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Luo Q.,Shanghai Academy of Environmental Science
Frontiers of Environmental Science and Engineering

The oxidation of aqueous monochlorobenzene (MCB) solutions using thermally-activated persulfate has been investigated. The influence of reaction temperature on the kinetics of MCB oxidation was examined, and the Arrenhius Equation rate constants at 20°C, 30°C, 40°C, 50°C, and 60°C for MCB oxidation performance were calculated as 0, 0.001, 0.002, 0.015, 0.057 min-1, which indicates that elevated temperature accelerated the rate. The most efficient molar ratio of persulfate/MCB for MCB oxidation was determined to be 200 to 1 and an increase in the rate constants suggests that the oxidation process proceeded more rapidly with increasing persulfate/MCB molar ratios. In addition, the reactivity of persulfate in contaminated water is partly influenced by the presence of background ions such as Cl-, HCO3 -, SO4 2-, and NO3 -. Importantly, a scavenging effect in rate constant was observed for both Cl- and CO3 2- but not for other ions. The effective thermally activated persulfate oxidation of MCB in groundwater from a real contaminated site was achieved using both elevated reaction temperature and increased persulfate/MCB molar ratio. © 2014 Higher Education Press and Springer-Verlag Berlin Heidelberg. Source

Xu J.,North Carolina State University | Shen G.,Shanghai Academy of Environmental Science
Water Environment Research

Harvest regime and water depth were investigated to determine their effects on nutrient recovery from swine wastewater by a Spirodela oligorrhiza system. The results show that harvesting less duckweed at shorter intervals favored nutrient removal and total biomass production. Harvesting 20% of duckweed twice a week led to 66.3 and 109.4% higher total nitrogen and total phosphorus removals, respectively, and a duckweed production of 20.0 g fresh biomass/m 2·d-39.6% higher than that of harvesting 80% of duckweed once every 4 weeks. The water depth of duckweed system was of great importance to total nutrient removal. At the water depth of 40 cm, total nitrogen and total phosphorus removals were 2.05 and 2.16 times higher, respectively, than those at the water depth of 10 cm. However, because of the larger amount of nutrients in a deeper system, it took a longer time for the nutrient concentrations to decrease. Source

Xu J.,North Carolina State University | Shen G.,Shanghai Academy of Environmental Science
Bioresource Technology

Spirodela oligorrhiza, a promising duckweed identified in previous studies, was examined under different cropping conditions for nutrient recovery from swine wastewater and biomass production. To prevent algae bloom during the start-up of a duckweed system, inoculating 60% of the water surface with duckweed fronds was required. In the growing season, the duckweed system was capable of removing 83.7% and 89.4% of total nitrogen (TN) and total phosphorus (TP) respectively from 6% swine lagoon water in eight weeks at a harvest frequency of twice a week. The total biomass harvested was 5.30 times that of the starting amount. In winter, nutrients could still be substantially removed in spite of the limited duckweed growth, which was probably attributed to the improved protein accumulation of duckweed plants and the nutrient uptake by the attached biofilm (algae and bacteria) on duckweed and walls of the system. © 2010 Elsevier Ltd. Source

Wang F.,Tongji University | Liu Y.,Shanghai Academy of Environmental Science | Ma Y.,Tongji University | Wu X.,Tongji University | Yang H.,Tongji University
Ecological Engineering

A shallow moss constructed wetland (SMCW) was constructed using a specific type of moss (Bryum muehlenbeckii) and ornithogenic soil collected from polar regions to enhance nitrogen treatment performance at cold temperatures. At different temperatures (20°C, 12°C, and 5°C), the first-order kinetics constants (K v) of 0.247-0.227d -1, 0.277-0.411d -1, 0.216-0.313d -1, and 0.379-0.394d -1, respectively. The temperature variation constants, θ, for ammonia oxidation and TN removal reaction rates were both 1.024, lower than in control wetland (CW). The highest dissolved oxygen (DO) was found around moss roots, ant it was also noticeably higher than that in the control wetlands. Ammonia oxidizing bacteria (AOB) concentration ranged from 0.32×10 7 to 8.54×10 7cellsg -1 with the maximum value in the shallow anterior half of the wetland. The dominant AOB community in SMCW was totally different from control wetland, including Nitrosococcus mobilis, Nitrosomonas eutropha, and Nitrosomonas marina. The capability of the moss wetland to maintain the nitrification rate at low temperatures may be attributed to the cold-adapted AOB community inoculated from ornithogenic soil and better oxygen transfer to moss roots. © 2012 Elsevier B.V. Source

Through the evaluation of the gains and losses of the key functions of regional ecological system under different management modes, various ecosystems functions and their spatial distribution patterns in Wanquan Town were analyzed. Based on different development needs, various scenarios were established and weighed. In 2009, the support function value supplied by the ecosystems in the Town was 58 million RMB, among which, oxygen release function ranked first(37 million RMB), and the regulation function value provided by the ecosystems was 1238 million RMB, among which, climate regulation ranked first(1127 million RMB). The total ecosystem services value was 1297 million RMB, being 1. 46 times of the local GDP(888 million RMB) in the same year. Compared with that in 2002, the service function value of the ecosystems declined in 2009, with the largest decrements in climate regulation and water yield. Under policy scenario and protection scenario, the variation trends of the values of various ecosystems functions were basically the same. Except that the values of the functions oxygen release and nutrient cycling decreased, the values of the others increased obviously. Under protection scenario, the total ecosystem services value had a higher increment than that under policy scenario, especially for the water yield and carbon sequestration functions. It was suggested that protection scenario could be the optimal land use management mode for the socio-economic sustainable development of the Town. Source

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