Enhancement of nitrification efficiency during sludge bulking by magnetic field under long sludge retention time
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ORIGINAL ARTICLE
Enhancement of nitrification efficiency during sludge bulking by magnetic field under long sludge retention time Nur Syamimi Zaidi1 · Khalida Muda1 · Johan Sohaili1 · Liew Wai Loan2 · Mika Sillanpää3 Received: 8 October 2019 / Accepted: 17 August 2020 / Published online: 27 August 2020 © King Abdulaziz City for Science and Technology 2020
Abstract The aim of the present study is to investigate the potential of magnetic field application as an alternative approach for controlling sludge bulking due to long sludge retention time (SRT) while enhancing nitrification efficiency upon the occurrence. Two sequencing batch reactors, reactor A ( SBRA, magnetic field intensity 88.0 mT) and reactor B ( SBRB, control) were operated under long SRT to induce the growth of filamentous microorganisms. The effect of magnetic field on nitrification, viz. ammonia–nitrogen ( NH4–N) and nitrite removal, as well as biomass properties were studied under the sludge bulking condition. Results indicated that nitrification efficiency of S BRA was consistently higher with 90% N H4–N removal and 74–81% nitrite removal, which could be credited to the enhanced biomass properties of activated sludge due to the induced magnetic field. Metabolism activity and biodegradability of aerobic bacteria were also enhanced through the application of magnetic field, even under long SRT condition. This was evidenced by the average oxygen uptake rate (OUR) in S BRA that was higher with 11.7 ± 1.2 mg/L·h compared to S BRB with 9.5 ± 0.4 mg/L·h. Occurrence of filamentous sludge bulking was likewise minimized. Keywords Nitrification · Sludge bulking · Magnetic field · Sludge retention time
Introduction
* Nur Syamimi Zaidi [email protected] Khalida Muda [email protected] Johan Sohaili [email protected] Liew Wai Loan [email protected] Mika Sillanpää [email protected] 1
Faculty of Engineering, School of Civil Engineering, Universiti Teknologi Malaysia, UTM, 81310 Johor Bahru, Johor, Malaysia
2
Centre for Degree Programme, School of Professional and Continuing Education, Universiti Teknologi Malaysia, UTM, 81310 Johor Bahru, Johor, Malaysia
3
Department of Civil and Environmental Engineering, Florida International University, Miami, USA
Sludge retention time (SRT) is an important factor affecting the performance of treatment systems. This is because SRT gives control over biomass activity. Experimentally, altering the sludge wastage rate can be done to control SRT. Theoretically, a low SRT ( 6 days) causes the accumulation of dead or inactive microorganisms to occur in the system, thus affecting the sludge activity. This negative condition gives rise to the growth of filamentous microorganisms, hence inducing a high risk of sludge bulking occurrences. Long SRT has been reported in inducing the growth of filamentous microorganisms such as Nocardioforms, Gordonia sp. and Microthrix parvicella (Comas et al. 2008; Dunkel et al. 2018). Sludge that has been retained too long in the clarifiers can become septic, lose
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