Recalcitrant organic matter removal from textile wastewater by an aerobic cell-immobilized pellet column

The treatment of textile wastewater is difficult because of its recalcitrant organic content. The biological removal of recalcitrant organics requires a long retention time for microbial growth. Activated sludge was immobilized in a polyethylene glycol pellet to allow for sufficient sludge retention time. The pellets were filled in an aerobic cell-immobilized pellet column (CIPC) reactor in order to investigate the removal of recalcitrant organics from textile wastewater. A textile wastewater effluent treated by a conventional activated sludge reactor was used as a target wastewater. The chemical oxygen demand (COD) removal efficiency of the aerobic CIPC reactor at various empty bed contact times was in the range of 42.2–60.5%. Half of the input COD was removed in the lower part (bottom 25% of the reactor volume) of the reactor when the organic loading rate was less than 1.5 kg COD/(m3•d). About 15–30% of the input COD was removed in the remaining part of the column reactor. The COD removed in this region was limitedly biodegradable. The biodegradation of recalcitrant organics could be carried out by the interactional functions of the various bacteria consortia by using a cell-immobilization process. The CIPC process could effectively treat textile wastewater using a short retention time because the microorganisms that degrade limitedly biodegradable organics were dominant in the reactor.

Reciprocal Regulation of Anaerobic and Aerobic Cell Wall Mannoprotein Gene Expression in Saccharomyces cerevisiae

ABSTRACT The DAN/TIR genes encode nine cell wall mannoproteins in Saccharomyces cerevisiae which are expressed during anaerobiosis (DAN1,DAN2, DAN3, DAN4,TIR1, TIR2, TIR3,TIR4, and TIP1). Most are expressed within an hour of an anaerobic shift, but DAN2 andDAN3 are expressed after about 3 h. At the same time, CWP1 and CWP2, the genes encoding the major mannoproteins, are down-regulated, suggesting that there is a programmed remodeling of the cell wall in which Cwp1 and Cwp2 are replaced by nine anaerobic counterparts. TIP1,TIR1, TIR2, and TIR4 are also induced during cold shock. Correspondingly, CWP1 is down-regulated during cold shock. As reported elsewhere, Mox4 is a heme-inhibited activator, and Mot3 is a heme-induced repressor of theDAN/TIR genes (but not of TIP1). We show that CWP2 (but not CWP1) is controlled by the same factors, but in reverse fashion—primarily by Mot3 (which can function as either an activator or repressor) but also by Mox4, accounting for the reciprocal regulation of the two groups of genes. Disruptions of TIR1, TIR3, orTIR4 prevent anaerobic growth, indicating that each protein is essential for anaerobic adaptation. The Dan/Tir and Cwp proteins are homologous, with the greatest similarities shown within three subgroups: the Dan proteins, the Tip and Tir proteins, and, more distantly, the Cwp proteins. The clustering of homology corresponds to differences in expression: the Tip and Tir proteins are expressed during hypoxia and cold shock, the Dan proteins are more stringently repressed by oxygen and insensitive to cold shock, and the Cwp proteins are oppositely regulated by oxygen and temperature.

Performance of fixed film media integrated in activated sludge reactors to enhance nitrogen removal

