The investigation of biological removal of nitrogen and phosphorous from domestic wastewater by inserting anaerobic/anoxic holding tank in the return sludge line of MLE-OSA modified system

Behzad Nikpour; R Jalilzadeh Yengejeh; A Takdastan; A H Hassani; M A Zazouli

doi:10.1007/s40201-019-00419-1

The investigation of biological removal of nitrogen and phosphorous from domestic wastewater by inserting anaerobic/anoxic holding tank in the return sludge line of MLE-OSA modified system

J Environ Health Sci Eng. 2020 Jan 16;18(1):1-10. doi: 10.1007/s40201-019-00419-1. eCollection 2020 Jun.

Authors

Behzad Nikpour^{1

2}, R Jalilzadeh Yengejeh², A Takdastan^{2

3}, A H Hassani⁴, M A Zazouli⁵

Affiliations

¹ 1Department of Environmental Engineering, Khuzestan Science and Research Branch, Islamic Azad University, Ahvaz, Iran and Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran.
² 2Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran.
³ 3Department of Environmental technologies research center, Ahvaz Jundishapur University of medical sciences, Ahvaz, Iran.
⁴ 4Faculty of Natural resources and Environment, Department of Environmental Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
⁵ 5Department of Environmental Health, Health Sciences Research Center, Faculty of Health, Mazandaran University of Medical Sciences, Sari, Iran.

Abstract

In this study, the biological removal of nitrogen and phosphorous (BNR) was investigated by applying modified MLE-OSA technique. To conduct this study, three pilot plants scale were designed and established: 1) MLE similar to the current method used in Sari Wastewater Treatment Plant as control reactor 2) MLE-OSA₄ with 4-h hydrolic retention time in sludge holding tank 3) MLE-OSA₆ with 6-h hydrolic retention time in sludge holding tank. In this modified process for combining OSA technique with MLE system, two anaerobic/anoxic tanks were installed in the return sludge line with capacities of 70 and 107 l for MLE-OSA₄ and MLE-OSA_6, respectively. To set up the process, outlet sewage of the primary settlement tank of Sari Wastewater Treatment Plant was used. After a period of 45-60 days and reaching the steady state, the reactors were operated and the main, controllable parameters and laboratory experiments such as DO, ORP, Temperature, pH, COD, BOD₅, MLSS, and nutrients (N&P) were precisely analyzed according to standard methods for examination of water and wastewater. The results showed that utilizing MLE-OSA system with 4 and 6 h hydraulic retention times decreased the ORP by around 109 ± 9 to 160 ± 25 mv and increased sludge retention time from 29 to 33 days. Moreover the percentages of phosphorus removal efficiency in MLE, MLE-OSA₄ and MLE-OSA₆ processes were 31 ± 5.2, 36.8 ± 1.9, and 39.4 ± 1.9 and the percentages of total nitrogen removal efficiency were 67.2 ± 7.6, 75.6 ± 4.8, and 78.5 ± 2.2 respectively. This study revealed that the modified MLE-OSA is more efficient than MLE for P and N removal. Hence it can replace this process.

Keywords: Biological nutrient removal; Domestic wastewater; MLE-OSA; Nitrogen; Phosphorous; Sludge holding tank.