[Comparison of two types of multi-soil-layering treatment system filled different paddings]

Two types of multi-soil-layering (MSL) systems, each of them was filled with different padding, including both the layers of mixture layers (ML) and permeable layers (PL), which designed for purifying polluted river water and for studying the difference of the pollutant removal efficiency between them under different operation conditions. The results indicated that the four systems all had great COD removal efficiency and the removal rate of each of them was above 50%. Zeolite-lightweight ceramic pellet system (Z-LCPS) has high removal efficiency of NH4(+) -N,and the concentration of the final outflow is below 1 mg/L. When the air and water ratio is 8:1, ceramisite-red clay system (C-RCS) has high NH4(+) -N removal rate which is up to 84%. However, the NH4(+) -N removal rate of C-RCS is below 40% under the un-aerated condition. The Z-LCPS under unaerated condition has the best TN removal efficiency that the average removal rate of TN is above 68% and reaches the 98% at best. Under the high pollutant loading, the TP removal efficiency of Z-LCPS (M1, M2) is better than C-RCS, and under the stable period, the TP removal rate is above 80%. At last, the difference of the nitrogen removal mechanism between the four systems is analyzed through the changes of nitrogen concentration along the flow direction.