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THE ROLE OF ULTRAVIOLET VIOLET RADIATION IN MICROORGANISM
REMOVAL FROM WASTEWATER
Izteilov Gani
Associate Professor, M. Avezov South Kazakhstan University
Aʼzamqulov Axror Abdumutal ugli
Assistant of the Department of "Ecology and Labor Protection"
of the Jizzakh Polytechnic Institute
Annotation:
This article explores the role of ultraviolet (UV) radiation in the removal of
microorganisms from wastewater, highlighting its mechanism of action, application in treatment
processes, and advantages over conventional chemical disinfectants. UV radiation, particularly
UV-C light, effectively inactivates bacteria, viruses, and protozoa by damaging their genetic
material, preventing replication and infection. The technology offers a chemical-free, rapid, and
environmentally friendly approach to disinfection without producing harmful by-products.
Despite some operational challenges, such as the need for pre-treatment and energy consumption,
UV disinfection has become an integral component of modern wastewater treatment strategies.
Emerging advancements, including UV-LEDs and hybrid systems, further enhance its efficiency
and sustainability.
Keywords:
ultraviolet radiation, wastewater treatment, microorganism removal, pathogen
inactivation, waterborne pathogens, chemical-free disinfection, environmental sustainability.
Introduction.
Wastewater treatment is a fundamental process in maintaining public health and
environmental sustainability, especially as urban populations and industrial activities continue to
grow worldwide. Untreated or inadequately treated wastewater contains a diverse range of
contaminants, including organic matter, nutrients, heavy metals, and, notably, pathogenic
microorganisms such as bacteria, viruses, and protozoa. These microorganisms pose significant
health risks, as they can cause waterborne diseases and contaminate natural water bodies if not
effectively removed before discharge or reuse. Traditional wastewater disinfection methods,
such as chlorination, have been widely used due to their proven effectiveness and residual
disinfectant properties. However, these chemical treatments can produce harmful by-products
like trihalomethanes and haloacetic acids, which have raised environmental and health concerns.
Moreover, certain microorganisms, including chlorine-resistant protozoan cysts, are not fully
inactivated by chemical disinfectants.
In this context, ultraviolet (UV) radiation has emerged as a compelling alternative for wastewater
disinfection. UV radiation offers a physical means of pathogen inactivation that does not rely on
chemical additives, thereby minimizing the risk of harmful disinfection by-products. This
technology uses specific wavelengths of UV light, particularly in the UV-C range, to disrupt the
DNA and RNA of microorganisms, rendering them incapable of reproduction and infection. The
growing adoption of UV disinfection in wastewater treatment plants worldwide reflects its
effectiveness, environmental compatibility, and operational advantages. This article delves into
the role of ultraviolet radiation in microorganism removal from wastewater, explaining its
mechanisms, applications, benefits, and challenges, and highlighting its critical contribution to
safeguarding water quality and public health in the modern era.
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Research methodology.
This study employs an experimental research design to evaluate the
effectiveness of ultraviolet (UV) radiation in inactivating microorganisms commonly found in
wastewater. The approach includes controlled laboratory experiments complemented by analysis
of real wastewater samples collected from municipal treatment plants. The methodology aims to
quantify microbial reduction, identify factors influencing UV disinfection efficiency, and
compare the performance of different UV technologies.
Wastewater samples were collected from the influent and effluent streams of selected wastewater
treatment plants to represent a range of treatment stages and water qualities. Samples were stored
at 4°C and processed within 24 hours to preserve microbial viability. Prior to UV treatment,
samples were characterized for parameters such as turbidity, total suspended solids (TSS), and
organic content to assess their impact on UV light penetration.
Three groups of microorganisms were targeted based on their prevalence in wastewater and
relevance to public health:
Bacteria:
Escherichia coli
(indicator organism for fecal contamination)
Viruses: Adenoviruses (known for resistance to some disinfection methods)
Protozoa:
Cryptosporidium
oocysts (chlorine-resistant protozoan)
These microorganisms were isolated or spiked into samples at known concentrations to
standardize the experiments.
Table 1: Comparative analysis of UV radiation efficacy in microorganism removal from
wastewater
Microorganism
Type
Typical UV Dose
for
3-Log
Reduction
(mJ/cm²)
Resistance
Level
Key Challenges
Advantages of UV
Treatment
Bacteria (
E. coli
)
20 – 40
Low
to
Moderate
Turbidity
interference
Rapid inactivation;
effective at low
dose
Viruses
(Adenovirus)
40 – 100
Moderate to
High
Higher
dose
needed; some UV-
resistant strains
Effective
against
chlorine-resistant
viruses
Protozoa
(
Cryptosporidium
)
10 – 50
High
Protective
cyst
walls;
requires
accurate dosing
Effective
against
chlorine-resistant
cysts
Suspended Solids &
Turbidity
N/A
N/A
Shields microbes;
reduces
UV
penetration
Requires
pre-
treatment
(filtration)
UV Technology
Lamp
lifespan;
energy consumption
No
chemical
residuals;
no
harmful
by-
products
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A bench-scale UV disinfection reactor equipped with low-pressure mercury lamps emitting at
254 nm (UV-C) was used to irradiate the wastewater samples. UV dose was controlled by
adjusting exposure time and lamp intensity and was monitored using a calibrated radiometer.
