C. E. Lin

Development of the sediment and water quality management strategies for the Salt-water River, Taiwan.

The Salt-water River watershed is one of the major river watersheds in the Kaohsiung City, Taiwan. Water quality and sediment investigation results show that the river water contained high concentrations of organics and ammonia-nitrogen, and sediments contained high concentrations of heavy metals and organic contaminants. The main pollution sources were municipal and industrial wastewaters. Results from the enrichment factor (EF) and geo-accumulation index (Igeo) analyses imply that the sediments can be characterized as heavily polluted in regard to Cd, Cr, Pb, Zn, and Cu. The water quality analysis simulation program (WASP) model was applied for water quality evaluation and carrying capacity calculation. Modeling results show that the daily pollutant inputs were much higher than the calculated carrying capacity (1050 kg day(-1) for biochemical oxygen demand and 420 kg day(-1) for ammonia-nitrogen). The proposed watershed management strategies included river water dilution, intercepting sewer system construction and sediment dredging.

Using a constructed wetland for non-point source pollution control and river water quality purification: a case study in Taiwan.

The Kaoping River Rail Bridge Constructed Wetland, which was commissioned in 2004, is one of the largest constructed wetlands in Taiwan. This multi-function wetland has been designed for the purposes of non-point source (NPS) pollutant removal, wastewater treatment, wildlife habitat, recreation, and education. The major influents of this wetland came from the local drainage trench containing domestic, agricultural, and industrial wastewaters, and effluents from the wastewater treatment plant of a paper mill. Based on the quarterly investigation results from 2007 to 2009, more than 96% of total coliforms (TC), 48% of biochemical oxygen demand (BOD), and 40% of nutrients (e.g. total nitrogen, total phosphorus) were removed via the constructed wetland system. Thus, the wetland system has a significant effect on water quality improvement and is capable of removing most of the pollutants from the local drainage system before they are discharged into the downgradient water body. Other accomplishments of this constructed wetland system include the following: providing more green areas along the riversides, offering more water assessable eco-ponds and eco-gardens for the public, and rehabilitating the natural ecosystem. The Kaoping River Rail Bridge Constructed Wetland has become one of the most successful multi-function constructed wetlands in Taiwan. The experience obtained from this study will be helpful in designing similar natural treatment systems for river water quality improvement and wastewater treatment.

Preliminary identification of watershed management strategies for the Houjing river in Taiwan

The Houjing River watershed is one of the three major river watersheds in the Kaohsiung City, Taiwan. Based on the recent water quality analysis, the Houjing River is heavily polluted. Both point and non-point source (NPS) pollutants are the major causes of the poor water quality in the Houjing River. Investigation results demonstrate that the main point pollution sources included municipal, agricultural, and industrial wastewaters. In this study, land use identification in the Houjing River watershed was performed by integrating the skills of geographic information system (GIS) and global positioning system (GPS). Results show that the major land-use patterns in the upper catchment of the Houjing River watershed were farmlands, and land-use patterns in the mid to lower catchment were residential and industrial areas. An integrated watershed management model (IWMM) and Enhanced Stream Water Quality Model (QUAL2K) were applied for the hydrology and water quality modeling, watershed management, and carrying capacity calculation. Modeling results show that the calculated NH₃-N carrying capacity of the Houjing River was only 31 kg/day. Thus, more than 10,518 kg/day of NH₃-N needs to be reduced to meet the proposed water quality standard (0.3 mg/L). To improve the river water quality, the following remedial strategies have been developed to minimize the impacts of NPS and point source pollution on the river water quality: (1) application of BMPs [e.g. source (fertilizer) reduction, construction of grassy buffer zone, and land use management] for NPS pollution control; (2) application of river management scenarios (e.g. construction of the intercepting and sewer systems) for point source pollution control; (3) institutional control (enforcement of the industrial wastewater discharge standards), and (4) application of on-site wastewater treatment systems for the polishment of treated wastewater for water reuse.

