Livestock Wastewater Treatment in Constructed Wetlands for Agriculture Reuse

Abstract

The aim of this study focused on the evaluation of constructed wetlands (CWs) microcosms, on a laboratory scale, for the removal of metals from a pig industry effluent while maintaining effluent organic matter and nutrients levels for its later used as a fertilizer. CWs with different macrophytes (Phragmites australis and Typha latifolia) and different substrates (light expanded clay aggregate and lava rock) were tested. Results showed high removals of metals during CWs treatment, with removal rates reaching >80% for Cd, Cr, Cu, Fe, Mn, and Zn after 2 days of treatment in CWs planted with T. latifolia and >60% in CWs planted with P. australis. Significant differences were only found between substrates for Fe and Mn in CWs with P. australis. Removal of organic matter (through chemical oxygen demand (COD)) was >77%, with no significant differences between substrates or plants. Removals of ammonium and phosphate ions ranged between 59–84% and 32–92%, respectively, in CWs with P. australis and 62–75% and 7–68% in CWs with T. latifolia, with no significant differences between substrates. Overall, CWs showed potential to be efficient in removing toxic contaminants, as metals, while maintaining moderated levels of nutrients, allowing the use of reclaimed water in agriculture, namely as fertilizer. If one aims for a short CW treatment, CW planted with T. latifolia and expanded clay as substrate could be the more suitable choice.

Constructed Wetlands to Face Water Scarcity and Water Pollution Risks: Learning from Farmers’ Perception in Alicante, Spain

“…Studies suggested that CWs were able to remove organics, total carbon, and nutrients effectively (e.g., fecal indicator bacteria removal ranged from 97% to 99%, such as coliforms and Escherichia coli) [35] but also biological contaminants, metals, or emergent pollutants by more than 85% [36]. In these processes, pollutant removal is reached through a combination of physical, chemical, and biological dynamics and efficiency indicators in which all the elements of CWs (plants, microorganisms, and substrates) can have a significant influence [37], including a positive effect on greenhouse gas emissions reduction [38].…”

A Review on Constructed Treatment Wetlands for Removal of Pollutants in the Agricultural Runoff

“…Herbicides were found to be more dominant in the agricultural runoff as it had been found as high as 530 mg/L. The prevalence of other contaminants, such as metals and fungicides, were much lower than the other CECs considered [42,66,68,70].…”

“…Studies conducted using the wide range of pollutants and various influent water types (fresh water and saline water) proved that CW microcosm design was adaptable to various wastewater treatments with satisfying removal efficiencies. Their study in 2020 using the same system even achieved toxic metal removal while maintaining the nutrient levels for agriculture reuse [70]. Another study in 2018 using the same system observed removal of organic micropollutants, such as atrazine, clarithromycin, fluoxetine, and norfluoxetine, from the freshwater aquaculture effluents [74].…”

“…A summary of occurrence of these pollutants in the agricultural wastewater (Figure 2) indicate presence of greater than 1000 mg/L biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total suspended solids (TSS); sub part-per-trillion to 30 part-per million of antibiotics, hormones, and veterinary pharmaceuticals, and up to 4.1 × 10 12 cells per mL of bacteria [42,65,[70][71][72]. Herbicides were found to be more dominant in the agricultural runoff as it had been found as high as 530 mg/L.…”

Removal and Survival of Fecal Indicators in a Constructed Wetland after UASB Pre-Treatment

“…Constructed wetlands (CW) are mainly used for sewage treatment of small communities, but there are also applications in industrial wastewaters and leachate of urban waste landfills [27][28][29][30]. In sewage treatment, CW can reduce 84% of total coliform, 96% of FIs, and 89% of EN [31].…”