This study investigated organic matter and nitrogen reduction and transformation mechanisms within a field-scale hybrid natural purification system. The system included an oxidation pond, two serial surface-flow wetlands with a cascade in between, and a subsurfaceflow wetland receiving secondary treated dormitory sewage. The average biochemical oxygen demand (BOD) and chemical oxygen demand (COD) removal was 81 and 48%, respectively. Microbial degradation was the primary process contributing to organic reduction. Total Kjeldahl nitrogen (TKN) and ammonium decreased from 7.1 to 3.9 and 5.58 to 3.25 mg/L, respectively, within the surface-flow wetlands. The results indicated that nitrification occurred within the aerobic compartments. The nitrate levels continued to decrease from 1.26 to 1.07 mg/L, indicating nitrate reduction occurred in the surface-flow wetland. Total nitrogen decreased from 8.61 to 5.12 mg/L, equivalent to a 41% reduction, within the surface-flow wetlands. Results revealed that denitrification might concurrently occur in the compartment of surface-flow wetland. Total nitrogen continued to decrease from 5.12 to 3.99 mg/L within the anoxic subsurface-flow wetlands through denitrification transformation. The significant total nitrogen reduction observed was 65%. The predominant reduction of total nitrogen might take place within the sediment of surface flow and the subsurface-flow wetland where denitrification occurred. The microbial identification results also indicated that nitrification/denitrification might occur concurrently within the sediments of surface-flow wetlands.The results of this study show that hybrid wetland systems are a viable option for organic matter and nitrogen transformation and removal in tropical regions where tertiary wastewater systems are too costly or unable to operate. Treated water from these systems can comply with local surface water criteria rendering water for reuse and groundwater recharge. Water Environ. Res., 82, 27 (2010).

Natural water purification systems including oxidation ponds and surface flow wetlands are commonly used to treat wastewater in tropic regions, however, the water quality of the effluent fluctuated and often failed to comply with regulatory water criteria due to algae bloom. Separation of algae is inevitable to produce high effluent quality and to comply with local effluent standards. Algal growth control measures including emergent and floating macrophytes as well as back cloth physical light shading and algaecide application were studied and were aimed to reuse the effluent for water resource conservation and groundwater recharge. The results demonstrated that emergent and free-floating macrophytes light shading on algal growth control were viable in both batch experiments and field-scale hybrid natural water purification systems such as surface flow wetlands. Water quality parameters including COD, turbidity, SS were positively correlated with the algal concentrations and could be used as indictors of the trophic status of aquatic systems. Emergent macrophytes assisted control algal growth by preventing sunlight from reaching the water column in surface flow wetlands. Results of this study can be used by similar hybrid natural water purification systems to control algal activity and to prevent effluent deterioration.

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In this paper, the leaching experiments are conducted with four kinds of environmental materials, polymer material (SAP), coal-based nutrient (HA), mineral adsorption material (FS) and mineral chemical material (SS), to explore the remediation effects of environmental materials on lead (Pb) and cadmium (Cd) contaminated soil. Electric conductivity (EC), pH value and Pb and Cd concentrations of leachates are measured to indicate the effects. The results show that the EC values of leachates reduce gradually in the four time leaching, and the pH values of leachates are insignificantly influenced by the environmental materials, meaning these environmental materials are suitable in farmland restoration. Environmental materials are effective in Pb and Cd contaminated soil remediation and could reduce heavy metal pollution of underground water.Among these materials, SS is the best material for Pb remediation, and the total content of Pb in leachates is 57.3% of CK after treated by SS; FS is the best for Cd, and compared with CK, the total Cd content is 66.4% after adding FS.

Since the traditional teaching mode ignores the cultivation of students' innovative and entrepreneurial ability, this paper proposes a new "full process, open and project driven course mode". This new teaching model was piloted in the course of "Experiment of Optoelectronic Materials and Devices". With the new course model, students will complete a project practice in group. Through this kind of practice, students have more solid knowledge of round management, and their interdisciplinary learning ability, application knowledge ability, team cooperation ability and pressure resistance ability can be cultivated. This course mode is conducive to the cultivation of university students with the ability of innovation and entrepreneurship.