Tài liệu Pollutants in urban waste water and sewage sludge doc

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Pollutants in urban waste
water and sewage sludge
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Executive Summary

Pollutants in Urban Waste Water and Sewage Sludge
2
Authors
I C Consultants Ltd London
Professor Iain Thornton
(scientific co-ordinator)
Dr David Butler
Paul Docx
Martin Hession
Christos Makropoulos
Madeleine McMullen
Dr Mark Nieuwenhuijsen
Adrienne Pitman
Dr Radu Rautiu
Richard Sawyer
Dr Steve Smith
Dr David White
Technical University Munich
Professor Peter Wilderer
Stefania Paris
IRSA Rome
Dr Dario Marani
Dr Camilla Braguglia
ECA Barcelona
Dr Juan Palerm
Executive Summary
Pollutants in Urban Waste Water and Sewage Sludge
3
Table of Contents
EXECUTIVE SUMMARY 5

1. INTRODUCTION 9
1.1 INTRODUCTION TO POLLUTANTS IN URBAN WASTEWATER (UWW) AND
SEWAGE SLUDGE (SS)
1.2 OBJECTIVES AND GOALS
2. POTENTIALLY TOXIC ELEMENTS, SOURCES, PATHWAYS, AND FATE THROUGH
URBAN WASTEWATER TREATMENT SYSTEMS 13
2.1.SOURCES AND PATHWAYS OF POTENTIALLY TOXIC ELEMENTS IN UWW AND SS
2.1.1 DOMESTIC SOURCES
2.1.2 COMMERCIAL SOURCES
2.1.3 URBAN RUNOFF
2.2 INFLUENCE OF VARIOUS TREATMENT PROCESSES ON THE FATE OF
POTENTIALLY TOXIC ELEMENTS THROUGH WASTEWATER TREATMENT SYSTEMS
(WWTS) AND SEWAGE SLUDGE TREATMENT (SST)
2.3 QUANTITATIVE ASSESSMENT OF POTENTIALLY TOXIC ELEMENTS IN
UNTREATED UWW, TREATED UWW AND TREATED SS
3. ORGANIC POLLUTANTS: SOURCES, PATHWAYS, AND FATE THROUGH URBAN
WASTEWATER TREATMENT SYSTEMS 64
3.1. SOURCES AND PATHWAYS OF ORGANIC POLLUTANTS IN UWW AND SS
3.1.1 DOMESTIC AND COMMERCIAL
3.1.2 URBAN RUNOFF
3.2 INFLUENCE OF VARIOUS TREATMENT PROCESSES ON THE FATE OF ORGANIC
POLLUTANTS THROUGH WWTS AND SS
3.3 QUANTITATIVE ASSESSMENT OF ORGANIC POLLUTANTS IN UNTREATED UWW,
TREATED UWW AND TREATED SS
4. HEALTH AND ENVIRONMENTAL EFFECTS OF POLLUTANTS IN UWW AND SS 94
4.1 POTENTIALLY TOXIC ELEMENTS
4.2 ORGANIC POLLUTANTS
Executive Summary
Pollutants in Urban Waste Water and Sewage Sludge
4

5. A REVIEW OF EU AND NATIONAL MEASURES TO REDUCE THE POTENTIALLY
TOXIC ELEMENTS AND ORGANIC COMPOUNDS CONTAMINATION OF UWW AND SS
102
6. CASE STUDIES 113
(A) PLATINUM GROUP METALS IN URBAN ENVIRONMENT
(B) SUSTAINABLE URBAN DRAINAGE
(C) POLLUTANT SOURCES AND LOAD FROM ARTISANAL ACTIVITIES IN URBAN
WASTEWATER (THE MUNICIPALITY OF VICENZA, INCL. GOLD JEWELLERY SHOPS)
(D) PHARMACEUTICALS IN THE URBAN ENVIRONMENT
(E) PERFUME COMPOUNDS IN WASTEWATER AND SEWAGE SLUDGE
(F) SURFACTANTS IN URBAN WASTEWATERS AND SEWAGE SLUDGE
(G) USE OF POLYELECTROLYTES; THE ACRYLAMIDE MONOMER IN WATER
TREATMENT
(H) CASE STUDY: LANDFILL LEACHATE
(I) PTE (POTENTIALLY TOXIC ELEMENTS) TRANSFERS TO SEWAGE SLUDGE
(J) EFFECT OF CHEMICAL PHOSPHATE REMOVAL ON POTENTIALLY TOXIC
ELEMENT CONTENT IN SLUDGE
7. REPORT SYNOPSIS, DISCUSSIONS AND CONCLUSIONS 205
7.1 COMMENTS, CHALLENGES AND STRATEGIES FOR THE NEXT FIVE TO TEN
YEARS
7.2 IDENTIFICATION OF GAPS IN THE AVAILABLE INFORMATION,
7.3 RECOMMENDATIONS FOR FURTHER RESEARCH
7.4 SUGGESTIONS
APPENDICES 232
APPENDIX A - URBAN WASTEWATER TREATMENT SYSTEMS (WWTS) AND SEWAGE SLUDGE
TREATMENT (SST) - EU AND REGIONAL ASPECTS
APPENDIX B - PHYSICO-CHEMICAL PROPERTIES OF SELECTED POLLUTANTS
DATABASES, REFERENCES
GLOSSARY AND ABBREVIATIONS
Executive Summary

