XENOBIOTIC ORGANIC COMPOUNDS IN GREY WASTEWATER:
A MATTER OF CONCERN?
E. Eriksson*, M. Henze and A. Ledin
Environment & Resources DTU, (Formerly Department of Environmental Science and
Engineering,) Technical University of Denmark, Bygningstorvet, Building 115, DK-2800
Lyngby, Denmark. E-mail: eve@er.dtu.dk, mh@er.dtu.dk, al@er.dtu.dk
*Corresponding author
ABSTRACT
A crucial point with respect to alternative handling of grey wastewater is the risk related to
the presence of different types of pollutants including xenobiotic organic compounds
(XOC’s). Low and variable efficiency in the treatment could be the result when biological
methods are used in the treatment steps before reuse for e.g. toilet flushing. Contamination of
soil and receiving waters will be of importance when grey wastewater is either used for
irrigation or infiltrated. It is necessary to know which compounds and concentration ranges
that are common in order to be able to evaluate the risk related to alternative handling of grey
wastewater. In this work, grey wastewater from bathrooms was analysed with respect to
XOCs, both qualitatively and quantitatively. The qualitative analyses positively identified 180
different XOC’s where the dominating compounds were long chained fatty acids and esters.
The quantitative analyses included 99 different compounds and summary parameters. Among
them were e.g. anionic detergents (up to 125 µg/l), cationic detergents (up to 2100 µg/l), di(ethylhexyl)-phthalate (up 39 µg/l) and 2,4- and 2,5-dichlorphenol (up to 0.13 µg/l). A
number of the compounds identified may present a risk to the environment if the wastewater
is infiltrated or irrigated without any previous treatment or to the active micro-organism
population in a biological filter that usually are used for treatment of grey wastewater before
reuse.
KEYWORDS
Grey wastewater; greywater; alternative handling; reuse; xenobiotic organic compounds
INTRODUCTION
There is a growing demand in the society for introducing integrated decentralised sanitary
systems providing opportunities to save and reuse wastewater. The awareness that the
centralised urban sanitation systems used for treatment of wastewater today may well be very
effective, but may also be expensive and resource consuming, is probably the main reason
behind this interest. Another reason to look for alternative handling of wastewater is the water
shortage, which is a problem in several parts of the world. One way to reduce the need for
freshwater is to reuse wastewater, after some decentralised, low or high tech treatment or
without any treatment at all depending on the sources and the reuse applications.
There is a focus today on the possibility for reusing the grey wastewater. The term refers to
wastewater produced in households, office buildings, hotels, schools as well as some types of
industries, where there is no contribution from toilets or heavily polluted process water. This
means that grey wastewater corresponds to wastewater produced from bath tubs, showers,
hand basins, washing machines, commercial laundries and dish washers, as well as kitchen
sinks. This fraction of wastewater has been estimated to account for roughly 75 volume-% of
the combined residential sewage (Hansen and Kjellerup, 1994 and references therein).
One possibility for recycling of grey wastewater is to use it for urinal and toilet flushing. It
has been estimated that 32 % of the total household water consumption could be saved by
reusing grey wastewater for flushing toilets (Karpiscak et al, 1990). Vehicle and window
washing, fire protection and concrete production are examples of other suggested usages.
Outdoor reuse like infiltration into the ground and thereby making a shortcut in the
hydrological cycle is an obvious alternative. The grey wastewater could also be used for
garden irrigation and in agriculture, and to develop and preserve wetlands.
The major problem related to all the suggested alternatives for reuse of grey wastewater is the
different types of risks related to handling and exposure (humans, animals, crops and
ornament plants) to grey wastewater. The risk for spreading of diseases, due to exposure to
micro-organisms in the water will be a crucial point for almost all alternatives suggested
above and has been given attention in published literature as well as in the regulations from
authorities (see e.g. Christova-Boal et al, 1996; Feachem et al, 1983). However,
contamination of soil and receiving waters (primary groundwater) as well as growing crops,
due to the content of different types of pollutants including XOC’s is another risk, that has not
yet been deeply discussed. This could e.g. lead to a deteriorating quality of the groundwater.
