Wastewater treatment processes and mechanisms of organic matter, phosphorus, and nitrogen removal in a multi-soil-layering system.

The treatment processes inside a Multi-Soil-Layering system (MSL) were investigated by using a laboratoryscale system, which was set up in a D10×W50×H23-73cm acrylic box enclosing “soil mixture blocks” alternating with permeable zeolite layers. Six MSL systems consisted of 1~6 layers of soil mixture layers were constructed. For the study of the treatment processes inside the system, wastewater, with mean concentrations (mg/L) of BOD: 28.1, COD: 65.7, T-N: 9.8, T-P: 1.0, was introduced into the system at a loading rate of 1000 L/m 2 /day. In the both of BOD and COD, the concentrations in soil mixture layers (SML) were lower than those in permeable layers between SML (PLb). As the flow rate in SML decreased and the rate in PLb increased, the concentrations in the PLb increased in each system. Phosphorus concentration was lower in the SML than in the PLb, probably because P was adsorbed mainly by soil and mixed iron particles. Therefore, phosphorus removal efficiency was strongly influenced by the flow rate in SML. The ammonia adsorption and nitrification were almost completed up to 3rd layer in this study. However, the removal of nitrogen did not so much proceed below 4th layer because of low denitrification efficiency.