Project Description: In the past several decades, the multi-functional constructed wetlands (CWs) have been applied as alternative for polluted river water purification and wastewater treatment. CWs have successfully been used for the treatment of landfill leachate, surface runoff, and various types of wastewater including agricultural, industrial, and domestic wastewaters. Application of CWs has been recognized as an environmental-friendly eco-technology, especially beneficial to small communities, towns, or industries that cannot afford traditional treatment systems with high installation and operational costs.

Constructed Wetland for Polluted River Remediation: The multi-function Kaoping River Rail Bridge Constructed Wetland (KRRBW) was constructed to improve the stream water quality and rehabilitate the ecosystem of the surrounding environment of Dashu Region, Kaohsiung, Taiwan. The KRRBW consists of five wetland basins with a total water surface area of 15 ha, a total hydraulic retention time (HRT) of 10.1 d at a averaged flow rate of 14,740 m3/day, and an averaged water depth of 1.1 m. The influent of KRRBW coming from the local drainage systems containing untreated domestic, agricultural, and industrial wastewaters. Based on the quarterly investigation results of water samples taken in 2011 to 2012, the overall removal efficiencies were 91% for biochemical oxygen demand (BOD), 75% for total nitrogen (TN), 96% for total phosphorus (TP), and 99% for total coliforms (TC). The calculated first-order decay rates for BOD, TN, TP, NH3-N, and TC ranged from 0.14 (TN) to 0.42 (TC) 1/day. This indicates that the KRRBW was able to remove organics, TC, and nutrients effectively. Results from this study show that constructed wetlands have the potential to be developed into an environmentally acceptable river water quality improvement and wastewater polishment alternative for practical application.

Natural Treatment System for Stream Water Purification and Habitat Creation: A constructed wetland type natural treatment (NT) system was built in southern Taiwan for stream water purification and natural habitat creation. The system influent (influent rate = 1,170 m3/day) was from the local stream containing secondary wastewater from hog farms. The system included a fully-vegetated (FV) free-water surface basin, followed by an open-water pond, the second FV free-water surface basin, and an eco-pond with isolated islands for natural habitat creation. The hydraulic loading rate, hydraulic retention time, water depth, and total volume of wetland system were 0.27 m/day, 7.5 days, 0.64 m, and 7,800 m3, respectively. Results show that the overall removal efficiencies for biochemical oxygen demand, TN, total phosphorus, and total chloroform were 71, 85, 82, and 75%, respectively. The calculated first-order decay rates for organics and nutrients ranged from 0.25 (TN) to 0.15 (ammonia nitrogen) 1/day. Thus, the system had a significant effect on water quality improvement and could remove most of the pollutants from influents through NT mechanisms..

Constructed Wetland for Post-treatment of Swine Wastewater: The objective of this study was to examine the efficacy of using a modified free water surface (FWS) constructed wetland to polish the treated swine wastewater. The FWS wetland was installed inside a hog farm to conduct the treatability study. The floating plant (Pistia stratiotes L.) and small gravels were used as plant species and media, respectively. Results indicate that the following two treatment processes are suggested to meet the swine wastewater discharge standards (COD: 600 mg/L, BOD: 80 mg/L, SS: 150 mg/L): (1) conventional three-stage treatment scheme (solid separation, anaerobic treatment, and aerobic treatment) followed by the modified FWS wetland, and (2) replacement of the aerobic unit in the current treatment scheme with the modified FWS wetland with a longer (seven day) HRT.

Constructed Wetland for Industrial Wastewater Treatment: To minimize the operational and maintenance cost of the conventional wastewater treatment utilities, some medium- and small-scale factories have applied less expensive wetland system for wastewater treatment. The main objective of this study was to examine the efficacy and capacity of using constructed wetlands on industrial pollutant removal. Results from the pilot-scale study indicate that the constructed wetland system with a 5-day hydraulica retention time and feed rate of 0.4 m3/d is able to effectively treat the industrial wastewater containing 170 mg/L of COD, 80 mg/L of BOD, 90 mg/L of SS, and 32 mg/L of NH3-N.

Conclusion: Constructed wetland has become a successful multi-function ecosystem for stream water, agricultural wastewater, and industrial wastewater treatment and purification. The multi-function constructed wetland can be designed for water purification, environmental education, and rehabilitating the natural ecosystem. Our pilot-scale and field-scale results also indicate that the constructed wetland system is a feasible and cost-effective alternative technology to replace traditional secondary biological system for treating industrial wastewater to meet the discharge standards. Thus, the constructed wetland scheme has the potential to be developed into an environmentally and economically acceptable wastewater treatment technology for developing countries. Results from our studies will be useful to assist environmental professionals in designing a scale-up system for practical application.