Reuse of grey wastewater for e.g. toilet flushing will require some treatment. Usually
decentralised, low-tech solutions are selected, like biological filters. However, there is an
obvious risk for low and variable efficiency of these filters due to the presence of toxic XOCs,
that will negatively affect the active micro-organism population in the filters. Other risks not
yet discussed are the possible development of resistant bacteria due to the continuous
exposure to preservatives that originates from the household chemicals.
In general terms, grey wastewater has lower concentrations of organic matter (measured as
the summary parameters BOD and COD), some of the nutrients (N and K) and microorganisms compared to traditional municipal wastewater (Ledin et al., 2001). The
concentration of phosphorus varies in a relatively broad range depending on the contribution
from washing detergents, which is the primary source for P in grey wastewater. The variations
are a function of the product used as well as the laws and regulations in the country. The
concentrations of heavy metals have been reported to be relatively low according to data
compiled by Ledin et al. (2001). No information with respect to the quantities of xenobiotic
organic compounds (XOC’s) has been found in the literature. However, two studies, reporting
on the presence of XOC’s in grey wastewater was found (Ledin et al., 2001). Santala et al.
(1998) used a screening method with GC-MS and showed that the major part of the organic
compound consisted of detergents and their amount corresponded to 60% of the measured
COD. The other study, also describing the results from a GC-MS screening of shower
wastewater, revealed that the even-numbered long chain fatty acids of C10 to C18 originating
from soap were present (Burrows et al., 1991).
These very limited results concerning the presence of XOC’s in grey wastewater are not
representative for the number of XOC’s that could potentially be present. There were 18
million synthetic substances known by science in 1998 (Platt McGinn, 2000) and it has been
estimated that some 20 000 substances are circulating in the Swedish technosphere
(Kemikalieutredningen, 2000). In municipal wastewater have at least 500 different
compounds been identified and quantified (Eriksson et al., 2001) and some these compounds
could be expected to be present in grey wastewater as well, since the main sources for the
XOC’s are different types of chemical products, such as laundry detergents, soaps, shampoos,
toothpaste’s and perfumes. It has been found from the information available in the declaration
of contents present on common household products that at least 900 different substances or
groups of substances could be present in grey wastewater (Table 1). The major compounds
were fragrances and flavours. Other large groups were preservatives, solvents and surfactants
used in detergents, dishwashing liquids and products for personal hygiene i.e. non-ionic,
anionic and amphoteric surfactants.
Table 1. Groups of compounds found in common household chemicals in Denmark and
Sweden (from Eriksson et al., 2001).
Compound group
Number of substances in the group
Amphoteric surfactants
Anionic surfactants
Cationic surfactants
Nonionic surfactants
Bleaches
Dyes
Emulsifiers
Enzymes
Fragrances & flavours
Preservatives
Softeners
Solvents
UV filters
Miscellaneous
20
73
34
65
16
26
28
4
197
79
29
67
23
238
211 of these approximately 900 different substances were selected to assess an environmental
risk assessment. This selection was based on the information possible to compile with respect
to fate (e.g. toxicity, bioaccumulation, biodegradation and mobility) in the environment. Out
of these identified to be potentially present in household chemicals. Out of them 66 were
categorised as priority pollutants. Among these were different types of surfactants (anionic,
nonionic, cationic and amphoteric), preservatives and softeners.
The objective for the present study was to evaluate the risk related to alternative handling of
grey wastewater with respect to the presence of XOCs. In order to be able to do that, it is
necessary to have a good characterisation of grey wastewater with respect to this very
heterogeneous group of compounds and that is why the major focus has been on analyses for
XOCs in grey wastewater form bathrooms.
