Humic Acid Can Enhance the Mineralization of Phenanthrene Sorbed on Biochars

Abstract

Biodegradation of hydrophobic organic contaminants by bacteria has been widely studied, but how dissolved organic matter (DOM) may affect their removal if accumulated on biochars is poorly understood. To address this knowledge gap, microbial mineralization of phenanthrene (PHE) spiked on various biochars by Mycobacterium vanbaalenii PYR-1 in the presence of humic acid (HA, a model DOM) at two concentrations was investigated. Our findings showed that HA greatly increased the rate and extent of PHE mineralization. This could be attributed to enhanced PHE desorption by HA, which facilitated access to it by bacteria in the aqueous phase. Furthermore, the high HA affinity for PHE facilitated PHE flow toward the bacterial cells with HA acting as a carrier in the aqueous phase. The mineralization enhancement of PHE by HA within 480 h was negatively influenced by the aromatic carbon contents and micropore volumes in biochars. This shows the importance of the physicochemical properties of biochars in altering the HA effect. Results of this study provide novel information on how to achieve complete removal of PHE accumulated on biochars with a strong sorption affinity for it, using a microbial technique and natural DOM.

The regenerative role of biofilm in the removal of pesticides from stormwater in biochar-amended biofilters

“…Desorption was negatively correlated with the microporosity of biochars: the authors argued that organics bound to the intraparticle surfaces and micropores may be inaccessible. 48 In our study, it is possible that a continuous source of DOC in the presence of a predominantly mesoporous biochar led to increased desorption rates and facilitated transport of atrazine, imidacloprid, and clothianidin in our biologically active columns.…”

“…Biotransformation of organic chemicals in the combined presence of a microbial biofilm and biochar may involve several mechanisms, which may occur simultaneously and are thus not mutually exclusive. In addition to degradation in the aqueous phase, literature indicates that biodegradation of biochar-bound organic compounds may be possible due to bioregeneration 63 or enhanced desorption 48 and due to the biochar's ability to serve as redox catalyst between microorganisms and organic compounds. 42 Bioregeneration occurs during water treatment employing combined biological and adsorptive processes, in which microorganisms renew the adsorption capacity of the black carbon.…”

“…69 Microbial degradation processes of biochar-sorbed organic chemicals are different compared to organics present in the dissolved phase and DOC may substantially impact their desorption and mineralization rates. Zhang et al 48 demonstrated that the presence of humic acid (HA) increased the mineralization rate of biochar-bound phenanthrene by accelerating its desorption rate into the aqueous phase. Desorption was negatively correlated with the microporosity of biochars: the authors argued that organics bound to the intraparticle surfaces and micropores may be inaccessible.…”

“…For instance, the addition of an external carbon source (e.g. woodchips, compost, humic acid) is known to facilitate biological processes and can benefit contaminant removal, 33,47,48 but may also lead to accelerated exhaustion of adsorption sites or pore clogging and concomitant biochar aging. 49,50 Generally, there are only a few studies providing insight into long-term performance of biochar-amended stormwater treatment systems.…”

Putting Biochar in Action: A Black Gold for Efficient Mitigation of Salinity Stress in Plants. Review and Future Directions

“…The large BC processing plants have the capacity to process 23 000 tons of biomass per day, thus a higher capacity is needed to handle, transport, and store the biomass. Further, the hard cellulosic structure of feedstock can also result in higher production costs. , If BC is not prepared according to environmental guidelines, then it can cause different problems, including deforestation, health problems, and greenhouse gas emissions. The presence of volatile compounds can also pose problems for seed germination, microbes, and crop productivity .…”