How the Activated Sludge Process Powers Modern Urban Wastewater Treatment

An article by Education Division IEEE SB IPB in collaboration with Himavo Likista. Written by Mikailla Khiva Nuandhe Nararya.

1. Understanding SDG 6: Why is water essential for life?

Addressing the global water crisis, Sustainable Development Goal (SDG) 6 emphasizes the importance of ensuring the availability and sustainable management of water and sanitation for all. This goal reflects a growing global recognition that water security is not only a basic human necessity but also a critical foundation for socio-economic development and environmental sustainability. Sustainable water management, including wastewater treatment, water reuse, and ecosystem protection, is essential to maintaining the balance between human needs and environmental capacity [1]. Furthermore, the water systems are closely interconnected with various sectors, indicating that achieving SDG 6 contributes directly to broader sustainable development outcomes [2]. Therefore, SDG 6 represents a comprehensive framework that integrates water quality, accessibility, and long-term sustainability as key pillars of global development.

Sustainable domestic wastewater management is a crucial factor in achieving SDG 6, particularly in developing countries facing rapid urbanization and infrastructure constraints [3]. This is closely aligned with Target 6.3, which emphasizes the reduction of pollution, improvement of wastewater treatment, and promotion of water reuse to protect both environmental quality and public health [4]. As urban populations continue to grow, the demand for water increases significantly, placing additional pressure on already limited and often degraded water resources. In response to these challenges, Target 6.5 highlights the need for implementing Integrated Water Resources Management (IWRM), which promotes coordinated planning across sectors, the integration of policies, and more efficient, non-fragmented water governance systems [2]. This integrated approach becomes even more critical when considering Target 6.6, which focuses on the prevention of water-related ecosystems. Maintaining healthy aquatic ecosystems is essential for sustaining water quality, regulating natural processes, and ensuring long-term water availability [5]. Consequently, achieving SDG 6 requires not only technological solutions for wastewater treatment but also strong institutional frameworks and ecosystem-based management strategies, ensuring that water resources are managed sustainably within an interconnected environmental system.

Achieving Sustainable Development Goal (SDG) 6 requires an approach that integrates effective wastewater treatment, sustainable resource management, and the protection of aquatic ecosystems. Without proper management, the increasing pressures resulting from urbanization and population growth will continue to threaten water quality and public health.

II. Challenges Posed by Domestic Wastewater in Achieving SDG 6

The world faces a major challenge because more than 80% of wastewater from human activities is discharged into the environment without treatment, leading to massive degradation of surface water quality [6]. This problem is exacerbated by institutional failures in implementing IWRM, where fragmented policies often fail to integrate environmental protection [2]. As a result, aquatic ecosystems that should be protected are suffering severe damage, with the rate of wetland loss reaching 0.2% per year globally [5].

In Indonesia, the challenges to Target 6.3 stem from local domestic wastewater management systems (on-site systems), the majority of which do not yet meet technical standards, as a result untreated wastewater directly pollutes water bodies and damages aquatic habitats [7]. Recent research emphasizes that effective ecosystem protection strategies must be based on the selection of appropriate prevention technologies before waste is released into the environment [8]. However, the implementation of these prevention technologies remains hindered by the lack of a detailed water quality monitoring system and infrastructure limitations, where the coverage of safe wastewater treatment systems in urban areas remains below 5% [7], [8]. Without integration between monitoring sensor technology and adequate treatment infrastructure, efforts to maintain the integrity of aquatic ecosystems will be difficult to achieve sustainably [3], [5].

III. Integration of Activated Sludge Process with AI and IoT for Smart Wastewater Treatment

The challenges caused by increasing domestic wastewater in achieving Sustainable Development Goal (SDG) 6 have led to the integration of conventional treatment technologies with digital systems. One of the most widely implemented and reliable wastewater treatment technologies is the Activated Sludge Process (ASP), which has been extensively used in domestic wastewater treatment plants due to its effectiveness in removing organic pollutants and suspended solids. Traditional ASP systems often face operational inefficiencies, including human error, a lack of real-time monitoring, and limited adaptability to fluctuating wastewater loads [9]. These limitations highlight the need for more advanced and adaptive systems to improve treatment performance and sustainability.