MATERIAL AND METHODS
Sampling
Grey wastewater samples were taken in Bo90, a tenant owner’s society located in the central
part of Copenhagen, Denmark. The building has 17 apartments, where 38 inhabitants are
living; 22 adults (age 18-74) and 16 children (age 2-15). The grey wastewater produced
originates from the showers and hand basins in the building, where the daily production is
approximately 750 L. All samples were taken at the inlet to a grey wastewater treatment
facility that has been installed in order to treat the wastewater on-site and reuse it for toilet
flushing. The samples were taken in glass bottles and transported cold and in the dark to the
laboratory, where the analyses started immediately.
Analyses
The grey wastewater was analysed with respect to; i) screening analyses with purpose to
identify the XOCs present and ii) quantitative analyses for a selected number of XOCs.
The analyses in the first part included solid phase extraction with four different solid phases.
The neutral polar organic compounds were extracted and pre-concentrated on C18 (IST
Isolute) and HLB (Waters Oasis) and were sequentially eluted with hexane, hexane:diethyl
ether (1:1), diethyl ether, methanol:water (1:1), methanol:water (8:2) and methanol according
to the procedure described by Paxéus and Schröder (1996). SCX (IST Isolute) columns were
used for extraction and pre-concentration of bases and the compounds were sequentially
eluted with acetonitrile and methanolic ammonia. All extracts were reduced to a volume of
200 µL by a stream of pure nitrogen gas or by rotary evaporation. The organic acids were
extracted and pre-concentrated on Empore anion exchange discs (Chrompack) and in-vialderivatised with methyliodide (Eriksson and Ledin, 2001). A Hewlett-Packard 6890 Series
chromatograph and a HP 5973 MS detector were used for the GC analysis, while the
injections were performed with a Varian 8200 CX Autosampler. Tentative identification of
the organic compounds were obtained from searching in the NIST MS-library (Version 1.1a)
and the library NBS75K in the Enhanced ChemStation G1701AA. The compounds were
considered positively identified if their spectra and retention time correlated with that of an
external standard or if the spectra corresponded with the spectra’s from the two libraries.
Quantitative analyses were performed, in the second part of the study, either in our laboratory
according to the methods give above, after calibration of the GC-MS signals with known
concentrations of standards or by a commercial laboratory according to their standard
methods. The analyses included 99 different compounds and summary parameters.
Furthermore, semi quantitative results were obtained from the qualitative analyses by
comparison between the chromatographic area of the selected compounds and the
chromatographic area of the internal standard with a known concentration.
General hydrochemical characterisation (pH, temperature, alkalinity, electrical conductivity,
oxygen content, BOD, COD, tot-N, and tot-P) was also included in the sampling protocol.
RESULTS AND DISCUSSION
Qualitative analyses
180 different XOCs were positive identified in the grey wastewater from the qualitative
analyses. The dominating compounds were the long chained fatty acids (C10-C24) and their
esters e.g. methyl-, butyl-, hexadecyl- and octadecyl-esters. Other important groups of
compounds were the fragrances and flavourings e.g. Eucalyptol, Eugenol, Coumarin, Menthol
and Hexyl cinnamic aldehyde, where in total more than 40 fragrances and flavours were
identified (Table 2). It can also be noted that several miscellaneous compounds, which not
directly were deriving from the household chemicals have been identified e.g. medicinal
residuals, flame-retardants as well as the drugs nicotine and caffeine. Notably was also the
insecticide Malathion, which was found in a number of samples.
The presence of medicine residuals and drugs can be explained by excretion from humans
during showering, tooth brushing and washing (present on the skin or in the mouth or
urination (during showering)). Flame-retardants could be originating from clothes and
therefore also be present on the skin, while Malathion is used as the active ingredient in a
louse shampoo and can be purchased at the Danish pharmacies. It was later confirmed that
the tenants had used this type of shampoo during the sampling period.
Table 2. Groups of compounds found by screening in grey wastewater from Bo90.
Compound group
Number of substances in the group
Emulsifiers
Fragrances & flavours
Preservatives
Softeners
Solvents
Surfactants
UV filters
Miscellaneous
8
40
8
9
29
21
1
65
The group “Preservatives” consists of six preservatives and two antioxidants. The
antioxidants found were butylated hydroxytoluene (BHT) and Ethyl antioxidant 762. Among
the observed preservatives were e.g. citric acid and phenoxy acetic acid as well as Triclosan.
