ISO 23152:2021

INTERNATIONAL ISO
STANDARD 23152
First edition
2021-07
Ships and marine technology —
Ballast water management systems
(BWMS) — Computational physical
modelling and calculations on scaling
of UV reactors
Navires et technologie maritime — Systèmes de gestion de l'eau de
ballast (BWMS) — Modélisation physique computationnelle et calculs
concernant les réacteurs UV
Reference number
ISO 23152:2021(E)
©
ISO 2021

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ISO 23152:2021(E)

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© ISO 2021
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ISO 23152:2021(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General requirements . 6
4.1 General principle . 6
4.2 Modelling best practices . 6
5 Modelling and calculations . 6
5.1 General . 6
5.2 Geometric model . 7
5.3 Turbulence model . 7
5.4 Radiation model . 7
5.5 Calculation of the UV dose . 8
5.5.1 General. 8
5.5.2 Lagrangian particle tracking . 8
5.5.3 Eulerian reacting tracer . 8
5.6 Scaling procedure . 8
5.6.1 Main steps . 8
6 Scaling metrics.12
6.1 General principles .12
Annex A (informative) RED calculation .13
Annex B (normative) Verification of model using empirical data .16
Bibliography .18
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ISO 23152:2021(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 23152:2021(E)

Introduction
Ballast water management systems (BWMS) are intended to treat ships' ballast water discharges to
comply with applicable standards (Reference [14]). Disinfection using ultraviolet (UV) light is common
to many BWMS. A key specification for a given model of a BWMS is its treatment rated capacity (TRC),
which indicates the unit’s rated volumetric flow rate during treatment of ballast water. A base system
(with a low range TRC) is empirically validated through land-based testing, while a unit with a larger
TRC (ideally at the highest rating) is validated through shipboard testing. The remaining models that
are not empirically tested can be validated through scaling, using a verified numerical approach to
predict performance at untested TRCs.
Effective 13 October 2019, the type approval of BWMS (both UV and other technologies) requires
[11]
testing in accordance with the BWMS Code (MEPC 72/17/Add.1 Annex 5) , adopted as an amendment
to the IMO International Convention for the Control and Management of Ships’ Ballast Water and
[14]
Sediments, 2004 . The BWMS Code specifies that a manufacturer of BWMS must provide technical
specifications for any scaling of TRC. Guidance on scaling is provided by the IMO through its ‘Guidance
[12]
on Scaling of Ballast Water Management Systems’ (BWM.2/Circ. 33/Rev. 1) . One of the requirements
is for validation of the modelling and calculations through comparison of predicted performance to
land-based, shipboard, or laboratory test data as appropriate. In scaled models, parameters affecting
performance must demonstrate equivalence to the base model, identify system design limitations
(SDL) for each scaled model, and conduct shipboard testing of the most vulnerable model as determined
through scaling.
This document is focused on the modelling of UV reactors for scaling purposes, i.e. justifying the
applicability of a UV reactor design across a range of TRCs, through the use of validated numerical
models and calculations. Numerical models are used to solve equations governing physical
characteristics of a computational domain that represents a model of the physical object (i.e. the UV
reactor). This requires numerical representation of the geometry of this system, a discretization of the
representation into volumetric sub-elements (meshing), and solving for parameters for various scales.
Results are submitted to an Administration to justify the type approval of UV reactors having TRC
ratings that have not been validated through type approval testing.
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INTERNATIONAL STANDARD ISO 23152:2021(E)
Ships and marine technology — Ballast water management
systems (BWMS) — Computational physical modelling and
calculations on scaling of UV reactors
1 Scope
This document specifies the methodology to conduct computational modelling of ultraviolet (UV)
reactor designs for ballast water management systems (BWMS) that incorporate ultraviolet
disinfection technology (UVBWMS). The computational modelling is used to calculate the UV reduction
equivalent dose (RED) and to compare calculated REDs of the scaled reactor to its base reactor. REDs
are determined using organisms with a given dose response.
NOTE The IMO requires validation of the computational model.
The simulation of a physical UV reactor using a computational model requires that the model be
validated (i.e. it performs as intended and reflects the correct physical constraints) and verified (i.e.
produces outputs consistent with empirical data). A model developed according to this document
is intended to validate the performance of simulated but untested, scaled UV reactors, where the
simulation has been verified with test data from base model UV reactors within the product line. As a
complete UV BWMS typically incorporates other treatment methodologies such as filters, the impact of
changes to external subsystem performance on the overall BWMS is not considered in this document.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
American Type Culture Collection
ATCC
repository of cell lines and cultured organisms used for research
3.2
base model
ultraviolet ballast water management system (UVBWMS) (3.30) model that has successfully completed
land-based testing as defined in the BWMS Code
Note 1 to entry: Typically, a base model is with low range TRC (3.28).
