Introduction Despite being only 27 kilometers long, the Pasig River contributes disproportionately to global ocean plastic pollution. The river accounts for about 6.43% of plastic waste entering the world’s oceans from rivers—roughly 63,000 tons each year—even though it is far smaller than major river systems in the People's Republic of China and India. Public agencies, private organizations, philanthropies, and communities have launched numerous cleanup initiatives. Yet pollution persists. Waste continues to flow into the Pasig River from upstream tributaries and a dense network of esteros (urban creeks), often offsetting the impact of traditional cleanup operations. These conditions highlight the need for new tools that can improve both river cleanup and pollution monitoring. Technologies that combine automation, continuous cleanup, and environmental monitoring may help cities manage complex urban waterways more effectively. By generating real-time data on pollution flows, these systems can help cities move from reactive cleanup toward more strategic river management. To explore this potential, the Metropolitan Manila Development Authority (MMDA) piloted AI-enabled autonomous cleanup vessels developed by Clear Robotics. The vessels collect floating waste while generating real-time data on river conditions and pollution flows. This explainer examines why urban rivers like the Pasig are difficult to clean and what lessons the pilot offers for scaling technology-enabled river management. Why are urban rivers like the Pasig so difficult to clean? The Pasig River connects Laguna de Bay to Manila Bay and flows through the heart of Metro Manila. It is fed by the Marikina and San Juan Rivers and a complex network of esteros that drain waste from densely populated communities. This interconnected river system creates several challenges: Tidal flow: The Pasig is a tidal river, meaning water flow can reverse depending on tides, seasons, and floodgate operations. As a result, floating waste and water hyacinth often circulate or accumulate instead of flowing downstream. Data gaps: Limited data on where waste originates and how it moves through the river system makes cleanup efforts largely reactive rather than preventive. Fragmented interventions: Cleanup efforts have historically been localized and fragmented, making it difficult to sustain long-term river rehabilitation. How does Clearbot work in practice? Clearbots are autonomous electric vessels that collect floating waste and water hyacinth from rivers and esteros. Designed as a plug-and-play system, the vessels run on electric power, are solar-ready, and operate for up to eight hours per charge. Quick battery swaps allow crews to maintain continuous cleanup operations. Several features allow the vessels to operate effectively in complex urban waterways. Minimal infrastructure: The vessels use standard four-point lift hooks, allowing municipal crews to deploy them with existing cranes. Cities do not need specialized docks or new infrastructure. Systematic coverage: Operators can program the vessels to follow predefined transects or grid patterns, enabling systematic surface coverage for routine river maintenance. Precision maneuvering: For targeted debris collection or navigation in tight waterways, operators can manually steer the vessel using a handheld controller within a 300-meter radius. Digital monitoring: A live video feed and onboard monitoring system allow operators to track battery levels, vessel status, and mission progress in real time. Beyond collecting waste, the vessels also generate valuable environmental data that can help improve river management. Waste characterization: The system identifies the type, location, and volume of debris collected. This helps authorities detect pollution hotspots and better understand how waste enters and moves through the river system. Water quality monitoring: Onboard sensors can be integrated to measure indicators such as dissolved oxygen, pH levels, and water temperature, helping track the river’s environmental condition over time. Operational metrics: The system records information such as area covered and energy consumption, providing data that can support government planning, budgeting, and performance monitoring. The vessels function not only as cleanup tools but also as mobile monitoring platforms that provide continuous insight into how pollution moves through urban waterways. Moreover, these vessels are designed to complement existing cleanup programs rather than replace them. They perform best in narrow waterways such as esteros and tributaries but cannot remove heavily entangled debris in very shallow water, typically below 30 centimeters. Long-term river rehabilitation therefore still depends on reducing waste at the source and strengthening upstream waste management systems. What did the six-month pilot test and what were the results? The Metropolitan Manila Development Authority, with support from ADB technical assistance, piloted Clearbot cleanup vessels in two tributaries of the Pasig River system: the Ilugin River in Pasig City and the San Juan River in San Juan City. The pilot examined how the vessels perform under different river conditions and what insights they can provide for river