The latter is mainly used as antibacterial agent in toothpaste. A semi quantification indicated
an average concentration of 0.6 µg triclosan/L. The emulsifiers identified were long chained
fatty esters, alcohols and amines e.g. hexa- and octadecanol and N,N-dimethyl-1dodecaneamine.
The three plasticizers; di-(ethylhexyl) phthalate (DEPH), di-(ethylhexyl) adipate (ester of
hexanedioic acid) and di-(ethylhexyl) sebacate (ester of decanedioic acid) were positively
identified as well as one UV-filter/sun screen agent, Parasol MOX.
Quantitative analyses
Quantitative analyses for the fatty acids (C8 to C18) showed that the dominating acids were
lauric acid (C12), oleic acid (C18:1) and stearic acid (C18:0) (Table 3). It was also shown that
some of the chlorophenols, which are preservatives and pesticides were present, as well as
four phthalates.
Relatively small amounts of the BTEX’s were measured in the inflow to the treatment plant
(Table 3). They are e.g. used as solvents for organic fragrances and dyes in the otherwise
water based chemicals.
Table 3. Concentration ranges (µg/L) for some XOC’s quantified in the grey wastewater.
Compound
Group
Compound
Fatty acids
(C8)
(C10)
(C12)
(C14)
(C16)
(C18:1)
(C18:0)
Concentration
range
(µg/L)
<1 – 639
<1 – 1190
<1 – 6900
<1 – 1890
<1 – 260
27 – 3580
2 – 27100
BTEX’s
Benzene
Toluene
Ethylbenzene
m-Xylene
o-Xylene
p-Xylene
N.D.
1.4 - 1.6
2.0
3.4 - 3.6
0.5 - 0.7
N.D.
Phthalates
Di-(ethylhexyl) phthalate
Dibutyl phthalate
Diethyl phthalate
Dimethyl phthalate
11 – 39
<1 – 12 sqa.
<1 – 13
<1 – 15 sqa.
Chlorophenols
2,4- & 2,5-Dichlorophenol
2,4,6-Trichlorophenol
2,3,4,5-Tetrachlorophenol
2,3,4,6-Tetrachlorophenol
Pentachlorophenol
0.06 - 0.13
<0.02 – 0.10
<0.02
<0.02
<0.02 – 0.04
Nonionic
detergents
Anionic
detergents
Nonylphenol
<0.5
Nonylphenolethoxylates
Octylphenol
Octylphenolethoxylates
<5.0
<0.25
<3.0
LAS
<25-125
Cationic detergents Summary
detergents
of
several
cationic
<100-2100
N.D. = not detected
sqa. = semi quantitative analyses
The anionic detergent LAS were found in the concentration range from <25 to 125 µg/L in the
grey wastewater (Table 3). Corresponding values for the cationic detergents were <100 to
2100 µg/L. In this case will the cationic detergents mainly derive from hair conditioners and
not from fabric softeners, since the laundry wastewater were not included. The content of the
nonionic detergents included were below the detection limits for the applied methods.
A majority of the compounds found by quantitatively and qualitatively analyses were also
found to be on the list of possible present compounds deriving from household chemicals
(Eriksson et al., 2001). Among these were the long chained fatty alcohols and acids, as well as
the long chained fatty esters. Several fragrances as citronellol, coumarin, eugenol, farnesol,
geraniol, isoeugenol and hexyl cinnamic aldehyde and some preservatives e.g. citric acid,
salicylic acid and triclosan were identified in the grey wastewater as well as present on the list
over potential compounds. Other examples are the phthalates e.g. dibutyl and dimethyl
phthalate and methyl phenol.
The major differences were that the grey wastewater also contained a number of chemicals
not deriving from household chemicals e.g. medicinal residuals as well as degradation
products mainly caused by hydrolyzation of some XOCs.
