How effective is biological activated carbon in removing micropollutants? A comprehensive review

In vitro bioanalytical assessment of the occurrence and variation of nine bioactivities in a drinking water treatment plant in Korea

Organic micropollutants in drinking water can pose a public health risk. Chemical analysis alone cannot capture the full range of contaminants or assess their associated risks, promoting the growing use of bioanalytical tools as a complementary approach. This study assessed a drinking water treatment plant in the Nakdong River basin, Korea, using in vitro bioassays targeting nine endpoints. The highest estrogen receptor (ERα) activity was observed in the influent and significantly decreased throughout treatment. Bioactivities related to xenobiotic metabolism (PAH, PPARγ, and PXR) and oxidative stress response (Nrf2) initially increased during pre-oxidation but decreased in later treatment stages. An increase in p53 activity was also noted during treatment. Both season and treatment processes were found to affect the bioactivity variation for most endpoints, based on correlation analysis. The bioactivities observed were consistent with those reported for treated drinking waters in other countries. PAH, PPARγ, PXR, and Nrf2 activities in the final treated waters exceeded some effect-based trigger (EBT) values, indicating potential risks, although uncertainty remain regarding the EBT values for PPARγ and PXR. Additionally, the bioanalytical equivalent concentrations of volatile disinfection byproducts detected after pre- and post-chlorination were lower than the measured Nrf2 activities by factors of 7.5 and 5.5, respectively. This study highlights the importance of monitoring of bioactive chemicals to safeguard public health and ecosystems, underscoring the value of in vitro bioassays in water quality assessment.

Effect of Soil-pH, temperature and moisture content on sorption dynamics of metformin and erythromycin

The rising soil-groundwater quality issues due to pharmaceuticals and personal care products (PPCPs) contamination have spurred significant concern. To understand the sorption characteristics of metformin (MTN) and erythromycin (ETM) in sandy and sandy loam soils with varying organic matter and particle composition, sorption kinetics (single and competitive), isotherms, and thermodynamics were studied. The effects of pH and soil moisture content (SMC) were also investigated at environmentally relevant concentrations. The equilibrium time of MTN and ETM sorption by the three soils in a competitive solute system was about 4 h, and the sorption process was in line with a pseudo-second-order model. The rate-determining step in the process involved both intraparticle diffusion and liquid film diffusion mechanisms for the two PPCPs. The highest pollutant uptake occurred in soils with higher organic matter, driven by enhanced H-bonding, electrostatic interactions, and π-π and n-π interactions facilitated by the organic matter. The equilibrium data in the three soils was well described by the Freundlich model and confirmed favourable adsorption (1/nf = 1.01-1.90). The sorption coefficient (Kd) on the three soils ranged from 2.1 to 332 L/kg for MTN and from 6.25 to 845 L/kg for ETM. The adsorption process was feasible at 293 K and 303 K (ΔG° = - 0.16 to -10.24 kJ/mol), physical and exothermic in nature (ΔH° = -75.21 to -10.30 kJ/mol) for both the contaminants. Observed alterations in Qe with pH confirmed the participation of electrostatic interactions. A low SMC favoured both MTN and ETM sorption onto the sandy soil. Overall, ETM exhibits higher expected sorption, whereas MTN has a greater tendency for migration in the soils and is thus liable to contaminate the groundwater. The study accentuates novel insights into the transport and fate of MTN and ETM in soil-groundwater systems at environmentally relevant concentrations.

Role of biochar pyrolysis temperature on intracellular and extracellular biodegradation of biochar-adsorbed organic compounds

Immobilizing organic pollutants by adsorption of biochar in farmland soil is a cost-effective remediation method for contaminated soil. As the adsorption capacity of biochar is limited, biodegradation of biochar-adsorbed organic pollutants was a potential way to regenerate biochars and maintain the adsorption performance of biochars to lower the cost. It could be affected by the biochar pyrolysis temperature, but was not evaluated yet. In this study, biodegradation of adsorbed phenanthrene on a series of biochars with pyrolysis temperatures from 150 to 700 °C by Sphingobium yanoikuyae B1 was investigated using batch experiments of biodegradation kinetics at 30 °C, to explore the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds. It was observed that 37.5-47.9% of adsorbed phenanthrene on moderate temperature-pyrolyzed biochars produced at 400 and 500 °C were biodegraded, less than that on high temperature-pyrolyzed biochars produced at ≥600 °C (48.8-60.8%) and low temperature-pyrolyzed biochars produced at ≤300 °C (63.4-92.5%). Phenanthrene adsorbed largely on the low temperature-pyrolyzed biochars by partition mechanism and thus is easily desorbed to water for a dominated intracellular biodegradation. On the high temperature-pyrolyzed biochars, phenanthrene is adsorbed largely by pore-filling mechanism and thus less desorbed to water for intracellular biodegradation. However, high temperature-pyrolyzed biochars can promote microbes to produce siderophore, H2O2 and thus release extracellular •OH for a dominated degradation of adsorbed phenanthrene by Fenton-like reaction. With the increase of biochar pyrolysis temperature, desorption and consequently the intracellular biodegradation of adsorbed phenanthrene on biochars decreased, while the secretion of siderophore and H2O2 by microbes on biochars increased to produce more extracellular •OH for degradation by Fenton-like reaction. The results could provide deep insights into the role of biochar pyrolysis temperature on biodegradation of biochar-adsorbed organic compounds, and optimize the selection of biochar with higher adsorption performance and easier regeneration for soil remediation.