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Bi D.,Shanghai Institute of Technology | Guo X.,Shanghai Academy of Environmental Science | Cai Z.,Dongguan Environmental Protection Monitoring Station | Yu Z.,Guangdong Institute of Eco environmental and Soil Sciences | And 2 more authors.
Environmental Technology (United Kingdom) | Year: 2014

The potential function of combining magnetic field (MF) pretreatment with cationic polyacrylamide (CPAM) additive on enhancing the dewaterability of waste-activated sludge was investigated in the present work. Two reactors were involved in a specially designed experimental apparatus, one of which was built with MF accessories. Several parameters were conducted, including CPAM dosages, MF strengths and processing times, respectively. Capillary suction time (CST) and specific resistance to filtration (SRF) were used to evaluate sludge dewaterability. Extracellular polymeric substances (EPS) concentration was also determined in an attempt to identify the observed changes in dewaterability. It was indicated by the results that both CPAM conditioning and MF pretreatment on sludge can lower CST and SRF values. However, subjecting to a combination of MF pretreatment and CPAM conditioning, sludge dewaterability was significantly enhanced beyond the level observed of CPAM addition alone. The lowest CST and SRF values of 36.5 s and 0.75 × 1012 m kg-1, respectively, were obtained when sludge was co-conditioned by CPAM (at a dosage of 40 mg L-1) and MF (at an induction of 40 mT) for 30 min, suggesting the optimal condition for enhancing sludge dewaterability. It is also shown from the significant correlations between EPS, protein, polysaccharide and CST/SRF that the increment of EPS concentration in sludge supernatant may be the major reason for the enhancement of dewaterability. © 2014 © 2014 Taylor & Francis. Source

Huang Q.,Hunan Agricultural University | Yu Z.,Guangdong Institute of Eco environmental and Soil Sciences | Pang Y.,Changsha University | Wang Y.,Guangdong Institute of Eco environmental and Soil Sciences | Cai Z.,Dongguan Environmental Protection Monitoring Station
Bulletin of Environmental Contamination and Toxicology | Year: 2015

In this study, bioleaching was coupled with electrokinetics (BE) to remove heavy metals (Cu, Zn, Cr and Pb) from contaminated soil. For comparison, bioleaching (BL), electrokinetics (EK), and the chemical extraction method were also applied alone to remove the metals. The results showed that the BE method removed more heavy metals from the contaminated soil than the BL method or the EK method alone. The BE method was able to achieve metal solubilization rates of more than 70 % for Cu, Zn and Cr and of more than 40 % for Pb. Within the range of low current densities (<1 mA cm-2), higher current density led to more metal removal. However, the metal solubilization rates did not increase with increasing current density when the current density was higher than 1 mA cm-2. Therefore, it is suggested that bioleaching coupled with electrokinetics can effectively remediate heavy metal-contaminated soils and that preliminary tests should be conducted before field operation to detect the lowest current density for the greatest metal removal. © 2015 Springer Science+Business Media New York. Source

Bi D.,Shanghai Institute of Technology | Guo X.,Shanghai Academy of Environmental Science | Cai Z.,Dongguan Environmental Protection Monitoring Station | Gao X.,Yangtze University | And 5 more authors.
Water Science and Technology | Year: 2012

The phosphorus (P) distribution in the sediments of Haizi Lake from the middle reach of the Yangtze River region, China, was investigated using a sequential chemical extraction procedure. P forms and concentrations of sediment samples taken at 25 sites over the whole lake were measured. The relationships between various forms of P in sediments and dissolved P in the overlying water were also discussed. Results showed that the concentrations of total P (TP) in the sediments ranged from 404 to 670 mg kg-1, with an average of 503 mg kg-1. The exchangeable P (Ex-P), Al-bound P (Al-P), Fe-bound P (Fe-P), occluded P (Oc-P), authigenic carbonate fluorapatite + biogenic apatite + CaCO3-associated P (ACa-P), detrital apatite + other inorganic P (De-P) and organic P (Or-P) accounted for, on average, 0.52, 0.04,10.9, 32.0, 7.4, 20.1 and 29.0% of TP, respectively. Relevance analysis indicated that Oc-P, ACa-P and De-P, as the majority forms of inorganic P, were less correlated to others. The significant correlations between Ex-P, Al-P, Fe-P, Or-P and TP suggested the probability of reciprocal transformation. It was suggested that Ex-P, Al-P, Fe-P, Or-P and TP in the sediments might be released easily to the water interface, resulting in sustained lake eutrophication. © IWA Publishing 2012. Source

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