Constructed Wetlands for Dairy and Livestock Wastewater Treatment: A Review

Abstract

Dairy and livestock farms produce considerable amounts of wastewater, which could pose an environmental risk if not properly treated and discharged. Conventional treatment plants can represent an inadequate and costly solution in terms of operation and maintenance, especially for small and medium-sized farms. Thus, a valid and sustainable alternative can be provided by constructed wetland (CW). This paper analyzed the use of CW systems at different scales to treat dairy wastewater (DWW) and livestock wastewater (LWW) all around the world over the last thirty years. This systematic review identified 50 case studies reported in 50 publications from 22 countries: 20 CW for LWW and 30 for DWW. Per each type of WW, the analysis reported and compared the following: CW layout, type of substrates, vegetations planted, design parameters, removal efficiencies and management aspects. Gravel and sand are the most common substrates used in CW to treat both types of WW. Regarding vegetation, Phragmites australis is the most commonly used species in CWs treating LWW, whereas Typha spp. are the most frequently used in CWs treating DWW. Hybrid CW showed the highest removal performance for all parameters reported. This review can improve knowledge on CW, offering a technical and practical overview of the status of CW for treating LWW and DWW.