Study on phosphorus removal efficiency and changes in phosphorus forms using three kinds of straw material to treat swine wastewater

Constructed wetlands have good effect on treating swine wastewater. However, wetland plants are difficult to tolerate the too high nutrient concentrations of swine wastewater. Here in, nutrient concentrations should be reduced using appropriate measures. In this study, three common crop straw materials were selected as the biological matrix materials, i.e. wheat, corn stalk, and rice straw. A three-stage biomatrix treatment system (BMTS) was established. A controlling field experiment treating swine wastewater was conducted for 6 months. The study aims to investigate the phosphorus removal efficiency and changes in phosphorus forms in BMTS . Results showed that phosphorus was effectively removed in the BMTS. The removal efficiency of TP and DIP were 40.1% and 35.9%, respectively. The average effluent concentrations of TP and DIP were reduced to 54.35 - 62.35 mg/L and 22.68 - 23.25 mg/L, respectively. These concentrations were within the tolerance range of Myriophyllum elatinoides (<73 mg/L). The phosphorus removal in the BMTS was mainly based on the physical precipitation of particulate phosphorus, and accounted for 57.5% of TP removal. The DIP removal was significantly positively related to water temperature (T) and pH (P< 0.05), but not significantly related to DO and Eh (P> 0.05). There were differences in removal ability in the studied three straw to a certain extent. Straw material needs to be added when the removal rate drops. Recommended addition cycle is 90 days for wheat straw and rice straw, but 120 days for corn stalk. This study is of importance both in theoretical value and in practice significance for guiding swine wastewater ecological treatment.