Hanoi explores ways to turn sludge into valuable resources

The management and treatment of sludge, from drainage systems, lake and canal dredging, to environmental sanitation works, have become a serious challenge in Hanoi. The city currently lacks a proper landfill site for sludge disposal, resulting in dredged sludge being temporarily stored at transfer yards or dumped in makeshift sites. This not only pollutes the environment but also wastes a potentially valuable resource that could be effectively utilized if treated properly.

The hidden aspect of urban environmental management

Every year, Hanoi generates hundreds of thousands of cubic meters of sludge from dredging its drainage systems and inner-city lakes. The problem is that most of this sludge is not classified, analyzed, or treated following standard procedures. Temporary storage, transportation, and even illegal dumping of sludge into the natural environment remain common, posing risks to soil, water, and air pollution.

Urban sludge not only contains decomposing organic matter but may also accumulate heavy metals, pathogens, and toxic chemical compounds. Without strict management, sludge can become a “ticking environmental bomb,” particularly in densely populated areas.

However, many experts see sludge from a different perspective. It can be turned into a valuable resource for the circular economy if properly treated and recycled. Nguyen Van Nguyen, former Deputy Director General of the Vietnam Department of Geology (now the Vietnam Department of Geology and Minerals), believes that sludge has a direct connection to the field of geology and minerals.

The Law on Geology and Minerals mentions the investigation of geological conditions, including the mapping of structures capable of storing waste, evaluating geological characteristics, and identifying suitable geological structures for waste storage or landfill purposes (Clause 3, Article 18, Point b).

“First, it is necessary to analyze and identify the material composition of sludge and its levels of environmental and biological toxicity in order to determine appropriate treatment methods,” he said.

According to Nguyen, many types of sludge can be processed for use in agriculture or construction. “Experience from Japan shows that treated sludge can be used as building materials such as bricks, paving blocks, or aggregate mixtures for road construction. If Vietnam applies similar technology, this would be an effective approach, protecting the environment while saving soil, sand, and cement resources,” said the former Deputy Director.

Following the global trend of turning waste into resources

The present world is approaching the matter of sludge treatment, specifically dredged sludge, through sustainable solutions as part of the circular economy. Developed countries have applied advanced methods to detoxify, recycle, or convert sludge into useful materials.

The Netherlands has adopted techniques to “mature” dredged sludge, transforming it into high-quality clay and soil for dike construction and agricultural land improvement. In the case of the USA, the U.S. Army Corps of Engineers (USACE) implements the “Beneficial Use of Dredged Material” program, which reuses dredged sludge to restore coastlines, create new aquatic habitats, and prevent erosion. As for France, the port city of Dunkerque successfully uses dredged sludge as a base layer for road construction projects, meeting all technical building standards.

These examples show that when properly treated, sludge need not be an “environmental burden” but can instead serve as a promising alternative material source.

The path forward for Hanoi

From Nguyen’s viewpoint, Hanoi needs a comprehensive strategy to effectively resolve its sludge problem, comprising two key steps: proper management and active reuse. First, sludge must be classified at the source to determine its composition, heavy metal content, and pollution level. Treatment facilities should invest in modern technologies such as bioremediation, chemical stabilization, or cement solidification to ensure safety.

Hanoi should also promote research and pilot projects to recycle sludge for beneficial purposes, including improving agricultural soils after treatment to enrich nutrient-poor land or produce building materials. Sludge mixed with additives can be used to make bricks, ceramics, or road aggregates. Clean sludge is a good material for land reclamation, riverbank restoration, and urban landscape improvement.

Nguyen emphasizes another important factor, which is the need for a clear legal framework that defines technical standards and assigns responsibilities to dredging, collection, and treatment units. The goal is to avoid the current situation where “sludge can be dumped anywhere.”

The lack of proper sludge landfills in Hanoi highlights a thought-provoking reality: we are treating sludge as garbage, while other countries view it as a valuable resource. Shifting this mindset through investment in technology and supportive policies for sludge utilization could open a new path for urban environmental management, simultaneously reducing pollution pressure and generating economic value.

“Sludge doesn’t necessarily have to be buried. When properly treated, it can become a resource for sustainable development and a crucial component of a circular economy,” said Nguyen Van Nguyen, former Deputy Director General of the Vietnam Department of Geology (now the Vietnam Department of Geology and Minerals).