Sludge inoculum soiling

Biodegradation average rate k = 25.0 mg COD g h based on measurements of COD decrease using activated sludge inoculum with 20-d of adaptation to the substrate (Pitter 1976 quoted. Scow 1982) time necessary for complete degradation of 16 m/L in 14-25 d by wastewater (Haller 1978) aerobic degradation in a non-sterile clay loam soil 91% loss at 0°C after 8 d at the termination of the experiment, 94% loss at 4°C after 8 d and 100% loss at 20°C after 10-15 d all under same exptl. conditions (Baker et al. 1980) ... 

FIGURE 6.15 Gas evolution data (filled symbols) plotted as percent mineralization for the biodegradation of bleached paperboard packaging material in a respirometer. Soil media (70 wt% humidity) with sewage sludge inoculum was used. Also included is a plot of the data (open symbols) as suggested by Equation 6.2. Source Reproduced with permission from Andrady and Song (1999). 

Biological. In activated sludge, 31.5% of the applied chlorobenzene mineralized to carbon dioxide after 5 d (Freitag et al., 1985). A mixed culture of soil bacteria or a Pseudomonas sp. transformed chlorobenzene to chlorophenol (Ballschiter and Scholz, 1980). Pure microbial cultures isolated from soil hydroxylated chlorobenzene to 2- and 4-chlorophenol (Smith and Rosazza, 1974). Chlorobenzene was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum. At a concentration of 5 mg/L, biodegradation yields at the end of 1 and 2 wk were 89 and 100%, respectively. At a concentration of 10 mg/L, significant... 

Biodegradation aqueous aerobic t,2 = 168-672 h, based on unacclimated aqueous aerobic screening test data (Gummer 1979 Kanazawa 1987 quoted, Howard et al. 1991) aqueous anaerobic t,/2 = 672-2688 h, based on estimated unacclimated aqueous aerobic biodegradation half-life (Howard et al. 1991) t, 2 = 44 d under aerobic conditions and t,/2 = 59 d under anaerobic conditions in water used a combination of activated sludge, silt loam soil and sediment as an inoculum t,/2 = 78 d under aerobic conditions and t, 2 = 125 d under anaerobic conditions at pH 6.9 (Howard 1991). 

Scope This Standard specifies a method by measuring the oxygen demand in a closed respirometer, for the determination of the degree of aerobic biodegradability of plastic materials, including those containing formulation additives. The test material is exposed in an aqueous medium under laboratory conditions to an inoculum from activated sludge, compost or soil. 

Principle The test item is placed into an aqueous mineral medimn, spiked with inoculum and incubated under batch conditions (this is a single, one-shot feeding). The inoculum can be either activated sewage sludge, compost eluate, soil eluate or a combination of 2 or 3 of these. The duration of the test is not really specified. The test should be run until a plateau in activity is reached. In practice, a minimum duration is typically 4 weeks. The maximum duration, in contrast, is defined precisely in the norm and is 6 months. 

The test might be carried in water or soil, but the latter is discussed here. In both cases a suitable volume of activated sludge to obtain complete mineralization of the sample in about a month is used as an inoculum. About lOcm per liter is recommended for aqueous systems and we have used 5cm per 50 g with soil media successfully. The inoculum must be used the same day as collected and kept aerated until used. Also sufficient urea and potassium hydrogen phosphate (0.1 and 0.05 percent of weight of polymer substrate) are added to the medium to fortify it and to promote faster microbial growth. 

Degradation results obtained in a compost environment at elevated temperatures or in soil differ significantly from those determined in a liquid system. In liquid media the degradation rate is usually much slower for the copolyesters. Besides the lower temperature, which is in most cases at ambient temperature, a different microbial population may be responsible for the differences. In degradation tests in liquid environment, the inoculum to provide microbial activity is often taken from sewage sludge. Although in some cases eluates from soil or compost are used to inoculate the media, a liquid environment is not optimal to... 

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