5
POLLUTANTS IN URBAN WASTE WATER AND SEWAGE SLUDGE
EXECUTIVE SUMMARY
Water policy in the European Union is aiming to promote sustainable water use and a major
objective of the new Water Framework Directive (2000/60/EC) is the long-term progressive
reduction of contaminant discharges to the aquatic environment in urban wastewater
(UWW). Sewage sludge is also a product of wastewater treatment and the Urban Waste
Water Treatment Directive (91/271/EEC) aims to encourage the use of sludge whenever
appropriate. Potentially toxic elements and hydrophobic organic contaminants largely
transfer to the sewage sludge during waste water treatment with potential implications for the
use of sludge although some may be emitted with the effluent water.
Inputs of metals and organic contaminants to the urban wastewater system (WWTS) occur
from three generic sources: domestic, commercial and urban runoff. A review of available
literature has quantified the extent and importance of these various sources and the inputs
from different sectors. In general, urban runoff is not a major contributor of potentially toxic
elements to UWW. Inputs from paved surfaces due to vehicle road abrasion and tyre and
brake-lining wear have been identified and losses from Pb painted surfaces and Pb and Zn
from roofing materials represent localised sources of these elements.
Platinum and Pd are components of vehicle catalytic converters and emissions occur as the
autocatalyst deteriorates. Catalytic converters are the main source of these metals emitted
to the environment and releases have increased with the expansion in use of autocatalysts.
Platinum group metals (PGMs) potentially enter UWW in runoff and transfer to sewage
sludge in a similar way to other potentially toxic elements. The Pt content in sludge is
typically in the range 0.1 – 0.3 mg kg
-1
(ds) and the background value for soil is 1 µg kg
-1
.
PGMs are inactive and immobile in soil.
In contrast to potentially toxic elements, inputs of the main persistent organic pollutants of

concern, including: PAHs, PCBs and PCDD/Fs, to UWW are principally from atmospheric
deposition onto paved surfaces and runoff. Combustion from traffic and commercial sources
accounts for the major PAH release to the environment, although inputs from food
preparation sources also represent an important and often under-estimated contribution of
certain PAH congeners. PCDD/Fs are released during waste incineration and also by coal
combustion. Soil acts as a long-term repository for these contaminant types and
remobilisation by volatilisation from soil is an important mechanism responsible for recycling
and redistributing them in the environment. For example, the industrial use of PCBs was
phased out in Europe during the 1980s-1990s, but 90 % of the contemporary emissions of
PCBs are volatilised from soil. Since emission controls are already in place for the main
point sources and PAHs, PCDD/Fs or PCBs enter UWW principally from diffuse atmospheric
deposition and environmental cycling, there is probably little scope, from source control, to
further reduce inputs and concentrations of these persistent organic substances in UWW or
sewage sludge.
Being strongly hydrophobic these organic pollutants are efficiently removed during urban
wastewater treatment (WWTS) and bind to the sludge solids. However, the increasing body
of scientific evidence has not identified a potential harmful impact of these substances on the
environment in the context of the urban wastewater system. Therefore, on balance, the
importance of these contaminants in UWW and sewage sludge has significantly diminished
and there may be little practical or environmental benefit gained from adopting limits or
controls for PAHs, PCBs or PCDD/Fs in UWW or sewage sludge. This is emphasised further
by the high cost and specialist analytical requirements of quantifying these compounds in
sludge and effluent.
Executive Summary
Pollutants in Urban Waste Water and Sewage Sludge
6
Potentially toxic element contamination of urban wastewater and sewage sludge is usually
attributed to discharges from major commercial premises. However, significant progress has
occurred in eliminating these sources and this is reflected in the significant reductions in
potentially toxic element concentration in sewage sludge and surface waters reported in all

European countries where temporal data on sludge and water quality have been collected.
However, potentially toxic element concentrations remain higher in sludge from large urban
wastewater treatment plant (WWTP) compared with small WWTP and they are also greater
in sludges from industrial catchments compared with rural locations. These patterns in
sludge metal content suggest that commercial sources may still contribute significantly to the
total metal load entering UWW. Indeed, recent regional surveys of metal emissions from
commercial premises confirm that further reductions in most elements could be achieved
from this sector. The primary targets for source control include health establishments, small
manufacturing industries (particularly metal and vehicle related activities) and hotel/catering
enterprises, as 30 % of medical centres and 20 % of the other types of activity could be
discharging significant amounts of potentially toxic elements in UWW. Mercury is a specific
case where compulsory use of dental amalgam separators, and substituting Hg with
alternative thermoreactive materials in thermometers, may be effective in reducing
discharges of this element to the WWTS wastewater treatment system .
Faeces contribute 60 – 70 % of the load of Cd, Zn, Cu and Ni in domestic wastewater and
>20 % of the input of these elements in mixed wastewater from domestic and industrial
premises. Faecal matter typically contains 250 mg Zn kg
-1
, 70 mg Cu kg
-1
, 5 mg Ni kg
-1
, 2 mg
Cd kg
-1
and 10 mg Pb kg
-1
(ds). The other principal sources of metals in domestic
wastewater are body care products, pharmaceuticals, cleaning products and liquid wastes.
Plumbing is the main source of Cu in hard water areas, contributing >50 % of the Cu load

and Pb inputs equivalent to 25 % of the total load of this element have been reported in
districts with extensive networks of Pb pipework for water conveyance. Adjusting water
hardness in order to reduce metal solubilisation from plumbing is technically feasible, but is
likely to be impractical at the regional scale necessary to significantly reduce metal
concentrations in UWW and sludge and may be unpopular with consumers in hard water
areas. The gradual replacement of Pb water pipes can be achieved during building renewal
and renovation programmes.
Reductions in domestic discharges of metals may be possible through increased public
awareness of appropriate liquid waste disposal practices and the provision of accessible
liquid waste disposal facilities. It may be impractical to eliminate the use of metals in body
care products when they are an important active ingredient, but advice and labelling could
be improved to minimise excessive use. Cadmium may be a contaminant present in
phosphatic minerals and removing phosphate from detergent formulations can reduce
associated potential discharges of Cd from domestic sources.
Detergent residues (e.g.nonyl phenol, NP), surfactants (e.g. linear alkyl benzene
sulphonates, LAS), plasticising agents (e.g. di-(2-ethylhexyl)phthalate, DEHP) and
polyacrylamide compounds, added to sludge to aid dewatering, are quantitatively amongst
the most abundant organic contaminants present in UWW and/or sewage sludge.
Dewatering agents based on polyacrylamide may contain traces of the potentially toxic
acrylamide monomer, but this is rapidly degraded and polyacrylamide itself is biologically
inactive. Detergent residues and DEHP are primarily of domestic origin and they are
effectively degraded during aerobic wastewater treatment and are not considered to
represent a potential environmental problem from the discharge of treated effluents to
surface waters. Anaerobic digestion is the principal method employed for stabilising sewage
sludge, but NP accumulates during anaerobic digestion, DEHP is not removed by this
conventional process and, although a significant amount of LAS is biodegraded, residues of
this substance remain because of the large concentrations initially present in raw sludge.
The inability to degrade detergent residues anaerobically and the large concentrations
present in sludge and UWW have prompted ecolabelling initiatives in a number of European
countries to influence consumer choice away from detergents containing these surfactants to

