Determination of trace chlorine dioxide based on the plasmon resonance scattering of silver nanoparticles.

A plasmon resonance scattering (PRS) method for chlorine dioxide is reported based on the oxidization of silver nanoparticles (NPs) by it, in pH 9.1 ammonia-ammonium nitrate buffer solutions. Silver NPs exhibit strong PRS signals at 470nm, and can be oxidized by ClO(2), which results in PRS quenching at 470nm. It was found that the PRS quenching intensity is proportional to the concentration of chlorine dioxide over the range of 0.0011-0.185microg/mL, with a detection limit (3sigma) of 0.00050microg/mL and the correlation coefficient of 0.9995. The method is simple, rapid and cost effective. It was applied to the determination of chlorine dioxide in drinking water, with satisfactory results.

Oxidation of industrial dyeing wastewater by supercritical water oxidation in transpiring-wall reactor.

Industrial dyeing wastewater was oxidized in supercritical water in a transpiring-wall reactor, using hydrogen peroxide as an oxidant. Experiments were performed at 595 to 704 K and 18 to 30 MPa, with an oxidant dosage ratio ranging from 0.6 to 2.0. A chemical oxygen demand (COD) removal of more than 98.4% was achieved at 704 K and 28 MPa, with a retention time less than 35 seconds, which increased with the temperature, pressure, and oxidant. A modified first-order rate expression was regressed from experimental data, taking into account the influence of induction time. The resulting pre-exponential factor, A, and activation energy, Ea, were 1.07 seconds(-1) and 12.12 kJ x mol(-1), respectively, while the reaction order for feed wastewater (based on COD) and oxidant were assumed to be 1 and 0, respectively. Gas chromatography/mass spectrometry analysis for effluents indicated that carbon dioxide, carbon monoxide, and nitrogen were the main reaction products, and phenol; benzenecarboxylic acid; 1, 2-benzenedicarboxylic acid; and isoquinoline were detected as intermediates.

Distribution characteristics and source analysis of dioxins in sediments and mussels from Qingdao coastal sea.

Seven of surface sediments, one sediment core and two mussel samples were collected from the Qingdao coastal sea of the western Yellow Sea and analyzed to determine the horizontal distribution, deposition flux, and toxicity equivalency (TEQs) of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). The total PCDD/Fs concentrations in the surface sediments ranged between 10.7 and 428 ng kg(-1) dry wt. The horizontal distribution of PCDD/F congeners in the sediments was characterized by elevated concentrations at the locations in the east of Jiaozhou Bay with the highest concentration occurring near the Haibo River mouth. Physical parameters (total organic carbon contents and sediment types) and the current circulation systems in Jiaozhou Bay can be important factors controlling the horizontal distribution pattern of PCDD/Fs in the bay. The influence of the Haibo River as a source of pollution was evidenced by PCDD/F homologue profiles, indicating a contribution from sewage sludge in addition to other possible sources. Records from the sediment core revealed that the total PCDD/Fs in the Qingdao coastal sea were nearly constant since 1951 till 1980s and increased remarkably after 1980s. The total 2,3,7,8-substituted PCDD/Fs and total TEQs of PCDD/Fs on the lipid basis in the mussel sample inside the bay were significantly higher than in the adjacent sediment. The homologue profiles of PCDD/Fs in the mussels were quite different from those of the sediments, characterized by high TCDF (50% of the total PCDD/Fs).

Quantitative structure-activity relationship study on the biodegradation of acid dyestuffs.

Quantitative structure-biodegradability relationships (QSBRs) were established to develop predictive models and mechanistic explanations for acid dyestuffs as well as biological activities. With a total of four descriptors, molecular weight (M(W)), energies of the highest occupied molecular orbital (E(HOMO)), the lowest unoccupied molecular orbital (E(LUMO)), and the excited state (E(ES)), calculated using quantum chemical semi-empirical methodology, a series of models were analyzed between the dye biodegradability and each descriptor. Results showed that E(HOMO) and M(W) were the dominant parameters controlling the biodegradability of acid dyes. A statistically robust QSBR model was developed for all studied dyes, with the combined application of E(HOMO) and M(W). The calculated biodegradations fitted well with the experimental data monitored in a facultative-aerobic process, indicative of the reliable prediction and mechanistic character of the developed model.

