Review and synthesis of engineered wetland treatment systems with application to phosphorus removal

Abstract

Nutrient contamination in point and non-point wastewater sources has led to an increased focus on the removal of phosphorus before reaching receiving waters. Phosphorus, typically a nutrient limiting contaminant is responsible for eutrophication and algae blooms in lakes and streams and the wastewater from agricultural, industrial and domestic sources is under continued scrutiny from the regulatory environment. Constructed wetlands mimic natural wetlands and are used worldwide for the removal of nutrients in wastewater streams but the research and applications for removal of phosphorus has lagged behind other nutrients and contaminants. This paper is an extensive literature review of construct wetlands and the ongoing applications for phosphorus removal. This review includes recent research on the mechanisms of removal, an evaluation of different plant species, a discussion of phosphorus partitioning in the wetland environment and a look at the use of chemical additives to improve the removal efficiency. Hybrid constructed wetland systems that closely mimic the biological nutrient removal systems for large scale WWTP facilities are being built around the world to improve effluent water quality and take advantage of the benefits of each type of constructed wetland. Maximizing the removal of phosphorus in wastewater will require a multi-pronged approach that includes biological, chemical and physical removal of the phosphorus in both the design phase and ongoing operation of the constructed wetlands system. Several trends in constructed wetlands phosphorus removal are emerging: the primary removal mechanism for phosphorus removal is accretion and new soil sediments, and the use of chemical additives for precipitate and final removal of phosphorus is required for the removal efficiencies required by regulation. The varied applications and results of constructed wetland systems with respect to phosphorus removal are discussed throughout the paper. Floating island technology, using a buoyant material that supports plants, is a newer unique application of constructed wetlands that can be used to remediate wastewater and remove contaminants. Based on the literature search, a series of experiments to further characterize floating islands and improve the removal of phosphorus from wastewater are recommended using this technology.