Aerobic granular sludge treating high strength citrus wastewater: Analysis of pH and organic loading rate effect on kinetics, performance and stability. (15th May 2018)

• Record Type: Journal Article
• Authors: Corsino, Santo Fabio; Di Trapani, Daniele; Torregrossa, Michele; Viviani, Gaspare
• Is Part Of: Journal of environmental management. Volume 214(2018)
• Page Start: 23
• Page End: 35
• Publication Date: 2018-05-15
• Subjects: Aerobic granular sludge -- Biokinetics -- Citrus wastewater -- pH -- OLR; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2018.02.087
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: In the present paper, the feasibility of citrus wastewater treatment with aerobic granular sludge sequencing batch reactors (AGSBR) was investigated. Two AGSBRs (named R1 and R2, respectively) were operated for 90 days under different organic loading rates (OLR) and pH in two experimental periods. The OLR ranged approximately between 3.0 kg TCOD m −3 d −1 and 7 kg TCOD m −3 d −1 during Period I, whereas between 7 kg TCOD m −3 d −1 and 15 kg TCOD m −3 d −1 during Period II. pH was maintained at 7.0 and 5.5 in R1 and R2, respectively. The results revealed that under high OLR and unbalanced feast/famine regime (Period I), the development of fast-growing microorganisms (fungi and filamentous bacteria) was favoured in both reactors, resulting in granular sludge instability. An extended famine phase and a proper balancing between feast and famine periods (Period II) were favourable for the development of bacteria with low growth rates (0.05 d −1 ) thus enhancing the granules stability. To the benefit of granular sludge stability and effluent quality, the length of the feast period should not exceed 25% of cycle length. Moreover, under OLR lower than 7 kg TCOD m −3 d −1 the removal efficiency of total chemical oxygen demand (TCOD) was approximately 90% in R1 and R2 and no side effects on the organic carbon removal performance related to the pH were observed. In contrast, at higher OLR a significant decrease in the removal efficiency (from 90% to less than 75%) was observed in R2. Results revealed also that under low pH, hydrolysis of proteins occurred and a decrease in the biological kinetic rates proportionally to the applied OLR was observed. Graphical abstract: Image 1 Highlights: Citrus wastewater was treated by means of AGS under different operating conditions. Short SBR cycle and high OLRs led to filamentous overgrowth, hence AGS instability. A proper feast/famine balancing, enhanced slow-growing microorganism selection. Under low pH, biological kinetic rates decreased proportionally to the applied OLR. Under low pH, hydrolysis of proteins caused the worsening of the EPS matrix.