Abstract
Low condition of dissolved oxygen (DO) is commonly associated with sludge bulking problem that was able to disrupt the efficiency of wastewater treatment performances. Relatively, very little attention was paid to the possibility of applying magnetic field in controlling the bulking problem. Hence, this study aims to investigate the performance of magnetic field on biomass properties and its effect on biodegradation under low condition of DO. Two continuous laboratory-scale sequencing batch reactors—Reactor A (SBRA) and Reactor B (SBRB)—were setup. SBRA was equipped with the magnetic device to exhibit magnetic field of 88 mT, while SBRB acted as a control system. The results showed that the biomass concentration in SBRA was higher compared to SBRB. High biomass concentration in SBRA resulted to better settleability with mean SVI of less than 30 mL/g. SBRA also showed consistently high removal performances of organic and inorganic contents compared to SBRB. These observations confirmed that the magnetic field was able to enhance the biomass properties, which further enhance the biodegradation ability of the aerobic bacteria under low DO condition. This also indicates that under the sludge bulking circumstances, the use of magnetic field stands a great chance in maintaining high biodegradation of the treatment system.
Highlights
In conventional activated sludge (CAS) systems, solid–liquid separation is performed in the secondary clarifier after the biological reaction tank, though a phase separation problem has not been completely solved to-date
The results indicated that dosing a relatively low concentration of 41 mmol/kg could only keep the diluted sludge volume index (DSVI) constant, and microthrix parvicella filaments were still free in the water phase, while higher concentrations (94 and 137 mmol) significantly improved the settleability (Durban et al 2016)
Based on the SRT obtained under low dissolved oxygen (DO) concentration, both reactors are able of simultaneous nitrification–denitrification process and chemical oxygen demand (COD) removal
Summary
In conventional activated sludge (CAS) systems, solid–liquid separation is performed in the secondary clarifier after the biological reaction tank, though a phase separation problem has not been completely solved to-date. As a major separation problem, bulking causes the washout of suspended solids from the clarifier, decreases the biomass concentration in the reaction tank, with poor waste activated sludge. Among all, dissolved oxygen (DO) is one of the prominent factors that can induce the filamentous growth, causing the bulking occurrence (Van den Akker et al 2010). Low DO conditions seem to be beneficial for the growth of this microorganisms, providing a metabolic advantage for the proliferation of microthrix parvicella in the CAS treatment system (Rossetti et al 2005). The decreased DO led toward high relative abundance of Kouleothrix, Page 2 of 12
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