Investigation of the microbial population dynamics during the waste treatment for the evaluation of the biodegradability by the means of impedance analysis
The biodegradability or the achieved stabilisation degree of biologically treated waste are required parameters to provide the evidence of the fulfilment for the German Waste Storage Ordinance.
The test procedures RA4 (respiration activity over 4 days) and GF21 (gas formation over 21 days) recommended in AbfAblV takes at least 4 or 21 days respectively. Moreover, despite uniform regulation, obtained results of analysis, show a strong dispersion of values particularly analysed by different laboratories (Bockreis, 2006).
Within this work basics for a new microbiological approach, the impedance analysis, are examined for the evaluation of the biodegradability. A new parameter for the evaluation of stabilization degree BBI (Biodegradability By Impedance) is invented. Further, a successful application of this fast impedimetric method could shorten the determination of the biodegradability to one day.
Impedance analytics have found a large attention in microbiology since the seventies (Cady, et al., 1978). Today this method is used for sterility control and germ number determination above all in the food industry and health care (Futschik, 1988). Some applications within the field of the wastewater and sludge characterisation are similarly published (Weichgrebe, 2004).
For the introduction of the impedance analysis as a fast method to characterise the waste’s stability, information is necessary about the microbial activity against the treatment of waste. Thus the investigation of the microbial population dynamics of full-scale waste treatment plants and the assessment of the suitability of the impedance analysis as a highspeed method are the aims of this investigation. By differential selective growth media, microorganism groups are screened, which can be used as indicators for the individual stabilisation of the waste at various degree levels. The investigation is carried out with compost material and MBT (Mechanical Biological Treatment) -output materials. Furthermore, the microbial population dynamics are correlated with the standard parameters RA4 and GF21. The results of the investigations show that the microbial population changes during the waste treatment considerably. Finally, no clear correlation between the germ number and the degree of stabilisation is determined. On the other hand, a clear correlation resulted in the case of impedance analysis and degree of stabilisation. The new parameter BBI can be used for the evaluation of the stabilization degree. In addition the impedance values can be converted with appropriate regression equations into the standard parameters RA4 and GF21. Hence, it seems suitable, that waste samples may becontrolled within a day on their depositing ability according to AbfAblV by impedance analysis
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