Effectiveness of a Constructed Wetland with Carbon Filtration in Reducing Pesticides Associated with Agricultural Runoff

Abstract

The Salinas Valley in Monterey County, California, USA, is a highly productive agricultural region. Irrigation runoff containing pesticides at concentrations toxic to aquatic organisms poses a threat to aquatic ecosystems within local watersheds. This study monitored the effectiveness of a constructed wetland treatment system with a granulated activated carbon (GAC) filter installation at reducing pesticide concentrations and associated toxicity to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus. The wetland was supplied with water pumped from an impaired agricultural and urban drainage. Across five monitoring trials, the integrated system’s average pesticide concentration reduction was 52%. The wetland channel and GAC filtration components individually provided significant treatment, and within each, pesticide solubility had a significant effect on changes in pesticide concentrations. The integrated treatment system also reduced nitrate by 61%, phosphate by 73%, and turbidity by 90%. Input water was significantly toxic to C. dubia and H. azteca in the first trial. Toxicity to C. dubia persisted throughout the system, whereas toxicity to H. azteca was removed by the channel, but there was residual toxicity post-GAC. The final trial had significant input toxicity to H. azteca and C. dilutus. The channel reduced toxicity to H. azteca and removed toxicity to C. dilutus. GAC filtration reduced H. azteca toxicity to an insignificant level. There was no input toxicity in the other three trials. The results demonstrate that a wetland treatment system coupled with GAC filtration can reduce pesticide concentrations, nutrients, suspended particles, and aquatic toxicity associated with agricultural runoff.

Application of Modified Biochar in the Treatment of Pesticide Wastewater by Constructed Wetland

“…According to the test results for effluent quality of the constructed wetland (Figure 6), the removal of the herbicide atrazine by the constructed wetland with modified biochar reached 70%, while that by the constructed wetland without modified biochar reached only 50%, the removal rate of which was at a medium level [26,27]. The herbicide content in the effluent of the constructed wetland was at a relatively higher level compared to those in the natural watershed since the reported highest atrazine content in surface water By comparing the effluent water quality with the national water quality standard, we found that when the HRT was 3 d, the removal effects for COD, TP, and TN by the constructed wetland reached the surface water quality standard of class III water (GB3838-2002) for the ATZ wastewater in which the inlet water pollution degree was worse than class V.…”

Removal of microplastics from agricultural runoff using biochar: a column feasibility study

“…Thus, it serves as an effective adsorbent for pollutant removal from aquatic systems (Lee et al, 2013;Abhishek et al, 2022;Jagadeesh and Sundaram, 2022;Sinha et al, 2022). Applying biochar to soil is an emergent practice and potentially cost-effective method to replenish nutrients, increase agricultural yields, remove contaminants, and sequester carbon (Kuppusamy et al, 2016;McCalla et al, 2022;Dong et al, 2023). Biochar has also been used to remove pollutants, including heavy metals, persistent organic compounds, and, most recently, MPs, from aquatic systems (Wang et al, 2020b;Siipola et al, 2020;Wang et al, 2021a;Magid et al, 2021;Dong et al, 2023;.…”