Determinants of variability of protein content, volume and pH of exhaled breath condensate.

Collection of exhaled breath condensate (EBC) is a simple and noninvasive method to obtain information on the respiratory system. Different mediators can be determined in EBC. However, determinants of variability are not well described. The aim of this study was to evaluate variability of pH, volume and protein concentration of EBC between individuals and between sampling times. Therefore, EBC was collected from 20 healthy volunteers on two different days. Median pH for all samples, measured 5 min after collection without deaeration, was 6.17. Median volume was 1.70 ml and median total protein concentration was 1.02 microg/ml. Coefficients of variation were 5.17%, 21.84% and 37.93%, respectively. No intra- or interday variability could be found, except for the first collection time. Between individuals, significant differences were observed for all three mediators. Age, height and gender can explain part of this variation. In conclusion, no significant difference between sampling times on the same day or on different days was obtained for pH, volume and total protein concentration, provided that subjects are experienced in collecting EBC.

Anaerobic digestion as a core technology in sustainable management of organic matter.

In the past decades, anaerobic digestion (AD) has steadily gained importance. However, the technology is not regarded as a top priority in science policy and in industrial development at present. In order for AD to further develop, it is crucial that AD profits from the current fuel issues emerging in the international arena. AD can provide low-cost treatment of sewage and solid domestic wastes, which represents a vast application potential that should be promoted in the developing world. Furthermore, the developments in the last decades in the domain of anaerobic microbiology and technology have generated some interesting niches for the application of AD, such as anaerobic nitrogen removal and the treatment of chlorinated organics. Recently, AD has also generated some serendipities, such as the use of AD in processes for sulphur and calcium removal and the coupling of AD with microbial fuel cells. The international developments in terms of bio-refineries and CO2-emission abatement are of crucial importance with respect to the impetus that AD will receive in the coming decade. There should be little doubt that by placing the focus of AD on the production of green energy and clean nutrients, the future of AD will be assured.

Wet oxidation treatment of organic household waste enriched with wheat straw for simultaneous saccharification and fermentation into ethanol.

Organic municipal solid waste enriched with wheat straw was subjected to wet-oxidation as a pre-treatment for subsequent enzymatic conversion and fermentation into bio-ethanol. The effect of temperature (185-195 degrees C), oxygen pressure (3-12 bar) and sodium carbonate (0-2 g l(-1) ) addition on enzymatic cellulose and hemicellulose convertibility was studied at a constant wet oxidation retention time of 10 minutes. An enzyme convertibility assay at high enzyme loading (25 filter paper unit (FPU) g(-1) dry solids (DS) added) showed that up to 78% of the cellulose and up to 68% of the hemicellulose in the treated waste could be converted into respectively hexose and pentose sugars compared to 46% for cellulose and 36% for hemicellulose in the raw waste. For all wet oxidation conditions tested, total carbohydrate recoveries were high (> 89%) and 44-66% of the original lignin could be converted into non-toxic carboxylic acids mainly (2.2-4.5 % on DS basis). Simultaneous saccharification and fermentation (SSF) of the treated waste at 10% DS by Saccharomyces cerevisae yielded average ethanol concentrations of 16.5 to 22 g 1(-1) for enzyme loadings of 5 and 25 FPU g(-1) DS, respectively. The cellulose to ethanol conversion efficiency during SSF was 50, 62, 65 and 70% for a total enzyme loading of 5, 10, 15 and 25 FPU g(-1) DS, respectively. Hence, this study shows that wet oxidation is a suitable pre-treatment for the conversion of organic waste carbohydrates into ethanol and that compatible conversion yields (60-65%) can be achieved at moderate enzyme loadings.

Solid waste digestors: process performance and practice for municipal solid waste digestion.

The most common types of anaerobic digesters for solid wastes have been compared based on biological and technical performance and reliability. Batch systems have the most simple designs and are the least expensive solid waste digesters. They have high potential for application in developing countries. Two-stage systems are the most complex and most expensive systems. Their greatest advantage lies in the equalisation of the organic loading rate in the first stage, allowing a more constant feeding rate of the methanogenic second stage. Two-stage systems with biomass accumulation devices in the second stage display a larger resistance toward toxicants and inhibiting substances such as ammonia. However, the large majority of industrial applications use one-stage systems and these are evenly split between "dry" systems (wastes are digested as received) and "wet" systems (wastes are slurried to about 12% total solids). Regarding biological performance, this study compares the different digester systems in terms of organic loading rates and biogas yields considering differences in input waste composition. As a whole, "dry" designs have proven reliable due to their higher biomass concentration, controlled feeding and spatial niches. Moreover, from a technical viewpoint the "dry" systems are more robust and flexible than "wet' systems.

Nitrous oxide emissions from waste water.

The estimation of nitrous oxide emissions is complicated by the high degree of uncertainty on the emission factors involved and by the limited acquaintance with all significant nitrous oxide sources. A potentially important source for which emission data are lacking is the sewage system transporting waste water from human activities. For this study an experimental measurement campaign has been carried out on waste water sampled at different sewage treatment plants. The nitrous oxide developing from the water samples was monitored by means of gas chromatography. The methodological analysis was based on the concentration/time curves obtained. Our results indicate that the formation of nitrous oxide from the waste water matrices results from microbiological denitrification. We deduced tentative emission factors for the waste water types studied.