Thongchai Panswad

Anaerobic decolorization of reactive dyebath effluents by a two-stage UASB system with tapioca as a co-substrate

This study investigates the anaerobic treatability of the reactive dyebath effluents in three different colors, namely, black, red and blue, by using a pilot scale two-phase UASB system which consisted of an acidification tank and a UASB reactor with a hydraulic retention time of about 12 h for each phase. In the first three experiments, the feed wastewater was prepared from real wastewaters to have a constant coloration of approximately 150 SU (space units) with three different concentrations of tapioca starch as a supplemental carbon source or a co-substrate. The fourth was an experiment on synthetic blue wastewater and the fifth was to study the effect of an initial coloration of 0, 50 or 100 SU with a constant tapioca concentration of 500 mg/l. In the black-dye experiment, using the tapioca concentrations of 500, 1000 and 1500 mg/l, the decolorization efficiencies were not much different, i.e., 67, 71 and 69%, respectively. Subsequently, concentrations of 0, 200 and 500 mg/l tapioca were used for the red-dye and the blue-dye experiments. The decolorization efficiencies of the red-dye experiment were 36, 57 and 56% and those of the blue-dye experiment were 48, 52 and 56%, respectively. In the synthetic wastewater, the decolorization efficiencies were 36, 54 and 57% for 0, 200 and 500 mg/l tapioca, respectively, and in the last experiment, also with the synthetic wastewater, the efficiencies of decolorization of 63% and 56% were found for the initial colorations of 50 and 100 SU, respectively. The supplement of tapioca starch as a co-substrate apparently gave a better color removal performance but the excessively high concentration of tapioca did not enhance the process capability in terms of color removal efficiency. Moreover, experimental results disclosed that sulfate reducing bacteria could increase the organic carbon comsumption of the system but they did not play an important role in color reduction. The acid forming bacteria could have some role in the decolorization process, and the strictly anaerobic methane producing bacteria were not the main and only microorganisms responsible for the color reduction.

Temperature effect on microbial community of enhanced biological phosphorus removal system

Microbial population dynamics to gradual temperature change in an enhanced biological phosphorus removal system was kinetically investigated. As the temperature rose from 20.0 degrees C to 30.0 degrees C, and to 35.5 degrees C, the predominant microbial group changed from the phosphorus-accumulating organisms, PAOs (47-70% of total VSS) to the glycogen-accumulating organisms (64-75% of total VSS), and to the ordinary heterotrophs (90% of total VSS), respectively. Despite the species alteration, the phosphorus contents of the PAOs appeared to be steady within 0.182-0.308 mg/mg VSS(PAO) regardless of the temperature level. The initial specific phosphorus release rates, which are solely due to the PAOs activities, increased with the temperature from 37.5-55.9 to 51.8-61.3, 52.0-76.9, 147.2-210.3, and 374.2-756.3 mgP/gmVSS(PAO) h, at 20.0 degrees C, 25.0 degrees C, 30.0 degrees C, 32.5 degrees C, and 35.0 degrees C, respectively. On the other hand, mean initial specific phosphorus uptake rates of the biomass decreased as the temperature increased; however, the data implied that the rate of the PAOs was higher than the other two microbial groups. These results indicate that the PAOs are lower-range mesophiles or possibly psychrophiles. As the temperature rises, the portion of energy required for maintenance increases substantially which reduces the energy availability for cell reproduction; hence, the PAOs are washed out from the system.

Specific oxygen, ammonia, and nitrate uptake rates of a biological nutrient removal process treating elevated salinity wastewater

Abstract Anaerobic/anoxic/aerobic systems inoculated without and with NaCl acclimated cultures, i.e., Models A and B, respectively, were fed with a synthetic wastewater at various salinity levels. After achieving a steady state, the systems were shocked with 70 g/l NaCl for four consecutive days before returning to pre-shock conditions. At the steady-state, the specific oxygen uptake rates (SOURs) increased with an increase of sodium chloride concentration (from 5.40 to 9.72 mg O 2 /g mixed liquor suspended solids (MLSS)-h at 0–30 g/l NaCl for Model A and from 6.84 to 17.64 mg O 2 /g MLSS-h at 5–30 g/l NaCl for Model B). In contrast, the specific ammonia uptake rate (SAUR) and specific nitrate uptake rate (SNUR) decreased with increasing chloride concentration (from 4.76 to 2.14 mg NH 3 –N/g MLSS-h and 2.50 to 1.22 NO3–N/g MLSS-h, for Model A, and from 3.84 to 2.71 mg NH 3 –N/g MLSS-hr and 2.54 to 1.82 mg NO 3 –N/g MLSS-hr, for Model B). During the shocked period, the SOUR in most scenarios increased whereas the SAUR and SNUR tended to decrease. The impact of the chloride shock on nitrifiers was more obvious than on denitrifiers; however, after a certain recovery period, the activities of both nitrifiers and denitrifiers in terms of SAUR and SNUR were approximately the same as those prior to shock.

Decolorization of azo-reactive dye by polyphosphate- and glycogen-accumulating organisms in an anaerobic–aerobic sequencing batch reactor

An anaerobic-aerobic sequencing batch reactor with a sludge age of 8 days and anaerobic + aerobic + settling times of 18 + 5 + 1 h, was used to decolorize an azo-reactive dye wastewater. The nutrient broth (NB) and sodium acetate (SA) solution at 500 + 0, 350 + 150, 250 + 250 and 0 + 500 mg/l as COD was fed to the system to promote the polyphosphate-accumulating organisms (PAOs), while only glucose (500 mg/l COD) was used as a glycogen-accumulating organisms (GAOs) promoting substrate. The decolorization capability of the process was about 73-77 and 59-64% in terms of ADMI for the systems which the PAOs and GAOs proliferated, respectively. The color reduction was mainly achieved within the first 2 h of the anaerobic stage.