Research on Anti-biofouling Technology of Ocean Observation

Instruments based on Ultraviolet Method

Xiaohong Wang

, Huibin Yu

1,*

, Xiaofeng Li

, and Jigang Zhou

Institute of Oceanographic Instrumentation, Qilu University of Technology (Shandong Academy of Sciences), Qingdao

266000, P. R. China

China Petrochemical Shengli Youtian Co.,Ltd. Dongxin Oil Extraction Factory, Dongying 257000, P. R. China

Keywords: Ocean observation, Anti-biofouling technologies, Ultraviolet rays

Abstract: Ocean observation equipment is an important tool for marine survey, development and protection. Because

of being placed in sea water for a long time, the research on its anti-biofouling technology is also of great

significance. This article discusses the formation principle of biological attachment, and introduces the

commonly used methods, according to the classification of active and passive manner, and development

status of seawater anti-biofouling technology. Then, according to the characteristics of marine observation

instruments, this article in particular introduces and recommends the principles and application cases of the

ultraviolet radiation method for anti-biofouling. Ultraviolet anti-biofouling technology can effectively

reduce the degree of biological attachment on ocean observation sensors and significantly increase the

deployment time of ocean observation instruments. Therefore, it can reduce maintenance costs and improve

data quality. It is a very important way for the cabled ocean observation sensor systems to prevent

biological attachment.

1 INTRODUCTION

Since the 20th century, countries around the world

have paid more and more attention to the impact on

humans and animals caused by the changes of

marine environment. Marine observation

instruments and equipment are important tools for

conducting marine surveys and research, ecological

observation, scientific development, and marine

environmental protection. Therefore, their work

characteristics and quality are directly related to the

level and benefits of these activities. These ocean

observation instruments generally use a large

number of optical, acoustic, electrical, chemical, and

biological sensors (Yebra et al., 2004). A small

amount of adhesion of marine organisms on the

surface of the sensitive components of these sensors

may cause serious damage to the working

performance of the devices (Babin et al., 2008; Onuf,

2006; Lobe & Das, 2010; National Marine

Information Center, 2013). As a result, serious

hazards such as the failure of the instrument

transmission mechanism, signal distortion,

performance degradation, shortening of service life

and even potential safety hazards may happen and

cause huge economic losses. Therefore, preventing

marine organisms from attaching is an important

guarantee for the long-term operation of marine

observation instruments and the acquisition of

accurate and reliable data (Yu et al., 2006; Wang et

al., 2016).

In summary, the research on methods and

technologies for marine observation instruments to

prevent biological attachment is of great

significance. A stable, reliable, flexible and

controllable technology for preventing biological

attachment of marine observation instruments with a

wide range of applications is essential for protecting

marine observation instruments and improving the

quality and stability of marine observation data. This

article will introduce the anti-biofouling

technologies and methods commonly used in marine

observation instruments and focus on the principles

and applications of the ultraviolet anti-biofouling

method used in this project. It is expected to provide

some technical guidance and application ideas for

those who want to use the ultraviolet method for

seawater anti-biofouling technology applications.

Wang, X., Yu, H., Li, X. and Zhou, J.

Research on Anti-biofouling Technology of Ocean Observation Instruments based on Ultraviolet Method.

In Proceedings of the 7th International Conference on Water Resource and Environment (WRE 2021), pages 251-256

ISBN: 978-989-758-560-9; ISSN: 1755-1315

251

2 DEVELOPMENT STATUS OF

SEAWATER ANTI-

BIOFOULING TECHNOLOGY

Anti-biofouling technology is a method to prevent

organisms from growing and accumulating on the

surface of underwater structures. There are many

classification methods for anti-biofouling

technologies. For example, Lehaitre et al. (2008)

divide them into active methods and passive

methods. There are many active anti-biofouling

strategies, such as physical decontamination

technology, interval immersion disinfection

technology, partial electrolytic chlorine technology,

ultraviolet(UV) light technology, etc. (Shan et al.,

2011). Passive methods are the most commonly used

methods in traditional industries, mainly using

various anti-fouling coating to prevent the

attachment of organisms (Lei et al., 2017). At

present, the common anti-biofouling technologies

applied to marine observation instruments mainly

include anti-fouling coatings, mechanical methods

(such as electric brushes), electrochemical methods

(electrolysis of copper sheets surrounding the

sensor), and UV light irradiation (Blanco et al., 2013;

Delauney & Compere, 2008).

The anti-fouling coating method is mainly used

for shell anti-fouling in the field of marine

observation instruments. At present, the commonly

used chemical anti-fouling coatings mainly include

tin-free self-polishing anti-fouling coatings, fouling

release anti-fouling coatings and conductive coating

anti-fouling coatings, etc. (Wu et al., 2017). These

chemical coatings are more or less toxic, which is

not conducive to the health of users and marine

environmental protection. Moreover, this method is

relatively mature in the application of ships, stations

and other large equipment, and most of the

applications in ocean observation sensors remain in

the research stage (Cao et al., 2020).

