Research On Removal Efficiency And Removal Pathways Of Carbon, Nitrogen, Phosphorus From Piggery Wastewater In Multi-Soil-Layering System

As the development of breeding, people pay more attention to the environment pollution that caused by the piggery wastewater, and to the sewage treatment method which utilize of soil resources. In this study, we use the method which used the soil as the main material in the system developed in Japan, it is important for the wastewater treatment in China.The efficiency and the pathway of organic matter, nitrogen, phosphous removal from piggery wastewater was investigated by using MSL system (500 mm x 100 mm×700 mm) made of acrylic. The experiment with 4 MSL systems lasted for 148 days at loading rate of 50,100,200, and 300 L·m-2·day-1. The results obtained were summarized as follows:1. The mean removal rates of organic matter were 74.8%,72.6%,59.5%和33.4% under different loading rates. The result of amounts of organic matter removed in the system showed that remained stable under low loading rates (50,100 L·m-2·day-1) and fluctuated under high loading rates (200,300 L·m-2·day-1). It could be concluded that organic matter in the wastewater could be efficiently removed by the MSL system, and the hydraulic loading rate is an important factor in terms of organic matter removal. The result indicated that biological decomposition process of microorganism is important for the organic matter removal, and adsorption of organic matter onto substrates is also an important process for organic matter removal. It is strongly suggested that MSL with appropriate substrates and at a proper hydraulic loading rate could be applied in the wastewater treatment for organic matter removal.2. The mean removal rates of ammonium nitrogen were 82.1%,71.0%,30.0%, and 18.9%, and the mean removal rates of total nitrogen 44.6%,42.7%,28.4%, and 21.2% under different loading rates, respectively. The result of amounts of nitrogen removed in the system showed that the highest nitrogen removal in quantity occurred at the loading rate of 100 L·m-2·day-1, that's 94.4 g·m-2·day-1. It could be concluded that nitrogen in the wastewater could be efficiently removed by the MSL system, and the hydraulic loading rate is an important factor in terms of nitrogen removal. The result indicated that adsorption of ammonium nitrogen onto substrates and followed by a nitrification/denitrification process could account for nitrogen removal mechanism. It is strongly suggested that MSL with appropriate substrates and at a proper hydraulic loading rate be applied in the wastewater treatment for nitrogen removal.3. The mean removal rates of phosphorus were 61.4%,56.0%,39.1%和23.0% under different loading rates. The result of amounts of phousphorus removed in the system showed that the phosphorus removal in quantity not very different under different loading rates except in the first three weeks. It could be concluded that phosphorus in the wastewater could be efficiently removed by the MSL system, and the hydraulic loading rate is an important factor in terms of phosphorus removal. The result indicated that adsorption of phosphorus onto substrates could account for nitrogen removal mechanism, and the process of metal irons oxidized into ferric hydroxides is a key factor for adsorption of phosphorus. It is strongly suggested that MSL with appropriate substrates and at a proper hydraulic loading rate be applied in the wastewater treatment for phosphorus removal.