[Running effects affected by sludge reducing by anaerobic hydrolysis-acidification and aerobic oxidation process of A1/A2/O bio-treatment system].

In the A1/A2/O bio-treatment system dealing with alkali minimization and dyeing-printing wastewater, residual sludge could be reduced effectively by recycling of sludge. The COD removal rate in A1 segment could be improved by residual sludge recycling to A1 segment. The COD elimination rate in A1 segment was raised from 15.9% to 23.9% and from 12.3% to 22.8% while the COD volume loading of A1 segment was 2.54 kg/(m3 x d) and the HRT of A1 was 9.45 h and 7.56 h respectively. The recycling of sludge is useful to color removal of the system. When the COD of influxion was 1000 mg/L, the COD volume loading of A1 was 2.54 kg/(m3 x d), the chroma of influxion was 450 and the temperature of the system was 30 degrees C, the chroma removal rate with sludge recycling decreased more than 30% and about 30% compared with the system without sludge recycling in A1 segment and in the whole process respectively. The pH in A1 segment with sludge recycling was a little lower than that without sludge recycling, but the performance of A1 and O segments was affected less severely by sludge recycling. The SS in every segment with sludge recycling was higher than that without sludge recycling. Inert substance could be accumulated because of long time sludge recycling and it's necessary to activate the sludge by aerating and washing.

Control of bromate and THM precursors using ozonation combined system.

OBJECTIVE: To investigate the feasibility of reducing THM precursors and controlling bromate taste and odor in drinking water taken from the Yellow River by an ozonation combined system. METHODS: The appropriate ozone dosage was determined, and then the changes of TOC, UV254 and THM formation potential (THMFP) in the combined system were evaluated. RESULTS: One mg/L ozone could effectively remove taste and odor and meet the maximum allowable bromate level in drinking water. The pre-ozonation increased THMFP, but the conventional treatment system could effectively reduce the odor. The bio-ceramic filter could partly reduce CHCl3FP, but sometimes might increase CHCl2BrFP and CHClBr2FP. The biological activated carbon (BAC) filter could effectively reduce CHCl3FP and CHCl2BrFP, but increase CHClBr2FP. Compared with other filters, the fresh activated carbon (FAC) filter performed better in reducing THMFP and even reduced CHClBr2FP. CONCLUSION: The combined system can effectively reduce taste, odor, CHCl3FP, and CHCl2BrFP and also bring bromate under control.

[A fluorescence quenching method for the determination of trace chlorite in water with rhodamine B].

In acidic sodium acetate-HCl buffer solution containing KI, Rhodamine B (RhB) has a fluorescence peak at 580 nm. When ClO2(-) exists fluorescence quenching occur. The fluorescence quenching intensity is linear with the concentration of ClO2(-) in the range of 0.0218-0.51 microg x mL(-1). Based on this, a new, simple, sentisive fluorescence method has been proposed for the determination of ClO2(-) in water, with satisfactory results.

PCBs, PCNs and PBDEs in sediments and mussels from Qingdao coastal sea in the frame of current circulations and influence of sewage sludge.

Influence of current circulation and sewage sludge on spatial distributions of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polybrominated diphenyl ethers (PBDEs) in sediments and mussels from the Qingdao coastal sea were investigated. Total concentrations of PCBs, PCNs and PBDEs in sediments ranged 6.5-32.9, 0.2-1.2, and 0.1-5.5 ngg(-1) dry wt, respectively. The maximum concentrations were all found near the Haibo River mouth, affected by sewage sludge input from the river. Under the current system in Jiaozhou Bay the organic pollutants were subject to deposit on the east side of the bay and trapped inside the bay. Sewage sludge was an important source of PCBs, PCNs and PBDEs in the bay and exponentially magnified the enrichment of PCBs. On the other hand, the congener profiles of PCBs in sediments outside the bay may signify an atmospheric source of PCBs. Total Concentrations of PCBs, PCNs and PBDEs in mussels were 61.4-88.6, 9.0, and 13.8 ngg(-1)lipid, respectively. Mussels enriched significantly PCBs, PCNs and PBDEs relative to the sediments. The total toxicity equivalent quantities (TEQs) of PCNs in mussels were generally lower than that of PCBs. The fluxes of the total PCBs and their TEQs have been decreased steadily since 1950s. The lower chlorinated/brominated congeners of PCNs and PBDEs may exhibit a greater tendency due to less lipophilic and thus a greater probability of being affected by the current circulation in the bay.