YSI's water quality multi-parameter sensor uses

a brush system to brush off the attachments on the

sensor probe. This method works better when the

brush system is normal and the components are

precisely matched, but once the bristles are

deformed and the gap between the brush head and

the sensor probe becomes larger, the effect becomes

worse (Shan et al., 2011). In addition, this method

has higher requirements on the reliability of the

motor rotating seal, and it is more difficult to be

applied to the protection of the spherical surface

(Wu et al., 2017).

Electrochemical methods are the most widely

used ways because they are effective for both micro

biofilms and large attachments. This kind of anti-

biofouling device generally uses titanium as an

electrode, and generates a sterilizing agent to kill

attachments through electrolysis. Delauney and

Compère selected a salinity sensor, a dissolved

oxygen sensor and a fluorometer to verify the

technology. Their experiments have shown that the

effect of this method is very good (Bixler &

Bhushan, 2012), but the sterilant produced during

the action of this method will affect the accuracy of

part of the data collected by the sensor which may

cause instrument measurement errors and reduce the

accuracy of the data.

The UV light irradiation method uses specific

wavelength UV light to destroy bacteria and other

microorganisms, thereby to prevent the adsorption of

bacterial biofilm on the surface of marine instruments

and the growth of plankton larval cells, and then to

eliminate the proliferation of high-grade marine

biological cells such as algae and shellfish in the later

period. Eventually, the growth and attachment of

organisms are completely stagnated (Bueley, 2014).

The advantage of the anti-biofouling methods based

on UV light irradiation is non-contact, non-chemical

and can be applied to a variety of sensor materials

and geometries without causing any marine

pollution. Therefore, it has wider applicability than

the above-mentioned various strategies, and it can

significantly increase the deployment time of ocean

observation instruments, thereby reducing

maintenance costs and improving data quality.

3 PRINCIPLES OF UV

ANTI-BIOFOULING

TECHNOLOGY

At present, people of this industry generally believe

the development of marine biological attachments is

divided into five stages

(Delauney et al., 2010;

Prakash et al., 2015). In the first stage, the attached

body immediately adsorbs organic and inorganic

molecules on its surface after being immersed in

seawater, thereby forming a primary film.In the

second stage, microbial cells such as bacteria are

transported and fixed on the surface of the primary

film.In the third stage, microbial cells such as

bacteria begin to produce extracellular polymer

networks to form microbial membranes.In the fourth

stage, an increasingly complex community composed

of simple multicellular organisms, microalgae and

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sediments began to develop.In the fifth stage, higher

marine organisms such as barnacles and mussels

gradually attach and grow, forming large-area, high-

coverage attachment forms.The development of the

above five stages is based on the biofilm formed by

bacteria and cell networks. Fundamentally, the main

mechanism of these biofilm formation is the

proliferation of colonizing cells. UV light exactly

prevents the further attachment of marine organisms

by destroying the reproduction of such cells.

When short-wave UV light (wavelength

240nm~280nm) irradiates microbial cells such as

bacteria, most of the UV radiation in the spectrum is

absorbed by the nucleotides in DNA, which leads to

the destruction of DNA and the growth,which in turn

leads to the growth and regeneration death of

microorganisms. The formation of organic film and

colonization tissue on the surface of the attached

body is further inhibited. Higher-order communities

cannot form and develop, so the purpose of

preventing biological attachment is achieved.

The performance of the UV anti-biofouling

technology depends on the UV radiation fluence,

that is, the fluence rate of the irradiated surface with

time. To calculate the fluence, the fluence rate need

to be obtained firstly. According to Beer Lambert's

law, the relationship between the fluence rate of a

ray and its propagation distance and the medium it

passes through is shown in the following equation

(Nabulsi et al., 2012):

()

I = I ,

ασ

−

(1)

In formula (1), I is the fluence rate. Ix is the

initial fluence rate. x is the ray length.

and

are

respectively the absorption coefficient and scattering

coefficient of a given medium. As we all know, at

the intersection of two media, light is both refracted

and emitted. The Fresnel equation describes the

relationship between the fluence rate of refracted

and reflected light and the transmittance and

reflectance (Gupta et al., 2019), which is shown

below:

𝑅



𝑛



−𝑛



𝑛



+𝑛



)



00 12

(1 )(1 cos ) ,

=(1)(1cos), ,

1, ,

ticrit

icrit

RR nn

RR R nn

θθθ

θθ



+− − ≤



+− − > ≤







(2)

