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Ti/TiO2-NTs/Ag2O/PbO2 anode was prepared by electrodeposition technique and characterized by scanning electron microscope-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), linear sweep voltammetry (LSV), and accelerated life test. Electrochemical oxidation of persistent organic pollutant wastewater perfluorooctane sulfonate (PFOS) was carried out with the novel PbO2 anode. Ti/TiO2-NTs/Ag2O/PbO2 anode exhibited a pyramid structure, which was the typical PbO2 electrodes prepared using electrochemical deposition method. XRD spectra indicated that diffraction peaks of PbO2 coating conformed to that of JCPDS (Joint Committee on Powder Diffraction Standards) card for β-PbO2. Ti/TiO2-NTs/Ag2O/PbO2 anode showed high oxygen evolution potential, and longer life service, compared with Ti/PbO2 and Ti/TiO2-NTs/PbO2 anodes. The degradation ratio of PFOS (90 mL of 0.0929 mmol L−1) was 74.87%, with a pseudo first-order kinetic constant of 0.0165 min−1 and a half-life of 43.18 min−1 at a constant current density of 30 mA cm−2 after 180 min of electrolysis. PFOS oxidation yielded sulfate, fluoride, and perfluorocarboxyl anions (i.e., C3F7COO−, C4F9COO−, C5F11COO−, C6F13COO−, and C7F15COO−). The electrospray ionization (ESI) mass spectrum confirmed that oxygen in the intermediate products originated from a heavy-oxygen water electrolyte, and the degradation of PFOS was initiated by the dissociation of a sulfonic group. A possible mechanism was revealed; that was, PFOS was desulfated at the anode to form C8F17· and then transformed into C8F17OH, followed by intramolecular rearrangement and hydrolysis reactions to form C7F15COO−. Kolbe decarboxylation occurred in C7F15COO− at the anode to generate C7F15·, which evolved into C6F13COO− in a similar way and the CF2 unit fell off from C7F15COO−. PFOS was gradually degraded into short-chain perfluorocarboxyl anions by repeating the CF2 unzipping cycle.

A long-term investigation, which covered 10 sampling campaigns over 3 years, was performed to evaluate the occurrence, removal and risk of 10 pharmaceuticals in 2 full-scale sewage treatment plants (STPs) in Guangdong, South China. Target pharmaceuticals except for clofibrate and ibuprofen were detected in every sample, with mean concentrations of 12.5–685.6 and 7.9–130.3 ng/L in the influent and effluent, respectively. Salicylic acid was the most abundant compound in both the influents and effluents in the two STPs. For most pharmaceuticals, the seasonal variation in the influent showed the highest concentrations in January and lowest concentrations in July due to their consumption and rainfall. Ibuprofen and fenoprofen presented high removal rates (>90%) and some of the targets such as gemfibrozil, mefenamic acid, tolfenamic acid and diclofenac were detectable with significantly higher mass loads in effluents than in influents. Studies of the five efficiently eliminated pharmaceuticals show that the primary treatment and secondary treatment contributed to most pharmaceutical removal, the anoxic tank made a negligible contribution to their elimination. According to the results produced from the calculation of the risk quotient, only diclofenac might pose a risk to the aquatic environment.

Removal of nonylphenol ethoxylates (NPEOs) in aqueous solution by Fenton oxidation process was studied in a laboratory-scale batch reactor. Operating parameters, including initial pH temperature, hydrogen peroxide, and ferrous ion dosage, were thoroughly investigated. Maximum NPEOs reduction of 84% was achieved within 6 min, under an initial pH of 3.0, 25°C, an H2O2 dosage of 9.74×10−3 M, and a molar ratio of [H2O2]/[Fe2+] of 3. A modified pseudo-first-order kinetic model was found to well represent experimental results. Correlations of reaction rate constants and operational parameters were established based on experimental data. Results indicated that the Fenton oxidation rate and removal efficiency were more dependent on the dosage of H2O2 than Fe2+, and the apparent activation energy (ΔE) was 17.5 kJ/mol. High-performance liquid chromatography and gas chromatograph mass spectrometer analytical results indicated degradation of NPEOs obtained within the first 2 min stepwise occurred by ethoxyl (EO) unit shortening. Long-chain NPEOs mixture demonstrated a higher degradation rate than shorter-chain ones. Nonylphenol (NP), short-chain NPEOs, and NP carboxyethoxylates were identified as the primary intermediates, which were mostly further degraded.

This paper investigates the relationship between water pollution and economic growth in four cities of Guangdong Province in China based on the environmental Kuznets curve hypothesis, using urban data over 1990–2009. Waste water is used as the environmental indicator and per capita GDP is used as the economic indicator. Cubic function is used to formulate the relationship, with quadratic function and logarithmic function as comparison. The results show that the relationship between waste water and per capita GDP of Guangzhou city is inverse U-shaped, those of Shenzhen, Heyuan and Huizhou are not inverse U-shaped until 2009. Several reasons are listed for the phenomenon, among which the change of industrial structure is analyzed in detail.

Recovery of cadmium in wastewater was investigated by an electrochemical deposition approach in a multianode and multicathode cell in this study. The effects of initial concentration, initial pH, c...

Excess sludge contains a large quantity of water with water content reaching about 97%-99%. Besides microorganisms and germs, the sludge is of complicated composition, including heavy metals, persistent organic pollutants, PPCPs, endocrine disrupters, etc. It covers a large area with harmfulness, so it needs further treatment. However, due to existence of extracellular polymeric substances in the sludge, the sludge has poor dehydration property, so how to improve dehydration of sludge is a difficult point in water treatment industry. Chemical conditioning—mechanical dehydration method is sludge dehydration technology which has been widely applied in China. Most sludge treatment plants use organic and inorganic conditioners like polyacrylamide (PAM), polyaluminum chloride (PAC) and polymerized ferrous sulfate (PFS), etc. With characteristics of low toxicity and degradation resistance, these conditioners pose potential risks to the environment and they are adverse to follow-up resource utilization. Therefore, influences of 17 conditioners on sludge dehydration ratio were discussed in this paper, expecting to seek for green, environmentally friendly and highly efficient conditioner so as to improve resource utilization ratio of sludge.

Bisphenol A (BPA) is a kind of a controversial endocrine disruptor, and is ubiquitous in environment. The degradation of BPA with the heterogeneous photo-Fenton system was demonstrated in this study. The Fe-Y molecular sieve catalyst was prepared with the ion exchange method, and it was characterized by X-ray radiation diffraction (XRD). The effects ofpH, initial concentration of H2O2, initial BPA concentration, and irradiation intensity on the degradation of BPA were investigated. The service life and iron solubility of catalyst were also tested. XRD test shows that the major phase of the Fe-Y catalyst was Fe2O3. The method of heterogeneous photo-Fenton with Fe-Y catalyst was superior to photolysis, photo-oxidation with only hydrogen, heterogeneous Fenton, and homogeneous photo-Fenton approaches. pH value had no obvious effects on BPA degradation over the range of 2.2-7.2. The initial concentration of H2O2 had an optimal value of 20 x 10(-4) mol/L. The decrease in initial concentration of BPA was favourable for degradation. The intensity of ultraviolet irradiation has no obvious effect on the BPA removal. The stability tests indicated that the Fe-Y catalyst can be reused and iron solubility concentration ranged from NA to 0.0062 mg/L. Based on the results, the heterogeneous photo-Fenton treatment is the available method for the degradation of BPA.