Effect of Chemical Oxygen Demand Concentration on Nutrient Removal in Simultaneous Nitrification, Denitrification and Phosphorus Removal System in High-Altitude Areas

Yani Zhao,Douzhi Ran,Shuping Li,Liling Zhang,Meng Zhang,Guangcan Zhu,Jingya Wu,Liwei Sun

doi:10.3390/w13192656

Abstract

The application of biological nitrogen and phosphorus removal processes in high-altitude areas faces severe challenges due to low temperature, low atmosphere pressure and low oxygen concentration. In this study, a simultaneous nitrification, denitrification and phosphorus removal (SNDPR) system was operated under low atmosphere pressure. The chemical oxygen demand (COD) concentrations in influent were decreased from 300 mg/L (stage I) to 200 mg/L (stage II), corresponding to the low COD concentration of sewage in high-altitude areas. The removal of COD and total phosphate was efficient at the H1 reactor (72 kPa). The removal rates of COD and total phosphate were 94.08% (stage I), 90.66% (stage II) and 98.43% (stage I), 99.34% (stage II), respectively, which were similar to L1 (100 kPa). The removal rates of total inorganic nitrogen and simulation nitrification and denitrification were from 81.21% (stage I) and 59.48% (stage I) to 72.86% (stage II) and 31.95% (stage II), respectively, which were also improved compared to L1. Cycle experiment results indicated that the activity of phosphorus accumulating organisms was enhanced, while the ammonia oxidation process was inhibited under low atmosphere pressure.

Highlights

Environmental characteristics of high-altitude areas are low temperature, low atmosphere pressure and low-oxygen content [1]
According to different chemical oxygen demand (COD) concentrations in influent, the operation of the SNDPR system was divided into two stages
Terhee1a8v.2e6ramgeg/efLflaunednt COD and Total phosphorus (TP) concentrations of the system at 53 days were 18.26 mg/L and 0.06 mg/L, 0.06 mg/L, respectively, similar to those of L1 operating at 100 kPa (COD: 17.08 mg/L; TP: 0.18 mg/L). (2) The TIN removal rate in the H1 reactor decreased from 81.21% to 72.86%, and the Simultaneous nitrification and denitrification (SND) rate decreased from 59.48% to 31.95% when the COD in influent was changed from 300 mg/L to 200 mg/L

Summary

Introduction

Environmental characteristics of high-altitude areas are low temperature, low atmosphere pressure and low-oxygen content [1]. In high-altitude areas, the actual dissolved oxygen (DO) content in water is only about 50% of that in low-altitude areas under the same aeration conditions, which decreases microbial growth, nitrification, and aerobic phosphorus uptake in biological treatment processes [3], reducing treatment efficiency and discharged water quality. The application of biological treatment processes for sewage nitrogen (N) and phosphorus (P) removal in high-altitude areas faces severe challenges [4,5]. In 2003, Zeng R.J. et al [6] successfully achieved SNDPR reactions in a single-stage reactor under low DO conditions (0.5 mg/L) in an alternating anaerobic/aerobic mode. It is expected to be suitable for domestic sewage treatment in high-altitude areas [18]

Methods

Results

Conclusion