SIST-TP CEN/TR 17614:2021
(Main)Standard method for assessing and improving the energy efficiency of waste water treatment plants
Standard method for assessing and improving the energy efficiency of waste water treatment plants
This document defines a methodology for determining and assessing the energy efficiency of Waste Water Treatment Plants (WWTP). The methodology aims at describing, in a systematic way, the various steps required to establish the Water Treatment Energy Index (WTEI) of a particular WWTP.
The methodology includes the classification of WWTPs in different types, identification of different stages of treatment, identification of key performance indicators (KPIs), overview of existing energy monitoring standards and the detailed description of the methodology, including a step by step guideline of how to apply and implement it.
The methodology is divided in 2 sub-methods that should be selected and followed according to the following goals:
- The Rapid Audit (RA) method allows for a quick estimation of the water treatment energy index (WTEI) based on existing information such as historical data pertaining to energy use records along with influent and effluent quality values. The aim of this methodology is to provide a WWTP energy benchmark, a rapid tool to identify energy efficiencies and inefficiencies so further actions can be planned, as well as to evaluate the impact of WWTP retrofitting.
The Rapid Audit methodology is detailed step by step in Clause 3 of this TR and can be used as a standalone document.
- The Decision Support (DS) method requires intensive monitoring across a WWTP of energy usage and water quality parameters that provides an accurate and detailed calculation of WTEI for each stage as well as its overall value for the plant. The goal of this assessment is to serve as a diagnosis of the functions/equipment in a plant that may lead to poor energy efficiency performance.
The Decision Support methodology is detailed step by step in Clause 4 of this TR and can be used as a standalone document.
Standardmethode zur Bewertung und Verbesserung der Energieeffizienz von Kläranlagen
Méthode standard d’évaluation et d’amélioration de l’efficacité énergétique des stations d'épuration
Standardna metoda za ocenjevanje in izboljšanje energijske učinkovitosti čistilnih naprav za odpadno vodo
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CEN/TR 17614:2021
01-marec-2021
Standardna metoda za ocenjevanje in izboljšanje energijske učinkovitosti čistilnih
naprav za odpadno vodo
Standard method for assessing and improving the energy efficiency of waste water
treatment plants
Standardmethode zur Bewertung und Verbesserung der Energieeffizienz von
Kläranlagen
Méthode standard d’évaluation et d’amélioration de l’efficacité énergétique des stations
d'épuration
Ta slovenski standard je istoveten z: CEN/TR 17614:2021
ICS:
13.060.30 Odpadna voda Sewage water
27.015 Energijska učinkovitost. Energy efficiency. Energy
Ohranjanje energije na conservation in general
splošno
SIST-TP CEN/TR 17614:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TP CEN/TR 17614:2021
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SIST-TP CEN/TR 17614:2021
CEN/TR 17614
TECHNICAL REPORT
RAPPORT TECHNIQUE
January 2021
TECHNISCHER BERICHT
ICS 13.060.30; 27.015
English Version
Standard method for assessing and improving the energy
efficiency of waste water treatment plants
Méthode standard d'évaluation et d'amélioration de Standardmethode zur Bewertung und Verbesserung
l'efficacité énergétique des stations d'épuration der Energieeffizienz von Kläranlagen
This Technical Report was approved by CEN on 4 January 2021. It has been drawn up by the Technical Committee CEN/TC 165.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 17614:2021 E
worldwide for CEN national Members.
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CEN/TR 17614:2021 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative References . 5
3 Terms and definitions . 5
4 General considerations of methodologies . 5
5 Methodology for Rapid Audit (RA). 6
5.1 General . 6
5.2 Identification of the WWTP typology . 6
5.3 Energy consumption data collection . 7
5.3.1 Energy consumption data . 7
5.3.2 Energy producing WWTPs and sludge imports . 9
5.3.3 Chemical energy consumption . 9
5.3.4 Total energy consumption estimation . 10
5.4 Identification of the WWTP boundaries and calculation of Key Performance
Indicators (KPIs) . 11
5.5 Calculation of the Water Treatment Energy INDEX (WTEI) as a single indicator. 15
6 Methodology for Decision Support (DS) . 18
6.1 General . 18
6.2 Identification of the WWTP typology . 18
6.3 WWTP boundaries . 19
6.4 Request required approvals and keep communication (operators, site managers,
process engineers, budget holders and other possible end users) and health safety
considerations . 22
6.5 Create database describing all equipment on site . 22
6.6 Select equipment for online monitoring and install online monitors according to
manual . 24
6.7 Energy consumption data collection . 24
6.7.1 Energy consumption data . 24
6.7.2 Chemical energy consumption . 26
6.7.3 Energy producing WWTPs and sludge imports . 27
6.7.4 Gross and net energy consumption at stage estimation . 28
6.8 Key Performance Indicators (KPIs) . 28
6.9 Monitor site for KPIs (how often to monitor, methods used for monitoring). 40
6.10 Water Treatment Energy Index (WTEI) as a composite indicator . 40
Annex A (informative) Rapid Audit methodology applied to a case study . 44
Annex B (informative) Decision Support methodology applied to a case study . 48
Annex C (informative) Overview of training of auditors . 58
Bibliography . 62
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CEN/TR 17614:2021 (E)
European foreword
This document (CEN/TR 17614:2021) has been prepared by Technical Committee CEN/TC 165 “Waste
water engineering”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
3
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CEN/TR 17614:2021 (E)
Introduction
Wastewater Treatment Plants (WWTPs) are one of the most expensive public industries in terms of
energy requirements, accounting for more than 1 % of consumption of electricity in Europe. Thus, there
is a need to stop the current unsustainable energy consumption of the sector in line with the objectives
of Europe 2020 and the EU Sustainable Development Strategy (SDS).
