Comparison of sapromat and oxitop-method for analysing respiration activity (AT4)

In the run-up for amending the Austrian landfill ordinance, parameters were developed to assess the stability/reactivity of mechanical-biologically pre-treated residual waste. The Landfill Ordinance 2008 (= Deponieverordnung 2008) regulates limit values for Respiration Activity (= 'Atmungsaktivitätâ€) AT4 < 7 mgO2/g DM, Gas Generation Sum GS21 < 20 Nl/kg DM and alternatively Gas Evolution (= 'Gasbildungâ€) GB21 < 20 Nl/kg DM). Methods for analysing these parameters were established by the Austrian Standards Institute (OE-NORM S2027 - 1 to 3, 2004a, b and c). As laboratory practice shows, these methods also are used for the assessment of other wastes (e.g. sewage sludge, commercial waste, material from abandoned sites, bio-waste compost). For measurement of respiration activity in Austria mainly two equipments are used - Sapromat® and OxiTop®. Whether respectively to what extent these two methods give same results, is discussed in this paper.

Since 2009 at ABF-BOKU 275 respiration activity tests of samples from different stages of MBT- resp. biowaste composting processes, samples from recultivation layers, materials from landfills resp. abandoned sites and residues from anaerobic treatment were analysed parallel by Sapromat® and OxiTop®. The range of AT4 for these 275 samples was between 0.1 and 109 mg O2/g DM (69 of them > 20 mg O2/g DM). Samples were ground wet to particle size < 20 mm. Water content was optimised by fist test. For Sapromat® test 30-50 g WM were put into 500 ml glass vessels; for OxiTop® test 40-65 g WM were put into 2,500 ml glass vessels. Both tests were started at same day with same well prepared sample in the same laboratory in duplicates each.
As already known there is a really good correlation between Sapromat® and OxiTop® method. First results (169 samples, R2 = 0.973) already were shown at the Sardinia symposium 2011. In this former investigation high reactive samples were underrepresented (just 6 samples in the range AT4 > 50 mg O2/g DM). Thus additional 'high reactive†samples were analysed. Correlations were evaluated for each type of material separately as well as for all materials together. OxiTop® shows lower findings than Sapromat®. For low reactive range (AT4 < 20 mg O2/g DM) readings for all the different materials show very high correlations (R2 between 0.983 and 0.995) and similar lower findings (mean 89 %, range from 88 to 90 %, just recultivation layers show 84 %) in OxiTop® compared to Sapromat®. The mean errors of prediction are 0.4 to 1.1 mg O2/g DM. For full range of reactivity coefficients of determination (R2) are 0.983 to 0.996. Lower readings vary between 90 % and 97 % (mean 95 %, again low reactive recultivation layers show lowest readings 84 %). The mean errors of prediction are 0.4 to 3.1 mg O2/g DM. The reason for increase of percentage found by OxiTop® seem to be inhibiting metabolic products of degradation, which are discharged more frequently by OxiTop® because necessity of daily opening of system for oxygen supply in case of high reactive material.



Copyright: © European Compost Network ECN e.V.
Quelle: Orbit 2012 (Juni 2012)
Seiten: 8
Preis: € 8,00
Autor: Dipl.-Ing Erwin Binner
Dr. Katharina Böhm
O.Univ.Prof. Dipl.-Ing. Dr. Peter Lechner
 
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