Effect of organic concentration on biological activity and nitrogen removal performance in an anammox biofilm system.

The effects of different concentrations of organic matter on the biological activity and nitrogen removal performance of the anaerobic ammonium oxidation (anammox) system was studied. The results showed that under the conditions of low influent total organic carbon (TOC ≤ 100 mg/L), the activity rate of anammox bacteria was basically unaffected, the anammox bacteria and denitrifying bacteria formed a good synergistic effect, and the maximum total nitrogen (TN) removal efficiency reached 95.77%. However, when the influent TOC concentration was up to 200 mg/L, the activity of anammox bacteria was seriously inhibited. At this time, denitrification becomes the main pathway of nitrogen removal, the effluent ammonia nitrogen content increases, and the TN removal efficiency decreases to 64.17%. High-throughput sequencing analysis showed that with the increase in organic matter concentration, the relative abundance of Proteobacteria and Planctomycetes changed significantly. In particular, the relative abundance proportion of Proteobacteria increased from 21.06% to 25.57%, the Planctomycetes dropped from 10.01% to 3.03% and the Candidatus Brocadia genus had the largest decrease. In conclusion, the concentration range of organic matter for collaborative denitrification was proposed in this study, which provided theoretical reference for the practical application of anammox biofilm process.

Determination of total phosphorus in soil and sludge by an effective headspace gas chromatographic method.

This paper reported a novel method for the determination of total phosphorus (TP) content in soil and sludge by a headspace gas chromatography (HS-GC) method. It was based on a reaction between the soluble phosphate in the digestion solution and calcium oxalate solid to form a calcium phosphate precipitate and release oxalate ions, which can react with permanganate to form carbon dioxide, which was then measured by HS-GC. The results showed the complete conversion of phosphate (meanwhile to free oxalate ions in calcium oxalate) in 15 min at 60 °C. The present method has good repeatability (RSD < 2.6%) and good accuracy (RD < 7.3%) compared to the reference method. Therefore, the present HS-GC method can become a more effective method for determining the TP content in soil and sludge samples.