Thermal degradation of emerging contaminants in municipal biosolids: The case of pharmaceuticals and personal care products.

The presence of emerging contaminants in water and wastewater resources is of ongoing concern for public health and safety. Pharmaceutical compounds are designed to be biologically active and therefore may have effects on nontarget organisms in terrestrial and aquatic environments, even at trace concentrations. The presence of pharmaceutical and personal care products (PPCPs) in wastewater treatment plants is reported in various countries worldwide, mostly in the levels of nanograms to micrograms per litre. The present study investigates the thermal degradation of municipal sewage sludge containing PPCPs at various heating rates. The examined characteristics of the samples include thermal decomposition behavior, volatile release characteristics, and pyrolytic product composition. Thermal characterization of the PPCPs was conducted using differential scanning calorimetry. The gaseous products and typical functional groups of the released volatiles detected by Fourier-transform infrared spectroscopy mainly contained CO2, CO, small-chain hydrocarbons, and oxygen- and nitrogen-containing functional groups together with other species. In addition, the potential of bioenergy production was investigated as a spin-off opportunity during thermal degradation of biosolids. Study results showed that PPCP concentrations can be lowered significantly by thermal treatment of municipal biosolids. Antifungal/antibacterial agents together with opioids, in particular triclosan and tramadol, showed less resistance to thermal degradation while antibiotics could be more recalcitrant to heat treatment. The thermodynamic results provide an important reference for future reactor design and the thermochemical treatment of biosolids as well as their conversion to value-added products.

Reverse Microemulsion-Synthesized High-Surface-Area Cu/γ-Al2O3 Catalyst for CO2 Conversion via Reverse Water Gas Shift.

Reverse microemulsion method was implemented to synthesize a CuO/γ-Al2O3 catalyst (18 wt % Cu) with a specific surface area (SSA) of 328 m2/g (after calcination at 400 °C). Catalytic performance was evaluated in the range of temperatures and space velocities (300-600 °C and 10,000-200,000 mL/(g h)). The catalyst was 100% selective to CO generation while attaining a nearly equilibrium CO2 conversion at 500 °C (ca. 50% at 10,000 mL/(g h) and H2/CO2 = 4). Despite the initial reduction of surface area under the reaction conditions, the reduced Cu/γ-Al2O3 catalyst demonstrated a stable performance for 80 h on stream, attaining a nearly equilibrium CO2 conversion at 600 °C (ca. 60% at 60,000 mL/(g h) and H2/CO2 = 4). The selectivity to CO generation remained complete during the stability test, and no significant carbon deposition was detected.

Energo- and exergo-technical assessment of ground-source heat pump systems for geothermal energy production from underground mines.

The objective of this study is to perform the energy and exergy analysis of an integrated ground-source heat pump (GSHP) system, along with technical assessment, for geothermal energy production by deployment of Engineering Equation Solver (EES). The system comprises heat pump cycle and ground heat exchanger for extracting geothermal energy from underground mine water. A simultaneous energy and exergy analysis of the system is brought off. These analyses provided persuasive outcomes due to the use of an economic and green source of energy. The energetic coefficient of performance (COP) of the entire system is 2.33 and the exergy efficiency of the system is 28.6%. The exergetic efficiencies of the compressor, ground heat exchanger, evaporator, expansion valve, condenser and fan are computed to be 38%, 42%, 53%, 55%, 60% and 64%, respectively. In the numerical investigation, different alteration such as changing the temperature and pressure of the condenser show promising potential for further application of GSHPs. The outcomes of this research can be used for developing and designing novel coupled heat and power systems.

The effects of co-substrate and thermal pretreatment on anaerobic digestion performance.

The influence of anaerobic co-digestion of leachate and sludge with organic fraction of municipal solid waste (OFMSW) under mesophilic condition in three batch digesters of 5 L capacity has been studied. OFMSW was mixed with leachate and sludge at three different ratios. Experimental results illustrated that the digester with a ratio of 2000/2500 (leachate (mL) or sludge/OFMSW (mL)) had significantly higher performance. Furthermore, this study compared the performance of anaerobic digestion of different substrates with three different mixing ratios with and without thermal pretreatment at low temperature (65°C) in terms of biogas production, chemical oxygen demand (COD) elimination as well as hydraulic retention time. In addition, to predict the biogas yield and evaluate the kinetic parameters, the modified Gompertz model was applied. Based on the results, the maximum biogas yield from adding different leachate and sludge ratios to OFMSW was recorded to be 0.45 and 0.38 m3 kg-1 COD which was higher about 7% in comparison with co-digestion original OFMSW without thermal pretreatment. In addition, thermal pretreatment accelerated the hydrolysis step. Moreover, the total COD elimination was relatively stable in the range of 52-60% at all types of substrate mixtures. Also, the modified Gompertz model demonstrated a good fit to the experimental results. ABBREVIATIONS: AD: anaerobic digester; BOD: biochemical oxygen demand; COD: chemical oxygen demand; FAAS: flame atomic absorption spectroscopy; HS: high solids; HRT: hydraulic retention time; LS: low solids; MS: medium solids; OFMSW: organic fraction of municipal solid waste; TCD: thermal conductivity detector; TS: total solid; TSS: total suspended solids.

Soil washing of chromium- and cadmium-contaminated sludge using acids and ethylenediaminetetra acetic acid chelating agent.

In this research, the effect of soil washing in the removal of chromium- and cadmium-contaminated sludge samples collected from Pond 2 of the Tehran Oil Refinery was investigated. These metals are considered as hazardous substances for human health and the environment. The carcinogenicity of chromate dust has been established for a long time. Cadmium is also a potential environmental toxicant. This study was carried out by collecting sludge samples from different locations in Pond 2. Soil washing was conducted to treat the samples. Chemical agents, such as acetic acid, ethylenediaminetetra acetic acid (EDTA) and hydrochloric acid, were used as washing solutions to remove chromium and cadmium from sludge samples. The results of this study indicated that the highest removal efficiencies from the sludge samples were achieved using a 0.3 M HCl solution with 82.69% and 74.47% for chromium and cadmium, respectively. EDTA (0.1 M) in the best condition extracted 66.81% of cadmium and 72.52% of chromium from the sludges. The lowest efficiency values for the samples, however, were achieved using 3 M acetic acid with 41.7% and 46.96% removals for cadmium and chromium, respectively. The analysis of washed sludge indicated that the heavy metals removal decreased in the order of 3 M acetic acid < 0.1 M EDTA<0.3 M HCl, thus hydrochloric acid appears to offer a greater potential as a washing agent in remediating the sludge samples.