[Selection and kinetic mechanism of psychrotrophs in low temperature wastewater treatment].

A study was carried out taking low temperature domestic wastewater as target in laboratory, the composition of bacteria in activated sludge was analyzed and the degradation kinetics of organics was investigated. Six preponderant psychrotrophs were selected out, belonging to Zoogloea, Aeromonas, Flavobacterium, Micrococcus, Bacillus and Pseudomonaus, respectively. Results show that TTC-dehydrogenase activity of the psychrotroph is 25.44 mg/(L x h) which is 20.5 times more than that of ordinary activated sludge at 4 degrees C. The efficiency of COD biodegradation by psychrotrophs at low and normal temperature is 80.9% and 73.4%, respectively. Mesophilic bacteria almost lost their activity at low temperature. Kinetic analysis shows that biodegradation of organics by psychrotrophs at low and mesothermal temperature as well as mesophilic bacteria at mesothermal temperature are in accordance with the model of first-order reaction. Psychrotrophs, which assure the removal efficiency of organic pollutants at low and normal temperature, could keep the uniform reaction velocity as the mesophilic bacteria and also adapt wide ecological amplitude of temperature. Efficient psychrotrophs were immobilized on soft polyurethane foams which acted as carriers in the experiment at 4 degrees C, as a result of that, the removal efficiency of COD was increased about 18% higher than that of mobilized ones at low temperature, the biodegradation kinetics of COD by immobilized psychrotrophs also followed the first-order reaction model. With glucose in water as the source of nutriment, the reaction velocity of immobilized bacteria is 2.35 times higher than that of the mobilized ones. By the immobilized psychrotrophs biodegradation of varied nutriment, the effluent could achieve the first-degree B of pollutants discharge standard for municipal wastewater treatment plant.

[Mechanism discussion of gamma-alumina catalyzed ozonation for 2-methylisoborneol removal].

The efficiency and mechanism in degradation of 2-methylisoborneol (MIB) as taste and odor compound in drinking water were studied under the condition where gamma-alumina catalyzed ozonation. As a result, gamma-alumina can behave distinct activity in enhancing the efficiency of ozonation MIB. Tert-butyl alcohol had a remarkable restrain effect on removal efficiency of catalytic ozonation MIB by gamma-alumina. The surface charge status and surface hydroxyl groups status of gamma-alumina and pH values of the solution can be linked together. When the pH value of solution was near the pH(zpc) of gamma-Al2O3, there was a most observable activity in catalyzed ozonation process. R(ct), which denoted the relative concentration of hydroxyl radical (*OH), was much higher in catalyzed ozonation process than in ozonation process. This result further illuminated that gamma-Al2O3 can promote ozone decomposition to produce *OH. Finally, it was investigated that the effect of r(P/I) on catalyzed ozone decomposition and ozone decomposition.

[Gamma-Al2O3 catalyzed ozonation for removing taste and odor substance 2-methylisoborneol in drinking water].

gamma-Alumina was used as a catalyst in ozonation, and efficiency and influencing factors in degradation of taste and odor substance 2-methylisoborneol (MIB) in drinking water were studied. The result shown that gamma-alumina was activated in catalytic ozonation for degradation MIB not only in distilled water, but also in tap water. In distilled water condition, catalyzed ozonation could enhance 47% removal efficiency; in tap water condition, catalyzed ozonation could increase 40% removal efficiency. The concentration of ozone, gamma-alumina, MIB can affect the degradation of MIB observably. gamma-Alumina catalyzed ozonation for removing MIB did not depend on rigidity in water, but was affected by inorganic negative ions. By capturing the hydroxyl radicals produced by gamma-alumina catalyzed ozone decomposition, the bicarbonate/carbonate in natural water can restrain the effect of gamma-alumina catalyzed ozonation for degradation of MIB. Lower concentration of humic acid can promote the effect of oxidation of the MIB, but higher concentration of humic acid may reduce the efficiency. As pH values can affect the process of catalyzed ozonation and tert-butyl alcohol can inhibit the efficiency of catalyzed ozonation efficiency of MIB, the mechanism of gamma-alumina enhanced ozone oxidation of MIB can be identified as that gamma-alumina catalyzed ozone to decompose into hydroxyl radicals which further break up the molecule of MIB.

[Effect and mechanism of removal of trace p-chloronitrobenzene in aqueous solution by ZnOOH/O3].

Zinc hydroxide prepared in laboratory was used as catalyst in catalytic ozonation of trace p-chloronitrobenzene (pCNB) in water. The catalytic mechanism was deduced through the effect of radical inhibitor t-BuOH on the reaction. Furthermore, affecting factors of catalytic activity were investigated. Results show that zinc hydroxide has excellent property of catalytic ozonation. Compared to ozonation alone, the catalytic removal rate of pCNB dissolved in distilled water increases by 51.3 percents at reacting time of 20 min. The catalysis, which is influenced by density of hydroxyl groups combined on the surface of hydroxide, follows a hydroxyl radical reaction pathway. The removal gets better with increasing dosage of catalyst. Zinc hydroxide was used for 3 times without obvious changes of pCNB removal rate. Bicarbonate in water and phosphate in buffer solution could greatly depress its catalytic activity. The optimal catalysis is achieved at solution pH = 7.

[Effect and mechanism of degradation of nitrobenzene in aqueous solution by O3/H2O2].

Nitrobenzene (NB) was selected as the model pollutant in water and the efficiency and mechanism of degradation of NB in aqueous solution by O3/H2O2 were investigated. The effects of pH, H2O2 dose and the inhibitor or accelerant of .OH on the removal rate of NB were studied. H2O2 could obviously improve the ozonation decay rate of NB when the pH value of the solution was below 7. The removal rate of NB was enhanced remarkably while H2O2 dose was increased from 1.0 m g/L. to 4.0 mg/L. However, as H2O2 dose increased from 4.0 mg/L to 20 mg/L, the removal efficiency of NB decreased. Different quantities of H2O2 were yielded in different reaction phases of single ozonation system. Both systems of single ozonation and H2O2-catalysed ozonation could not reduce TOC observably. During the NB degradation process, organonitrogen was almost completely converted to nitrate and the pH value of the solution reduced significantly. Results of LC-MS and GC-MS analysis showed that the main intermediate products were phenolic compounds and carbonyl compounds. A possible reaction pathway of the catalytic ozonation of NB was also proposed. It was found that the catalytic ozonation of NB could be divided into two steps. First, hydroxyl radical attacked phenyl ring to form phenolic compounds, then the ring was opened, forming into various aliphatic compounds or being mineralized to inorganic compounds.