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The Application of Integrated Constructed Wetlands for Contaminant Treatment and Diffusion Yu Dong A thesis submitted for the degree of Doctor of Philosophy School of Engineering The University of Edinburgh 2012 Declaration I declare that this thesis was composed by myself and that the work contained therein is my own, except where explicitly stated otherwise in the text. The work has not been submitted in any form for any other degree or professional qualification. Yu Dong November 2012 ii To my dearest grandpa, dad and mom. iii Abstract The sediment accumulation is an important characteristic in the ageing process of integrated constructed wetlands (ICW). Retained nutrient and other contaminants in wetland sediments have the potential to be remobilized and released to the overlying water column when environmental conditions change. In this study, mesocosms which filled with saturated sediments and planted with Phragmites australis and Agrostis stolonifera were set up to examine nutrient and other contaminants retention and/or release by wetland sediment and substrates. The effects of physico-chemical parameters on sediment-water contaminant exchange were also investigated through the application of multiple regression models, principal component analysis (PCA), redundancy analysis (RDA), and self-organizing map (SOM) model. The results demonstrated an average net release of chemical oxygen demand (COD), ammonia- nitrogen (NH3-N), nitrate-nitrogen (NO3-N) and molybdate reactive phosphorus (MRP) to the overlying water column, indicating that the ICW sediment and substrates acted as new contaminant sources. According to statistical analysis, electrical conductivity (EC) and redox potential (RP) values affected COD treatment efficiency. Chloride (Cl) concentration and RP value had an impact on NH3-N treatment performance. NO3-N removal was influenced by dissolved oxygen (DO) concentration and RP value. MRP treatment efficiency was related to DO concentration and EC value. The SOM model was selected as prediction tool to provide numerical estimations for the performance of ICW mesocosms. The model was validated, indicating that NH3-N, NO3-N, MRP, and COD treatment efficiencies iv could be predicted by input variables which are quick and cost-effective to measure. The SOM model can be seen as an appropriate method for monitoring the performance of mature ICWs. The type of vegetation played a minor role in releasing nutrients and other contaminants. However, the mesocosm planted with Phragmites australis outperformed the one planted with Agrostis stolonifera. No water reached bottom outlet of the mesocosm suggesting that there was little potential risk to contaminate groundwater. The clay liner and the biogeochemical processes taking place within sediments proved to be effective in preventing surface water from infiltration. Although no reduction in the overall performance has been observed for the full-scale ICW sites 7 and/or 11, this laboratory-scale study provided valuable warning signs regarding the loss of contaminant sequestration which may contribute to decline in wetland treatment performance over time. The impacts of hydraulic loading rate (HLR) and seasonal temperature fluctuations on contaminant removal efficiencies of a new ICW system receiving domestic wastewater were also assessed. The system showed good overall treatment performance in terms of effluent quality and removal efficiency. The influence of ICW removal efficiencies of the hydraulic loading rate, which was based on overall water balance, was negligible due to large footprint and multi-cellular configuration of the studied system. Relatively low temperature in autumns and winters resulted in decreased biological activities and lower contaminant removal efficiency. The long-term trends in nutrient removal have been investigated to five Wildfowl & Wetlands Trust constructed wetland systems. The results showed less v effective removal even release of NO3-N, total oxidised nitrogen (TON), ortho- phosphate-phosphorus (PO4-P) and total phosphorus (TP) in many of the systems as a result of wetland aging and lack of sediment management. vi Publication List Journal articles: 1. Xu, X.W., Huang, S.L., Scholz, M., Dong, Y. (2010). Remediation of polycyclic aromatic hydrocarbons. