[Effects of sulfate on the community structure of phytoplankton in freshwater].

In order to promote the understanding of sulfate enrichment on the growth and succession of phytoplankton communities in eutrophic freshwater body, laboratory experiment of phytoplankton in a landscape water body was conducted. Three treatment groups were set up in experiment:control (G0), step by step enrichment (G1) and enrichment at a time (G2). The result indicated that the addition of sulfate promoted the increase of Chlorophyta species and biomass, while inhibited the growth of native Cyanobacteria and diatom species. Species and biomass of G0, G1 group were similar and much higher than those of G2 group. Average biomass of GO, Gland G2 group was 98.46, 96.09 and 81.19 mg x L(-1), respectively. G0 group was almost always dominated by Cyanobacteria species such as P. corium and O. amphibia, dominant species in G1 and G2 groups changed from Cyanobacteria species to Chlorophyta species including S. quadricauda, G. radiate and S. obliqus. Compared with that of control group G0 (1.49 +/- 0.32, the average community diversity indices of G1 (1.70 +/- 0.18) and G2 groups (1.68 +/- 0.40) were elevated.

Seasonal dynamics of phytoplankton in relation to key aquatic habitat factors in a polluted urban small water body in Tianjin, China.

To evaluate the seasonal dynamics of phytoplankton and its relationships with aquatic habitat factors in polluted urban landscape lakes, annual investigations have been carried out in the West zone of Xinkai Lake. The results showed that the lake belongs to the eutrophic-supertrophic type in terms of key habitat factors measurement. The seasonal succession of phytoplankton community was determined. The dominant cyanobacterial species Oscillatoria tenuis Ag. bloomed in autumn, although the other species with higher degrees of dominance never bloomed in the year investigated. Significant correlations between some habitat factors and phytoplankton biomass were observed.

[Effects of silicate on the community structure of phytoplankton in enclosures].

Controlling the concentrations of silicate, enclosure experiments were conducted in Xinkai Lake to investigate the influence of Si concentration on the growth and succession of phytoplankton communities in a eutrophic freshwater. The results show that with the addition of silicate, the biomass of diatoms increased and the ratio of diatom species to the total significantly increased from 10.2% to 22.1% . While the species percent of Cyanobacteria and Chlorophyta decreased to 61.5%, as compared with 76.8% in control. Several diatom species, such as Synedra ulna, Nitzschia denticula, Nitzschia acicularis, Gomphonema constrictum var. capitata, Gomphonema olivaceum, which were not found in control, were observed in the silicate-enriched treatments. The Shannon indices of 2.17 +/- 0.40 and 2.12 +/- 0.21 were obtained from the medium-Si (atomic ratio N:Si:P = 16:8:1) and high-Si ( N:Si:P = 16:16:1) treatments, which were higher than that of the control enclosure (1.89 +/- 0.55, without silicate addition). At the late phase of the experiments, algal blooms mainly composed of Microcystis aeruginosa appeared in control but not in the silicate-enriched enclosures. The enrichment of silicate can promote the growth of diatoms and the other algal species and change the dominance of few Cyanobacteria and Chlorophyte species. Therefore, it can elevate the algal biodiversity of an aquatic ecosystem and weaken the cyanobacterial blooms to a certain degree.

[Effects of nitrogen source and aeration mode on algae growth in freshwater].

Aquarium microcosms were used to study the effects of nitrogen source and aeration mode on the growth and species changes of algae in freshwater. Nitrate nitrogen(NO3(-) -N) and ammonia nitrogen(NH4(+) -N) were used as nitrogen sources. For each nitrogen source, four modes of aeration were selected, including control, continuous aeration, aeration during the day, and aeration at night. In the early stage of the experiment, algae in the NH4(+) -N treatment experiment grew well. In the later stage, algae in the NO3(-) -N treatment experiment grew better. For different aeration modes, continuous aeration show varied effects on algae growth in the two nitrogen source treatments. Day-only aeration had little effect on algae growth. Night-only aeration inhibited algae growth considerably. In NH(+) -N treatments, cyanophyta became dominant species easily. In contrast, chlorophyta dominated in NO3(-) -N treatments.

Interaction between anionic dyes and cationic flocculant P(AM-DMC) in synthetic solutions.

Copolymer of acrylamide and 2-[(methacryloyloxy)ethyl]trimethylammonium chloride [P(AM-DMC)] is found to be effective to combine anionic dyes with strong aqueous solubility. This work aims mainly at revealing the interaction between anionic dyes and [P(AM-DMC)] by running jar test, spectra analysis and equilibrium dialysis experiments. The results show that P(AM-DMC) effectively decolorizes the tested strong water soluble anionic dyes, such as acidic, reactive and direct dyes, from their aqueous solutions under mild acidic and neutral conditions. Higher cationicity and optimal dose of flocculant P(AM-DMC) have to be used to achieve satisfactory and effective decolorization. Comparison of IR spectra of dye, flocculant P(AM-DMC) and the floc formed indicates chemical interaction occurred between sulfonic groups of dye and quaternary ammonium of flocculant. Plots of r-logC suggest cooperative interaction exists evidently for some dyes tested. Addition of KCl or urea reduces binding extent evidently, which shows the importance of electrostatic and hydrophobic interaction. Therefore the interaction between dyes tested and P(AM-DMC) might be controlled by hydrophobic, cooperative interaction and energetic interaction which includes chemical and electrostatic interactions.

Degradation of microcystin-RR by UV radiation in the presence of hydrogen peroxide.

