Search

Nanoscale zero-valent iron, named nano-Fe0, is a reagent used to degrade trichloroethylene in groundwater. However, the efficiency of nano-Fe0 is moderate due to issues of dispersion and reactivity. As an alternative we synthesized bentonite-supported nanoscale Fe/Ni bimetals, named bentonite-Fe/Ni, to test the degradation of trichloroethylene in the presence of Suwannee River humic acids, as a representative of natural organic matter. 0.1 mmol/L trichloroethylene was reacted with 0.5 g/L of nano-Fe0, bentonite-Fe, Fe/Ni, and bentonite-Fe/Ni nanoparticles. Results show first that without humic acids the reaction rate constants k obs were 0.0036/h for nano-Fe0, 0.0101/h for bentonite-Fe, 0.0984/h for Fe/Ni, and 0.181/h for bentonite-Fe/Ni. These findings show that bentonite-Fe/Ni is the most efficient reagent. Second, the addition of humic acids increased the rate constant from 0.178/h for 10 mg/L humic acids to 0.652/h for 40 mg/L humic acids, using the bentonite-Fe/Ni catalyst. This finding is explained by accelerated dechlorination by faster electron transfer induced by humic quinone moieties. Indeed, the use of 9, 10-anthraquinone-2, 6-disulfonate as a humic analogue gave similar results.

In this work, the occurrence and removal of polycyclic aromatic hydrocarbons (PAHs) were investigated in a combination process of anoxic baffled reactor (ABR)-hybrid coagulation/membrane bioreactor (HCMBR) for real textile dyeing wastewater treatment. It was found that the target compounds except for the chrysene, benzo(b)fluoranthene, dibenzo(a,h)anthracene, and benzo(g,hi)perylene occurred widely in raw textile dyeing wastewater, treated effluent and sludge samples. In the raw wastewater, two-ring naphthalene was the dominant compound, while three-ring PAHs predominated in the final effluent. The dominant compounds in the raw sludge samples were phenanthrene, while they were pyrene and indeno(1,2,3-cd)pyrene for final discharge sludge. The combination process achieved over 88% removal for all the PAHs. Low molecular weight (LMW) PAHs might be mainly removed by volatilization, adsorption, and sedimentation in the ABR treatment unit. High molecular weight (HMW) PAHs might be mainly removed by adso...

This study characterized sludge from an anoxic baffled reactor (ABR) used to treat textile dyeing wastewater. The process was run over 150 days. On day 152, five sludge samples were collected from compartments 1–5 of the ABR and a set of captive tests was conducted to investigate their particle size distributions (PSDs), dye biosorption and biodegradation properties, and dehydrogenase activity (DHA). The results indicated that the PSD of the five sludge samples from the ABR were similar. Methylene blue biosorption to the sludge samples followed the pseudo-second-order kinetic model and the actual biosorption process was controlled by external and intraparticle diffusion, simultaneously. After the sludge samples were cultivated for 24 h, the acid red GR dye removal efficiencies were 59.5, 68.3, 76.4, 61.5, and 65.4%, respectively. Eliminating dye biosorption, the dye biodegradation efficiencies were only 38.8, 46.3, 52.6, 48.3, and 46.0%, respectively. Furthermore, the DHA values were 28.2, 45.3, 56.5, 41.0, and 35.0 µg TF mL−1 h−1, respectively, and the DHA variation was in accordance with the dye biodegradation efficiency variation.

An experiment was conducted in a batch reactor for a real printing and dyeing wastewater pretreatment using Fenton process in this study. The results showed that original pH, hydrogen peroxide concentration and ferrous sulfate concentration affected ORP value and pretreatment efficacy greatly. Under experimental conditions, the optimal original pH was 6.61, and the optimal hydrogen peroxide and ferrous sulfate concentrations were 1.50 and 0.75 g L−1, respectively. The relationship among ORP, original pH, hydrogen peroxide concentration, ferrous sulfate concentration, and color (COD or BOD5/COD) was established, which would be instructive in on-line monitoring and control of Fenton process using ORP. In addition, the effects of wastewater temperature and oxidation time on pretreatment efficacy were also investigated. With an increase of temperature, color and COD removal efficiencies and BOD5/COD ratio increased, and they were in proportion to the exponent of temperature reciprocal. Similarly, color and COD removal efficiencies increased with increasing oxidation time, and both color and COD removal obeyed the first-order kinetics. The BOD5/COD ratio could be expressed by a second-degree polynomial with respect to oxidation time, and the best biodegradability of wastewater was present at the oxidation time of 6.10 h.

In order to investigate the effect of different carbon resource on enrichment of polyphosphate accumulating organisms (PAO) from sediment samples as well as the effect of PAO on the cycle of phosphorus in lake sediments, sedimentary samples in Lake Taihu were taken and enriched through using four kinds of carbon sources (glucose, cellulose, sodium acetate and propionate) in laboratory-scale sequencing batch reactors (SBRs). The COD/P ratio in the feeding was 15:1. The cycle time was 24 h and consisted of feeding, anaerobic period, aerobic period settle/decant period. The hydraulic retention time was 48 h, and the solids retention time was controlled at approximately 20 days. The dissolved oxygen concentration in aerobic period was maintained at 2-3 mg/L using an pump, where air was supplied at a flow rate of about 1 L/min. The reactor was operated at 25°C with an initial pH of 7.5 ± 0.1. The results showed that the orthophosphate concentration increased at the anaerobic phase in four reactors more or less, and decreased at the aerobic phase, which confirmed that there existed polyphosphate accumulating organisms in sediments of Lake Taihu. While phosphorus release rate using propionate as single carbon resource was the highest, acetate and propionate as substrate were benefit for accumulation of PAO.

Phenanthrene is a typical polycyclic aromatic hydrocarbon (PAH) found in contaminated water. This study investigated physiological responses of four submerged macrophytes to phenanthrene stress with time, following 40-day exposure to two concentrations of phenanthrene solutions in an outdoor-simulated experiment. A number of parameters including malondialdehyde, soluble carbohydrate and soluble protein contents were monitored. Results showed that the concentrations of phenanthrene in solution decreased obviously with duration of exposure. Subsequently, these four submerged macrophytes could recovered, although several days of phenanthrene exposure resulted in some adverse effects on these plants such as increased malondialdehyde and water soluble protein contents as well as reduced water soluble carbohydrate contents. Changes of these physiological parameters in these submerged macrophytes reflected their continuous tolerance to phenanthrene.