The energy consumption must be related with the performance of a WWTP and parameters such as
effluent flow, nutrient removal, biochemical oxygen demand (BOD), chemical oxygen demand (COD),
suspended solids, orthophosphate (PO ), ammonia (NH ) and nitrate (NO ) need to be estimated or
4 4 3
determined at various stages of the WWTP for an effective estimation and assessment of energy
efficiency in WWTP.
This document presents a methodology to guide water experts and auditors on how to evaluate the
energy performance of a WWTP reaching a final energy diagnosis and the calculation of a Water
Treatment Energy Index (WTEI).
The methodology intends to be a very simple and easy to follow document that can be effortlessly
understood and put in practice by operators, site managers, process engineers as well as energy
auditors. It includes: planning the estimation of energy consumption at a WWTP; requesting approvals
and keeping communication (operators, site managers, process engineers, budget holders and other
possible end users) and health safety considerations; compilation of a database describing all
equipment on site; selection of equipment for online monitoring and install online monitors according
to manual; monitoring site for KPIs; training of people on the online tool and audits; audit, data
collection and validation; calculation of the WTEI and classification of WWTPs. Furthermore the
application of the methodology was completed to 3 case studies as practical examples.
The methodology included in this document considers two approaches for the determination of energy
consumption in WWTPs, namely Rapid Audit and Decision Support.
Rapid Audit is aimed at a rapid estimation of the WTEI of a particular WWTP using existing information.
This method uses existing information including historical data on energy consumption as well as the
wastewater influent and effluent. A trained auditor can calculate the WTEI and the obtained values can
be compared against a large database.
Decision Support is aimed at establishing the WTEI of a particular WWTP and providing information
that can be used as decision support of an energy efficiency diagnosis. It requires online energy data
obtained over extended periods of time as well as intensive wastewater sampling campaigns to
establish KPIs for each individual treatment stage. The combined information from the online meters
and wastewater sampling can then be used to calculate the WTEI using carefully selected statistical
tools and energy performance indicators. The methodology described includes guidelines on how to
select equipment/processes to place energy monitors, how to monitor the WWTP and how data should
be processed and reported. The Decision Support methodology can be used to provide an WWTP energy
benchmark but also understand impact of seasonal variations, storm events, changes in maintenance
routines, implementation of new equipment (e.g.: screens, pumps, blowers, etc.) as well as retrofitting
of existing processes as well as implementation of new processes. This methodology can also be used as
a tool to identify energy efficiencies and inefficiencies so further actions can be planed and the impact
can be measured and verified online. The Decision Support methodology can also be used as training
tool as well as help water utilities to clearly communicate to operators, engineers and the general public
how changes in operation and behaviour that can lead to energy efficiency and reduce energy
consumption.
This document is based on the outcomes of the ENERWATER project, a coordination and support action
funded by European Commission under Programme H2020 (www.enerwater.eu).
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1 Scope
This document defines a methodology for determining and assessing the energy efficiency of Waste
Water Treatment Plants (WWTP). The methodology aims at describing, in a systematic way, the various
steps required to establish the Water Treatment Energy Index (WTEI) of a particular WWTP.
The methodology includes the classification of WWTPs in different types, identification of different
stages of treatment, identification of key performance indicators (KPIs), overview of existing energy
monitoring standards and the detailed description of the methodology, including a step by step
guideline of how to apply and implement it.
The methodology is divided in 2 sub-methods that should be selected and followed according to the
following goals:
— The Rapid Audit (RA) method allows for a quick estimation of the water treatment energy index
(WTEI) based on existing information such as historical data pertaining to energy use records along
with influent and effluent quality values. The aim of this methodology is to provide a WWTP energy
benchmark, a rapid tool to identify energy efficiencies and inefficiencies so further actions can be
planned, as well as to evaluate the impact of WWTP retrofitting.
The Rapid Audit methodology is detailed step by step in Clause 4 of this TR and can be used as a
standalone document. The application of the Rapid Audit methodology to one real WWTP is shown
in Annex A.
— The Decision Support (DS) method requires intensive monitoring across a WWTP of energy usage
and water quality parameters that provides an accurate and detailed calculation of WTEI for each
stage as well as its overall value for the plant. The goal of this assessment is to serve as a diagnosis
of the functions/equipment in a plant that may lead to poor energy efficiency performance.
The Decision Support methodology is detailed step by step in Clause 5 of this TR and can be used as
a standalone document. The application of the Decision Support methodology to one real WWTP is
shown in Annex B.
2 Normative References
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 General considerations of methodologies
Both Rapid Audit (RA) and Decision Support (DS) methodologies are structured in a similar way but
with a different level of detail. To sum up the procedures, first the type of WWTP according to its
functions is established; then, energy consumption and other measurements (flowrate, pollutant
concentrations, etc.) are combined to form relevant key performance indicators (KPIs). Guidelines for
the estimation of analytical results, in case actual measurements are not available, are also given.
Finally, the KPIs are normalized and combined according suitable weights in order to obtain the Water
Treatment Energy Index (WTEI).
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In facilities where (at least part of) the energy is produced on site, e.g. electricity from anaerobic
digestion of sludge, two different values of WWTP total energy consumption may be identified and have
been labelled here as Gross and Net energy consumption:
— A plant’s gross energy consumption is defined as the total amount of energy that is consumed by
the plant regardless of its source.
— A plant’s net energy consumption is defined as the amount of energy that is consumed by the
1
plant excluded the amount of renewable energy created on the site.
5 Methodology for Rapid Audit (RA)
5.1 General
This methodology is aimed at a establishing the Water Treatment Energy Index (WTEI) of a particular
WWTP, using existing information on site including historical data on energy consumption, as well as
influent and effluent quality to calculate the key performance indicators (KPIs).
