Estimation of the removal efficiency of heavy metals and nutrients from ecological drainage ditches treating town sewage during dry and wet seasons

Abstract

Vegetated drainage ditches (ecological drainage ditches, EDD) are commonly used for the treatment of nutrients, suspended solids, and pesticides, from agricultural lands and aquaculture effluent. However, their effectiveness to remove heavy metals/metalloids (HM/Ms) and fate remains largely unexplored. In addition, there exists some uncertainty concerning the performance of the EDD in treating HM/Ms. This study presents a thorough assessment on the removal efficiencies of HM/Ms and identifies the parameters affecting the HM/Ms removal process in the EDD receiving primary domestic sewage for 13 years. The mean concentrations of the studied HM/Ms in sediments were lower than those reported in the aquatic ecosystems affected by coal-mine drainage and industrial wastewaters. The results also showed that the concentrations of the selected HM/Ms in ditch sediment were generally far higher than the soil background values of Sichuan basin. Concentrations of all the studied HM/Ms and nutrients in water entering the EDD were significantly higher than the effluent. The annual mean removal efficiencies of Ni, Cu, Cr, Zn, Cd, Pb, As, Fe, Al, Mn, N, and P in the ecological drainage ditch were 50.6, 56.1, 63.3, 79.3, 67.5, 80.1, 60.3, 52.6, 19.8, 24.3, 72.0, and 59.7%, respectively. The study also displayed that dissolved oxygen levels at the outlet were significantly (p < 0.001) higher after passing into the EDD system. The pH was kept at neutral or alkaline. Removal of HM/Ms and nutrients was seasonal, generally peaking in the growing season. Sedimentation was the major mechanism removing HM/Ms within the EDD system. EDD was found to possess a favorable influence at mitigating HM/Ms and nutrients in situ and can be successfully utilized to resolve this type of environmental pollution.

Tile Drainage and Anthropogenic Land Use Contribute to Harmful Algal Blooms and Microbiota Shifts in Inland Water Bodies

“…In addition to tile drainage, nutrient runoff into watersheds occurs from nonpoint sources . Nonpoint source runoff acts as a transport system for fecal matter, and may contribute to nutrient loading in watersheds. − Runoff can also transport enteric pathogens, including Cryptosporidium , Campylobacter , Shiga-toxin producing E. coli , and various enteric viruses. , …”

North Carolina Coastal Plain ditch types support distinct hydrophytic communities

“…Drainage ditches are well associated with the loss of wetland ecosystems, habitat, and ecosystem services through hydrologic alteration (e.g. Zedler (Otto et al 2016, Phillips et al 2017) and other organic pollutants (Moeder et al 2017), metal retention (Kumwimba et al 2016, Kumwimba et al 2017, and mitigation of erosion (Levavasseur et al 2016). Better understanding of ditches can lead to better management outcomes (Dollinger et al 2015), so it is worthwhile to understand if ditches really can function at least partially like the wetlands that they often supplant (Clifford & Heffernan 2018).…”

North Carolina Coastal Plain Ditch Types Support Distinct Hydrophytic Communities

“…Drainage ditches are well associated with the loss of wetland ecosystems, habitat, and ecosystem services through hydrologic alteration (e.g. Zedler (Otto et al 2016, Phillips et al 2017) and other organic pollutants (Moeder et al 2017), metal retention (Kumwimba et al 2016, Kumwimba et al 2017, and mitigation of erosion (Levavasseur et al 2016). Better understanding of ditches can lead to better management outcomes (Dollinger et al 2015), so it is worthwhile to understand if ditches really can function at least partially like the wetlands that they often supplant (Clifford & Heffernan 2018).…”