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Abstract In-channel water treatment systems remove excess nutrients through biological, chemical, and physical processes associated with the hyporheic zone. However, the impact of surface and groundwater interactions on these treatment processes is poorly understood. This research aims to assess the influence of varying groundwater conditions (neutral, drainage, and seepage) and different bed sediment hydraulic conductivities on nitrogen and phosphorus dynamics in in-channel treatment systems. A flume containing bed sediment was used to study changes in surface water quality under different groundwater and bed sediment conditions. Results show that groundwater interactions influence nutrient concentrations in the surface water. An elevation in dissolved reactive phosphorus and ammoniacal nitrogen and a decrease in nitrate concentrations in the surface water under seepage groundwater conditions was evident. In addition, low hydraulic conductivity sediment led to greater changes in nutrients concentration while high hydraulic conductivity sediment led to greater variations in pH and Eh values. Water-saturated bed sediment promoted a reduction of nitrate concentrations in the surface water. The findings could assist the design and monitoring of in-channel treatment systems where groundwater and surface water interact.
Silveira et al. (Fri,) studied this question.