ISO/DIS 23152

Ships and marine technology -- Ballast water management systems (BWMS) -- Computational physical modelling and calculations on scaling of UV reactors

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DRAFT INTERNATIONAL STANDARD
ISO/DIS 23152
ISO/TC 8 Secretariat: SAC
Voting begins on: Voting terminates on:
2020-05-22 2020-08-14
Ultraviolet ballast water management systems —
Computational physical modelling and calculations on
scaling of ultraviolet reactors
ICS: 47.020.99
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ISO/DIS 23152:2020(E)
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ISO/DIS 23152:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 General requirements ..................................................................................................................................................................................... 5

4.1 General principle ................................................................................................................................................................................... 5

4.2 Modelling best practices ................................................................................................................................................................. 6

5 Modelling and calculations ........................................................................................................................................................................ 6

5.1 Physical model ......... ................................................................................................................................................................................ 6

5.2 Turbulence model ................................................................................................................................................................................ 6

5.3 Radiation model ..................................................................................................................................................................................... 6

5.3.1 Discrete ordinance (DO) ........................................................................................................................................... . 6

5.3.2 Eulerian Monte Carlo (MC) ..................................................................................................................................... 7

5.4 Calculation of the UV dose ............................................................................................................................................................ 7

5.4.1 Lagrangian ............................................................................................................................................................................. 7

5.4.2 Eulerian .................................................................................................................................................................................... 8

5.5 Scaling procedure ................................................................................................................................................................................. 8

6 Model verification and validation ...................................................................................................................................................11

6.1 Functional verification ..................................................................................................................................................................11

6.2 Empirical data from testing ......................................................................................................................................................11

6.3 Validation against empirical data ........................................................................................................................................11

6.4 Justification for acceptance of scaled performance predictions ...............................................................12

6.5 Additional evaluations ...................................................................................................................................................................12

7 Scaling metrics.....................................................................................................................................................................................................12

Annex A (normative) RED Calculation .............................................................................................................................................................13

Bibliography .............................................................................................................................................................................................................................16

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ISO/DIS 23152:2020(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

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

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

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

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on the ISO list of patent declarations received (see www .iso .org/ patents).

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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/DIS 23152:2020(E)
Introduction

Ballast water management systems (BWMS) that use ultraviolet (UV) are intended to treat ballast

water to comply with applicable (IMO D-2 or U.S.) ballast water discharge standards. 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. Typically, a base system (with a low range TRC)

is empirically validated through land-based testing, while a unit with a TRC near or at the highest

rating is validated through shipboard testing. The remaining models that are not physically tested may

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

testing in accordance with the BWM 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

Sediments, 2004. The BWM Code specifies that a manufacturer of BWMS must provide technical

specifications for ny scaling of TRC according to the following criteria:

“4.14 It shall be demonstrated, by using mathematical modelling and/or calculations, that any up

or down scaling of the BWMS will not affect the functioning and effectiveness on board a ship of

the type and size for which the equipment will be certified. In doing so, the manufacturer of the

equipment shall take into account the relevant guidance developed by the Organization.

4.15 Scaling information shall allow the Administration to verify that any scaled model is at least

as robust as the land-based tested model. It is the responsibility of the Administration to verify

that the scaling used is appropriate for the operational design of the BWMS.

4.16 At a minimum, the shipboard test unit shall be of a capacity that allows for further validation

of the mathematical modelling and/or calculations for scaling, and preferably selected at the upper

limit of the rated capacity of the BWMS, unless otherwise approved by the Administration.”

Guidance on scaling is provided by the IMO through ‘Guidance 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, and experimental validation to land-based, shipboard or laboratory testing 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. Here, 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. Thus, scaling parameters should

also include those parameters should also include those parameters associated with SDLs.

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DRAFT INTERNATIONAL STANDARD ISO/DIS 23152:2020(E)
Ultraviolet ballast water management systems —
Computational physical modelling and calculations on
scaling of ultraviolet reactors
1 Scope

This document specifies the methodology to conduct computational modelling of ultraviolet (UV)

reactor designs for ballast water management systems that incorporate ultraviolet disinfection

technology (UV BWMS). The computational modelling shall be used to calculate UV Reduction

Equivalent Dose (RED) and compare calculated REDs of the scaled model to its base model. It should be

noted that the IMO requires validation of the computational model. Also, to be noted is that a complete

UV BWMS typically incorporates other treatment methodologies such as filters, and the impact of

changes to external subsystem performance on the overall BWMS is not considered in this document.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

International Maritime Organization (IMO) G8, Harmonized Implementation of the Guidelines for

Approval of Ballast Water Management Systems, BWM Code, Resolution MEPC.300(72)

