A 104-mm (4-inch) diameter pilot-scale biological aerated filter (BAF) with a media depth of 2.5 m (8.3 feet) was operated with an anaerobic, anoxic and oxic zone at a temperature of 23 degrees C. The medium for the anaerobic and anoxic zones was 10 mm diameter sand while the medium for the oxic zone was 5 mm diameter sand. The influent sCOD and total nitrogen concentrations in the feedwater were approximately 250 mg/L and 35 mg N/L, respectively. sCOD removal at optimum hydraulic retention time (HRT) of 3 h with recirculation rates of 100, 200 and 300% in the column was above 96%. Nitrification was found to be more than 96% for 3 h HRT at 200 and 300% recirculation. Total nitrogen removal was consistent at more than 80% for 4 and 6 h HRT at 300% recirculation. For 3 h HRT and 300% recirculation, total nitrogen removal was approximately 79%. The ammonia loading rates for maximum ammonia removed were 0.15 and 0.19 kg NH3-N/m3-day for 100 and 200% recirculation, respectively. The experimental results demonstrated that the BAF can be operated at an HRT of 3h with 200-300% recirculation rates with more than 96% removal of sCOD and ammonia and at least 75% removal of total nitrogen.

Abstract:The heavy metals, such as Pb(II) and radioisotope Cr(III), in aqueous solutions are toxic even at trace levels and have caused adverse health impacts on human beings. Hence the removal of these heavy metals from the aqueous environment is of the utmost importance to protect biodiversity, hydrosphere ecosystems, and human beings. In this study, the reduced graphene oxide based inverse spinel nickel ferrite (rGONF) nanocomposite has been prepared and was utilized for the removal of Pb(II) and Cr(III) from aqueous solutions. The prepared rGONF has been confirmed by X-ray photoelectron (XPS) and Raman spectroscopy. The surface characteristics of rGONF were measured by scanning electron microscopy (SEM), High-Resolution Transmission Electron Microscope (HR-TEM), and Brunauer-Emmett-Teller (BET) surface analysis. The average particle size of rGONF was found to be 32.0 ± 2.0 nm. The surface site density for the specific surface area (Ns) of rGONF was found to be 0.00238 mol·g −1 , which was higher than that of the graphene oxide (GO) and NiFe 2 O 4 , which was expected. The prepared rGONF has been successfully applied for the removal of Pb(II) and Cr(III) by batch mode. The batch adsorption studies concluded that the adsorption of Pb(II) and Cr(III) onto rGONF was rapid and the adsorption percentage was more than 99% for both metal ions. The adsorption isotherm results found that the adsorptive removal of both metal ions onto rGONF occurred through monolayer adsorption on a homogeneous surface of rGONF. The pH-edge adsorption results suggest the adsorption occurs through an inner-sphere surface complex, which is proved by 2-pKa-diffusion model fitting, where the pH-edge adsorption data was well fitted. The adsorption of metal ions increased with increasing temperature. The overall obtained results demonstrated that the rGONF was an effective adsorbent for Pb(II) and Cr(III) removal from wastewater.

Due to health and pollution concerns of aquatic environments related to the presence of heavy metal toxic ions, the necessity of developing devices able to detect and to monitor such kinds of species has recently gained importance. Carbon paste electrodes (CPEs) a starting approach to obtain new ion-selective devices by supporting materials like bentonite and/or clay; which become sensitive to lead(II) when they are suitably modified by chemical treatments to obtain different hybrid materials. In this work, two natural clays and three different hybrid materials were produced and then were characterized by X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy to assess their physico-chemical properties. After this stage, the electrochemical characterization of the modified CPEs using hybrid materials was performed by cyclic voltammetry, using the standard Fe(CN) 6 4− /Fe(CN) 6 3− redox couple. Subsequently, this study performed electrochemical experiments on lead(II) containing solutions, to test the ability of the examined CPEs to detect this toxic ion present in very low amounts. Lead(II) exhibited a reversible two electron oxidation/reduction behaviour in the cyclic voltammetry analyses and a reasonably good linear behaviour of the current associated with the oxidation peak as a function of its concentration (5.0-40.0 µg/L). The detection limit was found to vary in the range of 3-5 µg/L for the different modified CPEs. The presence of several co-existing ions showed that an interference variation had occurred. These results, therefore, show a restriction of the selectivity of the electrode up to a certain extent in the lead(II) detection. Finally, tap water with spiked lead(II) was analyzed to verify the suitability of the electrodes in the low level detection of lead(II) from real matrix samples.

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This paper describes part of a comprehensive National Air Emissions Monitoring Study (NAEMS) conducted at a swine finishing farm located in the state of Indiana, in the United States. The NAEMS was a 2-year study of emissions from animal feeding operations that produce pork, chicken meat, eggs, and milk. It provided emission data for the US. Environmental Protection Agency (EPA) to develop tools for estimating emissions from livestock farms. The study in Indiana focused on quantifying and characterizing emissions of gases, particulate matter (PM), and volatile organic compounds (VOCs) from a swine finishing quad (four 1000-head rooms under one roof). Long-term continuous and quasi-continuous measurements were conducted with 157 on-line measurement variables using an array of instruments and sensors for gas and PM concentrations, fan operation, room static pressures, indoor temperature and humidity, animal activity and feeding times, and weather conditions. Pig inventory and weight, feed type and quantity, and manure accumulation and composition were also documented. Systematic tests of the measurement system were conducted. Monitoring methodologies, instrumentation applications, equipment maintenance, quality controls, and system performances are presented and can be used as a reference in assessing research quality and improving future environmental studies on livestock facilities.