Executive Summary
Pollutants in Urban Waste Water and Sewage Sludge
7
alternative products. This has been successful when supported by extensive public
awareness campaigning. For example, the market share for ecolabelled detergents in
Sweden increased to 95 % and the consumption of LAS has decreased to a similar extent.
Surfactant residues and plasticisers degrade quickly when added to aerobic soils. The
oestrogenic activity of NP is however, a principal concern and measures are proposed to
eliminate the discharge of this substance to UWW.
Natural and synthetic oestrogens are degraded in WWT, but trace amounts remain and
represent the main source of oestrogenic activity in treated effluents. Further work is
necessary to link these substances to oestrogenic responses in aquatic life, but it may be
necessary in future to consider the requirement for tertiary treatment processes (e.g.
ozonation) to eliminate these substances from treated effluents.
A number of other groups of organic compound are identified as being potentially resistant to
wastewater and sewage sludge treatment and the most significant of these are brominated
diphenyl ethers (PBDEs) and chlorinated paraffins. Further research is warranted, in
particular to assess the persistence and potential environmental significance of these
compounds. Synthetic nitro musks are used in perfumed products and traces may be
present in UWW and sludge. Little is known about the environmental fate of these
compounds, but effects on human health from this route seem unlikely given that the main
exposure route is through direct contact.
The degree of removal and biodegradation of pharmaceutical compounds during WWT
varies considerably, although many common analgesic drugs rapidly biodegrade. They are
soluble and transfer to sludge is only of minor concern. Significant amounts of prescribed
drugs are excreted from the body and controlling these inputs from the general population
would be impractical. However, the disposal of unused drugs into UWW should be reviewed
and alternative methods of disposal should be encouraged. The potential significance of
pharmaceuticals in the environment should be assessed in context of the major inputs and
presence arising from widespread veterinary administration of drugs to livestock and farm

waste disposal to land.
A general recommendation to protect the water and soil environment is that a hazard,
biodegradability and fate assessment should be required for all new synthetic chemicals,
irrespective of their purpose or end-use, to determine the potential from them to transfer to
UWW or sewage sludge and the subsequent implications for the environment. Specified
criteria regarding toxicity and biodegradation could be set for compounds that exhibit a
propensity to enter the WWTS and restrictions could be enforced regarding production and
use if these were not met. These decisions would need to balanced against the potential
benefits to health derived from the administration of pharmaceutical drugs.
Strategies aimed at controlling pollutant discharges can only focus on those sources that can
be identified and quantified. Published mass balance calculations indicate there is a high
degree of uncertainty regarding inputs of potentially toxic elements entering the WWTS.
Indeed, unidentified sources may contribute as much as 30 - 60 % of the total metal load
entering the WWTS, although more than 80 % of the Cd discharged is from identified inputs.
This apparent discrepancy could be related to difficulties in measuring the highly variable
inputs of metals in urban runoff and the underestimation of discharges from commercial
premises that have not been subjected to trade effluent control.
The European Commission has proposed a list of 32 priority and 11 hazardous substances
(COM/2001/17) with the aim of progressively reducing emissions and discharges of these
chemicals to the environment. Current developments also suggest that Zn, Cu and LAS may
be the most limiting constituents in sludge if the proposed maximum permissible
concentrations for these substances in soil (Zn and Cu) and sludge (LAS) are carried
through in the revised of Directive 86/278/EEC, but they are not listed as priority substances.
Consideration should be given to designating Zn, Cu and LAS as priority substances to
Executive Summary
Pollutants in Urban Waste Water and Sewage Sludge
8
minimise their to UWW as far as is practicable and to ensure there is a consistent link and
approach to defining the environmental quality standards for sludge with those for
sustainable water use and contaminant discharge reduction.

The main identified priorities for future research relating to contaminant sources, fate and
behaviour in the WWTS are:
• To reduce the uncertainty in quantifying contaminant discharges to UWW by identifying
and surveying specific sources to determine the potential for controlling inputs
particularly from small commercial sources and medical establishments;
• To establish the extent and variability of contaminant entry into UWW by catchment
investigations in relation to precipitation frequency and changes in sludge quality;
• To critically and independently review the fate, behaviour, degradability, toxicity and
environmental consequences of alternative surfactant and plasticing compounds, in
collaboration with the related chemical manufacturing industries, to inform decisions of
the benefits and disadvantages of product substitution in detergent formulations and
plastics manufacture;
• To determine the extent of volatilisation-deposition cycling of persistent organic
pollutants in the environment, identifying the processes controlling the extent and
magnitude of diffuse inputs of these substances to UWW and to provide long-term
predictions of changes in release patterns and the consequences for UWW and sludge;
• To develop a consistent statistical and reporting protocol for national chemical
composition data presented in surveys of sewage sludge quality.
1. Introduction
Pollutants in Urban Waste Water and Sewage Sludge
9
1. INTRODUCTION
The primary objective of this study is to determine the sources of pollution in urban
wastewater (UWW) treated in wastewater treatment systems (WWTS). This includes the
pollutants introduced into the UWW collecting system with run-off rainwater, from domestic
and small commercial sources. The pollutant contents in urban wastewater and sewage
sludge has been evaluated by review of the existing literature, in order that measures may
be proposed to reduce pollution at source.
1.1 Introduction to pollutants in urban wastewater
The pollutants of interest can be divided into two main groups;