CONCLUSIONS
Almost two hundred different XOCs were identified in grey wastewater from bathrooms in a
building with apartments (i.e. grey wastewater originating from showers and hand basins). A
majority of these compounds were among those compounds that earlier had been proposed as
potentially present compounds e.g. the long chained fatty alcohols and acids, e.g. hexa- and
octadecanol and octadecenoic acid as well as the long chained fatty esters e.g. isopropyl
myristate. Several fragrances like citronellol, coumarin, eugenol, farnesol, geraniol,
isoeugenol and hexyl cinnamic aldehyde were identified as well as some preservatives e.g.
citric acid, salicylic acid and triclosan. Other examples are the phthalates e.g. dibutyl and
dimethyl phthalate and methyl phenol. The measurements also showed that unwanted and
unexpected compounds like biocides and insecticides could be present as well as chemicals
not directly deriving from household chemicals e.g. flame retardants and medicine residuals.
Among the XOCs found in the grey wastewater were several characterised as high priority
compounds i.e. with high environmental impact. Among those compounds were e.g.
fragrances like hexyl cinnamic aldehyde. This means that the presence of XOCs in grey
wastewater may constitute a risk to the environment if the water is infiltrated or irrigated
without any previous treatment. However, the information about toxicity, bioaccumulation
and biodegradation for these compounds is limited and the number of compounds classified as
priority compounds may drastically increase if more information will become available.
Furthermore the number of XOCs could also be expected to increase if other analytical
methods are applied in the work for characterisation of grey wastewater.
REFERENCES
Burrows, W.D., Schmidt, M.O., Carnevale, R.M., and Schaub, S.A. (1991) Nonpotable reuse:
Development of health criteria and technologies for shower water recycle. Wat. Sci.
Tech. 24 (9) 81-88.
Christova-Boal, D., Eden, R.E., and McFarlane, S. (1996) An investigation into greywater
reuse for urban residential properties. Desalination 106: 391-397.
Eriksson, E. and Ledin, A. (2001) Analyses of organic acids by solid phase extraction in
combination with in-vial-derivatisation and elution. (Manuscript in preparation).
Eriksson, E., Auffarth, K., Henze, M. and Ledin, A. (2001) Characteristics of grey
wastewater. (Manuscript in preparation).
Feachem, R.G., Bradley, D.J., Garelick, H., and Mara, D.D. (1983) Sanitation and disease
Health aspects of excreta and wastewater management. Published for the World Bank,
John Wiley & Sons, p. 16-21.
Hansen, A.M. and Kjellerup, M. (1994) Vandbesparende foranstaltninger. Copenhagen:
Teknisk Forlag. (In Danish)
Karpiscak, M.M., Foster, K.E., and Schmidt, N. (1990) Residential water conservation: Casa
Del Agua. Wat.Res. 26 (6): 939-948.
Kemikalieutredningen
(2000)
Varor
utan
faror.
SOU2000:53.
Stockholm,
Miljödepartementet. (In Swedish)
Ledin, A., Eriksson, E. and Henze M. (2001) Aspects of groundwater recharge using grey
wastewater. Decentralised Sanitation and Reuse, DESAR EURO Summer School in
Wageningen The Netherlands, ed. Lens P., Lettinga G. and Zeeman G. (In Press)
Paxéus, N. and Schröder, H.F. (1996) Screening for non-regulated organic compounds in
municipal wastewater in Göteborg, Sweden. Wat. Sci. Tech. 33 (6): 9-15.
Platt McGinn, A. (2000) Avveckling av persistenta organiska föroreningar (POP). Tillståndet
i världen 2000, Naturvårdsverket. (In Swedish)
Santala, E., Uotila, J., Zaitsev, G., Alasiurua, R., Tikka, R., and Tengvall, J. (1998)
Microbiological greywater treatment and recycling in an apartment building. AWT98 Advanced Wastewater Treatment, Recycling and Reuse: Milan 14-16 September 1998.
pp. 319-324.