3.3
base reactor
UV reactor (3.41) of the base model (3.2)
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3.4
biodosimetry
measurement of biological response as a proxy for UV dose (3.34)
3.5
computational fluid dynamics
CFD
numerical methods and algorithms to solve and analyse problems that involve fluid flows
3.6
detached eddy simulation
DES
computational simulation used to numerically solve the Navier-Stokes equations (3.17), using RANS
modelling (3.23) to solve small length scales
3.7
discrete ordinates modelling
DO modelling
development and use of mathematical models to numerically solve the radiative transfer equation (3.18)
by discretizing the volume domain and directional vectors
3.8
direct numerical simulation
DNS
computational simulation used to numerically solve the Navier-Stokes equations (3.17) at all length
scales
3.9
emission spectrum
relative power emitted by a lamp at different wavelengths
3.10
germicidal range
range of UV wavelengths responsible for microbial inactivation in water (200 nm to 300 nm)
3.11
large eddy simulation
LES
computational simulation used to numerically solve the Navier-Stokes equations (3.17), excluding small
length scales
3.12
low pressure UV lamp
LP
discharge lamp of the mercury vapour type, without a coating of phosphors, in which the partial
pressure of the vapour does not exceed 100 Pa during operation and which mainly produces ultraviolet
radiation of 253,7 nm
3.13
medium pressure UV lamp
MP
medium pressure mercury arc lamp having a polychromatic emission spectrum (3.9) between 200 nm
and 400 nm
3.14
model validation
comparison between the output of the calibrated model and the measured data, independent of the
data set used for calibration
Note 1 to entry: Typically, the model outputs are compared to empirical results of real world experiments at
different scales to determine whether the accuracy of the prediction matches design requirements.
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3.15
model verification
process of confirming that a model is correctly implemented with regard to specifications and
assumptions of the design
Note 1 to entry: Typically, verification ensures that analysis logic follows the model design, checks for reasonable
outputs over the acceptable range of model parameters, and that the model can be run without errors.
3.16
MS2 phage
ATCC 15597-B1
non-pathogenic bacteriophage commonly used as a challenge organism in UV reactor (3.41) biodosimetry
(3.4)
3.17
Navier-Stokes equations
equations derived from the conservation equations to describe the motion of viscous fluid substances
3.18
radiative transfer equation
mathematical relation describing the variation along a path of the spectral radiance in an absorbing,
emitting and scattering medium.
Note 1 to entry: The solution of this equation depends on the radiative properties of the medium: spectral
extinction coefficient, spectral albedo and spectral phase function, and on the thermal and optical boundary
conditions.
3.19
reduction equivalent dose
RED
UV dose (3.34) derived by entering the log reduction after UV treatment using a collimated beam with
the same UV spectrum output as in the reactor testing into the UV dose-response (3.36) curve that was
derived through collimated beam testing, or the UV dose computed by combining the dose distribution
computed in CFD (3.5) modelling with the UV sensitivity (dose response) of the organism
Note 1 to entry: RED values are always specific to the challenge microorganism used during experimental testing
and the validation test conditions for full-scale reactor testing.
3.20
residence time
time period that a particle resides within the boundaries of the UV reactor (3.41) during treatment,
which varies with flow rate and path
3.21
residence time distribution
RTD
probability distribution of residence time (3.20) that microorganisms stay in a flow-through UV reactor
(3.41), typically shown as a histogram
3.22
Reynolds-averaged Navier-Stokes equations
RANS equations
time-averaged equations of motion for fluid flow derived from Navier-Stokes equations (3.17), primarily
used to describe turbulent flows
3.23
Reynolds-averaged Navier-Stokes modelling
RANS modelling
turbulence modelling (3.29) conducted by solving the Reynolds-averaged Navier-Stokes equations (3.22)
at all length scales
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3.24
scaled model
ultraviolet ballast water management system (UVBWMS) (3.30) model that is based on the base model
(3.2) but has been modified to accommodate to a higher or lower treatment rated capacity (TRC) (3.28)
3.25
scaled reactor
UV reactor (3.41) of the scaled model (3.24)
3.26
spectral output
distribution of wavelength and relative intensity emitted by a UV lamp
3.27
Tetraselmis sp.
ATCC 50244
marine phytoflagellate commonly used as a test organism and a representative of organisms in the
≥10 µm and <50 µm size class
3.28
treatment rated capacity
TRC
maximum continuous capacity expressed in cubic meters per hour for which the BWMS is type-
approved
Note 1 to entry: It states the amount of ballast water that can be treated per unit time by the BWMS to meet the
standard in regulation D-2 of the BWMS Convention.