Recent studies indicate that the integration of Artificial Intelligence (AI) into the Activated Sludge Process (ASP) enables the implementation of more advanced control strategies, particularly in aeration systems, which are the most energy-intensive component of wastewater treatment plants. AI-based models, such as neural networks and fuzzy logic, are used to analyze operational data in real-time and optimize key process parameters, including dissolved oxygen levels and biological activity. When combined with an IoT-based sensor network that continuously monitors system conditions, this integration enables more accurate predictions, adaptive control, and improved overall treatment performance [9], [10]

This integration supports the concept of a smart wastewater treatment system, where operational decisions no longer rely on manual control alone but are automatically optimized based on real-time data and predictive models. Such a system aligns with the goals of SDG 6, particularly in improving water quality (Target 6.3), strengthening integrated water management (Target 6.5), and protecting aquatic ecosystems by preventing harmful wastewater from flowing into the environment (Target 6.6) through more efficient and controlled wastewater treatment processes.

IV. Mechanism of Activated Sludge Process with AI and IoT Integration

The Activated Sludge Process (ASP) consists of a series of biological and physical treatment stages designed to remove organic pollutants from wastewater, as well as several classification steps.

Source : biologyreader.com

4.1. Preliminary and Primary Clarifier

The Activated Sludge Process (ASP) consists of a series of biological and physical treatment stages designed to remove macro-sized organic pollutants from wastewater. After undergoing preliminary and primary treatment, the wastewater enters the biological treatment stage in a clearer state. At this stage, an IoT system can be used to monitor influent characteristics such as flow rate and pollutant load, providing baseline data for early detection of abnormal conditions and supporting process optimization [9].

IoT Sensors for Inflow Monitoring → Measure flow rate, turbidity, and initial pollutant levels in real-time

Data Acquisition System → Collect and transmit inflow data for further analysis

4.2. Aeration Tank (Biological Treatment Core)

The aeration tank is the core unit of the ASP, where microorganisms break down organic pollutants under aerobic conditions. The efficiency of this process depends heavily on maintaining optimal parameters such as dissolved oxygen (DO), temperature, and nutrient balance. IoT-based sensors continuously monitor these parameters, while AI analyzes real-time data to predict system behavior and dynamically adjust the aeration rate, ensuring optimal microbial activity and energy efficiency [10].

IoT-Based Dissolved Oxygen (DO) Sensor → Real-time oxygen level monitoring

AI Machine Learning Model → Predicting oxygen demand and optimizing aeration control

Automated Aeration Control System → Dynamically adjusting airflow based on AI recommendations

Cloud-Based Monitoring Platform → Enabling centralized system monitoring and control

4.3. Secondary Clarifier and Sludge Management

After the aeration process, the liquid mixture flows into the secondary settling tank, where activated sludge settles and separates from the treated water. Some of the sludge is recycled back to the aeration tank, while excess sludge is discharged. AI optimizing the sludge recirculation rate and predicting sludge conditions, while IoT sensors monitoring sludge characteristics to ensure stable operation [10].

IoT-Based Sludge Level Sensor → Monitors sludge layer height and settling behavior

AI-Based Predictive Model → Predicts sludge bulking and settling efficiency

Automated Sludge Recirculation Control → Optimizes the rate of returned activated sludge (RAS)

4.4. Monitoring and System Optimization

In the final stage, treated water is discharged or reused for non-consume purposes. Maintaining consistent wastewater quality is crucial for protecting aquatic ecosystems. At this stage, the system continuously monitoring wastewater parameters, analyzing and decision-making to ensure conformity with environmental standards, as well as the warning system [9], [10].