International Maritime Organization (IMO) BWM, 2/Circ.33 Rev.1, Guidance on Scaling of Ballast Water

Management Systems, May 2018

National Water Research Institute, Ultraviolet Disinfection Guidelines for Drinking Water and Water

Reuse. Third Edition, August 2012

U.S. Environmental Protection Agency, Ultraviolet Disinfection Guidance Manual for The Final Long Term

2 Enhanced Surface Water Treatment Rule. Office of Water (4601), EPA 815-R-06-007, November 2006

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
ultraviolet light
UV light
light emitted with wavelength from 100 to 400 nm

Note 1 to entry: Light in the range of 200 to 280 nm is known as UVC and is considered germicidal. UV light in

the range of 260 to 270 nm is particularly effective in deactivating the DNA or RNA of bacteria, viruses and other

pathogens 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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ISO/DIS 23152:2020(E)
3.2
ultraviolet ballast water management system
UVBWMS

system which uses UV light (3.1) to process ballast water, generally in combination with filtration, to

remove, render harmless, or avoid the uptake or discharge of harmful aquatic organism and pathogens

within ballast water and sediments

Note 1 to entry: In addition to the UV reactor (3.4), 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 may impact UV transmission) and

organisms (that may be resistant to UV treatment).
3.3
base model

ultraviolet ballast water management system (UVBWMS) (3.2) model that has successfully completed

land-based testing as defined in the BWMS Code
3.4
UV reactor

vessel or chamber where exposure to UV light (3.1) 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.
3.5
base reactor
UV reactor (3.4) of the base model
3.6
scaled model

ultraviolet ballast water management system (UVBWMS) (3.2) that is based on the base model (3.3) but

has been modified to accommodate to a higher or lower TRC
3.7
scaled reactor
UV reactor of the scaled model (3.6)
3.8
spectral output
distribution of wavelength and relative intensity emitted by the UV lamp
3.9
Reynolds-Averaging Navier-Stokes (RANS) modelling

turbulence modelling conducted by solving the Reynolds-Averaging Navier-Stokes equations (3.35, 3.36)

at all length scales
3.10
direct numerical simulation
DNS

computational simulation used to numerically solve the Navier-Stokes equations at all length scales

3.11
detached eddy simulation
DES

computational simulation used to numerically solve the Navier-Stokes equations, using RANS (3.9)

modelling to solve small length scales
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ISO/DIS 23152:2020(E)
3.12
large eddy simulation
LES

computational simulation used to numerically solve the Navier-Stokes equations, excluding small

length scales
3.13
discrete ordinance (DO) modelling

development and use of mathematical models to numerically solve the radiative transfer equation by

discretizing the volume domain and directional vectors
3.14
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.
3.15
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
3.16
UV irradiance

UV light power per unit area incident to the direction of light propagation at all angles, including normal

3.17
UV exposure time
time elapsed between UV radiation initial and final exposures
3.18
UV intensity

measured flux passing through a unit area perpendicular to the direction of propagation

Note 1 to entry: UV intensity is used in this document to describe the magnitude of UV light measured by UV

sensors in a reactor and with a radiometer in bench-scale UV experiments.
3.19
UV dose
-2 -2

product of UV intensity and residence time, typically reported in units of mJ cm or J m

Note 1 to entry: The UV dose received by a waterborne microorganism in a reactor vessel; accounts for the effects

on UV intensity, residence time, UV absorbance of the water, UV absorbance of the quartz sleeves, reflection and

refraction of light from the reactor walls.
3.20
Residence time distribution
RTD

probability distribution of residence time that microorganisms stay in a flow-through UV reactor;

typically shown as a histogram
3.21
UV dose distribution

probability distribution of delivered UV doses that microorganisms receive in a flow-through UV

reactor; typically shown as a histogram
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ISO/DIS 23152:2020(E)
3.22
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
3.23
model validation

process used to substantiate that outputs of a model provide an accurate prediction of performance

Note 1 to entry: Typically, the model outputs are compared to empirical results of real world experiments at

different scales to determine the accuracy of the prediction matches design requirements.

3.24
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.

