Hu C.-Y.,Taipei Medical University |
Lo S.-L.,National Taiwan University |
Chang C.-L.,Feng Chia University |
Chen F.-L.,National Taiwan University |
And 2 more authors.
Separation and Purification Technology | Year: 2013
The high turbidity in surface water may make it difficult for water treatment plants to supply drinking water. Chitosan, a natural linear cationic polymer, and aluminum chloride, a metal salt, and the mixture of the two coagulants were used to treat highly turbid raw water in this study according to the residual turbidity, sludge volume and residual aluminum concentration. The residual turbidity was less than 50 NTU but the sludge/water volume ratio was over 150 mL/L after aluminum salt coagulation (135 mg/L as Al), which could stop the sedimentation process. The amount of sludge produced after chitosan coagulation (5 mg/L) was only about 1/5 of that for aluminum coagulation for the similar turbidity removal. Chitosan coagulation, however, still has two problems that need to be solved. First, the residual turbidity of treated water is still too high for sand filtration. Second, the colloid particles may restabilize if chitosan is overdosed. Adding a comparative low dosage of aluminum salt (13.5 mg/L as Al) with chitosan can successfully solve both of the problems. The sludge volume ratio only increased slightly and the residual turbidity was less than 10 NTU. Moreover, the restabilization of colloids did not occur. The residual aluminum concentration, which could lead to Alzheimer's disease, can also be reduced significantly after addition of chitosan. © 2012 Elsevier B.V. All rights reserved.
Lee K.T.,National Taiwan Ocean University |
Yang C.-C.,National Taiwan Ocean University |
Yang C.-C.,Water Resource Agency
Journal of Hydrology | Year: 2010
Concentrated rainfall usually results in serious soil erosion on steep hillslopes. Since the itinerary of the eroded sediment is complicated, estimating watershed erosion during storms is practically difficult. A physically-based approach for sediment yield estimation during storms was proposed in this study. By using soil and watershed geomorphologic information, analytical solutions for sediment travel time in different orders of overland areas and channels were derived to develop a geomorphologic instantaneous unit sedimentgraph (GIUS) which showed the temporal distribution of sediment discharge resulting from an instantaneous rainfall excess input. The resultant GIUS was a function of the rainfall excess intensity and sediment delivery ratio. The linearity restriction of the unit hydrograph theory was relaxed. Sediment yields during storm events were calculated by convoluting rainfall intensities with the proposed GIUS, which had been verified by using data from the Goodwin Creek Experimental Watershed in Mississippi, the United States. The simulated and the measured sediment yields were in good agreement for the test storms. Sensitivity of the sedimentgraph to the model parameters was also investigated. The proposed model was considered a promising application for sediment yield estimation in the field of water resources design. © 2009 Elsevier B.V. All rights reserved.
Wu R.-S.,National Central University |
Chen Y.-R.,Water Resource Agency |
Ge Y.-L.,National Central University
Chinese Journal of Applied Ecology | Year: 2012
Based on the HEC-RAS and River 2D modes, and taking 5% change rate of weighted usable area(WUA) as the threshold to define the spur dike-affected area of target fish species Acrossocheilus paradoxus in Fazi River in Taiwan, this paper studied the affected area of the fish habitat by spur dike, and, in combining with the references about the installations of spur dikes in Taiwan in recent 10 years, analyzed the relative importance of related affecting factors such as dike height, dike length(water block rate), average slope gradient of river way, single or double spur dike, and flow discharge. In spite of the length of the dike, the affected area in downstream was farther, and was about 2-6 times as large as that in upstream. The ratio of the affected area in downstream / upstream decreased with increasing slope gradient, but increased with increasing dike length and flow discharge. When the discharge was approximate to 10 years return periods, the ratio of the affected area would be close to a constant of 2. Building double spur dike would produce a better WUA than building single spur dike.
Chang F.-J.,National Taiwan University |
Tsai W.-P.,National Taiwan University |
Wu T.-C.,National Taiwan University |
Chen H.-K.,Water Resource Agency |
Herricks E.E.,University of Illinois at Urbana - Champaign
Journal of Hydrology | Year: 2011
Modern water resources management has adopted natural flow regimes as reasonable targets for river restoration and conservation. The characterization of a natural flow regime begins with the development of hydrologic statistics from flow records. However, little guidance exists for defining the period of record needed for regime determination. In Taiwan, the Taiwan Eco-hydrological Indicator System (TEIS), a group of hydrologic statistics selected for fisheries relevance, is being used to evaluate ecological flows. The TEIS consists of a group of hydrologic statistics selected to characterize the relationships between flow and the life history of indigenous species. Using the TEIS and biosurvey data for Taiwan, this paper identifies the length of hydrologic record sufficient for natural flow regime characterization. To define the ecological hydrology of fish communities, this study connected hydrologic statistics to fish communities by using methods to define antecedent conditions that influence existing community composition. A moving average method was applied to TEIS statistics to reflect the effects of antecedent flow condition and a point-biserial correlation method was used to relate fisheries collections with TEIS statistics. The resulting fish species-TEIS (FISH-TEIS) hydrologic statistics matrix takes full advantage of historical flows and fisheries data. The analysis indicates that, in the watersheds analyzed, averaging TEIS statistics for the present year and 3 years prior to the sampling date, termed MA(4), is sufficient to develop a natural flow regime. This result suggests that flow regimes based on hydrologic statistics for the period of record can be replaced by regimes developed for sampled fish communities. © 2011 Elsevier B.V.
Hsu Y.-C.,Sinotech Engineering Consultants |
Huang H.-H.,Sinotech Engineering Consultants |
Huang Y.-D.,Sinotech Engineering Consultants |
Chu C.-P.,Sinotech Engineering Consultants |
And 2 more authors.
Water Science and Technology | Year: 2012
Water shortage has become an emerging environmental issue. Reclamation of the effluent from municipal wastewater treatment plant (WWTP) is feasible for meeting the growth of water requirement from industries. In this study, the results of a pilot-plant setting in Futian wastewater treatment plant (Taichung, Taiwan) were presented. Two processes, sand filter - ultrafiltration - reverse osmosis (SF-UF-RO) and sand filter - electrodialysis reversal (SF-EDR), were operated in parallel to evaluate their stability and filtrate quality. It has been noticed that EDR could accept inflow with worse quality and thus required less pretreatment compared with RO. During the operation, EDR required more frequent chemical cleaning (every 3 weeks) than RO did (every 3 months). For the filtrate quality, the desalination efficiency of SF-EDR ranged from 75 to 80% in continuous operation mode, while the conductivity ranged from 100 to 120 μS/cm, with turbidity at 0.8 NTU and total organic carbon at 1.3 mg/L. SF-EDR was less efficient in desalinating the multivalent ions than SF-UF-RO was. However for the monovalent ions, the performances of the two processes were similar to each other. Noticeably, total trihalomethanes in SF-EDR filtrate was lower than that of SF-UF-RO, probably because the polarization effects formed on the concentrated side of the EDR membrane were not significant. At the end of this study, cost analysis was also conducted to compare the capital requirement of building a full-scale wastewater reclamation plant using the two processes. The results showed that using SF-EDR may cost less than using SF-UF-RO, if the users were to accept the filtrate quality of SF-EDR. © IWA Publishing 2012.