Microscopic nanoparticles disrupting the delicate balance of a wastewater treatment biofilm.

Nano No-Nos: How Cerium Dioxide Can Disrupt Wastewater Treatment

Reese Marlowe in Climate & Environment December 2025 • 4 min read.

"Emerging research reveals the long-term impact of cerium dioxide nanoparticles on the delicate ecosystems within wastewater treatment systems. Are our methods equipped to handle these tiny disruptors?"

Our world is increasingly reliant on nanotechnology, integrating nanoparticles into everything from cosmetics to electronics. Among these, cerium dioxide nanoparticles (CeO2 NPs) stand out due to their widespread use in catalysts, textiles, and biomedical applications. However, as production and utilization surge, the environmental release of CeO2 NPs becomes inevitable, raising critical questions about their impact on ecosystems.

Wastewater treatment plants (WWTPs) are often the final destination for many pollutants, including nanoparticles. These plants rely on complex microbial communities to break down waste and purify water. Recent studies suggest that CeO2 NPs can disrupt these communities, posing a threat to the efficiency and stability of wastewater treatment processes. Understanding the long-term effects of these nanoparticles is crucial for maintaining effective and safe water treatment.

A new study published in 'Bioresource Technology' delves into the chronic effects of CeO2 NPs on nitrogen removal in sequencing batch biofilm reactors (SBBRs). SBBRs are a type of wastewater treatment system that uses biofilms—communities of microorganisms attached to surfaces—to remove pollutants. The research explores how CeO2 NPs impact the microbial environment, community dynamics, and overall performance of these reactors, providing valuable insights for environmental scientists and treatment plant operators alike.

How Do Cerium Dioxide Nanoparticles Affect Nitrogen Removal in Biofilm Reactors?

Microscopic nanoparticles disrupting the delicate balance of a wastewater treatment biofilm.

The study investigated the impact of CeO2 NPs on nitrogen removal in biofilm reactors over an extended period. Researchers exposed the biofilm to varying concentrations of CeO2 NPs and monitored the effects on the microbial communities and the overall efficiency of the treatment process.

The results indicated that prolonged exposure to low concentrations (0.1 mg/L) of CeO2 NPs had minimal inhibitory effects on nitrogen removal. However, continuous addition of higher concentrations (10 mg/L) significantly decreased the treatment efficiency, reducing it to 53%. Interestingly, the reactors showed some resilience, with the removal efficiency stabilizing around 67% even with continued exposure to high concentrations.

Low Concentrations: Minimal impact on nitrogen removal.
High Concentrations: Significant decrease in treatment efficiency.
Acclimation: The biofilm community showed some ability to adapt and stabilize.

Microscopic analysis revealed that CeO2 NPs exposure led to distinct shifts in the microbial communities within the biofilm reactors. The micro-profiles of dissolved oxygen, pH, and oxidation-reduction potential suggested the development of protective mechanisms in microbes progressively exposed to CeO2 NPs, leading to a reduced impact on the microenvironment, denitrification bacteria, and enzyme activity.

The Future of Nanoparticle Monitoring in Wastewater Treatment

This research underscores the importance of understanding the long-term ecological consequences of nanoparticle pollution. As nanotechnology continues to advance, proactive measures are needed to mitigate potential environmental risks. Further studies should focus on developing strategies to prevent nanoparticle release and improve the resilience of wastewater treatment systems. With careful monitoring and innovative solutions, we can ensure the sustainable use of nanotechnology while safeguarding our planet's precious water resources.

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This article is based on research published under:

DOI-LINK: 10.1016/j.biortech.2017.08.201, Alternate LINK

Title: Long Term Effects Of Cerium Dioxide Nanoparticles On The Nitrogen Removal, Micro-Environment And Community Dynamics Of A Sequencing Batch Biofilm Reactor

Subject: Waste Management and Disposal

Journal: Bioresource Technology

Publisher: Elsevier BV

Authors: Yi Xu, Chao Wang, Jun Hou, Peifang Wang, Lingzhan Miao, Guoxiang You, Bowen Lv, Yangyang Yang, Fei Zhang

Published: 2017-12-01

Everything You Need To Know

What are cerium dioxide nanoparticles and why should I be concerned about them in wastewater treatment?

Cerium dioxide nanoparticles, also known as CeO2 NPs, are increasingly used in various industries like cosmetics, textiles, and biomedical applications due to advancements in nanotechnology. As their use grows, these nanoparticles inevitably end up in wastewater treatment plants. This is significant because these plants rely on microorganisms to purify water, and CeO2 NPs can disrupt these microbial communities, potentially reducing the effectiveness of wastewater treatment processes and affecting water quality.

What are sequencing batch biofilm reactors and how are they relevant to nanoparticle research?

Sequencing batch biofilm reactors, or SBBRs, are wastewater treatment systems that utilize biofilms—communities of microorganisms attached to surfaces—to remove pollutants. They are important because they offer an efficient method for wastewater treatment. However, the presence of cerium dioxide nanoparticles can disrupt the microbial environment within these reactors, affecting the overall treatment performance and potentially leading to reduced efficiency in removing pollutants like nitrogen.

How do cerium dioxide nanoparticles affect nitrogen removal in wastewater treatment processes?

Nitrogen removal in wastewater treatment is the process of eliminating nitrogen compounds from wastewater, which is crucial for preventing water pollution and maintaining environmental health. Cerium dioxide nanoparticles impact this process by affecting the microbial communities responsible for nitrogen removal in systems like sequencing batch biofilm reactors. High concentrations of CeO2 NPs can significantly decrease the efficiency of nitrogen removal, while prolonged exposure, even to low concentrations, can cause shifts in microbial community structure and function.

What are biofilms and why are they important in the context of cerium dioxide nanoparticle pollution?

Biofilms are communities of microorganisms that attach to surfaces and play a vital role in wastewater treatment by breaking down pollutants. Cerium dioxide nanoparticles can alter the microbial composition and function of these biofilms. This is significant because changes in the biofilm's microbial communities can affect the overall efficiency of wastewater treatment processes, potentially leading to reduced removal of pollutants and impacting the stability of the treatment system.

How were the effects of cerium dioxide nanoparticles studied and what concentrations were used?

The impact of cerium dioxide nanoparticles was studied using varying concentrations in sequencing batch biofilm reactors. At low concentrations (0.1 mg/L), the impact on nitrogen removal was minimal. However, at high concentrations (10 mg/L), the treatment efficiency significantly decreased. Over time, the reactors showed some resilience, with the removal efficiency stabilizing, indicating that the microbial communities can adapt to the presence of CeO2 NPs to some extent. This acclimation highlights the complex interactions between nanoparticles and microbial ecosystems in wastewater treatment.