5.2 Identification of the WWTP typology
Wastewater treatment plants can have various functions depending on the type of pollutants removed.
For instance, removal of solids and dissolved organic matter might be targeted whilst other WWTP
might target a wider range of pollutants, i.e. from solids all the way to pathogens and persistent
pollutants present in micrograms per litre. The need to remove different types of pollutants is linked
with the regulatory framework in Europe and the type/water quality of the receiving water body. There
are some key European Directives linked wastewater effluent discharges into waterways:
— Urban Waste Water Treatment Directive (UWWTD) (91/271/EEC);
— Nitrates Directive (ND) (91/676/EEC);
— Water Framework Directive (WFD) (2000/60/EC);
— Bathing Water Treatment Directive (2006/7/EC) replacing (76/160/EEC);
— Shellfish Directive (79/923/EEC);
— Freshwater Fish Directive (78/659/EEC).
These European Directives aim to protect the receiving waterways depending on its chemical quality,
ecological status, potential for eutrophication, or other activities such as bathing, fishing or shellfish
production etc. Sensitive areas are designated after surveys establishing that the receiving water body
is adversely impacted by WTTPs that discharge effluents just treated for solids (TSS) and dissolved
organic matter (BOD and COD) (usually designed as secondary treatment). Designated as sensitive
areas are:
1
A similar concept was approved and implemented by the European Union and other agreeing countries for the
residential sector, i.e. the net-zero energy building (NZEB): https://ec.europa.eu/energy/en/topics/energy-
efficiency/buildings/nearly-zero-energy-buildings.
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(i) eutrophic or could become so in the near future without tertiary protection;
(ii) abstraction sources that have or could have high nitrate levels without tertiary protection;
(iii) other directives’ water in need of or already receiving tertiary protection.
Overall, sensitive areas are in need of protection through the provision of tertiary treatment at the
WWTPs whose discharges adversely impact the waters. There are various types of sensitive areas and
their type will influence the form of tertiary treatment provided: for example bathing and shellfish
water sensitive areas will be protected by UV treatment, and waters adversely affected by nutrients in
discharges will receive phosphorus and/or nitrogen reduction.
This complexity of the WWTPs needs to be addressed in the methodology. Following of the work
completed by others on the life cycle analysis of WWTPs the following typologies are recommended:
Type 1: Discharge to non-sensitive - this includes WWTPs focused on the removal TSS, BOD, COD and
NH .
4
Type 2: Discharge to sensitive areas - this includes WWTPs focused on removing TSS, BOD, COD, NH ,
4
NO , total phosphorus (TP).
3
Type 3: Discharge for re-use (pathogens) - this includes WWTPs focused on removing TSS, BOD, COD,
NH , NO , TP and pathogens removal (e.g. coliforms log reduction).
4 3
5.3 Energy consumption data collection
5.3.1 Energy consumption data
Historical data on the energy consumed at the WWTP needs to be available, including electricity and
other fuels such as diesel, natural gas etc. Electricity consumption on the WWTPs can be obtained by
consulting electricity bills, meter readings or existing online meters. This information needs to be
collected to provide an estimation of kWh used at the entire WWTP per unit of time (i.e.: the
recommended period of time is 3 years of data to account for seasonal variability). If other fuels are
used, for example to drive generators to produce electricity, the fuel consumption (i.e.: in litres or tons),
these also need to be quantified and converted to kWh per unit of time using the conversion factors in
Table 1 to calculate the total energy consumption (Formula (1)).
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Table 1 — Energy carrier classification, conversion factor and equations to estimate specific
power consumption
Energy carrier Conversion factors Abbr Equations to estimate specific power
. consumption
Electric energy in
kWh
1
V1 Ep_V1 = P × T × U.F
( )
kWh kWh
Ep_V2 = equipment usage/year x usage time
(h) × 11,87 × diesel used [kg/h] × β
kWh
11, 87 g
Diesel in kg V2
( )
kg
where, β is efficiency of electrical generator (0,35)
g
Case I) Ep_V3 = Natural gas used in combined heat
and power engine
kWh_el = (Ncm/y) × 9,94 × β_el
†
Natural gas in Ncm kWh_th = (Ncm/y) × 9,94 × (1- β_el)) × β_th
(normal cubic
Case II) Ep_V3 = Natural gas used in a trigeneration
meters)
kWh system to provide power, heating and cooling
9, 94
V3
( )
Ncm
Normal conditions
kWh_el = (Ncm/y) × 9,94 × β_el
(0 °C, atmospheric
†
kWh_th = (Ncm/y) × 9,94 × (1- β_el)) × β_th
pressure)
† ‡
kWh_c = (Ncm/y) × 9,94 × (1- β_el)) × β_th × β_c
Case III) Ep_V3 = Natural gas used for heating only
†
kWh_th = Scm/y × 9,94 × β_th
Case I) Ep_V4 = Biogas used in combined heat and
power engine
kWh_el = Scm/y × × β_el *
9, 94 NGC
†
kWh_th = Scm/y × 9, 94 NGC × (1- β_el)) × β_th
Biogas in Ncm
kWh Case II) Ep_V4 = Biogas used in a trigeneration
9, 94 × NGC
(normal cubic
)
(
Ncm
system to provide power, heating and cooling
meters)
V4
where NGC is the natural
kWh_el = (Ncm/y) × 9, 94 NGC × β_el *
Normal conditions
gas content in the biogas
†
(0 °C, atmospheric
kWh_th = (Ncm/y) × 9, 94 NGC × (1- β_el)) × β_th
(vol/vol)
pressure)
kWh_c = (Ncm/y) × 9, 94 NGC × (1-
† ‡
β_el)) × β_th × β_c
Case III) Ep_V4 = Biogas used for heating only
†
kWh_th = Scm/y × 9, 94 NGC × β_th
* typical efficiency taken as 0,40 for electricity generation
† typical efficiency taken as 0,85 for heat production and recovery
‡ typical efficiency taken as 0,70 for an adsorber
NOTE All conversion factors have been taken from UNI/TS 11300-2:2014.
