In a previous study, it was determined that nonionic surfactants could be removed from wastewater using the typical soil. In this report, the recovery of nonionic surfactants was examined with the purpose of reusing the removed surfactants. It was found that a packed bed of soil employed with the nonionic surfactants and the use of alcohol as the recovery agent was most effective. In the case of polyoxyethylenenonylphenylether NP10 (50 ppm), 50 vol% i-PrOH was found to be the most effective for the recovery process. This resulted in a recovery rate of 100%. The following recovery rate was recorded in descending order of i-PrOH>t-BuOH>n-PrOH, EtOH>MeOH. Also, the maximum recovery value resulted between each of the 5 alcohol concentration and their respective recovery rates. The recovery rate of the nonionic surfactants of a low concentration was decreased. In addition, the recovery rate of nonionic surfactants decreased as the mole numbers of the added ethyleneoxide units increased for the nonionic surfactants NP10, NP15 and NP20.

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Continuous operation treating 100 g·L^-1 total solids (TS) simulated food waste was investigated using a novel methane fermentation reactor that enables the agitation of the fermentation liquid without electricity. In this study, the overall performance and reaction attributes of the reactor were evaluated. Under mesophilic condition and at different chemical oxygen demand (COD_Cr) loading rates (5 to 10 kg·m³·d^-1), the reactor achieved 220 days of stable continuous operation. Inside the reactor, the continuous change in the liquid level and the 5 to 16 times self-agitation occurred daily, which was likely responsible for the distribution of organic load near the inlet port of the reactor. The reactor attained 0.72-0.82 m³·g^-1-TS biogas production yield and 79.4-85.5% COD_Cr reduction on average, and a small amount of volatile fatty acid (VFA) was detected in the effluent. These results suggest that the novel reactor investigated is comparable in biogas production yield and COD_Cr reduction and superior in residual VFA level to the completely stirred tank reactor, in the treatment of same simulated food waste used in a previous study.

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