• potentially toxic elements (PTEs) including cadmium (Cd), chromium (Cr III and Cr
VI), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn),
• organic pollutants including PAHs, PCBs, DEHP, LAS, NPE, dioxins (PCDD) and
furans (PCDF). Over 6,000 organic compounds have been detected in raw water
sources most of which are due to human activities. While some of these are highly
persistent, others are easily biodegradable in WWTS.
Other pollutants of interest are the metalloids, arsenic and selenium and the metal silver.
Platinum group metals (PGMs), and pharmaceuticals are covered in detail in case studies.
The sources of metal pollution in the wastewater system can be classified into three main
categories:
• Domestic,
• Light industrial (connected to the WWTS) and commercial,
• Urban runoff (which also encompass lithospheric and atmospheric sources).
1. Introduction
Pollutants in Urban Waste Water and Sewage Sludge
10
Figure 1.1: Sources of pollutants in wastewater [after Lester, 1987]
A summary of the various inputs, outputs and pathways followed by water and associated
contaminants from both natural and anthropogenic sources encountered in urban
environments is shown in Figure 1.1. It depicts the drainage area as an open system [Ellis,
1986]. A more detailed urban catchment figure is included in Appendix A.
Wastewater contains many constituents and impurities arising from diffuse and point
sources. Large point sources are easily quantifiable and result from specific activities in the
area that are connected to UWW collecting systems. The contribution from small point
sources, such as households and small businesses, is much more difficult to identify and
quantify, compared to point sources which are usually regulated. UWW is also vulnerable to
illegal discharges of pollutants.
Diffuse sources, such as atmospheric deposition and road runoff have also been
characterised and this study will attempt to present an overview of the available information
in this area. Different methods have been used to estimate point sources and diffuse (non-

point) sources contributions to the pollution load [Vink, 1999]. Inventories of point and diffuse
sources, can link observed water quality trends to changes in socio-economic activities.
Atmosphere
Lithosphere
deposition
wet & dry
deposition
INDUSTRY
products
DOMESTIC
Wastes
Wastes Product wastes
RUNOFF
UWW COLLECTING
SYSTEMS
COMBINED UWW
COLLECTING SYSTEMS
STORM UWW
COLLECTING SYSTEMS
WASTEWATER
TREATMENT WORKS
Receiving
Water
1. Introduction
Pollutants in Urban Waste Water and Sewage Sludge
11
The type of pollutants and the magnitude of the outfall loadings are a complex function of:
• size and type of conurbation (commercial, residential, mixed)
• plumbing and heating infrastructure
• atmospheric quality, for example long range transport of pollutants

• factors affecting deposition of pollutants such as precipitation
• activity and intensity surface composition and condition
• urban land use
• traffic type and density
• urban street cleaning
• maintenance practices and stormwater controls
• specific characteristics of storm events
• accidental releases
A review of the sources and pathways of potentially toxic element pollutants in urban
wastewater is presented in Section 2.1 and for organic pollutants in Section 3.1
1.2 Objectives and Goals
The main goals of the study were:
• To determine the sources of potentially toxic elements and organic pollutants in
domestic, commercial, and urban run-off wastewater, which end up in the UWW
collecting system.
• To make a qualitative and quantitative assessment of the pollutants in urban
wastewater and runoff rainwater on the basis of the available data in the literature.
• To evaluate the percentage of inorganic and organic pollutants concentrated in
sewage sludge and the percentage of pollutants released in the environment with the
treated effluents.
• To review wastewater and sewage sludge treatment processes and possible
measures to prevent pollution at source. The most important practices to treat
wastewater and sewage sludge in Europe will be closely examined.
• Based on an overall assessment of the existing data from various sources, to identify
further research directions in those areas with insufficient data.
This report presents a thorough literature review and is primarily based on the analysis and
presentation of case studies from a wide variety of sources and test catchments across
Europe, covering a time range from 1975 to date. Databases used during this project are
listed in the reference section. As theoretical approaches, such as modelling of pollutant
sources and predicted concentrations, are scarce the report attempts to summarise the

monitoring, sampling and measurement of numerous studies, thus providing a concise
overview of pollution source types and concentration ranges. The reader must keep in mind
that there are significant differences between the experiments (in duration, location,
measurement methods, measurement targets and initial conditions), and thus conclusions
on mean or extreme values of pollutants will have to be drawn carefully.
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge
12
2. POTENTIALLY TOXIC ELEMENTS: SOURCES, PATHWAYS, AND FATE
THROUGH URBAN WASTEWATER TREATMENT SYSTEMS
The aim is to reduce inputs of pollutants entering the wastewater system to background
levels because this represents the minimum potential extent of contamination that can be
achieved. Potentially toxic elements are of concern because of their potential for long-term
accumulation in soils and sediments.
The majority of metals transfer to sewage sludge (see Fig 2.1). However, 20% may be lost in
the treated effluent, depending on the solubility and this may be as high as 40% - 60% for
the most soluble metal, Ni. Although the use of sludge on agricultural land is largely dictated
by nutrient content (nitrogen and phosphorus), the accumulation of potentially toxic elements
in sewage sludge is an important aspect of sludge quality, which should be considered in
terms of the long-term sustainable use sludge on land. Application of sludge to agricultural
land is the largest outlet for its beneficial use and this is consistent with EC policy of waste
recycling, recovery and use. This is a critical issue due to the increasing amount of sludge
produced, the increasingly stringent controls on landfilling, the public opposition to
incineration (a potential source of further atmospheric pollution), and the ban on disposal at
sea. Consequently sludge quality must be protected and improved in order to secure the
agricultural outlet as the most cost effective and sustainable option.
Figure 2.1: Origin and fate of metals during treatment of wastewater [from ADEME,
1995]
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge

13
2.1. Sources and pathways of potentially toxic elements in UWW
The average concentrations of potentially toxic elements in domestic and commercial
wastewater are given in Table 2.1. The maximum concentrations of potentially toxic
elements found in commercial wastewater are generally greater than those in domestic
wastewater. This is supported by Scandinavian studies [SFT-1997a, 1997b, 1999]
considering all urban sectors together, which judged that commercial and light industrial
sectors contributed larger loads of potentially toxic elements to urban wastewater than
household sources.
Table 2.1 Concentrations of metals in domestic and commercial wastewater
[Wilderer and Kolb, 1997 in Munich, Germany]
Element Domestic
Wastewater [mg.l
-1
]
Commercial
Wastewater [mg.l
-1
]
Pb 0.1 ≤ 13
Cu 0.2 0.04-26
Zn 0.1-1.0 0.03-133
Cd <0.03 0.003-1.3
Cr 0.03 ≤20
Ni 0.04 ≤7.3
Table 2.2 Potentially toxic elements in UWW from various sources
(% of the total measured in the UWW)
Pollutant Country Domestic
Wastewater
Commercial

