Full Scale Constructed Wetlands:
The landfill now operates this 5.66 acre constructed wetland treatment and irrigation system designed to treat up to 60,000 gallons/day. The treated leachate from the wetlands is irrigated onto closed landfill space as low grade liquid fertilizer. Currently the system treats approximately 7,000,000 gallons of leachate each year. This total represents approximately 40% of our permitted discharge to the Northeast Cape Fear river from the wastewater treatment plant. As additional landfill space is closed in the future, the irrigation system will be extended in order to irrigate more treated leachate. Eventually, the use of constructed wetlands and irrigation will allow us to eliminate the wastewater treatment plant and our discharge to the river. In essence, closing the loop by re-directing and reusing our treated leachate in an effort to protect the water quality of surface waters in southeast North Carolina from pollutants leaving our facility. This system serves as a model for other industries and municipalities as an alternative to conventional treatment practices. The wetland treatment system is cost effective, aesthetically pleasing and provides wildlife habitat. The irrigation of treated leachate also cuts costs by helping to maintain and increase the vegetative cover of our closed landfill space as well as to protect the landfill side slopes from storm water erosion.
Pilot Constructed Wetlands Project
The primary purpose of the Pilot Constructed Wetlands project was to determine the feasibility of using a natural ecosystem to assist in treating landfill generated waste water commonly called leachate.
By definition, leachate is liquid that comes in contact with solid waste. County Environmental Management began investigating leachate treatment options in 1990. The wetland treatment concept was chosen in 1992 for further consideration.
In July 1993, County Environmental Mangement was awarded a Coastal Area Management Act (CAMA) grant from the North Carolina Division of Coastal Management for an educational program in conjunction with a constructed wetland pilot project.
A second grant was awarded by the Water Environment Research Foundation to North Carolina State University to monitor the county project in October 1994. The North Carolina Sea Grant program was also involved in the project.
Wetland plant species were placed in Spring 1995 and allowed to establish. Leachate was gradually applied through the constructed wetlands on September 7, 1995 with monitoring occuring over the following four year period.
The system proved to be a viable treatment option. Results of the research indicated that the constructed wetlands could be used for either primary or temporary treatment. Using wetlands constructed include providing wildlife habitat,creating estheticially pleasing treatment system, offering educational opportunities, lower operation and maintenance costs, and lower capitial costs.
The results obtained led New Hanover County to pursue construction of a full scale systems, in 2002 New Hanover County was awardedgrant funding in the amount of $785,000 from the Clean Water Management & Trust Fund. This money was used in conjunction with $243,500 of matching funds from New Hanover County to design and construct the system.
The Pilot Project
The pilot project consists of two cells configured for surface flow wetlands (SFW), in which water flows above river rock bedding media, and two cells configured for subsurface flow (SSFW), in which leachate flows below the top of river rock bedding. A fifth control cell consists only of river rock and is used to compare treatment due to the bedding media.
Department technical staff members are responsible for monitoring and maintaining five constructed wetland cells at the county Landfill. Operation and maintenance of the cells, and data generation, analysis and reporting is done in cooperation with North Carolina State University and with the North Carolina Sea Grant Program.
In addition to the long-term benefit to the Landfill, the constructed wetlands project also offers several educational opportunities. The full scale wetlands project is currently under construction. Upon completion in late summer, the treated leachate effluent will be used for spray irrigation over a closed out Landfill cell. The use of the effluent for irrigation purposes will eliminate up to 60,000 gallons per day discharge to the receiving stream, the Northeast Cape Fear River. It is the desire of the Department Of Environmental Management staff to make the Landfill a non-discharge facility through the use of treated effluent for irrigation purposes. The project is designed as an educational program for middle and high school students. Water quality testing protocols are established for students to measure, including testing for ammonia, pH, nitrates/nitrites, total nitrogen, dissolved oxygen and other parameters. The obtained data is then entered into a computer program for data trending and analysis.
Numerous students and interns from the University of North Carolina at Wilmington and North Carolina State University have either participated in the various stages of development of the project or have used the wetlands for their studies including masters thesis and Ph.D. studies.
The project has also gained international attention. Representatives from the government of Thailand have visited the project to help determine whether wetlands are suitable for treating wastewater as that country continues to modernize.