Characteristics transformation of humic acid during ozonation and biofiltration treatment processes.

Characteristics transformation of humic acid extracted from natural water during the ozonation and biofiltration treatment processes was investigated based on the analyses of total organic carbon, UV absorbance, infrared spectroscopy, and gel permeation chromatography. With ozone doses of 1, 4, and 7 mg/L, high-molecular-weight humic acid was cleaved into low-molecular-weight particles and accumulated at group 6 (molecular weight < or = 4000 g/mole) on the Sephadex G-75 (Pharmacia Fine Chemicals, Uppsala, Sweden) fraction. Furthermore, the molecular-size distribution of organic compounds by Sephadex G-25 was shifted from groups 2 (molecular weight = 4000 to 400 g/mole) and 3 (molecular weight = 400 to 180 g/mole) to groups 2, 3, and 4 (molecular weight < or = 180 g/mole) under ozone doses of 1 and 4 mg/L. An increased ozone dose destroyed functional groups C=C and C-O of aromatic and phenolic compounds and increased UV-insensitive biodegradable organic carbon for subsequent biofiltration.

Effects of temperature and initial pH on biohydrogen production from food-processing wastewater using anaerobic mixed cultures.

This study attempted to determine the optimal temperature and initial cultivation pH by conducting a series of batch tests in stirred-tank bioreactor using fructose-producing wastewater as an organic substrate. The bioreactor temperature was controlled at 35-55°C with an initial pH of 4-8. Hydrogen production efficiency was assessed using specific hydrogen production potential (SHPP) and the maximum specific hydrogen production rate (SHPR(m)). Experimental results indicated that temperature and initial pH markedly affected SHPP and SHPR(m), volatile fatty acids distribution as well as the ratio of butyrate/acetate (BHu/HAc). Two-fold higher SHPP and SHPR(m) were obtained at thermophilic condition (55°C) than those at mesophilic condition (35°C). The optimal initial pH was 6 for hydrogen production with peak values of SHPP of 166.8 ml-H(2)/g-COD and SHPR(m) of 26.7 ml-H(2)/g-VSS-h for fructose-processing wastewater. Molasses-processing wastewater had a higher SHPP (187.0 ml-H(2)/g-COD) and SHPR(m) (42.7 ml-H(2)/gVSS-h) than fructose-processing wastewater at pH 6. The DGGE profiles indicated that molasses-processing wastewater is a better substrate than fructose-processing wastewater for growth of hydrogen-producing bacteria due to the high staining intensity of bands.