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources 6(003), 1–9. 2. Zang, C., Huang, S., Wu, M., Du, S., Scholz, M., Gao, F., Lin, C., Guo, Y., Dong, Y. (2010). Comparison of relationships between pH, dissolved oxygen and chlorophyll α for aquaculture and non-aquaculture waters. Water, Air, & Soil Pollution 219(1–4), 157–174. 3. Dong, Y., Wiliński, P., Dzakpasu, M., Scholz, M. (2011). Impact of hydraulic loading rate and season on water contaminant reductions within integrated constructed wetlands. Wetlands 31(3), 499–509. 4. Dong, Y., Scholz, M., Harrington, R. (2012). Statistical modelling of contaminants removal in mature integrated constructed wetland sediments. Journal of Environmental Engineering 138, 1009–1017. 5. Dong, Y., Scholz, M., Mackenzie, S. (2012). Performance evaluation of representative Wildfowl & Wetlands Trust (WWT) constructed wetlands treating vii sewage. Water and Environment Journal (Article first published online: 20 Sep 2012). 6. Dong, Y., Kayranli, B., Scholz, M., Harrington, R. (2012). Nutrient release from integrated constructed wetlands sediment receiving farmyard runoff and domestic wastewater. Water and Environment Journal (Article first published online: 8 Oct 2012). 7. Dong, Y., Dzakpasu, M., Scholz, M. Changes in treatment performance of integrated constructed wetlands under long-term operation (Article in progress). Conference articles: 1. Dong, Y., Kayranli, B., Scholz, M., Harrington, R. (2010). Nutrient release from integrated constructed wetlands sediment receiving either farmyard runoff or domestic wastewater. In Masi, F., Nivala, J. (Eds.), Proceedings of the 12th IWA International Conference on Wetland Systems for Water Pollution Control (4– 7th Oct, 2010), ISBN 978–88–6060–300–5, Vol. II, pp.1262–1269, Venice, Italy. 2. Hofmann, O., Scholz, M., Tumula, P., Harrington, R., Dong, Y., Hedmark, Å. (2010). Performance evaluation of integrated constructed wetlands treating domestic wastewater. In Masi, F., Nivala, J. (Eds.), Proceedings of the 12th IWA International Conference on Wetland Systems for Water Pollution Control (4– 7th Oct, 2010), ISBN 978–88–6060–300–5, Vol. II, pp.1324–1331, Venice, Italy. viii 3. Dong, Y., Scholz, M., Harrington, R. (2012). Assessing the impact of physico- chemical parameters on contaminant treatment. Submission for the SPARC 12 conference proceedings. ix Acknowledgement This thesis is the end of my journey in obtaining my PhD. It can hardly be completed without the support and encouragement of numerous people including my supervisor, colleagues, my family and friends. At the end of my thesis I would like to thank all those people who made this thesis possible and an enjoyable experience for me. At the moment of accomplishment, first and foremost I want to express my deeply-felt thanks to my supervisor, Professor Dr Miklas Scholz, for his guidance, support, inspiration and encouragement throughout my PhD study. Under his supervision, I successfully overcame various difficulties and made my PhD experience productive. The joy and enthusiasm he has for his research was contagious and motivational for me. Despite of his new role in The University of Salford, he regularly reviewed my research progress, gave his valuable suggestions and created collaborative opportunities for me as many as he can. It is to him that I dedicate this work. I also would like to thank Dr Rory Harrington for his valuable advice, constructive criticism and the extensive discussions around my research during I stayed at his house in Ireland. I want to express my gratitude to Dr Martin Crapper, Dr Blanca Antizar- Ladislao, Professor Dr José Torero, Dr Jana Schwarz-Linek, Dr Tanya Peshkur, and Mr Paul Banfield for providing necessary infrastructure and resources to accomplish my research. x I take this opportunity to sincerely acknowledge the China Scholarship Council and University of Edinburgh (CSC-UoE) for providing financial assistance which buttressed me to performance my study comfortably. Most of the results described in this thesis would not have been obtained without a close collaboration with few laboratories and colleagues. I owe a great deal of appreciation and gratitude to Ms Susan Cook, water laboratory, Waterford County Council, Ireland, who devoted so much her precious time to carry out water quality analysis for me. My heartfelt thanks