Precise determination of the total nitrogen content in activated sludge by ultrasonic pre-treatment assisted wet method

ABSTRACT

The study proposed a method for determining total nitrogen (TN) content in activated sludge by ultrasound pre-treatment assisted wet method. Based on the single-factor experiment, with the TN content as the response value, the response surface methodology was employed to examine the individual and interactive effects of three factors: the dilution multiple of the sludge mixture, ultrasonic time, and ultrasonic power. At the same time, the physico-chemical parameters and the digestion–oxidation parameters were optimised. The results indicated that the optimal parameters were as follows; sludge dilution multiple of 225 times, stirring rate of 400 r/min, ultrasonic time of 22 minutes, ultrasonic power of 720 W, and optimal added volume of potassium persulfate at 8 mL with a digestion time of 40 minutes. The relative standard deviation (RSD) for the parallel determination of TN in sludge samples using ultrasonic pre-treatment assisted wet method was ≤2.77%, with a spike recovery rate of 98.49–101.43%. The method, ultrasonic pre-treatment assisted wet method to determine TN concentration in activated sludge, was simpler to operate, more accurate.

GRAPHICAL ABSTRACT

KEYWORDS:

• Activated sludge
• total nitrogen content
• ultrasonic pre-treatment
• response surface analysis
• parameter optimization

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

The experiment was mainly conducted by Shangjing Zeng, and the manuscript was written through the contributions of all authors. All authors have given approval to the final version of the manuscript.

Additional information

Funding

This work was supported by the Jilin Provincial Science and Technology Development Project: [Grant Number 20210101082JC].