Publications

  1. Tu. Y.T., Chiang, P.C., Chen, S.H., Kao, C.M. Application of a Constructed Wetland System for Polluted Stream Remediation, published on line, Journal of Hydrology, 2014.
  2. Y.T. Tu, Y.M. Chang, S.F. Cheng, J.L. Lin, C.M. Kao. Using Constructed Wetland and Aerated Gravel-packed Contact Bed System for Polluted River Water Purification, Wat. Sci. Tech. – Water Supply, 2014.
  3. Jou, C.J., C.L. Lee, Y.T.V. Fu and C.M. Kao, Simulation of a long narrow type constructed wetland using the stream model QUAL2K. Sustain. Environ. Res., 22(4), 255-260.
  4. Chun-Yi Wu, Yu-Tung Fu, Zong-Han Yang, Chih-Ming Kao, Yao-Ting Tu. Using Multi-function Constructed Wetland for Urban Stream Restoration. Applied Mechanics and Materials Vols. 121-126 (2012) pp 3072-3076.
  5. Wu, Chun-Yi, Fu, Yu-Tung; Yang, Zong-Han; Kao, Chih-Ming; Tu, Yao-Ting. Using multi-function constructed wetland for urban stream restoration. Applied Mechanics and Materials, 121-126, 3072-3076, 2012, Frontiers of Manufacturing and Design Science.
  6. Wu CY, Liu JK, Cheng SH, Chen C.W. Constructed wetland for water quality improvement: a case study from Taiwan, Wat. Sci. Tech., 62(10), 2408-2418, 2010.
  7. Wu CY, Kao CM, Lin CE, Using a constructed wetland for non-point source pollution control and river water quality purification: a case study in Taiwan, Wat. Sci. Tech., 61, 2549-2555, 2010.
  8. C.J. Jou, S.W. Chen, K.H. Tseng, C.M. Kao, Efficiency and ecological benefits of purifying Wu-Lo Creek with constructed wetland system, Environmental Engineering Science, v 26, n 1, p 97-102, January 1, 2009.
  9. Jou CJ, Chen SW, Kao CM. Assessing the efficiency of a constructed wetland using a first-order biokinetic model, Wetlands, 28, 215-219, 2008.
  10. Liang, S.H., Kao, C.M., Kuo, Y.C., Chen, K.F. Application of persulfate-releasing barrier to remediate MTBE and benzene contaminated groundwater, J. of Haz. Mat., 185, 1162-1168, 2011.
  11. H.Y. Chien, C.M. Kao, R.Y. Surampalli, W.Y. Huang, F. Hou, Development of a four-phase remedial scheme to cleanup petroleum-hydrocarbon contaminated soils, J. of Environ. Engr.-ASCE, 137, 602-610, 2011.
  12. S.W. Chen, C.M. Kao, H.Y. Chien, Y.T. Fu, Y.I. Chang. Use of a Constructed Wetland for Post-treatment of Swine Wastewater, Environmental Engineering Science, 25(3), 407-417, 2008.
  13. T.Y. Chen, Kao, C.M., T.Y. Yeh. A.C. Chao. Application of a Constructed Wetland for Industrial Wastewater Treatment, Chemosphere, 64(3), 2006, 497-502.
  14. T. Y. Yeh, C. M. Kao (2006), Nitrogen transformation within constructed wetlands purifying secondary treated sewage, accepted to WSEAS Transactions on Information Science and Applications, 5(4), 2006.
  15. Kao, C.M., Wang, J.Y., Chen, K.F., Lee, H.Y., and Wu, M.J. Non-point source pesticide removal by a mountainous wetland, Wat. Sci. & Tech., 46, 199-206, 2002.
  16. Kao, C.M. and Wu, M.J. Control of non-point source pollution by a natural wetland. Wat. Sci. & Tech., 43(5), 169-174, 2001.
  17. Kao, C.M., Wang, J.Y., and Wu, M.J. Evaluation of atrazine removal processes in a wetland. Wat. Sci. & Tech., 44, 539-544, 2001.
  18. Kao, C.M., Wang, J.Y., Lee, H.Y., and Wen, C.K. Application of a constructed wetland for non-point source pollution control, Wat. Sci. & Tech., 44, 585-590, 2001.