In this study, we report an extensive set of analytical results on the quality of the biogas produced by a landfill of automotive shredder residues. In particular, the investigation was directed towards the identification of a spectrum of polycyclic aromatic hydrocarbons (16 compounds) and a wide range of volatile organic compounds (35 compounds). This article highlights the most important indications of toxicological concern for the detected compounds. Among the polycyclic aromatic hydrocarbons, chrysene shows the highest concentration, followed by pyrene and benzo(b)fluoranthene. Dibenz(a,h)anthracene, the most carcinogenic of the tested compounds, displayed results below the limit of analytical detectability. Benzo(a)pyrene, another typical carcinogenic compound, was detected at low concentrations. With regard to volatile organic compounds, the survey revealed a relevant concentration of toluene (found in fuels and paint thinner) significantly higher than the other compounds. Noticeable amounts of hexane, trichloromethane, and acetone were also found.
This article presents the results of an experimental study on the correlation among the specific denitrification rate (SDNR), the dissolved oxygen concentration (DO), the F:M ratio (F:M) and the mixed-liquor (ML) recycle in the pre-denitrification reactors fed by domestic sewage. The experimental curves reveal a 28.8-32.0% reduction in the SDNR at 20 degrees C (SDNR(20 degrees C)) with DO equal to 0.1 mgO2 L(-1) and F:M in the range 0.2-0.4 kgBOD5 kgMLVSS(-1) d(-1). The SDNR reduction increases to 50.0-55.9% with DO = 0.3 mgO2 L(-1). A mathematical correlation of these results and an equation for calculating SDNR(20 degrees C) as function of the F:M as well as the average DO and BOD5 in the total flow rate fed in the denitrification stage are proposed. The conducted experience gives useful suggestions for practical usage, in particular regarding the denitrification reactor design, and represents a good starting point for future applications with the aim to optimize the biological process in domestic sewage treatment plants.
Abstract:The great diurnal variation in the quality of wastewater of small communities is an obstacle to the efficient removal of high nitrogen with traditional activated sludge processes provided by pre-denitrification. To verify this problem, the authors developed a pilot plant, in which the domestic wastewater of community of 15,000 inhabitants was treated. The results demonstrate that average and peak nitrogen removal efficiencies of over 60% and 70%, respectively, are difficult to obtain because of the strong variations in the BOD 5 /NO 3 -N ratios and the unexpected abnormal accumulation of dissolved oxygen during denitrification when the BOD 5 load is low. These phenomena cause inhibitory effects and BOD 5 deficiency in the denitrification process. The results demonstrate the need for a more complex approach to designing and managing small wastewater treatment plants (WWTPs) provided with denitrification than those usually adopted for medium-and large-size plants.
Pollution control of surface water bodies requires stringent checks on wastewater treatment plants performances. The satisfactory operation of biological treatment, commonly performed by means of activated sludge processes, requires a number of controlling and monitoring procedures. Suitable respirometric techniques for the determination of the kinetic parameters that regulate biological processes have been implemented in order to achieve this aim. This paper describes the results of an experimental research carried out in a conventional Italian municipal wastewater treatment plant. Particularly, the research has been finalized to both evaluate the biological process for the removal of biodegradable pollutants, such as carbonaceous substrates and ammonia nitrogen, and to collect data in order to evaluate a possible plant upgrade. Heterotrophic and autotrophic biomass kinetic parameters have been examined using respirometric techniques based on oxygen uptake measurements. The research performed makes a OPEN ACCESS Sustainability 2014, 6 1834 valuable contribution toward verifying the reliability of the values proposed in the literature for some kinetic parameters, which have been commonly used for a long time.
In Brazil, and mainly in the State of Bahia, crude vegetable oils are widely used in the preparation of food. Street stalls, restaurants and canteens make a great use of palm oil and soybean oil. There is also some use of castor oil, which is widely cultivated in the Sertão Region (within the State of Bahia), and widely applied in industry. This massive use in food preparation leads to a huge amount of waste oil of different types, which needs either to be properly disposed of, or recovered. At the Laboratorio Energia e Gas-LEN (Energy & Gas lab.) of the Universidade Federal da Bahia, a cycle of experiments were carried out to evaluate the recovery of waste oils for biodiesel production. The experiences were carried out on a laboratory scale and, in a semi-industrial pilot plant using waste oils of different qualities. In the transesterification process, applied waste vegetable oils were reacted with methanol with the support of a basic catalyst, such as NaOH or KOH. The conversion rate settled at between 81% and 85% (in weight). The most suitable molar ratio of waste oils to alcohol was 1:6, and the amount of catalyst required was 0.5% (of the weight of the incoming oil), in the case of NaOH, and 1%, in case of KOH. The quality of the biodiesel produced was tested to determine the final product quality. The parameters analyzed were the acid value, kinematic viscosity, monoglycerides, diglycerides, triglycerides, free glycerine, total glycerine, clearness; the conversion yield of the process was also evaluated.
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