[Isolation of filamentous fungi capable of enhancing sludge dewaterability and study of mechanisms responsible for the sludge dewaterability enhancement].

To study the influence of filamentous fungi on the sludge dewaterability is very significant for the development of biological treatment methods for enhancing sludge dewaterability. In this study, filamentous fungi capable of enhancing sludge dewaterability were isolated from sewage sludge and the related mechanisms responsible for the sludge dewaterability enhancement were investigated. A filamentous fungus Mucor circinelloides ZG-3 was successfully isolated from sludge, and sludge dewaterability could be drastically improved by this fungus. Further study revealed that the enhancement of sludge dewaterability was influenced by inoculation method, inoculum size and solid content of sludge. The optimal inoculation method was mycelia inoculation, the optimal inoculum size was 10%, and the optimal solid content of sludge was about 4%. Under the optimized conditions, the specific resistance to filtration (SRF) of sludge could be decreased by 75.1% after being treated by M. circinelloides ZG-3. After the treatment, the COD value of sludge supernatant was only 310 mg x L(-1), and the treated sludge still exhibited good settleability. During the treatment of sewage sludge by M. circinelloides ZG-3, the mechanisms responsible for the sludge dewaterability enhancement included the degradation of sludge extracellular polymeric substances (EPS) and the decrease of sludge pH. Therefore, the treatment of sewage sludge using M. circinelloides ZG-3 is a useful and novel method for sludge conditioning.

[Biosynthetic schwertmannite as catalyst in Fenton-like reactions for degradation of methyl orange].

Biosynthesized schwertmannite was used as catalyst in photo-Fenton-like reaction to facilitate the degradation of methyl orange (MO). Schwertmannite was synthesized through the oxidation of FeSO4 by Acidithiobacillus ferrooxidans LX5 cell suspension at an initial pH 2.5 and 28 degress C for 3 days and characterized using X-ray diffraction spectroscopy and scanning electron microscope. The oxidative degradation of MO in the photo-Fenton-like reaction was studied at different initial pH values of suspension, concentrations of H2O2 and dosages of catalyst. The results suggested that the biosynthetic schwertmannite showed a good catalytic activity in the MO degradation via *OH radical mechanism. Considerable degradation efficiency of MO was still obtained in approximately neutral condition or in the presence of high concentrations of chloride, sulfate and nitrate. This work demonstrated that the heterogeneous photo-Fenton-like reaction catalyzed by the biosynthetic schwertmannite is a promising advanced oxidation technology for the treatment of wastewater containing MO.

[Elimination of pathogens in municipal sludge and tannery sludge by bioleaching approach].

Heavy metals could be removed from sludge by bioleaching approach, and pathogens in sludge may also be eliminated by the approach. Elimination efficiencies of pathogens in municipal sludge and tannery sludge during bioleaching were studied through batch trials. The results revealed that, after 6 - 7 days of bioleaching compared with the control without bioleaching, the amounts of bacteria in municipal sludge decreased from 1.38 x 10(8) cells/mL to 4.43 x 10(6) cells/mL, and the amounts of bacteria in tannery sludge decreased from 9.23 x 10(5) cells/mL to 4.26 x 10(4) cells/mL. The amounts of sludge bacteria in the control were maintained at the similar level before and after bioleaching. Elimination efficiencies of total coliforms (TC) and fecal coliforms (FC) in bioleached sludge exceeded 99% . But bioleaching approach couldn't eliminate ascarid eggs, as indicating similar levels for survival ascarid eggs before and after sludge bioleaching. Axenic culture of coliforms revealed that the low pH caused by the bioleaching was responsible for pathogens elimination instead of the increases of the concentrations of SO4(2-) and heavy metals.