IoT-Based Water Quality Sensors → Monitor COD, BOD, turbidity, and pH in wastewater

AI-Based Decision Support System → Analyze trends and ensure regulatory compliance

Real-Time Monitoring Dashboard → Provide actionable insights to operators

Early Warning System → Detect anomalies and prevent environmental risks

V. Conclusion

Water sustains human life, socio-economic development, and environmental sustainability, which are the key to achieving SDG 6. However, rapid urbanization and population growth have exacerbated challenges in domestic wastewater management, where treatment infrastructure and monitoring systems remain limited. The high proportion of untreated wastewater degrades water quality, threatens public health, and damages aquatic ecosystems. Addressing these challenges requires not only effective treatment technologies but also an integrated management approach that ensures long-term sustainability.

The Activated Sludge Process (ASP) is a reliable and widely used technology for treating domestic wastewater, but its conventional operation faces limitations. The integration of Artificial Intelligence (AI) and the Internet of Things (IoT) enhances ASP performance by enabling real-time monitoring, predictive analytics, and automated control across all treatment stages. This smart and adaptive system improve better performance and energy efficiency, water quality management, strengthens integrated water resource management, and contributes to the protection of aquatic ecosystems. Therefore, the combination of ASP with digital technologies is a promising and sustainable solution for achieving Sustainable Development Goal (SDG) 6 in modern urban environments.

VI. Reference

[1] Sustainable development goal 6 : synthesis report 2018 on water and sanitation. United Nations Publications, 2018.

[2] J. Evaristo et al., “Water woes: the institutional challenges in achieving SDG 6,” Sustainable Earth Reviews, vol. 6, no. 1, p. 13, 2023, doi: 10.1186/s42055–023–00067–2.

[3] T. Ihsan and F. Ilfan, “Challenges of Drinking Water Supply in Indonesian Cities: A Brief Review,” Andalasian International Journal of Applied Science, Engineering and Technology, vol. 5, no. 02, pp. 140–150, Jul. 2025, doi: 10.25077/aijaset.v5i02.160.

[4] WHO/UNICEF JOINT MONITORING PROGRAMME FOR WATER SUPPLY, SANITATION AND HYGIENE. [Online]. Available: https://washdata.org

[5] P. M. Acosta-Castellanos, K. León, H. F. Guerrero-Sierra, and L. Acosta-Castellanos, “Protection and restoration of water-related ecosystems under SDG 6.6: a global systematic review,” Frontiers in Water, vol. 8, Mar. 2026, doi: 10.3389/frwa.2026.1766735.

[6] Wastewater : the untapped resource : the United Nations world water development report 2017. United Nations Education, Scientivic and Cultural Organization, 2017.

[7] N. Paramita, “THE ACCELERATION SECRETS WATER, SANITATION AND HYGIENE (WASH).”

[8] I. Maliga, S. Purwono, R. Harini, and A. Soetarto, “Critical indicators for determining sustainable domestic wastewater management for the achievement of SDG goal 6,” Discover Water, vol. 5, no. 1, p. 39, 2025, doi: 10.1007/s43832–025–00235–9.

[9] T. Tak et al., “Digitalization for sustainable wastewater treatment: a way forward for promoting the UN SDG#6 ‘clean water and sanitation’ towards carbon neutrality goals,” Discover Water, vol. 4, Sep. 2024, doi: 10.1007/s43832–024–00134–5.

[10] C. Monday, M. S. Zaghloul, D. Krishnamurthy, and G. Achari, “A Review of AI-Driven Control Strategies in the Activated Sludge Process with Emphasis on Aeration Control,” Jan. 01, 2024, Multidisciplinary Digital Publishing Institute (MDPI). doi: 10.3390/w16020305.

This article was produced by the Education Division of IEEE SB IPB, authored by Mikailla Khiva Nuandhe Nararya. This piece is a collaborative effort with the Himavo Likista to promote SDG 6 awareness.