Abstract
To improve aquatic environmental quality and maintain channel stability against soil erosion, ecological bank slope revetments for surface water bodies were developed using a combination of prefabricated porous concrete spheres and vegetation methods, and a model set-up consisting of two equal-sized ditches with different types of bank slope revetments was constructed to evaluate the purification effects of ecological and hard revetments on water quality. The slope of one ditch was embanked with ecological revetments as an experimental treatment, while the other was embanked with hard revetments as a control. Pollutant removal from the ecological bank revetment ditch was significantly better in terms of the overall removal efficiencies of the chemical oxygen demand of manganese (CODMn), ammonia, total nitrogen (TN), and total phosphorus (TP), with two- to four-fold greater removal compared with that from hard slope revetments under the same operational conditions. Nutrient pollutants, including ammonia, TN, and TP had higher removal efficiencies than that for CODMn in both experimental ditches. The dependence of the first-order rate constant (k20) and temperature coefficient () obtained from the Arrhenius equation indicated that the removal efficiencies for ammonia, TN, and TP were higher with greater rate constants (k20) in the experimental ditch. In the ecological revetment ditch, the k20 values for CODMn, ammonia, TN, and TP were 0.054, 0.378, 0.222, and 0.266 respectively, around three-fold the values observed in the hard revetment ditch, but there was no obvious difference in values between the two ditches. The k20 values of TN and TP in both ditches showed significant positive correlations with seasonal shifts, as the removal of nutrient pollutants is highly sensitive to water temperatures.
Highlights
In recent years, the deterioration of aquatic environments in China has become a growing environmental problem due to accelerating development in many regions
Compared with the average pollutant removal rates obtained from Ditch B with hardened slope revetments, those obtained from Ditch A with ecological slope revetments were higher by 6.6% for chemical oxygen demand of manganese (CODMn), 45.8% for ammonia, 26.0% for total nitrogen (TN), and 19.9% for total phosphorus (TP), with an hydraulic retention time (HRT) of 2 d
The increase in HRT from to 6 d led to significant increases in the average removal efficiencies, which were 25.5% for CODMn, 87.7% for ammonia, 68.5% for TN, and 79.0% for TP in Ditch A, but there was no obvious effect on pollutant removal in Ditch B
Summary
The deterioration of aquatic environments in China has become a growing environmental problem due to accelerating development in many regions. Energy, and organisms meet within the river corridor and interact over both space and time This movement fulfills critical functions for life such as cycling of nutrients, filtering contaminants from runoff, absorbing and gradually releasing floodwaters, maintaining fish and wildlife habitat, recharging ground water, and maintaining stream flow [4,5]. Because of their specific hydrological, hydrochemical and ecological conditions, riverine slopes play an important role
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