Nitrification and denitrification were evaluated in multiple CSTR continuous flow fixed film systems at 12°C. Three systems were operated with three types of media installations and a fourth as a control without media. The media configurations evaluated included: (i) frame mounted fine pore sponge media supported on wires; (ii) free floating fine pore sponge media; and (iii) fixed location frame mounted rope media (ringlace). The pore size for sponge media was 14 pores per centimeter. Each system included a two-cell anaerobic zone with 17 percent of total volume, two-cell anoxic zone with 17 percent of total volume, and a three-cell aerobic zone with 64 percent of total volume. The multi-cell configuration was used to maximize kinetics of removal with suspended growth biomass and evaluate improvements in nitrogen removal beyond the levels achieved with suspended growth. At the optimum location (aerobic cells 1 and 2), the nitrification in cells containing free-floating sponges was 143 percent of the control at aerobic MCRTs of 3.1 and 3.4 days, with 35 percent media volume to cell volume. The nitrification with rope media was 136 percent of the control in middle third of the aerobic zone. Removals with ringlace were poorer in the first aerobic cell operating at higher COD levels, and in the third aerobic cell which did not contain sufficient biofilm growth at low levels of COD. Nitrification was 14 percent higher in Systems 1 and 2 with fixed and free floating sponges, respectively, and 8 percent higher in System 3 (ringlace) when all systems were spiked with 20 mg/L additional ammonium over a 24 hour period. Optimizing location of the media, with higher density of media at locations where adequate COD and ammonium-N are available for biofilm growth increase nitrification on media. Studies in full scale systems show that COD and ammonium-N concentrations at downstream locations in the activated sludge basin increase during peak flows and with step feed of wastewater. This helps increase biofilm growth and improve nitrification on the media downstream locations. Denitrification observed in the aerobic cells of the fixed film systems was in excess of the control. All aerobic cells were operated at D.O. levels in excess of 6.0 mg/L. The fraction of total denitrification under aerobic conditions was 0.0 in the control as compared to 0.14 to 0.24 with ringlace media and fixed sponge media, respectively, at an aerobic MCRT 3.1 days. Fraction aerobic denitrification in all systems increased with an increase in MCRT of suspended growth - to 0.21 in the control and 0.35 and 0.39 with ringlace and sponges, respectively, at aerobic MCRTs of 3.4 to 7.7 days.

Characterization of F390 synthetase activity in cell extracts of Methanobacterium thermoautotrophicum Marburg

The F390 synthetase activity in cell extracts of Methanobacterium thermoautotrophicum Marburg increased by two times upon preincubation at 37 °C with its substrates, ATP (or GTP) and coenzyme F420, but not with either of these compounds alone. In the 0–37 °C range, preincubation at 37 °C gave maximal enhancement in activity. F390 synthetase activity in cell extracts of strain Marburg was maximal at 45 °C, whereas F390 synthetase from M. thermoautotrophicum ΔH had maximal activity at 55 °C; both strains grew optimally at 65 °C. Data derived from the Arrhenius plot supported our earlier conclusion that the F390 synthetase activity of strain Marburg could lead to a loss of 70% of the available F420 during extraction of this factor from cells via an aerobic cell extract procedure even if the temperature was maintained at 4 °C.Key words: Methanobacterium thermoautotrophicum, F390 synthetase, activation, coenzyme F420

Production of nitrous oxide by Nitrosomonas europaea: effects of acetylene, pH, and oxygen

Aerobic cell suspensions of Nitrosomonas europaea oxidized ammonium [Formula: see text] to nitrous oxide (N2O) and nitrite [Formula: see text], and exogenous [Formula: see text] in the presence or absence of [Formula: see text] did not stimulate N2O formation. Acetylene (C2H2) inhibited the production of [Formula: see text] and N2O from [Formula: see text] but not from hydroxylamine (NH2OH). The total amount of N2O formed in air was proportional to the amount of [Formula: see text] oxidized; however, the total N2O N formed as a percentage of [Formula: see text] N formed varied very little (0.05–0.15%) over the range of [Formula: see text] concentrations examined (0.05–20.4 mM). Rates of production of N2O and [Formula: see text] showed similar response to pH over the range of 5.4–9.5, with maxima at pH 8.5. Anaerobically, five times more N2O was formed than under aerobic conditions. The highest rates of anaerobic N2O formation were observed in the presence of [Formula: see text] and [Formula: see text] combined (2 and 1 mM, respectively) and C2H2 reduced this rate of N2O formation to that observed with 1 mM[Formula: see text] alone in the presence or absence of C2H2. The presence of the [Formula: see text] oxidizer Nitrobacter winogradskyi had no effect on the formation of N2O by Ns. europaea either in liquid culture or in sterile soil. However, the presence of sterile soil as a suspending matrix increased by 10-fold the production of N2O, and broadened the range of O2 concentrations under which relatively high rates of N2O production occurred. Maximum N2O production by Ns. europaea occurred at 0.75 kPa O2 in liquid suspension and at 2.5 kPa O2 in sterile soil.