1TR=−

where R and T are respectively reflectance and

transmittance. 𝜃



and 𝜃



are the incident angle and

refraction angle.𝜃



is the critical angle at which

total internal reflection occurs. The calculation

method is: 𝑠𝑖𝑛 𝜃











. It can be concluded that

when a given light interacts with the interface of two

media, the fluence rates of reflected light and

transmitted light are respectively the product of

incident light fluence rate and the reflectance and

transmittance. The equations are as follows (Gupta et

al., 2019):

reflected

transmitted

(3)

Therefore, when UV rays travel through different

media, formulas (1) ~ (3) can be used to calculate

the energy density and angle of the light source,

which can be used to estimate the fluence rate of the

UV lamp irradiation position. Based on this, a

fluence rate contour map is generated for each UV

LED module, and an air-calibrated model is used to

estimate the fluence rate incident on the surface of

each sensor placed in seawater.

4 APPLICATIONS OF UV

ANTI-BIOFOULING

TECHNOLOGY

At present, in the field of ocean observation,

company AML launched anti-biofouling products

based on the principle of UV light in 2014. It was

applied on the Folger Pinnacle scientific platform of

the Canadian Ocean Observation Network. The

biological attachment at the location of this scientific

platform is very serious. After the instrument has

been placed on the seabed for 12 months, the

unprotected sensor has been heavily attached,

including the probe, but the probe of the protected

sensor is clean, and the degree of contamination of

the remaining part is better than that of the

unprotected sensor. The actual situation is shown in

Figure 1. As shown, the left and middle sensors are

protected, and the right one is unprotected. The

detection probes and adjacent structures of left and

middle sensors are effectively protected, and only

light microorganisms are attached. The detection

probe and adjacent structures of unprotected sensor

have been covered a large number of medium and

high-level attachments. The comparison of test data

shows that the turbidity and conductivity data of

unprotected sensor gradually deviated from the true

value after 1 month, while the protected sensors

followed the true value well within 12 months (Wu et

al., 2017).

Research on Anti-biofouling Technology of Ocean Observation Instruments based on Ultraviolet Method

253

Figure 1: Test results of UV anti-biofouling products from AML.

Figure 2: Domestic CTD without anti-biofouling measures.

The National Ocean Technology Center designed

and developed a CTD anti-biofouling device based

on the principle of UV sterilization, and conducted a

comparative test on the coast of the Bohai Sea from

June to September in 2017 (Lan et al., 2019). The

test equipment includes a Domestic CTD (No.1702#)

without any anti-biofouling device, a Domestic CTD

(No.1610#) with a UV anti-biofouling device, and a

SBE37 CTD with a slow-release anti-biofouling

component (No.5500#). The working modes of the

three instruments are basically synchronized, and

they perform measurement and data storage tasks

independently without affecting each other. After

nearly 3 months of continuous testing and

comparison, it was found that the diversion tube in

No.1702# conductivity probe was almost completely

blocked by organisms such as oysters and polyps,

and normal measurement was no longer possible.

which is shown in figure 2. The No.1610#

conductivity probe is located in the UV radiation

range and there is no sign of marine attachments.

which is shown in figure 3. The inner wall of the

ceramic draft tube is clean and free of foreign matter,

which has a significant effect of preventing

biological attachment. There are a large number of

marine organisms attached to the exterior of

No.5500# conductivity cell protective cover, and the

slow-release anti-biofouling component of the

conductivity cell has been partially invalidated due

to the long deployment time. At the same time,

analysis of the collected data found that No.1610#

was significantly better than No.1702# in terms of

the stability and accuracy of salinity data

determination and the amount of instrument drift.

Oyster

Hydra

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Figure 3: Domestic CTD with UV anti-biofouling device.

5 CONCLUSIONS

In summary, the UV anti-biofouling technology and

method can effectively slow down and prevent the

biological adhesion on ocean observation sensors. At

the same time, compared with other methods, the

UV irradiation method can achieve more efficient

and targeted fixed-point protection effects on any

angle and area, any material and shape, and it can

achieve a good anti-biofouling attachment effect on

ocean observation sensors and their connecting

accessories and frame structures. This method can

effectively extend the maintenance cycle and service

life of ocean observation instruments, greatly

improve the deployment time of sensors and the

stability of monitoring data. This method can greatly

save human and material resources, and improve the

technical capabilities of ocean observation and

development.

ACKNOWLEDGMENTS

This study was supported by Shandong Academy of

Sciences Real Estate Research Collaborative

Innovation Fund (No.2019CXY1, 2018CXY-32,

2018CXY-37).

REFERENCES

Babin, M., Roesler, C. S., & Cullen, J. J. (2008). Real-time

Coastal Observing Systems for Marine Ecosystem

Dynamics and Harmful Algal Blooms: Theory,

Instrumentation and Modelling. Paris: Unesco

Publishing.