3.25
computational fluid dynamics
CFD

an analysis that simulates the fluid flow of ballast water through a UV reactor (3.4) to solve fluid

interactions with boundary conditions and characterize the flow properties and operating range

3.26
Reduction equivalent dose
RED

UV dose (3.19) derived by entering the log inactivation measured during full-scale reactor testing into

the UV dose-response (3.31) curve that was derived through collimated beam testing

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.
3.27
biodosimetry
measurement of biological response as a proxy for UV dose
3.28
emission spectrum
relative power emitted by a lamp at different wavelengths
3.29
germicidal range

range of UV wavelengths responsible for microbial inactivation in water (200 to 300 nm)

3.30
UV absorbance
transmitted radiant power through a material
3.31
UV dose-response
inactivation kinetics of a microbial species resulting from UV exposure
3.32
American Type Culture Collection
ATCC
repository of cell lines and cultured organisms used for research
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ISO/DIS 23152:2020(E)
3.33
MS2 Bacteriophage (ATCC 15597-B1)

non-pathogenic bacteriophage commonly used as a challenge organism in UV reactor validation testing

3.34
Tetraselmis sp. (ATCC 50244)

marine phytoflagellate commonly used as a test organism and a representative of organisms in the ≥10

and <50 µm size class
3.35
Navier-Stokes equations

equations derived from the conservation equations to describe the motion of viscous fluid substances

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.
3.36
Reynolds-Averaged Navier-Stokes
RANS

time-averaged equations of motion for fluid flow derived from Navier-Stokes equations (3.35); primarily

used to describe turbulent flows
3.37
turbulence modelling

development and use of mathematical models to predict the evolution of turbulence in fluid flows

3.38
radiative transfer equation

equation that characterizes a traveling beam of radiation, losses to energy absorption, gains beam

emission, and redistribution from scattering
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. Here the UV

reactor is considered independently of the complete BWMS, but may be affected by the inlet and outlet

conditions imposed by those other system components. Thus, those parameters defining the range of

inlet and outlet conditions must be defined. One 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 is

determined from the hydraulic conditions, the radiative conditions, and the particle residence time

within the reactor. These are modelled separately and the results are used to calculate to UV dose.

Alternately, the efficacy could be modelled using a Eulerian approach.

The key internal and external performance parameters required to assess the UV reactor efficacy are

identified as follows:
1. 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

organisms with a known spectral and dose response, or may be validated by using dyed microspheres (Shen et

al., 2009).

2. UV sensor irradiance and flow rate measured during validation testing and during operation on a

scaled system.
NOTE Consider flow rate measurement uncertainty in models.
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4.2 Modelling best practices

The simulation shall be conducted using a recognized flow and radiation solver, e.g., computational

fluid dynamics software. The simulation effort should use software that is appropriate for the type o

modelling being conducted. The basis for the type of software selected for the simulations should be

thoroughly explained. 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 (ho, et

al., 2011).
5 Modelling and calculations

The principle of scaling performed is to ensure that all scaled UV reactors will demonstrate that the

scaled reactors will produce a simulated reduction equivalent does that is the same or higher than the

base UV reactor, subjected to empirical tests. This is achieved by following the computational modelling

guidance described in the following subclauses.
5.1 Physical model

Computational models necessitate that the computational domain accurately represent the physical

characteristics of the systems they are intended to simulate. Three-dimensional (3-D) 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). A discussion and justification

should address any components excluded from the geometric model.

The process for mesh generation shall be defined, and 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.

5.2 Turbulence model

Hydraulic modelling simulates the flow characteristics in each UV reactor. It is expected that the

simulations will approximate turbulent flows as the normal hydraulic flow condition in a BWMS. Many

different turbulent models are used to simulate turbulent flows; therefore, turbulent flow fields should

use an appropriate numerical model. A common turbulence model used in UV reactor design is RANS

(Ho, et al., 2011). Other existing models include DNS, DES, or LES (note that this is not an all-inclusive

list). New models are continually being developed, therefore it is important that the appropriate

turbulence model is selected for the simulation. The turbulence model and basis for selection should be

described in the hydraulic modelling section.
5.3 Radiation model
5.3.1 Discrete ordinance (DO)

A well-established method of radiation modelling is discrete ordinance (DO). The UV radiation model

adopts the following equation (Ho, et al., 2011). The discrete ordinate (DO) radiation model solves the

radiative transfer equation over a finite number of solid angles, each associated with a vector direction

s , the global Cartesian system (x,y,z). The DO radiation model does not perform ray tracing. Instead,

the radiative transfer equation is transformed into as many transport equations as there are solid

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ISO/DIS 23152:2020(E)

angles with direction s . The solution method is the same as that used for the momentum and energy

equations.
 σT 
2 ' '
∇⋅ Ir(),,ss ++aIσ ()rs =+an Ir,ssΦ ,,sdΩ′ (1)
() () () ()
π 4π
where
is the nabla symbol which is a vector differential operator.
r = position vector, m
s = direction vector
= scattering direction vector
= path length, m
a -1
= absorption coefficient, m
= refractive index
σ = scattering coefficient, m
σ 2 4
= Stefan-Boltzmann constant (5.672e-8 W/m K )
 
= radiation intensity which depends on position ( r )and direction ( s ), W/m
...