Note 2 to entry: The TRC is measured as the inlet flow rate of the BWMS.
Note 3 to entry: TRC values pertain to stated intake water quality conditions.
3.29
turbulence modelling
development and use of mathematical models to predict the evolution of turbulence in fluid flows
3.30
ultraviolet ballast water management system
UVBWMS
system that uses UV light (3.31) to process ballast water, generally in combination with filtration, to
remove, render harmless, or avoid the uptake or discharge of harmful aquatic organisms and pathogens
within ballast water and sediments
Note 1 to entry: In addition to the UV reactor (3.41), the UVBWMS includes ballast water treatment equipment, all
associated control equipment, monitoring equipment, piping, and sampling facilities.
Note 2 to entry: Most UVBWMS include a filter to remove larger particles (that can impact UV transmission) and
organisms (that can be resistant to UV treatment).
3.31
ultraviolet light
UV light
light emitted with a wavelength ranging from 100 nm to 400 nm
Note 1 to entry: Light in the range of 200 nm to 280 nm is known as UVC and has the capacity to be germicidal. UV
light in the range of 260 nm to 270 nm can be particularly effective in deactivating the DNA or RNA of bacteria,
viruses and other pathogens at appropriate requisite doses and thus destroys their ability to multiply and cause
disease.
Note 2 to entry: Specifically, UVC light causes damage to the nucleic acid of microorganisms by forming covalent
bonds between certain adjacent bases in the DNA or RNA. The formation of such bonds prevents the DNA or RNA
from being unzipped for replication, and the organism is unable to reproduce.
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3.32
user-defined function
UDF
function provided by the user of a program or environment, in a context where the usual assumption is
that functions are built into the program or environment
3.33
UV absorbance
radiant power absorbed within a material
3.34
UV dose
-2 -2
product of UV intensity (3.38) and residence time (3.20), typically reported in units of mJ cm or J m
3.35
UV dose distribution
probability distribution of delivered UV doses (3.34) that microorganisms receive in a flow-through UV
reactor (3.41), typically shown as a histogram
3.36
UV dose-response
inactivation kinetics of a microbial species resulting from UV exposure
3.37
UV exposure time
time elapsed between UV radiation initial and final exposures
3.38
UV intensity
intensity of UV radiation at a specific geometric location with respect to the UV source, measured in
-2
mW cm
Note 1 to entry: UV Intensity measures the “amount” of UV energy actually penetrating through the water being
treated.
3.39
UV irradiance
power passing through a unit area perpendicular to the direction of propagation
2
Note 1 to entry: UV irradiance is typically reported in watt per square metre (W/m ). It is also usually reported
2 2
in mW/cm or µW/cm .
Note 2 to entry: Irradiance varies with UV lamp output power, efficiency and focus of its reflector system, and
distance to the surface.
3.40
UV light emitting diode
UV LED
semiconductor source, in this context providing narrow wavelength emission at a given wavelength in
the UV spectrum
3.41
UV reactor
vessel or chamber where exposure to UV light (3.31) takes place, generally consisting of UV lamps,
quartz sleeves, UV sensors, quartz sleeve cleaning systems, and baffles or other hydraulic controls
Note 1 to entry: The UV reactor also includes additional hardware for monitoring UV dose delivery; typically
comprising (but not limited to) UV intensity sensors.
Note 2 to entry: The wavelengths emitted by a UV lamp are dependent on the lamp type (e.g. LED, low pressure
[LP], medium pressure [MP]).
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3.42
UV transmittance
UVT
fraction of incident light transmitted through a material (e.g. water sample or quartz), measured at
specific wavelengths (e.g. 254 nm) and path length (e.g. 1 cm)
4 General requirements
4.1 General principle
Numerical modelling and calculations are used to demonstrate that any parameters of the scaled UV
reactors that affect reactor performance are equivalent to those of the base reactor. The UV reactor is
considered independently of the complete BWMS, but can be affected by the inlet and outlet conditions
imposed by those other system components. Thus, those parameters describing the range of inlet and
outlet conditions shall be defined.
In the Lagrangian approach of modelling, the efficacy of the UV reactor is determined by the UV dose
received by particles traversing the reactor. The UV dose received by each particle is determined
from the hydraulic conditions, the radiative conditions, and individual particle trajectories through
the reactor. Multiple particles (usually in the thousands or tens of thousands), each with a unique
trajectory, then define the dose distribution. The dose distribution is combined with the UV sensitivity
(dose response) of an organism, usually in a separate model, to determine the RED.