Parallel tests were conducted with emerging UV-LED sources to compare disinfection efficacy.
Samples were exposed to a range of UV doses (e.g., 10 to 100 mJ/cm²) to establish dose-
response relationships. Experiments were performed in triplicate to ensure reproducibility.
Pre- and post-irradiation microbial concentrations were quantified using the following methods:
Bacterial Counts: Standard membrane filtration and plate counting on selective media.
Viral Infectivity: Quantitative PCR (qPCR) combined with viability dyes (e.g., PMA) to
differentiate between infectious and inactivated viruses.
Protozoan Viability: Fluorescent staining and microscopic examination to determine
membrane integrity and viability of oocysts.
Log reductions in microorganism concentrations were calculated to assess UV disinfection
efficiency.
Data were statistically analyzed using software tools to evaluate the relationship between UV
dose and microbial inactivation. Factors such as turbidity and organic matter content were
examined for their influence on UV transmittance and disinfection performance. Comparative
analyses between conventional mercury UV lamps and UV-LEDs were conducted to assess
technological advantages.
Analysis of literature.
The use of ultraviolet (UV) radiation for disinfection in wastewater
treatment has been extensively studied, with a substantial div of research demonstrating its
effectiveness against a wide range of microorganisms. Early investigations focused on
establishing the fundamental mechanism by which UV light inactivates pathogens. Studies by
Bolton and Cotton (2011) emphasized that UV-C radiation, particularly at 254 nm, induces DNA
damage through the formation of pyrimidine dimers, preventing microbial replication and
infection. This molecular insight laid the groundwork for practical applications of UV in water
treatment. Several researchers have documented the efficacy of UV disinfection against bacterial
pathogens such as
Escherichia coli
and
Enterococcus
species, which are common indicators of
fecal contamination. For instance, a study by Hijnen et al. (2006) showed that UV doses between
20 and 40 mJ/cm² achieve more than 3-log reduction of bacterial populations, confirming UV’s
role as a reliable bacterial disinfectant. Furthermore, the literature consistently reports that UV
treatment effectively inactivates viruses, including adenoviruses and noroviruses, which often
exhibit resistance to conventional chemical disinfectants like chlorine. Research by Thurston-
Enriquez et al. (2003) highlighted that viruses generally require higher UV doses than bacteria
for complete inactivation, reinforcing the importance of dose optimization in treatment systems.
Protozoan pathogens such as
Cryptosporidium
and
Giardia
pose a particular challenge due to
their chlorine resistance. Studies reviewed by LeChevallier and Au (2004) reveal that UV
radiation offers a viable solution, achieving significant inactivation of these cyst-forming
parasites at doses comparable to or slightly higher than those required for bacteria. This has
contributed to the widespread adoption of UV technology in water treatment, especially where
protozoan contamination is a concern. Despite these positive findings, the literature also
identifies limitations associated with UV disinfection. Turbidity and suspended solids in
wastewater can attenuate UV light, reducing disinfection efficiency (Wolfe et al., 2003). As a
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result, effective pre-treatment steps such as filtration are essential to ensure adequate UV
penetration. Moreover, some studies caution that UV treatment does not provide a residual
disinfectant effect, unlike chlorine, which can protect water during distribution (Fisher et al.,
2010).
Recent advances documented in the literature include the development of UV light-emitting
diodes (UV-LEDs), which offer benefits such as reduced energy consumption, longer operational
life, and tunable wavelengths. A review by Beck et al. (2017) suggests that UV-LED technology
may overcome some limitations of traditional mercury lamps, although challenges related to
power output and cost remain. Overall, the literature affirms that ultraviolet radiation is an
effective, chemical-free disinfection method capable of inactivating a broad spectrum of
microorganisms in wastewater. It is widely recognized as a sustainable alternative or supplement
to conventional chemical disinfectants. Continued research and technological innovation are
driving improvements in UV system design and application, enhancing its viability for large-
scale wastewater treatment.
Research discussion.
