Cocopeat for Wastewater Treatment in the Developing World. II: Field Evaluation of Constructed Wetlands Packed with Cocopeat for Wastewater Treatment in Can Tho, Vietnam

Abstract

Cocopeat, a byproduct of coconut processing, was evaluated as a packing medium in vertical flow constructed wetlands for the treatment of septic tank effluent in the Mekong Delta of Vietnam. Vertical flow constructed wetlands are typically packed with gravel and then planted with ornamental plants. For this study, varying percentages of cocopeat were added to the gravel and the systems assessed for supplemental treatment efficiency. A secondary treatment step of gravel planters with ornamental plants was assessed for supplemental treatment efficiency. Removal efficiencies of nitrogen, phosphorus, coliform, and biological oxygen demand were measured. Microbial community samples were collected periodically in order to chronologically analyze community shifts within and between different wetland cells. Ammonium transformation and removal was greater than 95% in each wetland containing cocopeat throughout the course of the study. Ammonium concentrations were significantly higher in the effluent of the wetland without cocopeat, indicating reduced nitrification activity, suggesting that cocopeat was critical for supporting nitrification. At steady state, each wetland had significantly lower phosphate concentrations than the influent. Complete removal of ammonium or phosphate in the constructed wetlands was not achieved; however, a secondary treatment step consisting of ornamental planters provided additional removal. This field study suggests that cocopeat is an adequate packing medium for constructed wetlands treating wastewater in Southeast Asia.