Wastewater
Urban
Runoff
Not
Identified
Reference
France 20 61 3 16
ADEME, 1995
Norway 40
SFT report 97/28
Cd
UK 30 29 41
WRc, 1994
France 62 3 6 29
ADEME, 1995
Norway 30
SFT report 97/28
Cu
UK 75 21 4
WRc, 1994
France 2 35 2 61
ADEME, 1995
Norway 20
SFT report 97/28
Cr
UK 18 60 22
WRc, 1994
Hg France 4 58 1 37
ADEME, 1995
France 26 2 29 43

ADEME, 1995
Norway 80
SFT report 97/28
Pb
UK 43 24 33
WRc, 1994
France 17 27 9 47
ADEME, 1995
Norway 10
SFT report 97/28
Ni
UK 50 34 16
WRc, 1994
France 28 5 10 57
ADEME, 1995
Norway 50
SFT report 97/28
Zn
UK 49 35 16
WRc, 1994
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge
14
Cd distribution
Domestic
Storm events
Commercial
Non Identified
Cu distribution
Domestic

Storm events
Commercial
Non Identified
Cr distribution
Domestic
Storm events
Commercial
Non Identified
Hg distribution
Domestic
Storm events
Commercial
Non Identified
Pb distribution
Domestic
Storm events
Commercial
Non Identified
Ni distribution
Domestic
Storm events
Commercial
Non Identified
Zn distribution
Domestic
Storm events
Commercial
Non Identified
Figure 2.2 Pie charts showing the breakdown of potentially toxic elements entering
UWW from different sources in France (ADEME 1995) This uses the French data in Table

2.2 but is included to give a clearer visual representation of the source breakdown for the
different metals.
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge
15
The data in Table 2.2 and Figure 2.2 show that for some elements over 50% of the
potentially toxic elements in wastewater are unaccounted for. This is in line with findings by
Critchley & Agy [1994] Better source inventory data is essential in order to effectively target
reductions in emissions from all the different sources. It may be that identification of some of
the industrial sources will require increased trade effluent discharge controls if
concentrations of pollutants are to be reduced. Domestic and urban run-off sources may
require different types of action, such as changes in products used.
Emissions of potentially toxic elements from industrial point sources were the major sources
of pollution to urban wastewater. However, stringent and more widespread limits applied to
industrial users has reduced the levels of potentially toxic elements emitted by industry into
urban wastewater considerably. This continues a general decline of potentially toxic
elements from industrial sources since the 1960s, due to factors such as cleaner industrial
processes, trade effluent controls and heavy industry recession. For example, the liquids
used in metal finishing typically contain 3-5 mg.l
-1
of copper, 5-10 mg.l
-1
of chromium, 3-5
mg.l
-1
of zinc, 5-10 mg.l
-1
of zinc, 1-5 mg.l
-1
of cyanide, and 10-50 mg.l

-1
of suspended solids
[Barnes, 1987]. However, metal finishing industries are now required to pre-treat these
liquids before disposal, reducing toxic discharges by 80-90%.
In the Netherlands, a survey of potentially toxic element load in UWW influent [SPEED,
1993], also made estimations for 1995 and forecasts up to 2010. The overall prevalence of
potentially toxic elements in the UWW system is expected to decrease, mainly due to a
decrease in runoff and industrial sources, while the potentially toxic elements share in
WWTS loads from households was expected to increase. As industrial sources of potentially
toxic elements in UWW decline, the relevant importance of diffuse sources will increase.
Wiart and Reveillere [1995] carried out studies at the Achères WWTS in France. Their
studies showed a significant decrease (50-90%) in the potentially toxic element content of
sewage sludge since 1978, following the application of the "at-source discharge reduction"
policy [Bebin, 1997]. However, the main concern is now with organic pollutants, and current
regulations require monitoring of the influent, in order to set up a baseline database from
which limits may then be devised.
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge
16
2.1.1 Domestic sources
Domestic sources of potentially toxic elements in wastewater are rarely quantified due to the
difficulty in isolating them. Domestic sources include the potentially toxic elements
discharged from the household to UWW collecting systems and, in addition, corrosion from
materials used in distribution and plumbing networks, tap water and detergents.
A study by RIVM (Dutch Institute of Public Health and the Environment) in the Netherlands
[SPEED, 1993], quantified the waterborne emissions of potentially toxic elements from
household sources, dentistry and utility buildings in the urban environment. Table 2.3 shows
the data of waterborne potentially toxic elements emissions in tonnes per annum.
Table 2.3 Emissions by Dutch households of potentially toxic elements
[adapted from SPEED, 1993].

Gross waterborne emissions* tonnes.y
-1
to surface
water (1993)
Potentially
toxic element
Household
sources
Dentistry Utility buildings
Copper 94 0.6 27
Zinc 118 - 26
Lead 13 - 3.1
Cadmium 0.7 - 0.2
Nickel 7.3 - 0.9
Chromium 2.9 - 0.3
Mercury 0.3 2.3 0.01
* 96 % of the waterborne emissions are expected to go to the UWW collecting systems, with 4% going
directly to surface waters.
Domestic products containing potentially toxic elements used on a regular basis at home
and/or at work, are also reviewed by Lewis [1999]. The following lists the principal PTEs and
products containing them that may enter urban wastewater;
Cadmium: is predominantly found in rechargeable batteries for domestic use (Ni-Cd
batteries), in paints and photography. The main sources in urban wastewater are from
diffuse sources such as food products, detergents and bodycare products, storm water
[Ulmgren, 2000a and Ulmgren, 2000b].
Copper: comes mainly from corrosion and leaching of plumbing, fungicides (cuprous
chloride), pigments, wood preservatives, larvicides (copper acetoarsenite) and antifouling
paints.
Mercury: most mercury compounds and uses are now banned or about to be banned,
however, mercury is still used in thermometers (in some EU countries) and dental

