Sustainable municipal wastewater treatment using an innovative integrated compact unit: microbial communities, parasite removal, and techno-economic analysis

Background The upflow anaerobic sludge blanket (UASB) reactors rely on bacterial communities to break down pollutants in wastewater (municipal or industrial). Methods and results In this study, a novel combination of UASB followed by aerobic treatment has been proposed for the treatment of municipal wastewater focusing on bacterial communities using high-throughput sequencing and parasite removal in this novel combination of reactors. Moreover, economic estimation of the compact unit composed of two overlapping UASB reactors, followed by a downflow hanging non-woven fabric (DHNW) reactor, the anaerobic baffled reactor (ABR), and chlorine unit was investigated in this study based on community populations of 1000 and 10,000 inhabitants, with a municipal plant capacity of 54,000 and 540,000 m 3 /year. Cost estimation was conducted based on two scenarios, one considering the contingency cost and auxiliary facility, and the other excluding them. Non-metric multidimensional scaling (nMDS) revealed that the treatment stages structured the microbial communities. Proteobacteria was the most prevalent phylum in all treatment stages, followed by Bacteroidota in most stages. Firmicutes and Actinobacteria were also present in significant amounts. The treatment system achieved from 40 to 66.67% removal of parasites (parasitic nematode, Cryptosporidium , and microsporidia). Redundancy analysis (RDA) indicated a strong positive correlation between chemical and biological oxygen demand (COD/BOD) with Campylobacterales and could be used as a bioindicator of treatment performance. Conclusion These findings can inform the development of more efficient and sustainable wastewater treatment systems that take into account microbial ecology and economic considerations.