OMSWOlive Mill Solid Waste
OMSWOntario Medical Students' Weekend (Ontario, Canada)
OMSWOh My Sweet Wesley
OMSWOh My Sky Wizard
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Figures 1, 2, 3, and 4 show the evolution of methane production with time for ultrasonically pretreated two-phase OMSW at 20, 90, and 180 min and untreated OMSW, respectively.
[4] with thermally pretreated OMSW: a first-order exponential model for the first stage which is commonly applicable to easily biodegradable substrates [33] and a second sigmoidal or logistic model with its three characteristic phases, that is, lag, exponential increase, and final stabilization step [34].
Table 5 shows the specific rate constants (K) obtained for the first stage of digestion (untreated two-phase OMSW and pretreated two-phase OMSWs at 200 W during 20, 90, and 180 min) with values ranging between 0.82 [+ or -] 0.06 and 1.21 [+ or -] 0.14 [days.sup.-1].
For the logistic model the maximum methane production obtained in the second stage (P) had the maximum value for the 90-minute pretreatment (200 mL C[H.sub.4]/g [VS.sub.added]) followed by the 180-minute pretreatment (174mLC[H.sub.4]/g [VS.sub.added]), untreated OMSW (171 mL C[H.sub.4]/g [VS.sub.added]), and pretreatment during 20 minutes (130 mL C[H.sub.4]/g [VS.sub.added]) (Table 6).
The shortest lag phase (A) was obtained for US (20 min), that is, 6.3 days, while the longest lag phase was achieved for the untreated OMSW, that is, 9.4 days.
The degradation rate of ultrasound pretreated OMSW during 90 minutes was the fastest of the four conditions tested, achieving a maximum methane production rate ([R.sub.m]) of 70.5 mL C[H.sub.4]/(g VS x day) after 7.9 days of digestion period.
Ultrasound pretreatment during 90 minutes gives the most promising results for a fast OMSW degradation process making available a large concentration of soluble and biodegradable components.
Anet balance of the consumed energy in the pretreatment and the produced energy through BMP for the ultrasound pretreated OMSW was found to be negative for all pretreatment times and specific energies studied.
Ultrasound pretreatment of two-phase OMSW at a power of 200 W (100% amplitude) and a constant frequency of 24 kHz during 20, 90, and 180 minutes increased the COD solubilization of this substrate compared to the untreated sample.