Application of integrated GIS and multimedia modeling on NPS pollution evaluation

In Taiwan, nonpoint source (NPS) pollution is one of the major causes of the impairment of surface waters. I-Liao Creek, located in southern Taiwan, flows approximately 90xa0km and drains toward the Kaoping River. Field investigation results indicate that NPS pollution from agricultural activities is one of the main water pollution sources in the I-Liao Creek Basin. Assessing the potential of NPS pollution to assist in the planning of best management practice (BMP) is significant for improving pollution prevention and control in the I-Liao Creek Basin. In this study, land use identification in the I-Liao Creek Basin was performed by properly integrating the skills of geographic information system (GIS) and global positioning system (GPS). In this analysis, 35 types of land use patterns in the watershed area of the basin are classified with the aid of Erdas Imagine® process system and ArcView® GIS system. Results indicate that betel palm farms, orchard farms, and tea gardens dominate the farmland areas in the basin, and are scattered around on both sides of the river corridor. An integrated watershed management model (IWMM) was applied for simulating the water quality and evaluating NPS pollutant loads to the I-Liao Creek. The model was calibrated and verified with collected water quality and soil data, and was used to investigate potential NPS pollution management plans. Simulated results indicate that NPS pollution has significant contributions to the nutrient loads to the I-Liao Creek during the wet season. Results also reveal that NPS pollution plays an important role in the deterioration of downstream water quality and caused significant increase in nutrient loads into the basin’s water bodies. Simulated results show that source control, land use management, and grassy buffer strip are applicable and feasible BMPs for NPS nutrient loads reduction. GIS system is an important method for land use identification and waste load estimation in the basin. Linking the information of land utilization with the NPS pollution simulation model may further provide essential information of potential NPS pollution for all subregions in the river basin. Results and experience obtained from this study will be helpful in designing the watershed management and NPS pollution control strategies for other similar river basins.

Integrated Water Resource Management for Kaoping River Basin

The Kaoping River Basin, located in southern Taiwan, flows through approximately 171 km and drains toward the South Taiwan Strait. It is the largest and the most intensively used river basin in Taiwan. However, due to the concentrated rainfall in the wet season, short rivers and rapid flows, poor flow conditions, uneven time distribution of flows, and rapid rise of flow peak cause the unevenly distributed water resource in this region. Based on the results from the water resource analysis and water demand evaluation, a shortage of water supply in the basin would occur in 5 years. Sustainable water resource management strategies have been proposed to effectively utilize the limited water resource in the basin. The proposed strategies include construction of water collection gallery system, installation of riverbank infiltration system, installation of groundwater recharge and extraction systems, recycling the effluent from the secondary wastewater-treatment plant, and replacement of old water supply pipes....

Super Critical Fluid Technique to Enhance Current Output on Amorphous Silicon-Based Photovoltaic

A low temperature, non-destructive treatment technique with supercritical carbon dioxide mixing water was demonstrated on thin film type photovoltaic devices to enhance current output. Assembled P-I-N amorphous Si-based devices were treated in a high pressure reaction chamber. Generation of light current under indoor illumination was improved by about 80% after treatment. To clarify the origin of improvement, the drive-level capacity profiling method with capacitance–voltage (C–V) measurement was used, as it shows the relationship between defect density and location. Such measurements reveal that the amount of interface defects was significantly reduced after treatment. A dynamic reaction model was also proposed to explain the defect passivation reaction. This technique can be effectively applied to amorphous silicon solar cell devices to enhance performance.

PRESSURE-ASSISTED CYCLIC WASHING OF HEAVY-METAL-CONTAMINATED SEDIMENTS

Remediation of heavy-metal-contaminated sediment is often hampered by the availability of heavy metals to the added chemical agents because the heavy metals are often shielded by the sediment matrix. Effective heavy-metal extraction technique becomes an important factor in enhancing the treatment efficiency. A novel extraction/washing technique utilizing chelating agent and elevated pressure in consecutive cycles of compression and decompression has been developed for heavy-metal-contaminated sediment washing in the presence of chelating agent. In this study, the optimal operational conditions of pressure-assisted cyclic washing of Cu-contaminated sediments (initial Cu concentrationxa0=xa023.177xa0mg/kg) were determined in a laboratory-scale system. The control factors included applied pressure level, washing time, applied chelant [ethylenediamine-tertraacetic (EDTA)] concentration (0.01–0.5xa0M), pressure times, and application of consecutive batches washing. Results from the bench-scale study showed that up to 70xa0% of Cu can be removed from the sediments when 10xa0atm of pressure was applied for washing. The efficiency dropped to 55xa0% when the pressure dropped to 6xa0atm. Under the same operational conditions, the optimal cyclic washing time was 60xa0min. Results from the particle size analyses indicate that the mean particle size dropped from 100 to 50xa0μm after the pressure-assisted cyclic washing. Thus, cyclic pressure caused the fracture of sediment aggregates resulting in the exposure of Cu to chelating agents. With the assistance of pressure cyclic system, the total washing time and the amount of added chemical agent used can be significantly reduced.