Effects of hydraulic load on nitrate removal in surface-flow constructed wetlands

Abstract: Abstract Constructed wetlands had been widely used as economical and environment friendly treatment systems for agriculture runoff in southwest Sweden to limit the transport of nutrients to Kattegat, thereby aiding in the effort of abating eutrophication. The extensive use and acceptance of wetlands as treatment systems had been an incentive to develop performance models. Even recent studies showed that first order models are inadequate to guide the design of constructed wetlands, these are still commonly used. The main assumption of such models is tested here, which states that the removal rate of pollutant(s) is proportional to concentration in a constructed wetland. For this purpose experimental wetlands in Plonninge near Halmstad (southwest of Sweden) were selected and divided into two groups (9 each). They were fed with different hydraulic loads achieving 4 and 8 days residence times. The data obtained from the analysis of total nitrogen and nitrate were tested with first order equations and found that these models are sufficient to describe the nitrate removal in nitrate rich experimental wetlands. Key words: constructed wetlands, hydraulic load, first order kinetic models, eutrophication, nitrogen removal