Poly[[aqua-(1-naphthyl-acetato)cadmium(II)]-µ(3)-pyridin-3-olato].

In the title complex, [Cd(C(5)H(4)NO)(C(12)H(9)O(2))(H(2)O)](n), each Cd(II) atom is coordinated by two carboxylate O atoms from one 1-naphthyl-acetate ligand, two hydroxyl O atoms from two pyridin-3-olate ligands, one N atom from another pyridin-3-olate ligand and one water mol-ecule, and displays a distorted octa-hedral coordination geometry. The compound forms infinite chains of pyridin-3-olate ligands bridging 1-naphthyl-acetate-Cd(II) units parallel to the b axis, with a Cd⋯Cd separation of 3.578 (2) Å. The chains are further self-assembled into a supra-molecular network through inter-molecular O-H⋯O hydrogen-bonding inter-actions.

[A new fluorescence quenching method for the determination of trace ClO2 in water using silver nanoparticles].

In pH 9.1 NH4Cl-NH3 x H2O buffer solution, there is a fluorescence peak at 470 nm for silver nanoparticles. A fluorescence quenching takes place when it was oxidized by ClO2. The intensity of fluorescence quenching is linear with the concentration of ClO2 in the range of 0.0011-0.185 microg x mL(-1). The detection limit is 0.004 7 microg x mL(-1). A new fluorescence method has been proposed for the determination of ClO2 in water samples with satisfactory results.

[Factors affecting residual sludge reducing by anaerobic hydrolysis-acidification and aerobic oxidation process of A1/A2/O bio-treatment system].

Hydrolysis-acidification and aerobic oxidation process could realize sludge reducing without those strengthening conditions such as high temperature, high pressure, strong oxidant or alkali which may destroy the cell structure of microorganisms, so it has good maneuverability and is economical. The purpose of sludge reducing system is mainly to degrade the pollutants in it ant its reducing effect is related to organic loading, HRT and temperature, etc. In the A1/A2/O bio-treatment system dealing with alkali minimization and dyeing-printing wastewater, residual sludge can be reduced effectively by recycling sludge to A1 segment. It proved that sludge could be reduced effectively and treated water could reach the grade I standard of GB8978-96 for long time operation of the system, when the volume loading of A1 (COD) was 2.54 kg x (m3 x d)(-1), the HRT of A1 was 7.56 h and the temperature of the system was 25 degrees C - 40 degrees C. The sludge reducing could be realized through recycling to A1 segment, and the N, P released from the broken bacteria cell could compensate the shortage of N and P of alkali minimization and dyeing-printing wastewater, and then the cost of adding the nutrition of N and P to the system could be reduced greatly.

A novel, simple and sensitive resonance scattering spectral method for the determination of chlorite in water by means of rhodamine B.

A new resonance scattering method was proposed for the determination of chlorite, basing on the resonance scattering effect of rhodamine dye. In HCl-sodium acetate buffer solution, chlorite oxidizes I- into I2 and the reaction of I2 and excess I- results in I3- It is respectively combined with rhodamine dyes, including rhodamine B (RhB), butyl rhodamine B (b-RhB), rhodamine G (RhG) and rhodamine S (RhS), to form association complex particles, which exhibit stronger resonance scattering (RS) effect at 400 nm. The chlorite concentration of ClO2- in the range of 0.00726-0.218 microg/ml, 0.0102-0.292 microg/ml, 0.00726 0.145 microg/ml and 0.0290 0.174 microg/ml is respectively linear to the RS intensity of association complex particle systems at 400 nm for the RhB, b-RhB, RhG and RhS. The detection limits of the four systems were respectively 0.00436, 0.00652, 0.00580 and 0.01450 microg/ml ClO2-. In the four systems, the RhB system possesses good stability and high sensitivity. It has been applied to the analysis of chlorite in wastewater with satisfactory results.

A novel and selective spectral method for the determination of trace chlorine in water basing on the resonance scattering effect of rhodamine B-I(3) association nanoparticles.