amalgams. Also, mercury can still be found as an additive in old paints for water proofing
and marine antifouling (mercuric arsenate), in old pesticides (mercuric chloride in fungicides,
insecticides), in wood preservatives (mercuric chloride), in embalming fluids (mercuric
chloride), in germicidal soaps and antibacterial products (mercuric chloride and mercuric
cyanide), as mercury-silver-tin alloys and for "silver mirrors".
Nickel: can be found in alloys used in food processing and sanitary installations; in
rechargeable batteries (Ni-Cd), and protective coatings.
Lead: The main source of lead is from old lead piping in the water distribution system. It can
be found in old paint pigments (as oxides, carbonates), solder, pool cue chalk (as
carbonate), in certain cosmetics, glazes on ceramic dishes and porcelain (it is banned now
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge
17
for uses in glazes), also in "crystal glass". Lead has also been found in wines, possibly from
the lead-tin capsules used on bottles and from old wine processing installations.
Zinc: comes from corrosion and leaching of plumbing, water-proofing products (zinc
formate, zinc oxide), anti-pest products (zinc arsenate - in insecticides, zinc dithioamine as
fungicide, rat poison, rabbit and deer repellents, zinc fluorosilicate as anti-moth agent), wood
preservatives (as zinc arsenate), deodorants and cosmetics (as zinc chloride and zinc
oxide), medicines and ointments (zinc chloride and oxide as astringent and antiseptic, zinc
formate as antiseptic), paints and pigments (zinc oxide, zinc carbonate, zinc sulphide),
printing inks and artists paints (zinc oxide and carbonate), colouring agent in various
formulations (zinc oxide), a UV absorbent agent in various formulations (zinc oxide), "health
supplements" (as zinc ascorbate or zinc oxide).
Silver: originates mainly from small scale photography, household products such as
polishes, domestic water treatment devices, etc. [Shafer, et.al, 1998, Adams and Kramer,
1999]
Arsenic and Selenium: are among the potentially toxic metalloids found in urban
wastewaters. These are of importance due to their potential effects on human/animal health.
Only a limited number of studies have taken these into account. Arsenic inputs come from

natural background sources and from household products such as washing products,
medicines, garden products, wood preservatives, old paints and pigments. Selenium comes
from food products and food supplements, shampoos and other cosmetics, old paints and
pigments. Arsenic is present mainly as DMAA (dimethylarsinic acid) and as As (III) (arsenite)
in urban effluents and sewage sludge [Carbonell-Barrachina et.al., 2000].
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge
18
Household products
Household products were investigated as potential sources of PTE pollution entering the
WWTS. Table 2.4 shows metal concentrations in various household products in UK
Table 2.4 Metal concentrations in household products
[Comber and Gunn, 1996, WRc report, 1994].
Product Zinc
(µg g
-1
)
Copper
(µg g
-1
)
Cadmium
(µg g
-1
)
Nickel
(µg g
-1
)
Washing Powders

‘Big Box’
a
b
c
37.9
35.9
3.3
1.4
<0.5
<0.5
74.3
136.0
6.6
<0.5
<0.5
<0.5
Washing Powders ‘Ultra’ a
b
c
<0.1
2.3
1.0
<0.5
1.40
1.38
24.0
10.6
11.8
<0.5
<0.5

<0.5
Fabric Conditioners a
b
c
0.1
<0.1
0.1
<0.5
<0.5
<0.5
9.4
9.0
10.7
0.6
<0.5
<0.5
Hair Conditioners a
b
c
d
<0.1
1.0
1.7
0.5
<0.5
1.4
<0.5
1.4
16.8
17.2

8.6
68.0
<0.5
<0.5
<0.5
1.0
Cleaners a
b
0.3
<0.1
2.8
<0.5
26.0
17.8
<0.5
<0.5
Shampoo (medicated) a 4900 1.4 17.4 <0.5
Washing Up Liquid a 0.2 1.1 11.0 0.8
Bubble bath a
b
0.2
<0.1
<0.5
1.4
13.6
10.4
<0.5
As can be seen from Table 2.4 there is a great deal of variability between products and also
between types of the same products in terms of potentially toxic element content.
The high variability of cadmium concentrations found in the big box washing powders can be

explained by the differences in the composition of phosphate ores used in their production.
Cadmium impurities in these phosphate ores have been shown to vary greatly depending on
mining source [Hutton et al reported in WRc report 1994]. Reducing the amount of
phosphate in washing powders, or choosing phosphate ores with low Cd concentration could
lead to a reduction in Cd in wastewater from diffuse sources. In Sweden the amount of
cadmium in sewage sludge was reduced from 2 mg kg
-1
ds to 0.75 mg kg
-1
ds [Ulmgren,
1999], and cadmium discharges from households in the Netherlands have been substantially
reduced due to the switch to phosphate-free detergents [SPEED, 1993]. The 'Ultra' washing
powders, usually phosphate-free, have smaller potentially toxic element contents than the
traditional powders, and are designed to be used in smaller quantities. A shift to these newer
products will reduce the overall metal load from this source.
The products with the highest metal contents are shown in bold in Table 2.4. The medicated
(anti-dandruff) shampoos contain zinc pyrithione and the high zinc concentrations will thus
raise the zinc inputs to the UWW collecting system. In 1991 these shampoos were estimated
to represent 26% of the market [*BLA Group 1991- reported in Comber and Gunn 1996 and
WRc 1994]. Cosmetics are not included here but they may also contain high levels of zinc
and several of these products are likely, at least in part, to enter in the waste water system.
One study in France [ADEME, 1995a] identified that the main sources of potentially toxic
elements in domestic wastewater came from cosmetic products, medicines, cleaning
products and liquid wastes (including paint), which were directly discharged from the
household sink.
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge
19
Table 2.5 provides a general picture of some of the potentially toxic elements in various
domestic products including food products [after Lester, 1987 and WRc report 1994].

