Application of molecular tools in activated sludge for joint removal of nitrogen and phosphorus from sanitary sewage in real scale
The last 10 years have been essential for sustainable solutions aimed at recovering resources in sewage treatment plants to stand out and be the focus of worldwide research. For this to happen, several national and international reference institutions in the area of basic sanitation, such as the International Water Association (IWA), the Water Environment Federation (WEF) and the Water Environment and Reuse Foundation (WE&RF), have advocated the dissemination of this approach. (Solon, Jia, and Volcke, 2019; Arabi and Lynne, 2018). One of the technologies that enables the recovery of resources is the treatment of wastewater by activated sludge, already consolidated worldwide, with different configurations for more advanced treatments, mainly in the removal of macronutrients - nitrogen and phosphorus (Rodriguez-Serin et al, 2022; Aghalari , et al. 2020; Quang et al. 2019; Jaramillo et al. 2018; Michael et al. 2013). Despite this experience with the technology, the microbial diversity responsible for the removal of phosphorus and nitrogen is still not consolidated (Escenhagen, Schuppler and Röske, 2003). Even so, this theme has been gaining notoriety and there is considerable information to advance the knowledge of microbial diversity, an example being the enhanced biological removal of phosphorus (RBAP), where there is the presence of phosphorus accumulating organisms (PAOs). Recently, studies have shown that the alternation conditions necessary for nitrogen and phosphorus removal offer the possibility of simultaneous nitrification and denitrification and combined with phosphorus removal (NDS + RP) in the same biological system (Wang X. et al, 2015 ; Yang et al, 2016; Salehi et al, 2019; Izadi and Eldyasti, 2020; and Onnis-Hayden et al, 2020). But most of these studies are carried out empirically, focusing on changes in the system, but with little - or no - knowledge of the microbiota present. Although the feasibility of simultaneous nitrification and denitrification with removal of phosphorus (NDSRP) has been demonstrated in laboratory scale systems at ambient temperatures between 18-25°C, NDSRP has not yet been reported in a continuous flow activated sludge system, in scale real under tropical climate and we do not know its application in Brazil. The main challenges with NDSRP in a full-scale WWTP lie in (1) lack of precise process control for the simultaneous occurrence of three different biological processes and (2) low chemical oxygen/nitrogen (COD/N) demand, typical of coastal regions (Onnis-Hayden et al, 2020). All of these mechanisms potentially result in changes in microbial ecology in an NDSRP system compared to a conventional RBP system, and consequently in differences in their function and performance (Wang X. et al 2016; Izadi and Eldyasti, 2020). Thus, the objective of this study is to identify and quantify the groups of microorganisms active in the process of nitrogen and phosphorus removal by activated sludge, associated with the lateral flow reactor at the Itatinga Sewage Treatment Station, in São Sebastião -SP, considering that there may be an increase in the richness and abundance of bacteria in the nitrogen and phosphorus cycle after the structural modification of the ETE and that there is a relationship between bacterial diversity and the rates of removal of these nutrients.