E1 : Energy consumed at WWTP = electric energy according to historical data
(1)
kWh/ year ++Ep___V1 Ep V2 + Ep V3 + Ep_V4
( )
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5.3.2 Energy producing WWTPs and sludge imports
WWTPs can have a range of technologies that produce energy/electricity on site. Technologies such as
anaerobic digestion (of sludge, imported sludge, other wastes, etc.), hydraulic-power, wind turbines,
solar panels, fuel-cells, etc., are currently used. The generation of electricity on the WWTP can offset the
energy requirements to produce a high effluent quality. The energy produced on site that is used on site
can be estimated taking in consideration Formula (2). The recommended period of time is 3 years of
data to account for seasonal variability.
L
(2)
E2 : Energy produced at WWTP = i
∑
iA=
Where, A to L are the types of energy produced in the WWTP, A – energy from biogas (kWh/year); B -
hydraulic-power (kWh/year); C – wind turbines (kWh/year); D – solar panels (kWh/year); E - fuel-cells
(kWh/year); F-L – other (kWh/year).
Many WWTPs with anaerobic digesters act as sludge treatment centres receiving sludge from nearby
sites. The imported sludge is often mixed with the sludge produced at the WWTP for further treatment
such as dewatering, anaerobic digestion etc. potentially accounting for both energy consumption and
production on the WWTP. Sludge imports can be very significant in some WWTPs (up to twofold the
sludge produced on site). As such, the volume of sludge imports, respective total suspended solids as
well as an estimation of the energy consumed and produced for its treatment needs to be taken into
consideration (Formula (3)).
E3 : Energy produced and consumed by sludge imports =
Energy produced by sludge imports kWh/ year - Energy consumed by (3)
( )
sludge imports kWh/ year
( )
5.3.3 Chemical energy consumption
Some WWTPs also use chemicals, as well as energy to drive wastewater treatment and produce clean
effluents. Chemicals such as iron sulphate or iron chloride can be added to the wastewater to remove
pollutants such as phosphorus. Other chemicals that are frequently used in WWTPs include alum, poly-
electrolyte, acetate, methanol and carbonates, lime etc. Hence, the use of chemicals and respective
amounts can impact on the pollutants removal efficiency of WWTPs and replace, to a certain extent, the
use of other sources of energy. In order to account for the use of chemicals on the methodology, the
embedded energy in chemicals should also be estimated. This can be done using the Cumulative Energy
2
Demand (CED) method developed by Frischknecht et al. (2007) . CED is a widely used indicator for
3
environmental impacts . It investigates the direct and indirect consumption of energy necessary to
obtain a product or service. The CED is used to indicate the equivalent of primary energy consumption
in the chain of a product or the energy consumed in a certain system over its entire lifecycle, from the
extraction of raw materials to the end of life of the product or system. Examples of CED conversion
factors are reported in Table 2, while Formula (4) represents the formula used for estimating the
embedded energy of chemical for common products used for wastewater treatment and accounted for
when calculating the WTEI.
2
Frischknecht, R., et al. (2007) Implementation of Life Cycle Impact Assessment Methods: Data v2.0. ecoinvent
report No. 3, Swiss centre for Life Cycle Inventories, Dübendorf, Switzerland.
3
Remy C,et al (2014). Proof of concept for a new energy-positive wastewater treatment scheme. Water Science
and Technology; 70(10):1709-1716.
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In order to account for the use of chemicals on the methodology, the chemical “energy for production”
should also be estimated using the conversion factors (Table 2 and Formula (4)) and accounted for
when calculating the WTEI. The chemical “energy for production” refers the amount of energy required
to produce a certain chemical. These values are relatively stable and are currently reported through
compulsory life cycle assessments.
L
E 4 : Chemical energy consumption = cec · M (4)
ii
∑
iA=
where
A to L are the chemicals used in the WWTP;
is the mass (in kg) consumed of each chemical; and
M
i
is the specific chemical energy consumption (in kWh/kg) all chemicals used in the WWTP
cec
i
from A to L.
Hence, the chemical energy consumption is calculated by multiplying the kg chemical used as pure
product per unit of time (over the past 3 years) by the specific chemical energy of production in Table 2.
Table 2 — Chemical energy of chemicals commonly used in WWTPs as commercial products
Specific chemical energy
Chemical
(kWh/kg)
Acetic acid 80 % sol. 10,3
Aluminium sulphate 50 % sol. 1,04
Iron(III) chloride 40 % sol. 3,40
Iron(III) sulphate 12,5 % sol. 1,90
Iron(II) sulphate 100 % 0,90
Methanol 100 % 9,21
NaOH 50 % sol. 4,17
Peracetic acid 15 % sol. 6,90
Polyaluminium chloride (PAC) 25 % sol. 1,94
Polyelectrolyte (polymer 5 %) 1,40
5.3.4 Total energy consumption estimation
The gross and net energy consumed at a WWTP can be estimated by combining the results from
Formulae (1) to (4) as well as sludge imports (Formula (5) and (6), respectively).
