Effect of nitrogen, phosphorus, and sulfur on the start-up of a biological 1,4-dioxane removal process using Pseudonocardia sp. D17

Abstract

Nitrogen (N), phosphorus (P), and sulfur (S) are the major essential nutrients required for stable 1,4-dioxane treatment by the cylindrical-type bioreactor using gel-entrapped Pseudonocardia sp. D17. In this paper, the minimum concentrations of N, P, and S were determined in a series of continuous feeding start-up tests. When the influent 1,4-dioxane concentration was 20 mg L−1, concentrations of greater than 2.0 mg-N L−1, 0.4 mg-P L−1, and 0.1 mg-S L−1 were required to smoothly start the bioreactor to maintain the effluent 1,4-dioxane level lower than 0.5 mg L−1 (i.e., the Japanese effluent standard level). These essential concentrations indicate that the feed of the essential nutrients requires the ratio of 1,4-dioxane: N: P: S = 20: 2.0: 0.4: 0.1 for efficient treatment. The bioreactor could be successfully started with higher concentrations of 1,4-dioxane (i.e., up to 100 mg L−1) when the essential nutrients were fed at this ratio. The measurement of cell concentration in the gel beads indicated that 7.3 × 107 CFU (mL-beads)−1 is the reference value to achieve efficient 1,4-dioxane removal. The bioreactor started with sufficient nutrient levels demonstrated stable treatment performance even when severe nutrient limitations were provided after the start-up.