Optimising the performance of a lab-scale tidal flow reed bed system treating agricultural wastewater

A gravel-based tidal flow reed bed system was operated with three different strategies in order to investigate its optimal performance for the treatment of high strength agricultural wastewaters. According to the three strategies, individual reed beds of the system were saturated and unsaturated with the wastewaters for different periods while steady hydraulic and organic loadings were maintained. Experiment results demonstrated that the system produced highest pollutant removal efficiencies with relatively short saturated period and long unsaturated period, highlighting the importance of O2 transfer into reed bed matrices during the treatment of high strength wastewaters. Significant removals of some major organic and inorganic pollutants were achieved with all the three operation strategies. Nitrification was not the major route of NH4-N removal when the system was under high organic loading. Due to the filtration of suspended solids and accumulation of biomass, gradual clogging of the reed bed matrices took place. The clogging caused concerns over the long-term efficiency of the current tidal flow reed bed system.