Integrated constructed wetlands for treatment of dairy operation runoff in Eastern Tennessee during first year establishment

•We used integrated constructed wetlands to treat dairy runoff.•First flush exceeded critical levels for N and P in six of eight sample events.•Wetland outflow rates were lower and less frequent than inflows.•Over 2200 kg solids and 0.22 kg N were retained in four sampled events.

Integrated constructed wetlands (ICWs) were implemented to reduce nutrient and sediment transport from a confined-animal dairy operation in East Tennessee. The objectives of this study were to (1) characterize first flush concentrations of potential pollutants from a typical confined animal dairy operation, and (2) determine if two ICWs have acted as hydrologic and physicochemical buffers in agricultural drainages during the establishment phase (first year after construction). Nine events between the two ICWs were sampled within the first year of construction and flow rates were continuously measured at the inlets and outlets. First flush sampling showed that phosphorus concentrations exceeded critical levels in six of the eight sampled events and nitrogen concentrations exceeded critical levels in half of the sampled events. Suspended solids, organic carbon, and phosphate were the most commonly detected pollutants of concern carried by runoff leaving the dairy operation. The documented performance of ICWs indicated that the practices generally reduced sediment and nutrient concentrations in runoff flowing to receiving waterways during wet weather conditions during the first year following construction and acted to buffer hydrologic pulses by reducing peak flow rates. In four sampled storm events spanning the time of late summer through winter, a total of over 2200 kg of suspended solids and 0.22 kg of nitrogen were retained in one ICW. Organic carbon was exported from the ICW practices during most events. Overall, the practice removed significant amounts of suspended solids and nitrogen, and event-based phosphorus.