management. It assessed operational performance, analyzed pollution patterns in the Pasig River system, evaluated impacts on worker safety and operational efficiency, identified local constraints such as tides, currents, and water depth, and explored potential circular economy uses for collected biomass and plastic waste. The six-month pilot generated several operational and policy insights. It also demonstrated how combining autonomous cleanup with environmental monitoring can support more data-driven approaches to river management. Measurable impact: In the Ilugin River, the vessel cleared more than 7,000 square meters of water hyacinth, equivalent to about 277 truckloads or 138 metric tons, over three months from October 2025 to January 2026. This helped restore water flow and reduce health risks for nearby communities. In the San Juan River, the vessel collected 5.3 metric tons of floating waste in two months, complementing the MMDA’s existing equipment and personnel. A systems perspective: The pilot showed that cleanup technology alone cannot solve river pollution. Even with continuous cleanup operations in the San Juan River, new waste continued to arrive from upstream sources. Effective river rehabilitation therefore requires a broader set of interventions, including improved upstream waste management and changes in community behavior. Labor upskilling: The technology reduced workers’ exposure to hazardous debris by shifting operations from manual waste handling to remote vessel control. This transition allows workers to move from high-risk manual labor to roles as operators of autonomous systems. Adaptive operations: The pilot also highlighted the need to adjust deployment based on local river conditions. Water depth, tidal patterns, and heavy rainfall all affect when and where the vessels can operate effectively. Circular economy potential: Collected biomass, particularly water hyacinth, as well as plastic waste could be repurposed into products such as biofuel or sustainable construction materials. This creates opportunities to transform river cleanup from a municipal cost center into a resource recovery system. What would it take to scale this up? Local governments can move beyond traditional equipment procurement toward service-based models, public–private partnerships, or private sector sponsorships that support continuous operations. Strong alignment with local solid waste management strategies and circular economy initiatives is essential to sustain operations and integrate cleanup technology into existing programs. Integrating these technologies with national frameworks such as the Ecological Solid Waste Management Act (Republic Act 9003) and the Extended Producer Responsibility Act can help ensure regulatory compliance and reinforce upstream waste reduction. Collaboration across cities can help build shared platforms for river data and operational learning. Over time, these networks could help cities move beyond reactive cleanup toward more coordinated and data-driven approaches to managing urban waterways. Ask the Experts Christine Po King Chan Principal Urban Development Specialist (Finance and Investment), Sectors Department 3, Asian Development Bank Christine Po King Chan has more than 24 years of international experience in structured and project finance, private equity, capital markets, and sustainable investing. She serves as Principal Urban Development Specialist at ADB, leading private capital structuring for urban and water infrastructure. She previously served as Senior Advisor to ADB’s Vice President (Market Solutions), providing guidance on strategic and transactional matters. Before joining ADB, she held investment roles in New York, Hong Kong, and Manila. She holds an MBA from the Wharton School and a BA from UC Berkeley. Samyuktha Sriram Head of Business Development, Clear Robotics Ltd (Hong Kong, China) Samyuktha Sriram is the Head of Business Development at Clearbot, a marine technology company that develops intelligent electric vessels for marine services, including the collection of plastic and pollution from coastal and inland waters. She leads strategic partnerships with ports, municipalities, and multinational corporations to support the deployment of Clearbot’s solutions across Asia. Her work focuses on advancing the economic viability of innovative environmental technologies and promoting circular economy approaches and collaborative financing models to address plastic and chemical waste in developing countries. Christian Rieza Knowledge Management Specialist (Consultant), Asian Development Bank Christian Rieza is a development communication and knowledge management consultant with experience in climate change, governance, urban resilience, and public health in Asia and the Pacific. He supports knowledge management, communications, and coordination for water and urban development initiatives at the Asian Development Bank, including the Rejuvenating Pasig River for a Livable Manila initiative. He previously supported COVID-19 response efforts with the Philippine Department of Health and USAID. He holds a BS in Development Communication, cum laude, from the University of the Philippines. Leave your question or comment in the section below: View the discussion thread.