Gross energy consumption (kWh/year) = E1 (energy consumed at WWTP) + E2 (chemical energy
consumption) (kWh/year) – E3 (energy produced and consumed by sludge imports) (5)
Net energy consumption (kWh/year) = E1 (energy consumed at WWTP) + E2 (chemical energy
consumption) (kWh/year) – [E3 (energy produced at WWTP) – E4 (energy produced and consumed
by sludge imports)] (6)
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5.4 Identification of the WWTP boundaries and calculation of Key Performance
Indicators (KPIs)
WWTPs can be composed of a very wide variety of processes designed for removal pollutants from used
water that has been discharged to a central facility. For the purpose of the methodology for Rapid Audit,
only the influent and effluent characterization and respective removals should be considered; the
WWTP is taken as a black box (Figure 1).
Various methodologies have been described to estimate energy consumption in WWTPs including:
utilization of the equipment specifications (power and usage time), power loggers and modelling. In
Europe, the methodologies adopted vary from country to country and even amongst water utilities. The
limitations of exiting methodologies are related with the need to compare similar wastewater pollutant
loads at the influent, including carbon to nitrogen ratios, and effluent consents (discharge limit
...
SLOVENSKI STANDARD
kSIST-TP FprCEN/TR 17614:2020
01-november-2020
Standardna metoda za ocenjevanje in izboljšanje energijske učinkovitosti čistilnih
naprav za odpadno vodo
Standard method for assessing and improving the energy efficiency of waste water
treatment plants
Standardmethode zur Bewertung und Verbesserung der Energieeffizienz von
Kläranlagen
Méthode standard d’évaluation et d’amélioration de l’efficacité énergétique des stations
d'épuration
Ta slovenski standard je istoveten z: FprCEN/TR 17614
ICS:
13.060.30 Odpadna voda Sewage water
27.015 Energijska učinkovitost. Energy efficiency. Energy
Ohranjanje energije na conservation in general
splošno
kSIST-TP FprCEN/TR 17614:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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kSIST-TP FprCEN/TR 17614:2020
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kSIST-TP FprCEN/TR 17614:2020
FINAL DRAFT
TECHNICAL REPORT
FprCEN/TR 17614
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
September 2020
ICS 13.060.30; 27.015
English Version
Standard method for assessing and improving the energy
efficiency of waste water treatment plants
Méthode standard d'évaluation et d'amélioration de Standardmethode zur Bewertung und Verbesserung
l'efficacité énergétique des stations d'épuration der Energieeffizienz von Kläranlagen
This draft Technical Report is submitted to CEN members for Vote. It has been drawn up by the Technical Committee CEN/TC
165.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
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notice and shall not be referred to as a Technical Report.
EUROPEAN COMMITTEE FOR STANDARDIZATION
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EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TR 17614:2020 E
worldwide for CEN national Members.
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Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 General considerations of methodologies . 5
3 Methodology for Rapid Audit (RA). 6
3.1 Identification of the WWTP typology . 6
3.2 Energy consumption data collection . 7
3.2.1 Energy consumption data . 7
3.2.2 Energy producing WWTPs and sludge imports . 8
3.2.3 Chemical energy consumption . 8
3.2.4 Total energy consumption estimation . 10
3.3 Identification of the WWTP boundaries and calculation of Key Performance
Indicators (KPIs) . 10
3.4 Calculation of the Water Treatment Energy INDEX (WTEI) as a single indicator. 13
4 Methodology for Decision Support (DS) . 16
4.1 Identification of the WWTP typology . 16
4.2 WWTP boundaries . 17
4.3 Request required approvals and keep communication (operators, site managers,
process engineers, budget holders and other possible end users) and health safety
considerations . 20
4.4 Create database describing all equipment on site . 20
4.5 Select equipment for online monitoring and install online monitors according to
manual . 22
4.6 Energy consumption data collection . 22
4.6.1 Energy consumption data . 22
4.6.2 Chemical energy consumption . 23
4.6.3 Energy producing WWTPs and sludge imports . 24
4.6.4 Gross and net energy consumption at stage estimation . 25
4.7 Key Performance Indicators (KPIs) . 25
4.8 Monitor site for KPIs (how often to monitor, methods used for monitoring). 37
4.9 Water Treatment Energy Index (WTEI) as a composite indicator . 37
Annex A (informative) Rapid Audit methodology applied to a case study . 41
A.1 Introduction . 41
A.2 Case Study Structure . 41
Annex B (informative) Decision Support methodology applied to a case study . 45
B.1 Introduction . 45
B.2 Case Studies Structure . 45
Annex C (informative) Overview of training of auditors. 55
C.1 Training of people on the online tool and audits . 55
C.2 Audit, data collection and validation . 56
Bibliography . 59
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European foreword
This document (FprCEN/TR 17614:2020) has been prepared by Technical Committee CEN/TC 165
“Waste water engineering”, the secretariat of which is held by DIN.
This document is currently submitted to the Vote on TR.
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Introduction
Wastewater Treatment Plants (WWTPs) are one of the most expensive public industries in terms of
energy requirements, accounting for more than 1 % of consumption of electricity in Europe. Thus, there
is a need to stop the current unsustainable energy consumption of the sector in line with the objectives
of Europe 2020 and the EU Sustainable Development Strategy (SDS).
The energy consumption must be related with the performance of a WWTP and parameters such as
effluent flow, nutrient removal, biochemical oxygen demand (BOD), chemical oxygen demand (COD),
suspended solids, orthophosphate (PO ), ammonia (NH ) and nitrate (NO ) need to be estimated or
4 4 3
determined at various stages of the WWTP for an effective estimation and assessment of energy
efficiency in WWTP.
This Technical Report presents a methodology to guide water experts and auditors on how to evaluate
the energy performance of a WWTP reaching a final energy diagnosis and the calculation of a Water
Treatment Energy Index (WTEI).