Experiments were conducted to investigate the degradation of microcystin-RR in order to assess the effectiveness and feasibility of the combined UV/H(2)O(2) catalytic system for purification of water polluted by microcystins. The operating parameters such as hydrogen peroxide dosage, pH value, UV light intensity, initial concentration of microcystin-RR and reaction time were evaluated, respectively. The degradation efficiency increased nonlinearly with increasing UV light intensity and hydrogen peroxide dosage, respectively. There existed an optimal hydrogen peroxide dosage, beyond which the reagent exhibited an inhibitory effect, for degrading microcystin-RR. The degradation process could be fitted by both of the pseudo-first-order and second-order kinetics well and primarily followed a mechanism of both direct photolysis and hydroxyl radical oxidation. Compared with the treatment using UV radiation and hydrogen peroxide individually, the combined UV/H(2)O(2) system could significantly enhance the degradation efficiency due to the synergetic effect between UV radiation and hydrogen peroxide oxidation. The observed rate constants decreased and the corresponding half-lives prolonged as the concentrations of microcystin-RR increased. The combined UV/H(2)O(2) process provides an effective technology for the removal of microcystins from drinking water supplies.

Study on the photocatalysis performance and degradation kinetics of X-3B over modified titanium dioxide.

In this paper, reactive brilliant X-3B was used as a model compound to study the photocatalytic activity of TiO2. Experimental results showed that the adulteration of iron and silver on TiO2 could greatly improve the activity of TiO2, and the optimum adulteration amount of iron and silver was 0.1 wt.% (Fe/TiO2) and 0.05 wt.% (Ag/TiO2), respectively, at the adulteration range of experiments. The photocatalytic degradation kinetics of X-3B on TiO2, Fe/TiO2 and Ag/TiO2 were also studied. The results showed that the degradation of X-3B on all of them were in accordance with the Langmiur-Hinshelwood kinetics model well, and the sequence of apparent reaction rate constants k of X-3B degradation catalyzed by TiO2, Fe/TiO2 and Ag/TiO2 was Ag/TiO2>Fe/TiO2>TiO2, while adsorption equilibrium constants KA of X-3B on Fe/TiO2 and Ag/TiO2 were approximately the same, and both were greater than that of TiO2.

Dye removal from wastewater using the adsorbent developed from sewage sludge.

Sewage sludge was used to develop an effective carbon adsorbent. This adsorbent was employed for the removal of azo dye such as Direct Dark Brown M and Acid Mordant Brown RH. The adsorption of dyes on this adsorbent was studied as a function of contact time, concentration, pH and temperature by batch method. The equilibrium adsorption capacity of a carbonaceous adsorbent prepared from city wastewater treatment plant was 502, and 329.7 mg/g of Direct Dark Brown M and Acid Mordant Brown RH, respectively. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Langmuir model. The rates of adsorption were found to conform to the Lagergren second-order kinetics with good correlation. The equilibrium adsorption capacity of the carbonaceous adsorbents was determined with the Langmuir equation as well as the Lagergren second-order rate equation. The most ideal pH for adsorption of two dyes onto adsorbents was found to be 3 and below. The results indicate that the carbonaceous adsorbents could be employed as a low cost adsorbent in the removal of dyes from wastewater.

[Decolorization conditions for reactive brilliant blue KN-R by three fungi].

Seventeen strains with wideranging decolorization ability were screened from contaminated soil and were applied on the decoloring of dye wastewater. Three strains were selected due to their high decolorization capacity on azo dyes, anthraquinone dyes and triphenylmethane dyes. The three strains were named as Strain I, Strain II, Strain III. This three superior strains were identified as penicillium link (Strain I & strain II) and Cephalosporium corda (strain III). Using aqueous samples, the influences of several factors on decolorization were reported, such as pH, carbon source, temperature and so on. And then applying of these strains for treatment of actual wastewater have also been done. The results showed that the optimal pH, temperature and carbon source were 5-9, 18-37 degrees C and 0.5% respectively, under those conditions the decolorization removal rate was 70%. And these fungi have a good prospect for the treatment of dye wastewater.

Adsorption of water-soluble dyes onto modified resin.

Adsorption behavior of five kinds of water-soluble dyes onto functionalized resin NKY has been dynamically and thermodynamically investigated. The results showed that the adsorption rates of dye K-GN, K-2BP, KN-R, AAB and 2G are all controlled by liquid film diffusion and particle diffusion. Equilibrium adsorption data can be well described by three-parameter equation. The first layer adsorption is the physical enhanced by chemical effect but multilayer adsorption is typically physical adsorption. Standard free energy change DeltaG(0) and standard entropy change DeltaS(0) indicate the adsorption of the dyes onto NKY can occur spontaneously.

Decomposition of aniline in supercritical water.

The decomposition of aniline in supercritical water (SCW) was studied. Experiments were performed at various temperatures, pressures, residence times, dosage of oxidant H2O2 and initial aniline concentrations to investigate their effect on the destruction efficiency. Manganous sulfate and ferrous sulfate were screened out during the experiment to study the effect of the homogenous catalysts on destruction efficiency. The effect of pH was also studied. The experiments showed that the dosage of oxidant H2O2, experimental temperature, pressure, reaction residence time and even initial concentration of the aniline in wastewater have a significant affect on the TOC removal; manganous sulfate and ferrous sulfate improve the oxidation; TOC removal improves slightly with a decrease in the initial pH value. At a system temperature 450 degrees C, pressure 28 MPa, initial pH 4.0, residence time 46 s and K value 1.1, TOC removal can reach 100%.