Sources for each metal are marked with a tick. In addition to the main metals considered in
this study, cadmium, chromium (III and VI), copper, mercury, nickel, lead and zinc, silver,
arsenic, selenium and cobalt are also included. Other metals and metalloids for which more
information is necessary include manganese, molybdenum, vanadium, antimony and tin.
TABLE 2.5 Domestic sources of potentially toxic elements in urban wastewater
[modified from Lester, 1987, and WRc, 1994]
Product type Ag As Cd Co Cr Cu Hg Ni Pb Se Zn
Amalgam fillings
and thermometers
√
Cleaning products
√ √
Cosmetics,
shampoos
√ √ √ √ √ √ √
Disinfectants
√
Fire extinguishers
√
Fuels
√ √ √ √
Inks
√ √
Lubricants
√ √ √
Medicines and
Ointments
√ √ √ √ √
Health supplements
√ √ √ √ √

Food products
√ √ √ √ √
Oils and lubricants
√ √ √ √
Paints and
pigments
√ √ √ √ √ √ √ √ √ √
Photographic
(hobby)
√ √ √
Polish
√ √ √
Pesticides and
gardening products
√ √ √ √ √
Washing powders
√ √ √
Wood-
preservatives
√ √ √
Other sources
Faeces and Urine
√ √ √ √ √ √ √ √ √
Tap Water
√ √ √ √ √
Water treatment
and heating
systems
√ √ √ √ √
Domestic activities

The main domestic sources of potentially toxic elements in wastewater were estimated by
WRc [1994] to be (in order of importance):
cadmium: faeces > bath water > laundry > tap water > kitchen
chromium: laundry > kitchen > faeces > bath water > tap water
copper: faeces > plumbing >tap water > laundry > kitchen
lead: plumbing > bath water > tap water > laundry > faeces > kitchen
nickel: faeces > bath water > laundry > tap water > kitchen
zinc: faeces > plumbing > tap water > laundry > kitchen.
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge
20
Estimates of the mean potentially toxic element inputs to UWW collecting systems from
domestic activities are presented in Table 2.6. The results show that for the particular UK
(hard water) catchment studied in 1994, the domestic inputs of copper and zinc are major
contributors to the overall level of potentially toxic elements reaching the WWTS. Most of the
zinc is derived from faeces and household activities such as washing and cleaning.
Chromium, lead and cadmium were also found to be mainly from domestic activities rather
than from plumbing.
Table 2.6 Potentially toxic element loads to the UWW collecting systems from
domestic activities [adapted from Comber and Gunn, 1996]
Load (µg.person
-1
.day
-1
)Activity (study in a hard
water catchment area)
Zn Cu Pb Cd Ni Cr
Washing Machine Input Water
Washing
662

4452
6859
977
36.0
515
0.6
11
27
52
4
238
Dishwashing
(machine)
Input Water
Washing
39
42
69
8
2.9
6
0.03
1.3
2
2
0.3
10
Dishwashing
(hand)
Input Water

Washing
591
1010
6125
<20
32
46
0.5
7.8
24
138
3.7
136.7
Bathing Input Water
Bathing
1140
1095
10651
67
46
45
1.0
13.1
40
9
5.9
7.4
Toilet Input Water
Faeces
2531

11400
8082
2104
63
121
2.0
48.0
77
284
8.5
51.5
Miscellaneous Input Water 1453 6951 62.7 1.2 54 7.0
Predicted Total 24416 41894 978 86 710 464.2
Measured mean from
housing estates
Catchment
Population
50 000
15314 46772 1237 71 925 686
Predicted load to UWW
collecting systems from
domestic sources (kg/day)
1.2 2.1 0.05 0.01 0.04 0.02
Measured mean total load to
the WWTS kg per day
2.6 3.3 0.3 N/A 0.1 0.15
% of potentially toxic
elements from domestic
sources in the UK
46.0 64.2 16.9 N/A 25.7 15.3

Based on the above results, changes in population behaviour, such as a shift to dishwasher
use rather than washing up by hand, would reduce potentially toxic element input into the
WWTS.
It is noted that, while the quantities of potentially toxic elements dissolved in water from
plumbing will vary across the Europe they will make up a significant proportion of the
potentially toxic element loading going to any WWTS.
Table 2.7 summarises the percentages of the domestic inputs at the Shrewsbury WWTS, in
the UK. As can be seen over a fifth of the copper, zinc, cadmium and nickel entering the
wastewater treatment plant from domestic sources are from faeces. This emphasises the
fact that faeces are an important source of potentially toxic elements pollution. This source is
also very difficult to reduce. The percentage inputs of chromium and lead from this source
are much lower.
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge
21
Table 2.7 Potentially toxic elements entering wastewater, breakdown by source [WRc,
1994]
Cu Zn Cd Ni Pb Cr
Percentages of total load
Break down of domestic sources as percentage of total metal entering WWTS
Bathing 12.4 1.2 0.3 1.6 4.4 0.1
Toilet 8.9 2.1 0.5 4.3 8.1 0.2
Washing
Machine
8.0 0.7 0.2 0.9 3.2 0.1
Miscellaneous 8.0 1.2 0.3 2.4 6.1 0.2
Plumbing Input
(% of total entering WWTS)
Dishwashing 7.1 0.6 0.2 0.8 2.7 0.1
Faeces 20.6 28.0 20.0 23.6 3.1 2.1

Washing
Machine
9.53 10.8 4.6 4.4 18.6 9.3
Bathing 0.2 2.6 0.9 0.8 1.1 0.3
Activities
(% of total metal entering
WWTS)
Dishwashing 2.6 4.6 11.2 1.1 5.1
Human faeces contain high concentrations of potentially toxic elements from normal dietary
sources and this represents a principal input of metals to domestic wastewater and sludge of
domestic origin. The normal dietary contribution of metals represents the background metal
concentration represents the background metal concentration and is the minimum
achievable in waste water and sludge.
Concentrations are expected to vary with the intake of metals in the diet, drinking water and
medication and may also be influenced by the increasing prevalence of mineral
supplementation of food, for example with zinc, iron, selenium, and manganese. One study
in France (ADEME 1997) found the following concentrations of potentially toxic elements in
faeces (as dry matter): Zn: 250mg kg
-1
, Cu: 68mg kg
-1
, Pb: 11mg kg
-1
, Ni: 4.7mg kg
-1
, and
Cd: 2mg kg
-1
. Differences can also occur due to geographical variations in the dietary habits.
For some elements, such as Cd, the weighted average concentration in sludge (e.g. 3.3 mg

kg
-1
in the UK) is typical of the amount originating naturally in faeces from the normal trace
amounts of this element ingested in food (typically 18.8 µg d
-1
). Other differences in reported
concentrations of Cd in different EU member states is discussed in section 2.3.
Domestic water and heating systems
Studies in the USA [Isaac et.al, 1997], and Europe [WRc 1994] show that corrosion of the
distribution-plumbing-heating networks contribute major inputs of Pb, Cu and Zn. Lead
concentration for instance can vary between 14 µg.l
-1
at the household input and 150 µg.l
-1
at
the output.
It has been found that concentrations of copper in sewage sludge are directly proportional to
water hardness [Comber et al 1996]. Hard water (high pH) is potentially more aggressive to
copper and zinc plumbing, increasing leaching. However, the opposite is true for lead in that
it dissolves more readily in than soft, acidic water. The high lead levels in drinking water in
Scotland due to its soft waters are a major concern.
Reductions in the amounts of copper and lead in wastewater have been reported by pH
adjustment of tap water and addition of sodium silicate. The addition of alkali agents to water
at the treatment stage and the replacement of much lead piping has led to reductions in lead
concentration [Comber et al., 1996]. Adjusting the pH of tap water may be limited by
practical and economic factors.
Zinc in domestic plumbing comes from galvanised iron used in hot water tanks but is less
problematic than lead and copper because the amount decreases with the ageing of the
installations. Copper corrosion and dissolution is also greater in hot water than in cold water
2. Potentially Toxic Elements