The methodology intends to be a very simple and easy to follow document that can be effortlessly
understood and put in practice by operators, site managers, process engineers as well as energy
auditors. It includes: planning the estimation of energy consumption at a WWTP; requesting approvals
and keeping communication (operators, site managers, process engineers, budget holders and other
possible end users) and health safety considerations; compilation of a database describing all
equipment on site; selection of equipment for online monitoring and install online monitors according
to manual; monitoring site for KPIs; training of people on the online tool and audits; audit, data
collection and validation; calculation of the WTEI and classification of WWTPs. Furthermore the
application of the methodology was completed to 3 case studies as practical examples.
The methodology included in this Technical Report considers two approaches for the determination of
energy consumption in WWTPs, namely Rapid Audit and Decision Support.
Rapid Audit is aimed at a rapid estimation of the WTEI of a particular WWTP using existing information.
This method uses existing information including historical data on energy consumption as well as the
wastewater influent and effluent. A trained auditor can calculate the WTEI and the obtained values can
be compared against a large database.
Decision Support is aimed at establishing the WTEI of a particular WWTP and providing information
that can be used as decision support of an energy efficiency diagnosis. It requires online energy data
obtained over extended periods of time as well as intensive wastewater sampling campaigns to
establish KPIs for each individual treatment stage. The combined information from the online meters
and wastewater sampling can then be used to calculate the WTEI using carefully selected statistical
tools and energy performance indicators. The methodology described includes guidelines on how to
select equipment/processes to place energy monitors, how to monitor the WWTP and how data should
be processed and reported. The Decision Support methodology can be used to provide an WWTP energy
benchmark but also understand impact of seasonal variations, storm events, changes in maintenance
routines, implementation of new equipment (e.g.: screens, pumps, blowers, etc.) as well as retrofitting
of existing processes as well as implementation of new processes. This methodology can also be used as
a tool to identify energy efficiencies and inefficiencies so further actions can be planed and the impact
can be measured and verified online. The Decision Support methodology can also be used as training
tool as well as help water utilities to clearly communicate to operators, engineers and the general public
how changes in operation and behaviour that can lead to energy efficiency and reduce energy
consumption.
This Technical Report is based on the outcomes of the ENERWATER project, a coordination and support
action funded by European Commission under Programme H2020 (www.enerwater.eu).
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1 Scope
This document defines a methodology for determining and assessing the energy efficiency of Waste
Water Treatment Plants (WWTP). The methodology aims at describing, in a systematic way, the various
steps required to establish the Water Treatment Energy Index (WTEI) of a particular WWTP.
The methodology includes the classification of WWTPs in different types, identification of different
stages of treatment, identification of key performance indicators (KPIs), overview of existing energy
monitoring standards and the detailed description of the methodology, including a step by step
guideline of how to apply and implement it.
The methodology is divided in 2 sub-methods that should be selected and followed according to the
following goals:
— The Rapid Audit (RA) method allows for a quick estimation of the water treatment energy index
(WTEI) based on existing information such as historical data pertaining to energy use records along
with influent and effluent quality values. The aim of this methodology is to provide a WWTP energy
benchmark, a rapid tool to identify energy efficiencies and inefficiencies so further actions can be
planned, as well as to evaluate the impact of WWTP retrofitting.
The Rapid Audit methodology is detailed step by step in Clause 3 of this TR and can be used as a
standalone document.
— The Decision Support (DS) method requires intensive monitoring across a WWTP of energy usage
and water quality parameters that provides an accurate and detailed calculation of WTEI for each
stage as well as its overall value for the plant. The goal of this assessment is to serve as a diagnosis
of the functions/equipment in a plant that may lead to poor energy efficiency performance.
The Decision Support methodology is detailed step by step in Clause 4 of this TR and can be used as
a standalone document.
2 General considerations of methodologies
Both Rapid Audit (RA) and Decision Support (DS) methodologies are structured in a similar way but
with a different level of detail. To sum up the procedures, first the type of WWTP according to its
functions is established; then, energy consumption and other measurements (flowrate, pollutant
concentrations, etc.) are combined to form relevant key performance indicators (KPIs). Guidelines for
the estimation of analytical results, in case actual measurements are not available, are also given.
Finally, the KPIs are normalized and combined according suitable weights in order to obtain the Water
Treatment Energy Index (WTEI).
In facilities where (at least part of) the energy is produced on site, e.g. electricity from anaerobic
digestion of sludge, two different values of WWTP total energy consumption may be identified and have
been labelled here as Gross and Net energy consumption:
— A plant’s gross energy consumption is defined as the total amount of energy that is consumed by
the plant regardless of its source.
— A plant’s net energy consumption is defined as the amount of energy that is consumed by the
1)
plant excluded the amount of renewable energy created on the site.
1)
A similar concept was approved and implemented by the European Union and other agreeing countries for the
residential sector, i.e. the net-zero energy building (NZEB): https://ec.europa.eu/energy/en/topics/energy-
efficiency/buildings/nearly-zero-energy-buildings .
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3 Methodology for Rapid Audit (RA)
This methodology is aimed at a establishing the Water Treatment Energy Index (WTEI) of a particular
WWTP, using existing information on site including historical data on energy consumption, as well as
influent and effluent quality to calculate the key performance indicators (KPIs).
3.1 Identification of the WWTP typology
Wastewater treatment plants can have various functions depending on the type of pollutants removed.
For instance, removal of solids and dissolved organic matter might be targeted whilst other WWTP
might target a wider range of pollutants, i.e. from solids all the way to pathogens and persistent
pollutants present in micrograms per litre. The need to remove different types of pollutants is linked
with the regulatory framework in Europe and the type/water quality of the receiving water body. There
are some key European Directives linked wastewater effluent discharges into waterways:
— Urban Waste Water Treatment Directive (UWWTD) (91/271/EEC);
— Nitrates Directive (ND) (91/676/EEC);
— Water Framework Directive (WFD) (2000/60/EC);
— Bathing Water Treatment Directive (2006/7/EC) replacing (76/160/EEC);
— Shellfish Directive (79/923/EEC);
— Freshwater Fish Directive (78/659/EEC).
