Large Constructed Wetlands for Phosphorus Control: A Review

Abstract

This paper reviews aspects of the performance of large (>40 ha) constructed treatment wetlands intended for phosphorus control. Thirty-seven such wetlands have been built and have good data records, with a median size of 754 ha. All are successfully removing phosphorus from a variety of waters. Period of record median concentration reductions were 71%, load reductions 0.77 gP¨m´2¨year´1, and rate coefficients 12.5 m¨year´1. Large wetlands have a narrower performance spectrum than the larger group of all sizes. Some systems display startup trends, ranging to several years, likely resulting from antecedent soil and vegetation conditions. There are internal longitudinal gradients in concentration, which vary with lateral position and flow conditions. Accretion in inlet zones may require attention. Concentrations are reduced to plateau values, in the range of about 10-50 mgP¨m´3. Vegetation type has an effect upon performance measures, and its presence facilitates performance. Trends in the performance measures over the history of individual systems display only small changes, with both increases and decreases occurring. Such trends remove little of the variance in behavior. Seasonality is typically weak for steady flow systems, and most variability appears to be stochastic. Stormwater systems display differences between wet and dry season behavior, which appear to be flow-driven. Several models of system performance have been developed, both steady and dynamic.

Domestic Wastewater Depuration Using a Horizontal Subsurface Flow Constructed Wetland and Theoretical Surface Optimization: A Case Study under Dry Mediterranean Climate

“…This surface is higher than that found considering BOD 5 or TN, and nearer to the actual dimension of the experimental HF-CW, and the recommendations of 6 to 13 m 2 ·PE −1 [29]. On the other hand, if K p = 3.29 cm·d −1 [53] is taken into account, an area of 19.8 m 2 is obtained, which is lower than that obtained following Reed's method. However, such large areas are not suitable in areas of dry Mediterranean climate due to the risk of drying in the summer season (July Q out = −10.6 m 3 and August Q out = −8.7 m 3 ).…”

“…The ability of CWs to retain P depends on the phosphorus HLR, the type of substrate bed, vegetation and the HRT [53]. The abatement of TP is linked to different mechanisms.…”

Phosphorus removal performance and biological dephosphorization process in treating reclaimed water by Integrated Vertical-flow Constructed Wetlands (IVCWs)

“…2), thus they were apparently higher in autumn than in summer (p < 0.05). The lower TP removal rate in summer might have been because high temperature had a negative influence on microbial phosphorus-accumulating processes (Kadlec, 2016). The enzyme activity of phosphorus-accumulating bacteria (PAB) was suppressed at high temperature, and thus the TP removal rate reduced (Li et al, 2013).…”

How Efficient Are Semi-Natural Ponds in Assimilating Wastewater Effluents? Application to Fuente de Piedra Ramsar, Mediterranean Salt Lake (South of Spain)

“…The decision between one or another pathway is taken by the managing organisms of the natural reserve. The actions carried out were financed by Project LIFE03NAT/E/000055 and consisted of (i) desiccation of Laguneto wetland and removal of organic matter and debris [27], (ii) dredging 866 m 3 of mud from canals and building new canals including floodgates to allow regulation of water flow, (iii) the construction of some islands in the centre of the Laguneto wetland to increase the nesting habitat for birds, and (iv) revegetation of the perimeter of Laguneto and the channels previously mentioned. The vegetation surrounding Laguneto is composed of Tamarix canariensis, Tamarix africana, Phragmites australis, Scirpoides holoschoenus, Juncus acutus, and Bolboschoenus maritimus.…”