Selection of Agricultural Straws as Sustained-Release Carbon Source for Denitrification in a Drawer-Type Biological Filter

The aim of this paper is to select feasible agricultural straws as high-quality sustained-release carbon source and examine the effect of determined agricultural organic waste on improving denitrification efficiency. Five kinds of agricultural straws, i.e., the rice straw, the corn straw, the wheat straw, the broomcorn straw, and the reed straw, were evaluated in a self-designed drawer-type biological filter. Results showed that the contents of C, H, and N in the five straws were 34.0 similar to 41.0%, 4.9 similar to 5.4%, and 1.1 similar to 1.5% respectively. The highest TOC release capacity of the rice straw was 12.4 +/- 1.3mgg(-1) and the average TOC release of other waste straws ranged from 6.0 to 9.2mgg(-1). The TN release capacities of all the five straws were at a low level, ranging from 0.2 to 1.4mgg(-1). Preliminary denitrification studies showed that the corn and the rice straw could be used as high-quality carbon sources, achieving a COD removal rate of 47.3 similar to 50.2% and a TN removal rate of 21.8 similar to 24.8% for wastewater with low C/N ratio. The rice straw and the corn straw founctioned both as favorable solid carbon sources and biofilm carriers; the carbon source quality of the corn straw lixivium is more beneficial to microbial utilization. The drawer-type biological filter has showed a good efficiency of denitrification for nitrogen removal when using agricultural straws as biofilm carriers.