These European Directives aim to protect the receiving waterways depending on its chemical quality,
ecological status, potential for eutrophication, or other activities such as bathing, fishing or shellfish
production etc. Sensitive areas are designated after surveys establishing that the receiving water body
is adversely impacted by WTTPs that discharge effluents just treated for solids (TSS) and dissolved
organic matter (BOD and COD) (usually designed as secondary treatment). Designated as sensitive
areas are:
(i) eutrophic or could become so in the near future without tertiary protection;
(ii) abstraction sources that have or could have high nitrate levels without tertiary protection;
(iii) other directives’ water in need of or already receiving tertiary protection.
Overall, sensitive areas are in need of protection through the provision of tertiary treatment at the
WWTPs whose discharges adversely impact the waters. There are various types of sensitive areas and
their type will influence the form of tertiary treatment provided: for example bathing and shellfish
water sensitive areas will be protected by UV treatment, and waters adversely affected by nutrients in
discharges will receive phosphorus and/or nitrogen reduction.
This complexity of the WWTPs needs to be addressed in the methodology. Following of the work
completed by others on the life cycle analysis of WWTPs the following typologies are recommended:
Type 1: Discharge to non-sensitive - this includes WWTPs focused on the removal TSS, BOD, COD and
NH .
4
Type 2: Discharge to sensitive areas - this includes WWTPs focused on removing TSS, BOD, COD, NH ,
4
NO , total phosphorus (TP).
3
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Type 3: Discharge for re-use (pathogens) - this includes WWTPs focused on removing TSS, BOD, COD,
NH , NO , TP and pathogens removal (e.g. coliforms log reduction).
4 3
3.2 Energy consumption data collection
3.2.1 Energy consumption data
Historical data on the energy consumed at the WWTP needs to be available, including electricity and
other fuels such as diesel, natural gas etc. Electricity consumption on the WWTPs can be obtained by
consulting electricity bills, meter readings or existing online meters. This information needs to be
collected to provide an estimation of kWh used at the entire WWTP per unit of time (i.e.: the
recommended period of time is 3 years of data to account for seasonal variability). If other fuels are
used, for example to drive generators to produce electricity, the fuel consumption (i.e.: in litres or tons),
these also need to be quantified and converted to kWh per unit of time using the conversion factors in
Table 2 to calculate the total energy consumption (Formula (1)).
Table 1 — Energy carrier classification, conversion factor and equations to estimate specific
power consumption
Energy carrier Conversion factors Abbr Equations to estimate specific power consumption
.
Electric energy in
kWh
1
V1 Ep_V1 = P × T × U.F
( )
kWh kWh
Ep_V2 = equipment usage/year x usage time
(h) × 11,87 × diesel used [kg/h] × β
kWh
11, 87 g
Diesel in kg V2
( )
kg
where, β is efficiency of electrical generator (0,35)
g
Case I) Ep_V3 = Natural gas used in combined heat
and power engine
kWh_el = (Ncm/y) × 9,94 × β_el
†
kWh_th = (Ncm/y) × 9,94 × (1- β_el)) × β_th
Natural gas in Ncm
(normal cubic
Case II) Ep_V3 = Natural gas used in a trigeneration
meters)
system to provide power, heating and cooling
kWh
9, 94
V3
( )
Ncm
Normal conditions
kWh_el = (Ncm/y) × 9,94 × β_el
(0 °C, atmospheric
†
kWh_th = (Ncm/y) × 9,94 × (1- β_el)) × β_th
pressure)
† ‡
kWh_c = (Ncm/y) × 9,94 × (1- β_el)) × β_th × β_c
Case III) Ep_V3 = Natural gas used for heating only
†
kWh_th = Scm/y × 9,94 × β_th
Case I) Ep_V4 = Biogas used in combined heat and
power engine
kWh_el = Scm/y × 9, 94 NGC × β_el *
†
kWh_th = Scm/y × 9, 94 NGC × (1- β_el)) × β_th
Biogas in Ncm
kWh
9, 94 × NGC
(normal cubic
)
(
Case II) Ep_V4 = Biogas used in a trigeneration
Ncm
meters)
system to provide power, heating and cooling
V4
where NGC is the natural
Normal conditions
kWh_el = (Ncm/y) × 9, 94 NGC × β_el *
gas content in the biogas
(0 °C, atmospheric
(vol/vol)
†
pressure) kWh_th = (Ncm/y) × 9, 94 NGC × (1- β_el)) × β_th
kWh_c = (Ncm/y) × 9, 94 NGC × (1-
† ‡
β_el)) × β_th × β_c
Case III) Ep_V4 = Biogas used for heating only
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Energy carrier Conversion factors Abbr Equations to estimate specific power consumption
.
†
kWh_th = Scm/y × 9, 94 NGC × β_th
* typical efficiency taken as 0,40 for electricity generation
† typical efficiency taken as 0,85 for heat production and recovery
‡ typical efficiency taken as 0,70 for an adsorber
NOTE All conversion factors have been taken from UNI/TS 11300-2:2014.
E1 : Energy consumed at WWTP = electric energy according to historical data
(1)
kWh/ year ++Ep___V1 Ep V2 + Ep V3 + Ep_V4
( )
3.2.2 Energy producing WWTPs and sludge imports
WWTPs can have a range of technologies that produce energy/electricity on site. Technologies such as
anaerobic digestion (of sludge, imported sludge, other wastes, etc.), hydraulic-power, wind turbines,
solar panels, fuel-cells, etc., are currently used. The generation of electricity on the WWTP can offset the
energy requirements to produce a high effluent quality. The energy produced on site that is used on site
can be estimated taking in consideration Formula (2). The recommended period of time is 3 years of
data to account for seasonal variability.