Bixler, G. D., & Bhushan, B. (2012). Biofouling: lessons

from nature. Philosophical Transactions A:

Mathematical, Physical and Engineering Sciences,

370(1967), 2381-2417.

Blanco, R., Shields, M. A., & Jamieson, A. J, (2013).

Macrofouling of deep-sea instrumentation after three

years at 3690 m depth in the charlie gibbs fracture

zone, mid-atlantic ridge, with emphasis on hydroids

(cnidaria: hydrozoa). Deep-Sea Research Part II,

98(B), 370-373.

Bueley, C. (2014). A new kind of antifoulant. Ocean News

& Technology, 12(2), 10-12.

Cao, J. Y., Fang, Z. G., Yang, Y. G., Li, L., & Zhao, Y.

(2020). The use requirements and research progress of

antifouling coatings for ships. Progress in Chinese

Materials, 3, 174-178.

Delauney, L., & Compere, C. (2008). An example:

biofouling protection for marine environmental

sensors by local chlorination. Springer Berlin

Heidelberg (Chapter 9).

Delauney, L., Compere, C., & Lehaitre, M. (2010).

Biofouling protection for marine environmental

sensors. Ocean Science, 6(2), 503-511.

Gupta, P., Pandey, A., Vairagi, K., & Mondal, S. K,

(2019). Solving fresnel equation for refractive index

using reflected optical power obtained from bessel

beam interferometry. Review of Scientific Instruments,

90(1), 015110.

Lei, H., Xiong, M. N., Xiao, J., Zheng, L. P., Zhu, Y. R.,

Li, X. X., Zhuang, Q. X., & Han, Z. W. (2017).

Fluorine-free low surface energy organic coating for

anti-stain applications. Progress in Organic Coatings,

103, 182-192.

Lan, H., Li, H. Z., Wang, L., Xu, L. P., Wu, S., & Zhang,

T. (2019). Design and test of a ctd anti-biofouling

device based on ultraviolet sterilization technology.

Advances in Marine Science, 37(2), 332- 341.

Lehaitre, M., Delauney, L., & Compère, C. (2008).

Biofouling and underwater measurements. Paris:

Unesco Publishing.

Research on Anti-biofouling Technology of Ocean Observation Instruments based on Ultraviolet Method

255

Lobe, H., & Das, A, (2010). The clearsignal™ biofouling

control system for oceanographic instrumentation. In

Proceeding of OCEANS 2010 MTS/IEEE SEATTLE,

20-23 Sept., Seattle, WA, USA.

National Marine Information Center. (2013). Marine

environmental observations must ensure the

representativeness, continuity and uniformity of

marine observation data-report on the verification of

tidal level benchmarks at Yantai Marine

Environmental Monitoring Center in 2012 [EB/OL].

http://www.cocc.net.cn/gzdt/201302/

Nabulsi, A. Al., Abdallah, O., Angermann, L., & Bolz, A.

(2012). New modification of Lambert-Beer's law using

simulation of light propagation in tissue for accurate

non-invasive hemoglobin measurements. In

Proceeding of International Conference on Applied

Mathematics and Pharmaceutical Sciences

(ICAMPS'2012), Jan. 7-8, 2012, Dubai.

Onuf, C. P. (2006). Biofouling and the continuous

monitoring of underwater light from a seagrass

perspective. Estuaries & Coasts, 29(3), 511-518.

Prakash, S., Ahila, N. K., Ramkumar, V. S., Ravindran, J.,

& Kannapiran, E. (2015). Antimicrofouling properties

of chosen marine plants: an eco-friendly approach to

restrain marine microfoulers. Biocatalysis and

Agricultural Biotechnology, 4(1), 114-121.

Shan, C., Wang, J. D., Chen, H. S., & Chen, D. R, (2011).

Progress of marine biofouling and antifouling

technologies. Chinese Science Bulletin, 56(7), 598–

612.

Wang, Y., Yan, L. I., & Gao, Y. B, (2016). Discussion on

development of operational ocean observing

instruments (OOOI) in China - comparative analysis

on differences, trends and countermeasures of OOOI

in ocean station between China and the United States.

Journal of Marine Sciences, 3, 69-75.

Wu, Z. W., Zhou, H. Y., & Lv, F. (2017). Bio-fouling

prevention techniques for ocean observing

instruments. The Ocean Engineering, 5, 110-117.

Yebra, D. M., Kiil, S., & Dam-Johansen, K, (2004).

Antifouling technology - past, present and future steps

towards efficient and environmentally friendly

antifouling coatings. Progress in Organic Coatings,

50(2), 75-104.

Yu, L., Zhao, H., & Li, C, (2006). Comparison study of

antifouling technology for ocean monitor instruments.

Paint & Coatings Industry, 36(10), 56-58.

WRE 2021 - The International Conference on Water Resource and Environment

256