Impact of Dissolved Oxygen on the Performance and Microbial Dynamics in Side-Stream Activated Sludge Hydrolysis Process

Abstract

Dissolved oxygen (DO) plays an important role in the performance of biological wastewater treatment systems. This study investigated the effect of the DO concentration on nutrient removal performance and microbial community structure in side-stream activated sludge hydrolysis (SSH) and conventional anaerobic/anoxic/aerobic (A2O) processes. The results showed that the change in DO had little effect on the removal performance of chemical oxygen demand (COD), and the removal efficiencies were about 90% for both reactors. Compared with the high DO level (4.1–6.9 mg/L), the A2O and SSH reactors had better nitrogen removal performance at low (0.5–2.2 mg/L) and moderate (2.2–3.9 mg/L) DO levels, with ammonia (NH4+-N) removal efficiencies of 88–89% and 89–91%, respectively, and total nitrogen (TN) removal efficiencies of 74–76% and 75–81%, respectively. Directly reducing the DO concentration from high to low reduced the phosphate removal efficiencies of the A2O and SSH reactors from 80.2% and 86.2% to 63.1% and 70.6%, respectively, while re-elevating the DO concentration to moderate levels significantly improved the phosphate removal efficiencies to 94.6% and 96.0%, respectively. Compared to the A2O reactor, the SSH reactor had more stable and better nutrient removal performance under different DO conditions, partly due to the additional carbon sources produced through the sludge fermentation in the side-stream reactor. The decrease in the DO concentration resulted in a decrease in the relative abundance of Acinetobacter but an increase in the relative abundance of Competibacter, potentially leading to the deterioration in phosphorus removal.

Efficiency of Water Hyacinth (Eichhornia crassipes) in the Phytoremediation of Copper-Contaminated Waters of Lake Tempe, South Sulawesi Indonesia

“…In the form of nutrients and gases, oxygen generated under anaerobic conditions broke down chemical molecules into simpler variants. DO played a crucial role in reducing the contamination load on natural water and in aerobic treatment, which cleaned domestic and industrial wastewater due to the oxidation and reduction process [22]. Table 2 shows that water experienced a decrease in dissolved oxygen concentration after 30 days of phytoremediation.…”

Impacts of Polylactic Acid Microplastics on Performance and Microbial Dynamics in Activated Sludge System

“…Notably, the relative abundance of potential PAO (i.e., Acinetobacter) increased from 0.08% to 5.81-12.57% with the addition of PLA MPs. Although Acinetobacter's contribution to EBPR remains controversial, many studies have shown that Acinetobacter has the ability to accumulate polyP and PHA [66][67][68], and it has previously been proposed to behave as PAOs in EBPR systems [69,70]. The relative abundance of Competibacter increased from 0.05% in R0 to 0.16% in R1, but decreased to 0.03% in R3 as PLA MPs concentration continued to increase.…”