coal conversion processes, coke ovens, petroleum refineries and petrochemical industries, resin and fibreglass manufacturing and herbicide production. Moreover, for their characteristics of toxicity to humans and aquatic life (1 mgl(-1) is enough to detect the effects), they are included in the USEPA list of priority pollutants. Toxicity is higher in substituted phenols and is dependent on the nature and numbers of substituent groups. Objective of the present paper is to give a contribution to the modelling of phenolic mixture biodegradation by kinetic studies in which the different compounds are followed separately: this can be easily attained with an experimental apparatus such as the Sequencing Batch Reactor (SBR). Two substituted phenols, 4-nitrophenol (4NP) and 3,4-dimethylphenol (3,4DMP), were utilized as substrates and their degradation kinetics were investigated to evaluate the process parameters both in single compound and in mixture tests. METHODS: Single compound and mixture kinetic tests have been carried out during the reaction phase of the working cycle of the SBR reactor. The single substrates and their mixture were utilized as sole carbon and energy sources. Moreover, in order to verify data reproducibility, all kinetic tests have been carried out in at least two replicates under the same operating conditions. RESULTS AND DISCUSSION: Kinetic data showed the presence of substrate inhibition, to model this experimental evidence the Haldane equation, that is usually employed for substrate inhibited kinetics, was rearranged in a different form with parameters which have a precise meaning in relation to the process kinetics and, at the same time, make the integration procedure easier. The derivation of the equation is shown in an Appendix at the end of the paper. Kinetic parameters obtained are suitable for application. It was observed that the 4-nitrophenol removal rate in single compound tests is significantly higher than the 3,4-dimethylphenol removal rate in the whole range of investigated concentrations (up to 80 mg COD l(-1)). A faster 4-nitrophenol biodegradation was also observed in mixture tests. Moreover, it is worth noting that the two compounds were simultaneously degraded and no diauxic growth was observed. The comparison between single compound and mixture degradation kinetics showed that the 4-nitrophenol degradation rate was comparable in the two cases while a significantly beneficial effect (by increase by about 80% of the maximum removal rate) was detected for 3,4-dimethylphenol degradation in the mixture. CONCLUSIONS: Results of this study showed that the biodegradation kinetics of substituted phenols in mixture can be significantly different from that observed in single compound tests: in fact, the presence of a faster degradable compound (the 4NP) seems to exert a positive effect on the removal of a slower degradable compound (the 3,4DMP). The higher removal rate detected for 4NP, both in single compound and mixture tests, confirmed the key role of the biomass acclimatization in determining the biodegradation kinetics of xenobiotic compounds. The experimental approach and the original method applied for data analysis are of general validity and can be extended to the investigation of different classes of compounds. RECOMMENDATIONS AND PERSPECTIVES: A relevant aspect related to the process applicability is the demonstrated possibility of easily adapting an enriched culture grown on a specific xenobiotic (in our case the 4NP) for the removal of similar single compounds or in mixtures. When biological process are considered for xenobiotic removal, this suggests a possible strategy of developing enriched cultures on target compounds that can be efficiently utilized on more complex matrices with reduced start up and acclimatization periods.     

Substitutable biodiesel feedstocks for the UK: a review of sustainability issues with reference to the UK RTFO

The sustainability performance of five potential UK biodiesel feedstocks is reviewed and their greenhouse gas performance investigated using the carbon and sustainability reporting methods of the UK Renewable Transport Fuel Obligation (RTFO). Of the feedstocks examined, and for which the RTFO supplies default carbon intensity values, only used cooking oil has guaranteed sustainability benefits. The other feedstocks have CO₂e payback periods of 25–5503 years if grown on converted forest or grassland, yet the RTFO currently requires no guarantee that this conversion has not taken place and requires no avoidance of indirect effects. As currently designed, the RTFO risks substantial, adverse environmental effects.     

Performance of sequential anaerobic/aerobic digestion applied to municipal sewage sludge

A promising alternative to conventional single phase processing, the use of sequential anaerobic-aerobic digestion, was extensively investigated on municipal sewage sludge from a full scale wastewater treatment plant. The objective of the work was to evaluate sequential digestion performance by testing the characteristics of the digested sludge in terms of volatile solids (VS), Chemical Oxygen Demand (COD) and nitrogen reduction, biogas production, dewaterability and the content of proteins and polysaccharides. VS removal efficiencies of 32% in the anaerobic phase and 17% in the aerobic one were obtained, and similar COD removal efficiencies (29% anaerobic and 21% aerobic) were also observed. The aerobic stage was also efficient in nitrogen removal providing a decrease of the nitrogen content in the supernatant attributable to nitrification and simultaneous denitrification. Moreover, in the aerobic phase an additional marked removal of proteins and polysaccharides produced in the anaerobic phase was achieved. The sludge dewaterability was evaluated by determining the Optimal Polymer Dose (OPD) and the Capillary Suction Time (CST) and a significant positive effect due to the aerobic stage was observed. Biogas production was close to the upper limit of the range of values reported in the literature in spite of the low anaerobic sludge retention time of 15 days. From a preliminary analysis it was found that the energy demand of the aerobic phase was significantly lower than the recovered energy in the anaerobic phase and the associated additional cost was negligible in comparison to the saving derived from the reduced amount of sludge to be disposed.