Laboratory scale batch experiments were conducted at 20 degrees C to investigate the acidogenic fermentation for the conversion of wasted sludge into short chain fatty acids (SCFA) to be utilized as a carbon source in the denitrification process. Hydraulic retention time (HRT), volatile solid (VS) loading rate and pH were studied as these are the important parameters governing the production of volatile fatty acids (VFA). Four different phases were investigated by varying these parameters. HRT was varied from 2.7 to 8.2 days whereas VS loading rate was varied from 1.2 to 3.6 g d(-1). VFA production decreased with the increase in HRT above 2.7 days. 538.37+/-19.39 mg VFA(produced) x d(-1) (0.176+/-0.010 mg VFA(produced) mg(-1) VS(feed) was found as the maximum value of VFA at 2.7 days. The present results based on wasted sludge showed that almost 0.0483+/-0.0016 mg VFA (as COD mg(-1) initial COD) and about 5% of soluble COD production were achieved, which are slightly less than the results reported for primary sludges. The rates of VFA production increased with the increase in VS, however, opposite results were obtained when pH was increased in the reactor. SCFA/FA ratios during fermentation were found in the range of 67-73%. The specific denitrification rates (SDNR) of methanol (2.20+/-0.44 mg NO3-N g(-1) MLVSS x h(-1)) and the fermenter supernatant (2.00+/-0.45 mg NO3-N g(-1) MLVSS x h(-1)) were found to be comparable. Fermenter supernatant, therefore, has the potential to be utilized as a carbon source. However, the results need to be investigated further on a larger scale to ascertain their validity.

The purposes of this study are to obtain information on the leachability of dioxins depending on the samples, to confirm the effect of dissolved humic matter (DHM) on the leachability of dioxins, and to evaluate the suitability of the detoxification treatments specified by the Japanese government for the reduction of leachability of dioxins. In this study, the leachability of dioxins from raw and treated fly ash was evaluated by a 24-hour batch leaching test and by an extraction test repeated three times with DHM solution, whose concentration was determined to be 700 mg-OC/L as an initial concentration based on organic carbon (OC) from adsorption tests of DHM to fly ash. The leaching concentration from fly ash samples having high DHM adsorption capacity was low regardless of pH, and that from samples having relatively low adsorption capacity and high pH was largely increased. Therefore, it is expected that the leachability of dioxins from treated fly ashes would be reduced by avoiding high pH and enhancing the DHM adsorption capacity rather than by using the detoxification method specified. We also confirmed that increase of the leachability of HOPs due to DHM is not as large as known in condition that is composed of three phases of HOPs, DHM, and solid matrix.