Pharmaceuticals consist of many recalcitrant compounds that are not readily biodegradable and, in some cases, inhibitory to wastewater treatment systems. While we often hear about forever chemicals such as PFAS, many common pharmaceuticals also can have a negative impact on aquatic ecosystems and human health. While biochar, activated carbon, and advanced oxidation technologies can remove the pharmaceutical compounds, it is most efficient to use natural degradation as much as possible.
Strategies to Enhance Biological Removal of Pharmaceuticals
The efficiency of pharmaceutical removal can vary significantly depending on several factors, including hydraulic retention time (HRT), food-to-microorganism ratio (F/M), and solids residence time (SRT). In this blog post, we will explore how these factors impact the removal efficiency of pharmaceutical compounds in wastewater treatment systems.
- Hydraulic Retention Time (HRT)
Hydraulic retention time (HRT) refers to the average time that wastewater remains in a treatment system. It is a critical parameter that influences the removal efficiency of pharmaceutical compounds. Studies have shown that prolonged HRT conditions can enhance the removal of pharmaceutical compounds. For instance, a study on membrane bioreactors (MBRs) found that increasing the HRT from 3 to 6 hours significantly improved the removal efficiency of compounds like gemfibrozil and trimethoprim. This improvement is attributed to the extended contact time between the wastewater and the microorganisms, allowing for more effective biodegradation and adsorption of the pharmaceutical compounds. - Food-to-Microorganism Ratio (F/M)
The food-to-microorganism ratio (F/M) is another important factor that affects the removal efficiency of pharmaceutical compounds in wastewater treatment systems. F/M ratio represents the amount of organic matter (food) available to the microorganisms in the treatment system. A balanced F/M ratio is essential for maintaining an active and healthy microbial community capable of degrading pharmaceutical compounds. High F/M ratios can lead to excessive microbial growth, which may result in poor treatment performance and reduced removal efficiency. Conversely, low F/M ratios can limit microbial activity and slow down the degradation process. Therefore, optimizing the F/M ratio is crucial for achieving efficient removal of pharmaceutical compounds. - Solids Residence Time (SRT)
Solids residence time (SRT), also known as sludge age, refers to the average time that solids (biomass) remain in the treatment system. SRT is a key parameter that influences the microbial community structure and activity, which in turn affects the removal efficiency of pharmaceutical compounds. Longer SRTs generally promote the growth of slow-growing microorganisms that are more effective at degrading complex organic compounds, including pharmaceuticals. For example, a study on the impact of SRT on pharmaceutical removal found that increasing the SRT improved the removal efficiency of compounds like acetaminophen and fluoxetine2. This is because longer SRTs provide sufficient time for the microorganisms to adapt and develop the necessary enzymatic pathways for degrading pharmaceutical compounds. - Targeted Bioaugmentation
Bioaugmentation with select cultures can help build and reinforce biomass capable of degrading pharmaceutical and other recalcitrant compounds in wastewater treatment plants. In nature, complex organic compounds are degraded by both bacteria and fungi cultures with enzyme pathways for the substrate or by co-metabolism. Often this is a complex ecological web of organisms and degradation steps. Aster Bio has successfully treated projects with polyaromatic hydrocarbons (PAH), chlorinated organics, and wastewater using organisms including genera Pseudomonas and Rhodococcus both of which have diverse metabolic capabilities. We are also currently developing enhanced fungal cultures from genera in the White Rot and other fungi.
In conclusion, the removal efficiency of pharmaceutical compounds in wastewater treatment systems is influenced by several factors, including hydraulic retention time (HRT), food-to-microorganism ratio (F/M), and solids residence time (SRT). Optimizing these parameters is essential for enhancing the performance of wastewater treatment systems and reducing the release of pharmaceutical compounds into the environment. By understanding and controlling these factors, we can improve the effectiveness of wastewater treatment processes and protect our water resources from pharmaceutical pollution.
For further reading:
Dolatimehr, A., Mahyar, A., Barough, S. P. H., & Mahmoodi, M. (2024). Insights into the efficiencies of different biological treatment systems for pharmaceuticals removal: A review. Water Environment Research, 96(11), e11153. https://doi.org/10.1002/wer.11153
Nzila A, Razzak SA, Zhu J. Bioaugmentation: An Emerging Strategy of Industrial Wastewater Treatment for Reuse and Discharge. Int J Environ Res Public Health. 2016 Aug 25;13(9):846. doi: 10.3390/ijerph13090846. PMID: 27571089; PMCID: PMC5036679
Neibergs, M., Strade, E., Nikolajeva, V., Susinskis, I., Rozitis, D., Kalnina, D., 2019. Application of Bioaugmentation to Improve Pharmaceutical Wastewater Treatment Efficiency. KEM 800, 122–131. https://doi.org/10.4028/www.scientific.net/kem.800.122