## 4 Insights into Bacterial-Algal Biomass in Different Operational Configurations  
Due to the diverse microbial community present in aerobic sludge aggregates, various metabolic pathways contribute to energy acquisition and carbon uptake. The success of process like SND (simultaneous nitrification and denitrification) and phosphorus removal hinges on the operational conditions applied during the development of aerobic granular sludge, including factors such as the composition of the feed, the duration of cycle phases, and the characteristics of the treated effluent [55; 81]. Photogramulation alongside these factors is influenced by the species of microalgae attached to the biomass. Excessive growth of _Stigeocolonium_ sp. accelerates the disintegration of photograpules, whereas the presence of cyanobacteria promotes the formation of more stable granules that are less prone to disintegration [82]. [PERSON] et al. (2019) [79] associate luminosity with the presence of filamentous microalgae on the granular surface, which contributes to destabilization, resulting in less stable granules prone to disintegration. Conversely, [PERSON] et al. (2018) [53] suggest that filamentous bacteria act as bridges, providing ample space for microalgae to adhere to aerobic granules. In contrast with bacterial granular sludge systems, the microalgae-bacterial consortium demonstrates the ability to maintain granule stability even at low COD/N ratios [53; 79]. Extracellular polymeric substances (EPSs) play a crucial role in understanding granule stability, as variations in protein (PN) and polysaccharide (PS) concentrations alter the physicochemical characteristics of the cell surface, including charge and hydrophobicity [83]. During the dark phase of the system, the increase in biomass within the granular consortium is attributed to the assimilation of CO\({}_{2}\) in the form of HCO\({}_{3}\), which is deposited as a reserve in the form of EPSs [51]. Consequently, there is a greater production of EPSs compared to aerobic granule systems, which may contribute to reducing the negative charge of the algal cell surface [44; 84]. [PERSON] and [PERSON] (2016) [58] suggest that the presence of nitriifying bacteria influences granule formation and stability, leading to the production of more sedimentable granules. With the aim of developing systems with excellent performance in wastewater treatment, as well as promoting more efficient and less expensive microalgae-harvesting techniques, granular microalgae-bacteria were developed. Consortia have been extensively studied under different configurations. The main systems studied include sequential batch reactors (SBRs), single-batch photobioreactors (SBPs), high-rate ponds (HRPs), and continuous flow reactors (CFRs), which are shown in Table 2. The table shows each article's type of reactor; the effluent concentration in terms of the main parameters of monitoring, such as chemical oxygen demand (COD), total nitrogen (TN), NH4\({}^{+}\), NO\({}_{2}\)\({}^{-}\), NO\({}_{3}\)\({}^{-}\), PO\({}_{4}\)\({}^{3}\), and total phosphorus (TP); operational conditions; treatment performance; biomass characteristics; microalgae species; remarks; and reference numbers. Figure 4 shows the main cycles and operation of each configuration discussed in this work. \begin{table}
\begin{tabular}{c|c|c|c|c|c|c|c} \hline \hline
**Reactor Model** & **Efficient Concentration** & **Operational Conditions** & **Treatment Performance** & **Biomass Characteristics** & **Micoralge Species** & **Remarks** & **References** \\ \hline \multirow{4}{*}{SIR} & Synthetic wastewater & Volume = 1.4 L & 99\% CCD removal & MLWS = 5.4-5.5 g/L & \multirow{4}{*}{-} & The digit-digit granules showed an excellent nutrient removal rate. \\  & XH\({}^{+}\) = 100 mg/L & Natural Biphone & 99\% NH\({}^{+}\)-N removal & SV\({}_{00}\) = 30-40 mL/g & & Good ES operation contributed to \\  & Y\({}_{0}^{+}\),-P = 23 mg/L & & HRT = 8 & 46\% TN removal & & & grama stability.