Pollutants in Urban Waste Water and Sewage Sludge
22
supplies [Comber et al 1996]. The 'first draw' (initial flow of water in the morning) has higher
amounts of copper and lead compared to subsequent draws [Isaac et.al., 1997]. The Cu
content was found to be between 73.7 and 1430 µg l
-1
, and Pb content between 8.3 and
22.3 µg l
-1
, much greater than in the average effluent from households. Water treatment
would be recommended for certain water domestic uses, such as boilers and heating
systems, in order to reduce the metal corrosion.
The type of housing was also found to be important by the WRc report [1994]. Table 2.8
gives an average concentration of effluent from two types of estates, "1960s residential" and
"1990s residential" from daily bulk- and flow-weighted samples. The larger copper levels
from the "modern estate" can be explained by the newer plumbing system. In many
countries copper is the major element used in plumbing. In the UK it has been estimated that
leaching from copper plumbing accounts for over 80% of the copper entering domestic
wastewater [Comber et al 1996]. The higher lead level found in the newer housing did not
correlate with similar studies comparing old and new housing and could not be explained
satisfactorily; as in general older houses in the UK contain more lead plumbing. Lead from
solders in the piping system may also be an important source. In other regions of the EU
steel and zinc galvanised iron are used widely. This may explain why zinc in sludge is
proportionally greater than Cu in other member states compared with the UK.
Table 2.8 Mean concentration of potentially toxic elements in the effluent from
households in two types of residential areas [WRc Report, 1994]
Zn Cu Ni Cd Pb Cr HgPotentially toxic
element concentration
µg.l
-1

" 1960s residential" 74.3 219.4 5.2 0.71 9.02 5.65 0.114
" 1990s residential" 147.0 458.3 7.56 0.34 90.61 3.3 0.088
In summary, potentially toxic elements entering UWW collecting systems from domestic
sources are related to:
• household water consumption
• the plumbing and heating system in the household
• the concentrations of potentially toxic elements in the products used in the household
and quantities of the products used
• any grey water recycling schemes
• how much of the products are discharged into wastewater.
2. Potentially Toxic Elements
Pollutants in Urban Waste Water and Sewage Sludge
23
2.1.2 COMMERCIAL SOURCES
Limited data is available for the potentially toxic element contribution from commercial
sources and health care inputs (such as hospital and clinical wastes). Inputs from artisanal
sources are looked at in more detail in a separate Case Study in Section 6.
Cadmium could originate from laundrettes, small electroplating and coating shops, plastic
manufacture, and also used in alloys, solders, pigments, enamels, paints, photography,
batteries, glazes, artisanal shops, engraving, and car repair shops. Data from ADEME
[1995], estimated that worldwide, 16000 tonnes of cadmium were consumed each year; 50-
60% of this in the manufacture of batteries and 20-25% in the production of coloured
pigments.
Chromium is present in alloys and is discharged from diffuse sources and products such as
preservatives, dying, and tanning activities. Chromium III is widely used as a tanning agent
in leather processing. Chromium VI uses are now restricted and there are few commercial
sources.
Copper is used in electronics, plating, paper, textile, rubber, fungicides, printing, plastic, and
brass and other alloy industries and it can also be emitted from various small commercial
activities and warehouses, as well as buildings with commercial heating systems.

Lead, as well as being used as a fuel additive (now greatly reduced or banned in the EU) it
is also used in batteries, pigments, solder, roofing, cable covering, lead jointed waste pipes
and PVC pipes (as an impurity), ammunition, chimney cases, fishing weights (in some
countries), yacht keels and other sources.
Mercury is used in the production of electrical equipment and is also used as a catalyst in
chlor-alkali processes for chlorine and caustic soda production. The main sources in effluent
are from dental practices, clinical thermometers, glass mirrors, electrical equipment and
traces in disinfectant products (bleach) and caustic soda solutions.
Nickel is used in the production of alloys, electroplating, catalysts and nickel-cadmium
batteries. The main emission of nickels are from corrosion of equipment from launderettes,
small electroplating shops and jewellery shops, from old pigments and paints. It also occurs
in used waters from hydrogenation of vegetable oils (catalysts).
Zinc is used in galvanisation processes, brass and bronze alloy production, tyres, batteries,
paints, plastics, rubber, fungicides, paper, textiles, taxidermy (zinc chloride), embalming fluid
(zinc chloride), building materials and special cements (zinc oxide, zinc fluorosilicate),
dentistry (zinc oxide), and also in cosmetics and pharmaceuticals. The current trend towards
electrolytic production of zinc which, in contrast to thermally produced zinc, has virtually no
cadmium contamination. This means that cadmium pollution to UWW due to the corrosion of
galvanised steel will in time become negligible. [SPEED 1993].
Platinum and platinum group metals (PGMs) such as palladium and osmium can enter
UWW from medical and clinical uses, mainly as anti-neoplastic drugs. The amount in
hospital/clinical effluent has been estimated to be between 115 and 125 ng l
-1
[Kümmerer
and Helmers, 1997, Kümmerer et.al., 1999] giving a total emission of 84-99 kg per annum
from hospitals in Germany. Other sources of platinum metals in the environment related to
commercial activities come from catalysts used in petroleum/ammonia processing and
wastewaters, from the small electronic shops, jewellery shops, laboratories and glass
manufacturing. Section 6 contains a detailed Case Study (a) on PGMs in urban waste water
and sewage sludge.