Respirometric assays at fixed and process temperatures to monitor composting process

Abstract

A static respirometer was built to determine the Respirometric Index (RI) of composting samples at different temperatures. Composted materials were dewatered sludge (DS) and dewatered anaerobically digested sludge (ADS) obtained from a wastewater treatment plant. Respirometric indexes were obtained at a fixed value of 37 ºC (RI 37 ) and at the in situ temperature of the reactor at the moment of sampling (RI T ). Results indicated that both indexes correlated well with temperature evolution in the composter.However, RI T were more representative of the metabolic activity in the reactor and were also more sensitive to temperature and composition variations of the composting material. Nevertheless, when process temperature felt below optimum mesophilic conditions, RI T were useful for the monitoring but not for determining the actual stability of the material. Moreover, the importance of the units used to express RI was also analysed during the composting of sludge from the paper industry, a highly compostable residue. RI expressed on dry matter basis indicated that this was a stable

In search of a reliable technique for the determination of the biological stability of the organic matter in the mechanical–biological treated waste

“…Static Respiration Index (SRI) was determined using a static respirometer based on the model previously described by Ianotti et al (1993) and according to the method described by Barrena et al (2005). Briefly, the drop of oxygen content in a flask containing a waste representative sample (250 g) was monitored with an oxygen meter (Lutron 5510, Lutron, Taiwan) connected to a personal computer (RS232 communication protocol) with in-house developed software to register oxygen values.…”

“…However, in the solid waste treatment, there is no a consensus within the research community. At this moment, some assays have been developed, under aerobic (Scaglia et al, 2000;Adani et al, 2001;Adani et al, 2004a;Barrena et al, 2005) and anaerobic conditions (Ligthart and Nieman, 2002;Hansen et al, 2004). These assays are usually based on respirometric techniques (static and dynamic) and methanogenic activity assays.…”

“…Although some authors present partial comparisons between static and dynamic respirometric approaches or some correlations between indices used for biodegradable organic matter determination (Adani et al, 2003;Gea et al, 2004;Barrena et al, 2005), this is, to our knowledge, the first study where a massive comparison of indices and methods is P r e -p r i n t carried out. The objectives of this research are therefore: i) to study the suitability of the methods proposed by different authors or institutions for the determination of the biological stability in samples from a MBT plant, which were obtained at different stages of their biodegradation; ii) to compare the two main groups of methods proposed (aerobic and anaerobic), iii) to determine the correlations among the methods studied and iv) to determine the efficiency of the treatment of biodegradable organic matter in the MBT studied, based on some selected indices.…”

Prediction of temperature and thermal inertia effect in the maturation stage and stockpiling of a large composting mass

“…A static respirometer was built according to an original model previously described (Ianotti et al, 1993) (Barrena et al, 2005).…”

“…Results of the static respiration index (RI) are presented as an average of three replicates. A detailed description of the RI calculation can be found elsewhere (Barrena et al, 2005). Samples for respiration index were periodically obtained at day 0, 14, 28, 42 and 50.…”