In the Eulerian approach, the concentration of viable organisms is determined as the organisms pass
through the reactor by calculating the inactivation of organisms in each mesh element. This is done by
combining the irradiance and residence time to get the dose applied in that mesh element with the UV
sensitivity (dose response) of the organism. Multiple organisms of different sensitivity can be tracked
simultaneously through the reactor. The number of viable organisms exiting the reactor divided by the
number entering the reactor determines the overall inactivation of the organism and hence RED.
The key internal and external performance parameters required to assess the UV reactor efficacy are
identified as follows:
a) UV dose distribution as a function of UV transmittance and flow rate;
NOTE UV dose distribution can be validated with testing of the base UV reactor using standard test
[7]
organisms with a known spectral and dose response, or can be validated by using dyed microspheres .
b) UV intensity as measured with a UV sensor, and flow rate measured during validation testing and
during operation on a scaled system.
4.2 Modelling best practices
The choice of software and methodology for the modelling effort shall be identified and chosen
for capabilities in the flow and radiation domains. Typically, the approach includes computational
fluid dynamics (CFD). The modelling approach shall be based on Clause 5, and additional modelling
parameters are based on computational modelling best practices as described in the literature (see
References [4], [15]).
5 Modelling and calculations
5.1 General
The principle of computational physical modelling and calculations on scaling of ultraviolet reactors is
to ensure that all scaled UV reactors demonstrate that the scaled reactors produce a simulated RED that
is equal or higher than the base UV reactor. Here the base reactor has been subjected to empirical [dose
response] tests to validate the model. The same model base reactor shall also have been used in land-
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based type approval testing. The numerical model shall be calibrated to experimental data to validate
the modelling method. If calibration shows the model does not represent experimental results, then
the model shall be updated to reduce fit error with the experimental data. Additionally, a sensitivity
analysis shall be supported with conclusions on numerical model accuracy and the impact of varying
parameters between the models.
5.2 Geometric model
Computational models necessitate that the computational domain accurately represent the geometric
characteristics of the systems they are intended to simulate. Three-dimensional (3D) computer
generated geometric models of all UV reactors should include the fundamental components and
features in contact with water that are included in the computational domain (e.g. lamps, baffles,
cleaning wipers, UV sensors, support structures). This should also include dimensionally accurate
representation of all geometries (e.g. number and position of lamps). Assumptions and exclusions
used to create the 3D model such as wall smoothness, baffles, rivets, welds, wiper mechanisms, etc.
shall ensure the computational models mimic the physical models. A discussion and justification shall
address any components excluded from the geometric model if these components affect the reactor's
treated efficacy to ballast water.
The process for mesh generation shall be defined, and shall provide a description of mesh element
geometry and methodology to ensure the meshing provides sufficient density and resolution to
capture all relevant flow features. Particular importance should be placed on the mesh adjacent to wall
boundaries to resolve the boundary layer flow, and in areas around the UV lamps where more resolution
in the mesh may be needed. Generally, an iterative mesh convergence study is used to demonstrate that
further refinement in the meshing provides no additional resolution of the hydraulic condition.
5.3 Turbulence model
Turbulence modelling is used to simulate flow characteristics in the UV reactor (see Reference [1]).
The behaviour of fluid in a flow field is described by the Navier-Stokes equations (NSE). While direct
numerical simulation (DNS) can be used to numerically solve the NSE, this can be computationally
expensive due to the calculation of the complex turbulence component. Instead, Reynolds-averaged
Navier-Stokes (RANS) models are employed that simplify turbulence using time-averaging and save
on computational resources. Common RANS models include Spalart-Allmaras, κ-ε, and κ-ω. Other
turbulence models numerically solve the NSE at larger scales and use RANS models to simulate
smaller scales (detached eddy simulation [DES]) or exclude the smaller scales completely (large eddy
simulation [LES]). This is not an all-inclusive list of all turbulence models. New models are continually
being developed, therefore it is important that the appropriate turbulence model be selected for the
simulation. The turbulence model and basis for selection shall be described and justified in the hydraulic
modelling section.
5.4 Radiation model
Radiative transfer modelling is used to simulate light fields in the UV reactor. The radiative transfer
equation (RTE) characterizes a traveling beam of radiation, losses to energy absorption, gains from
beam emission, and redistribution from scattering. The RTE can be numerically solved using the
discrete ordinates (DO) modelling method by discretizing the volume domain and directional vectors.
The Monte Carlo (MC) radiation model is a Eulerian method that simulates the paths of individual
particles of radiation, or photons, from the source by randomly sampling from the probabilistic
distribution functions that govern their interaction lengths, scattering angles, emi
...