Marianne Smits

Enhanced biomethanation of kitchen waste by different pre-treatments

Five different pre-treatments were investigated to enhance the solubilisation and anaerobic biodegradability of kitchen waste (KW) in thermophilic batch and continuous tests. In the batch solubilisation tests, the highest and the lowest solubilisation efficiency were achieved with the thermo-acid and the pressure-depressure pre-treatments, respectively. However, in the batch biodegradability tests, the highest cumulative biogas production was obtained with the pressure-depressure method. In the continuous tests, the best performance in terms of an acceptable biogas production efficiency of 60% and stable in-reactor CODs and VFA concentrations corresponded to the pressure-depressure reactor, followed by freeze-thaw, acid, thermo-acid, thermo and control. The maximum OLR (5 g COD L(-1) d(-1)) applied in the pressure-depressure and freeze-thaw reactors almost doubled the control reactor. From the overall analysis, the freeze-thaw pre-treatment was the most profitable process with a net potential profit of around 11.5 € ton(-1) KW.

Transesophageal Endoscopic Ultrasound with Fine Needle Aspiration in the Preoperative Staging of Malignant Pleural Mesothelioma

Purpose: Surgical resection as part of a multimodality approach in malignant pleural mesothelioma (MPM) has a high morbidity and mortality. Because mediastinal lymph node (MLN) metastases are a negative prognostic factor, preoperative staging is of paramount importance. Transesophageal endoscopic ultrasound with real-time guided fine needle aspiration (EUS-FNA) enables accurate MLN staging in lung cancer. Experimental Design: The feasibility and yield of EUS-FNA in MLN staging were prospectively analyzed in patients with presumed early-stage MPM considered for multimodality therapy. MLN reference pathology was defined by either pathologic staging or the formal demonstration of malignant cells by either EUS-FNA or mediastinoscopy. Results: Thirty-two consecutive patients (81% males; median age, 61 years) with proven MPM underwent EUS-FNA. In 11 (34%) patients, a negative EUS-FNA or mediastinoscopy was not confirmed by surgical MLN dissection because of clinical deterioration or disease progression. In 21 (66%) patients, a formal pathology of the MLN was obtained and staging with EUS-FNA was positive in 4 (19%). Mediastinoscopy did not result in a greater yield of MLN metastasis as compared with EUS-FNA. Thoracotomy with complete lymph node dissection was done in 17 (81%). The overall prevalence of MLN metastasis was 24%, and the sensitivity of EUS-FNA was 80% (95% confidence interval, 28-99%) with a specificity of 100% (95% confidence interval, 79-100%). One patient had esophageal perforation related to EUS-FNA. Conclusions: EUS-FNA is feasible and sensitive for MLN staging in patients with MPM who are candidate for multimodality treatment. These data warrant further evaluation.

Concept and Validation of a Fully Automated Photocatalytic Test Setup

Photocatalytic activity can be studied by several methods, each with its own strengths and weaknesses. To study photocatalytic activity in an easy, user-friendly, and realistic way, a completely new setup has been built. The setup is modularly constructed around Fourier transform infrared spectroscopy (FTIR) spectroscopy at the heart of it, resulting in great versatility. Complementary software has been written for automatic control of the setup and for processing the generated data. Two pollutants, oil and n-octane, are tested to validate the performance of the setup. These validation experiments confirm the usefulness and added value of the setup in general and of the FTIR detection methodology as well. It becomes clear that a system of online measurements with good repeatability, accuracy, and user-friendliness has been created.

Photocatalytic Removal of Soot: Unravelling of the Reaction Mechanism by EPR and in situ FTIR Spectroscopy

Photocatalytic soot oxidation is studied on P25 TiO(2) as an important model reaction for self-cleaning processes by means of electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) spectroscopy. Contacting of carbon black with P25 leads on the one hand to a reduction of the local dioxygen concentration in the powder. On the other hand, the weakly adsorbed radicals on the carbon particles are likely to act as alternative traps for the photogenerated conduction-band electrons. We find furthermore that the presence of dioxygen and oxygen-related radicals is vital for the photocatalytic soot degradation. The complete oxidation of soot to CO(2) is evidenced by in situ FTIR spectroscopy, no intermediate CO is detected during the photocatalytic process.

Effect of Operating and Sampling Conditions on the Exhaust Gas Composition of Small-Scale Power Generators

Small stationary diesel engines, like in generator sets, have limited emission control measures and are therefore responsible for 44% of the particulate matter (PM) emissions in the United States. The diesel exhaust composition depends on operating conditions of the combustion engine. Furthermore, the measurements are influenced by the used sampling method. This study examines the effect of engine loading and exhaust gas dilution on the composition of small-scale power generators. These generators are used in different operating conditions than road-transport vehicles, resulting in different emission characteristics. Experimental data were obtained for gaseous volatile organic compounds (VOC) and PM mass concentration, elemental composition and nitrate content. The exhaust composition depends on load condition because of its effect on fuel consumption, engine wear and combustion temperature. Higher load conditions result in lower PM concentration and sharper edged particles with larger aerodynamic diameters. A positive correlation with load condition was found for K, Ca, Sr, Mn, Cu, Zn and Pb adsorbed on PM, elements that originate from lubricating oil or engine corrosion. The nitrate concentration decreases at higher load conditions, due to enhanced nitrate dissociation to gaseous NO at higher engine temperatures. Dilution on the other hand decreases PM and nitrate concentration and increases gaseous VOC and adsorbed metal content. In conclusion, these data show that operating and sampling conditions have a major effect on the exhaust gas composition of small-scale diesel generators. Therefore, care must be taken when designing new experiments or comparing literature results.

Immobilization of TiO_{2} into self-supporting photocatalytic foam : influence of calcination temperature

Immobilization of photocatalytic powder is crucial to obtain industrially relevant purification processes. To achieve this goal, self-supporting TiO2 foams were manufactured by a polyacrylamide gel process. These gels were calcined at different temperatures to study the effect of the calcination temperature on foam characteristics (rigidity, crystallinity, and porosity) and its influence on photocatalytic activity. The results show that an optimal degradation is achieved for those foams calcined between 700 and 800°C. Calcination at higher temperatures results in a steep decrease in activity, explained by stability issues of the material due to formation of Na2SO4 phases and a larger rutile fraction.