Introduction: The influence of Dissolved organic carbon (DOC) and Volatile Organic Compounds (VOCs) on
both human health and the environment is significant and cannot be overlooked. VOCs not only
play a role in photochemical processes but also directly influence physiological and disease-
related mechanisms (1,2). Research indicates that the presence of VOCs correlates with
respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD) (3).
Continuous presence of VOCs has been linked to neurological impairments, heart-related
illnesses, and premature deliveries. Additionally, about one-third of people may face an
increased risk of cancer due to VOCs.
Meanwhile, DOC have been implicated in raising the likelihood of cancers—especially those
affecting the bladder, colon, and liver—and are associated with reproductive health issues,
including infertility, a higher risk of miscarriage, developmental problems in fetuses, and
complications involving the liver and digestive systems (4,5,6,7). Using algae-based systems is
one of the reliable and green solutions for pollution reduction.
Methods: This approach simultaneously reduces pollution and generates valuable biomass. In
algae-based methods—whether utilizing microalgae or macroalgae—several key
mechanisms are involved: (1) adsorption and bioaccumulation of organic compounds on
the cell membrane and within the biofilm matrix, (2) biodegradation or biotransformation
carried out by the algae themselves or by symbiotic bacteria within their surrounding
phycosphere, and (3) gas transfer or phase absorption in liquid-gas systems such as
photobioreactors, which enable the metabolism of VOCs dissolved in the aqueous
phase(8,9).
• For water pollutants such as DOC, mixotrophic algae—particularly species like Galdieria
sulphuraria—have demonstrated the ability to effectively reduce DOC and BOD levels.
These algae have also shown remarkable efficiency at the pilot scale. This means that
algae not only remove carbon but also convert it into usable biomass (10).
• According to the research by Lebrero et al. the alga Chlorella vulgaris has been found
effective in the removal of VOCs such as toluene and benzene (12). In another study,
Hank et al. reported that Galdieria sulphuraria has a high capacity for DOC removal and
can thrive under harsh environmental conditions (13). Olivia et al. also stated that a
species of Scenedesmus sp. is effective in eliminating organic pollutants, including VOCs
(14). Similarly, Satya et al. presented comparable findings by Chlamydomonas
reinhardtii (15). In another report, Sia and collaborators introduced an algal–bacterial
consortium aimed at enhancing the removal of organic compounds and improving
treatment efficiency (16).
Results: In the treatment of DOC, Galdieria sulphuraria and Chlorella sorokiniana have demonstrated a
direct and favorable role (17, 18). Also, In the case of Chlorella sp. D046 and Navicula sp.,
water quality improvement has been reported, although the main focus of the study was on the
growth of the algae (19).
• . Experiments conducted on photobioreactors and algae-bacteria aerated reactors have
shown that the removal efficiency of compounds such as toluene can be very high, with
some integrated systems achieving up to approximately 99% removal. Meanwhile, the
CO₂ produced from the degradation process can be absorbed by algae and converted into
biomass, thereby supporting the concept of a circular economy. These findings have been
confirmed through both pilot-scale and field studies (8).
• One significant advancement is the use of algae–bacteria consortia; in this system,
bacteria are capable of breaking down hydrophobic or more complex compounds and
producing intermediate products that algae can utilize. As a result, the efficiency of VOC
removal is significantly enhanced. Recent studies have introduced "bottom-up"
approaches for designing and screening such consortia (11).
• Gas–liquid mass transfer for highly volatile VOCs, toxicity at high concentrations (which
can inhibit both algae and bacteria), and industrial-scale issues such as lighting, biomass
harvesting, and costs remain practical obstacles. Circular economy considerations—such
as utilizing wastewater or flue gas CO₂ as resources—and integration with systems like
MBBR, bio trickling filters, and photobioreactors have shown promising solutions (9,
10).
• Integrated algal–bacterial systems in photobioreactors (or hybrid configurations such as
MBBR–PBR) have proven to be effective for the simultaneous removal of VOCs and
DOC. These systems not only reduce contaminants but also facilitate biomass production
and CO₂ sequestration. Nevertheless, further advancements in mass transfer, strain
optimization, and reactor engineering are essential for successful industrial-scale
applications (11).
Conclusion: In conclusion, algae-based technologies for the removal of VOCs and DOC offer a
sustainable and reliable solution, making them a promising component of future green
remediation strategies.