L
E2 : Energy produced at WWTP = i (2)
∑
iA=
Where, A to L are the types of energy produced in the WWTP, A – energy from biogas (kWh/year); B -
hydraulic-power (kWh/year); C – wind turbines (kWh/year); D – solar panels (kWh/year); E - fuel-cells
(kWh/year); F-L – other (kWh/year).
Many WWTPs with anaerobic digesters act as sludge treatment centres receiving sludge from nearby
sites. The imported sludge is often mixed with the sludge produced at the WWTP for further treatment
such as dewatering, anaerobic digestion etc. potentially accounting for both energy consumption and
production on the WWTP. Sludge imports can be very significant in some WWTPs (up to twofold the
sludge produced on site). As such, the volume of sludge imports, respective total suspended solids as
well as an estimation of the energy consumed and produced for its treatment needs to be taken into
consideration (Formula (3)).
E3 : Energy produced and consumed by sludge imports =
Energy produced by sludge imports kWh/ year - Energy consumed by (3)
( )
sludge imports kWh/ year
( )
3.2.3 Chemical energy consumption
Some WWTPs also use chemicals, as well as energy to drive wastewater treatment and produce clean
effluents. Chemicals such as iron sulphate or iron chloride can be added to the wastewater to remove
pollutants such as phosphorus. Other chemicals that are frequently used in WWTPs include alum, poly-
electrolyte, acetate, methanol and carbonates, lime etc. Hence, the use of chemicals and respective
amounts can impact on the pollutants removal efficiency of WWTPs and replace, to a certain extent, the
use of other sources of energy. In order to account for the use of chemicals on the methodology, the
embedded energy in chemicals should also be estimated. This can be done using the Cumulative Energy
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2)
Demand (CED) method developed by Frischknecht et al. (2007) . CED is a widely used indicator for
3)
environmental impacts . It investigates the direct and indirect consumption of energy necessary to
obtain a product or service. The CED is used to indicate the equivalent of primary energy consumption
in the chain of a product or the energy consumed in a certain system over its entire lifecycle, from the
extraction of raw materials to the end of life of the product or system. Examples of CED conversion
factors are reported in Table 2, while Formula (4) represents the formula used for estimating the
embedded energy of chemical for common products used for wastewater treatment and accounted for
when calculating the WTEI.
In order to account for the use of chemicals on the methodology, the chemical “energy for production”
should also be estimated using the conversion factors (Table 2 and Formula (4)) and accounted for
when calculating the WTEI. The chemical “energy for production” refers the amount of energy required
to produce a certain chemical. These values are relatively stable and are currently reported through
compulsory life cycle assessments.
L
E 4 : Chemical energy consumption = cec · M (4)
ii
∑
iA=
where
A to L are the chemicals used in the WWTP;
is the mass (in kg) consumed of each chemical; and
M
i
is the specific chemical energy consumption (in kWh/kg) all chemicals used in the WWTP
cec
i
from A to L.
Hence, the chemical energy consumption is calculated by multiplying the kg chemical used as pure
product per unit of time (over the past 3 years) by the specific chemical energy of production in Table 2.
Table 2 — Chemical energy of chemicals commonly used in WWTPs as commercial products
Specific chemical energy
Chemical
(kWh/kg)
Acetic acid 80 % sol. 10,3
Aluminium sulphate 50 % sol. 1,04
Iron(III) chloride 40 % sol. 3,40
Iron(III) sulphate 12,5 % sol. 1,90
Iron(II) sulphate 100 % 0,90
Methanol 100 % 9,21
NaOH 50 % sol. 4,17
Peracetic acid 15 % sol. 6,90
Polyaluminium chloride (PAC) 25 % sol. 1,94
Polyelectrolyte (polymer 5 %) 1,40
2
)
Frischknecht, R., et al. (2007) Implementation of Life Cycle Impact Assessment Methods: Data v2.0. ecoinvent
report No. 3, Swiss centre for Life Cycle Inventories, Dübendorf, Switzerland.
3
)
Remy C,et al (2014). Proof of concept for a new energy-positive wastewater treatment scheme. Water Science
and Technology; 70(10):1709-1716.
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3.2.4 Total energy consumption estimation
The gross and net energy consumed at a WWTP can be estimated by combining the results from
Formulae (1) to (4) as well as sludge imports (Formula (5) and (6), respectively).
Gross energy consumption (kWh/year) = E1 (energy consumed at WWTP) + E2 (chemical energy
consumption) (kWh/year) – E3 (energy produced and consumed by sludge imports) (5)
Net energy consumption (kWh/year) = E1 (energy consumed at WWTP) + E2 (chemical energy
consumption) (kWh/year)– [E3 (energy produced at WWTP) – E4 (energy produced and consumed by
sludge imports)] (6)
3.3 Identification of the WWTP boundaries and calculation of Key Performance
Indicators (KPIs)
WWTPs can be composed of a very wide variety of processes designed for removal pollutants from used
water that has been discharged to a central facility. For the purpose of the methodology for Rapid Audit,
only the influent and effluent characterization and respective removals should be considered; the
WWTP is taken as a black box (Figure 1).
Various methodologies have been described to estimate energy consumption in WWTPs including:
utilization of the equipment specifications (power and usage time), power loggers and modelling. In
Europe, the methodologies adopted vary from country to country and even amongst water utilities. The
limitations of exiting methodologies are related with the need to compare similar wastewater pollutant
loads at the influent, including carbon to nitrogen ratios, and effluent consents (dischar
...
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