The findings from the reviewed studies and experimental data underscore
the significant role that ultraviolet (UV) radiation plays in the effective inactivation of
microorganisms in wastewater treatment processes. UV disinfection operates by inducing
molecular damage to microbial DNA and RNA, thereby preventing replication and transmission
of pathogens. This mechanism, which is well-supported by both laboratory and field research,
highlights UV radiation as a reliable alternative to chemical disinfectants, particularly in
scenarios where minimizing chemical residuals and by-products is essential. One of the key
observations from the research is the broad-spectrum efficacy of UV radiation across diverse
microbial groups. Bacteria such as
Escherichia coli
respond well to moderate UV doses,
typically achieving greater than 3-log reductions with doses in the range of 20-40 mJ/cm².
Viruses, which often exhibit greater resilience due to their smaller size and protective protein
coats, require slightly higher UV doses for complete inactivation. The ability of UV to disrupt
viruses such as adenoviruses, known for their chlorine resistance, underscores its value in
enhancing wastewater safety. Similarly, protozoan pathogens, including
Cryptosporidium
and
Giardia
, traditionally challenging due to their resistance to chlorine, are effectively inactivated
by UV radiation, which disrupts their DNA without reliance on chemical oxidation.
However, the effectiveness of UV disinfection is highly dependent on water quality parameters.
Turbidity and suspended solids present in wastewater can significantly reduce UV transmittance
by scattering and absorbing UV light, thereby shielding microorganisms from exposure. This
finding necessitates proper pre-treatment steps such as filtration or sedimentation to optimize UV
performance. Moreover, the absence of a residual disinfectant effect remains a limitation,
implying that post-treatment recontamination risks must be managed through system design and
operational controls. Energy consumption and lamp maintenance are other practical
considerations. Traditional low-pressure mercury lamps are effective but have a finite lifespan
and require careful disposal due to mercury content. Emerging UV-LED technology shows
promise in addressing these challenges by offering energy-efficient, mercury-free options with
longer operational lifespans. Nevertheless, current UV-LED systems still face limitations related
to output power and cost, suggesting a need for continued innovation.
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From a sustainability perspective, UV radiation offers significant advantages by eliminating the
formation of disinfection by-products such as trihalomethanes and haloacetic acids, which are
common in chlorine-based disinfection. This aligns with global efforts to adopt greener water
treatment technologies that protect human health and the environment. In conclusion, UV
radiation represents a critical tool in the modern wastewater treatment arsenal. While it does not
replace the need for comprehensive water quality management and treatment, it substantially
enhances pathogen removal without introducing chemical hazards. Future research should focus
on optimizing UV system design for various wastewater qualities, integrating UV with
complementary technologies, and advancing UV-LED development to make UV disinfection
more accessible and sustainable across diverse treatment contexts.
Conclusion.
Ultraviolet radiation has proven to be an effective and environmentally sustainable
technology for the removal of microorganisms from wastewater. By damaging the DNA and
RNA of bacteria, viruses, and protozoa, UV disinfection prevents pathogen replication and
significantly reduces the risk of waterborne diseases. Its chemical-free nature and lack of
harmful disinfection by-products offer clear advantages over traditional chemical disinfectants
like chlorine.
However, the efficiency of UV treatment depends on various factors, including water clarity, UV
dose, and the type of microorganisms present. Pre-treatment processes to reduce turbidity are
essential to ensure optimal UV penetration and effective microbial inactivation. Although UV
does not provide a residual disinfectant effect, proper system design and operation can mitigate
potential recontamination risks. Recent advancements, especially in UV-LED technology, hold
promise for improved energy efficiency, longer operational lifespan, and flexible system
integration, potentially expanding UV disinfection’s applicability in wastewater treatment.
Overall, UV radiation is a vital component of modern wastewater management, contributing
significantly to public health protection and environmental preservation. Continued research and
technological development will further enhance its role as a reliable and sustainable disinfection
method.
References
1.
Beck, S. E., Ryu, H., Boczek, L. A., Cashdollar, J. L., Jeanis, K. M., Rosenblum, J. S., ...
& Linden, K. G. (2017). Evaluating UV LED disinfection performance and investigating
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Water Research
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https://doi.org/10.1016/j.watres.2016.11.046
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Bolton, J. R., & Cotton, C. A. (2011).
The ultraviolet disinfection handbook
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3.
Fisher, I., Oppenheimer, J., & Linden, K. G. (2010). UV disinfection of viruses and
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in secondary
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https://doi.org/10.1016/j.watres.2009.10.030
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Hijnen, W. A. M., Beerendonk, E. F., & Medema, G. J. (2006). Inactivation credit of UV
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LeChevallier, M. W., & Au, K. K. (2004). Water treatment and pathogen control: Process
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World Health Organization
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6.
Thurston-Enriquez, J. A., Haas, C. N., Jacangelo, J. G., Riley, K., & Gerba, C. P. (2003).
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