This review highlights the limitations faced by conventional wastewater treatment plants (WWTPs) in effectively removing contaminants of emerging concern (CECs), heavy metals (HMs), and Escherichia coli (E. coli). This emphasises the limitations of current treatment methods and advocates for innovative approaches to enhance the removal efficiency. By following the PRISMA guidelines, the study systematically reviewed relevant literature on detecting and remedying these pollutants in wastewater treatment facilities. Conventional wastewater treatment plants struggle to eliminate CECs, HMs, and E. coli owing to their small size, persistence, and complex nature. The review suggests upgrading WWTPs with advanced tertiary processes to significantly improve contaminant removal. This calls for cost-effective treatment parameters and standardised assessment techniques to enhance the fate of MPs in WWTPs and WRRFs. It recommends integrating insights from mass-balance model studies on MPs in WWTP to overcome modelling challenges and ensure model reliability. In conclusion, this review underscores the urgent need for advancements in wastewater treatment processes to mitigate the environmental impact of trace anthropogenic biomarkers. Future efforts should focus on conducting comprehensive studies, implementing advanced treatment methods, and optimising management practices in WWTPs and WRRFs.

Digital Twins (DTs) are on the rise as innovative, powerful technologies to harness the power of digitalisation in the WRRF sector. The lack of consensus and understanding when it comes to the definition, perceived benefits and technological needs of DTs is hampering their widespread development and application. Transitioning from traditional WRRF modelling practice into DT applications raises a number of important questions: When is a model's predictive power acceptable for a DT? Which modelling frameworks are most suited for DT applications? Which data structures are needed to efficiently feed data to a DT? How do we keep the DT up to date and relevant? Who will be the main users of DTs and how to get them involved? How do DTs push the water sector to evolve? This paper provides an overview of the state-of-the-art, challenges, good practices, development needs and transformative capacity of DTs for WRRF applications.

With the rising cost of energy and continuously increasing pressure to be more conscious of the amount of energy used in processes, aerobic wastewater treatment methods are becoming less desirable. However, anaerobic treatment is becoming more popular, especially with the development of high-rate activated sludge processes that can handle variations in operating conditions with small energy requirements. This short review aims to summarize the characteristics of anaerobic processes, with eventual emphasis on the upflow anaerobic sludge blanket (UASB) reactor and its performance under various conditions. Modeling of processes is helpful in making design decisions, and therefore the various modeling techniques applied to UASB reactors have also been included. Specific consideration has been given to anaerobic digestion model 1 (ADM1) due to its potential to be integrated with activated sludge models (ASM) to provide a single framework to describe aerobic post-treatments of the UASB effluent. Finally, an example test case involving the modeling of a pilot-scale UASB reactor has been included to indicate the usability of ADM1 in modeling anaerobic bioprocesses.