In Na(2)HPO(4)-citric acid buffer solution, Cl(2) can oxidize I(-) to form I(2) and then it reacts with excess I(-) to form I(3)(-). The I(3)(-) combines respectively with rhodamine dyes, including rhodamine B (RhB), butyl rhodamine B (b-RhB), rhodamine 6G (RhG) and rhodamine S (RhS), to form association particles which give stronger resonance scattering (RS) effect at 400 nm. The RS intensity of the RhB, b-RhB, RhG and RhS systems is proportional to chlorine concentrations in the range of 0.008-1.74, 0.019-1.33, 0.021-2.11 and 0.019-2.04 microg/mL Cl(2), respectively. The detection limits of the systems were 0.0020, 0.0048, 0.0063 and 0.0017 microg/mL, respectively. In them, the RhB system has good stability and high sensitivity, and has been applied to the analysis of chlorine in drinking water, with satisfactory results which is in agreement with that of the methyl orange (MO) spectrophotometry.

[Studies on the performance of bioferric-SMBR].

To enhance removal efficiency and to mitigate membrane fouling, submerged membrane bioreactor and Bioferric process are combined to Bioferric-SMBR. Parallel compared experiment of Bioferric-SMBR and common SMBR dealing with dyeing wastewater was carried out. Bioferric-SMBR show great superiority and can enhance removal efficiency, reduce membrane fouling and improve sludge characteristic. When volume load rate is 25% higher than that of common SMBR, the removal efficiency of Bioferric-SMBR on COD, chroma and NH3-N is 1.0%, 9.5% and 5.2% higher than that of the latter respectively. The trans-membrane pressure of Bioferric-SMBR is just only 36% of that in common SMBR while it's membrane flux is 25% higher than that of common SMBR. It's stably running day is 2.5 folds of which in common SMBR when there is no surplus sludge discharged. The MLSS concentration of Bioferric-SMBR is higher than that of the latter with more different kinds microorganism such as protozoan, metazoan, etc. It's mean particle diameter value and sludge oxygen use rate (SOUR) of the former are 3.10, 1.23 times of the latter respectively.

Decolorization and biodegradation of dye wastewaters by a facultative-aerobic process.

BACKGROUND: Dye wastewater is one of the main pollution sources of water bodies in China. Conventional biological processes are relatively ineffective for color removal, the development of alternative treatment methods will become important. Our subjective was that of introducing a new biotreatment technology which combined a facultative biofilm reactor (FBR) with an aerobic reactor (AR) to treat a dye wastewater. The efficiencies of color and chemical oxygen demand (COD) removal and the mechanism of dye degradation were investigated. METHODS: The anthraquinone acid dye (acid blue BRLL) concentration, organic loading rate (OLR) and hydraulic retention time (HRT) were varied in the experiments to evaluate the treatment efficiency and process stability. The biodegradation products were detected by infrared (IR) and high performance liquid chromatography and mass spectrometry (HPLC-MS). RESULTS AND DISCUSSION: The results demonstrated that the facultative biofilm process was more effective for decolorization than the anaerobic stage of an anaerobic-aerobic process. Most color removal occurred in the facultative reaction (maximum to 88.5%) and the BOD (biochemical oxygen demand): COD of the FBR effluent increased by 82.2%, thus improving the biodegradability of dyes for further aerobic treatment. The dye concentration, OLR and HRT will be the factors affecting decolorization. Color removal efficiency falls as the influent dye concentration increases, but rises with increased HRT. The infrared and HPLC-MS analyses of the effluents of FBR and AR reveal that the dye parent compound was degraded in each reactor during the process. CONCLUSION: The Facultative-aerobic (F-A) system can effectively remove both color and COD from the dye wastewater. The FBR played an essential role in the process. The average overall color and COD in the system were removed by more than 93.9% and 97.1%, respectively, at an OLR of 1.1 kg COD m(-3) d(-1) and at the HRT of 18-20 hours in the FBR and 4-5 hours in the AR. The color removal mechanism in each reactor was not only a sort of biosorption on the floc materials, but even more an effect of biodegradation, especially in the facultative process. Recommendation and Outlook. In applying the F-A system to treat a dye wastewater, the control of facultative processes and the set up of appropriate operation conditions appear to be critical factors. Also, it is suggested a moderate COD loading rate and about a 24-hour HRT will favor the F-A system.