Reciprocating Subsurface Wetlands for Drainage Water Treatment - A Case Study in Egypt.

Document Type : Research Studies

Author

Researcher, Drainage Research Institute, National Water Research Center, El Kanater, Egypt

Abstract

A new patented constructed wetlands treatment technology for enhanced nutrients reduction has been developed by Tennessee Valley Authority. This new treatment technology is known as Reciprocating Flow Constructor Wetland (RFCW) through increasing oxygen content in the treatment processes. The RFCW has a process of operating two adjacent subsurface flow gravel beds by alternately draining and filling the wastewater on a recurrent basis to achieve tertiary levels of wastewater treatment. In Egypt, A pilot-scale RFCW was built near Lake Manzala as a demonstration of low cost treatment technology to treat a portion of Bahr El-Baqar drain wastewater that carries drainage water contains domestic and industrial pollution loads. The pilot wetland consists of one sedimentation basin followed by two subsurface flow cells working in a fill-empty sequence mechanism. The treatment capacity is 100 m per day. Treatment detention time is 4 days including 2 days in the gravel bed RFCW cells. Objectives of this paper are to describe operational flow inside the alternate cells, and to evaluate the treatment performance of reciprocating wetland for such polluted drainage water and to estimate removal rate constants (K) of the treated pollutants applying mixed flow reactor model. Water samples were collected from both influent and effluent wetland cells. Samples were analyzed to measure concentrations and loads of DO, BOD, TSS, NH4-N, NO3-N, TP, Fe, and FC. Results showed that RFCW managed to polish pollutants of drainage influent especially ammonia and nitrates reaching a limit which it could be used in a safe manner for the agricultural purpose or dumping it into Lake Manzala without negative impacts on its ecosystem. 

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