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EFFECTS OF HOSPITAL WASTEWATER ON AQUATIC ECOSYSTEM
Evens EMMANUEL (*)
Université Quisqueya, LAQUE, BP 796, Port-au-Prince, Haïti
ENTPE, L.S.E., Rue Maurice Audin, 69518 VAULX-EN-VELIN
École Nationale Vétérinaire de Lyon, BP 83, 69280 MARCY l’ETOILE
INSA de Lyon, LAEPSI, 20 avenue Albert Einstein, 69621 Villeurbanne Cedex
INSA de Lyon, LAEPSI, 20 avenue Albert Einstein, 69621 Villeurbanne Cedex
(*) He is teaching drinking water and wastewater treatments and he is the Director of the Laboratory of Water Quality
and Environment at Quisqueya University in Haiti. Actually, he is doing his Ph’D in management and treatment of
waste at the National Institute of Applied Sciences (INSA) of Lyon (France), in collaboration with the National School
of State Public Works (France), and the National Veterinaire School of Lyon where he works on “Ecotoxicological and
sanitary risk assessment related to hospital wastewater”.
Address of corresponding author (*): École Nationale des Travaux Publics de l’État, Laboratoire des Sciences de
l’Environnement, Rue Maurice Audin, 69518 VAULX-EN-VELIN, France – Tel : + (33) 4 72 04 72 89 – Fax + (33) 4
72 04 77 43. e-mail : firstname.lastname@example.org , email@example.com
Hospitals generate on average 750 liters of wastewater by bed and a day. These effluents are loaded with pathogenic
microorganisms, pharmaceutical partially metabolised, radioactive elements and other toxic chemical substances. The
dosage of pollutants of hospital origin shows that certain substances, such as anti-tumor agents, antibiotics, 131I and
organohalogen compounds (OHC) like AOX, leave mostly wastewater treatment plants (WWTP) without any
degradation. By leaving the WWTP, these chemical compounds can provoke the pollution of the natural environment by
entailing a biological imbalance. In case the environmental conditions allowing the degradation of these substances are
not gathered, they can exercise negative effects on the receiving waters and the living species. This study aims at
presenting both the primary results on the biological, physico-chemical and ecotoxicological characterisation of the
hospital wastewater before their discharge in the municipal sewage system and their effects on the urban wastewater
systems and the environment. The application of the ecotoxicity tests Daphnia magna Strauss on the hospital wastewater
samples, in a big city of the southeast of France, indicated a maximal acute toxicity of 116.8 équitox/m3. The high
results obtained for the ecotoxicological tests confirm the existence of hazardous substances in hospital wastewater.
Considering the volume of wastewater generated by the hospitals and of the extreme diversity of physical, chemical and
biological evolutions that these effluents can know it seems important to make their ecotoxicological and sanitary risk
Keywords: hospital wastewater, WWTP, ecotoxicity, drugs and environment, risk assessment.
Hospitals consume an important volume of water a day. Indeed the consumption of domestic water, is on average 100
liters/person/day (Gadelle, 1995), while the value generally admitted for hospitals varies from 400 to 1200 liters/day/bed
(Deloffre-Bonnamour, 1995 ; CCLIN, 1999). In France, the average needs in water of a university hospital center is
estimated at 750 liters/bed/day (CCLIN, 1999). This important consumption in water of hospitals gives significant
volumes of wastewater loaded with micro-organisms, heavy metals, toxic chemicals, and radioactive elements (CCLIN,
XXVIII Congreso Interamericano de Ingeniería Sanitaria y Ambiental
Cancún, México, 27 al 31 de octubre, 2002
1999 ; Leprat, 1998). As a result the hospitals generate hybrid wastewater, at the same moment domestic, industrial and
effluents of care and medical research (Deloffre-Bonnamour, 1995 ; Jehannin, 1999 ; Emmanuel et al., 2001).
The characterisation works realized on the microbiology of the hospital effluents put in evidence in a systematic way the
presence of germs having acquired the characters of resistance in antibiotics (Leprat, 1998). A concentration of bacteria
flora of 3x105/100mL (Leprat, 1998 ; Bernet and Fines, 2000) is deducted for the hospital effluents. These
concentrations are lower than that of the 108/100mL generally present in the municipal sewage system was deducted for
the hospital wastewater (Metcalf and Eddy, 1991). Markers of viral pollution of surface water, such as enterovirus and
other viruses such adenovirus, were identified in the hospital effluents [Mansotte and Jestin, 2000]. Enterovirus appears
in important quantity in wastewater. Their presence, as marker of viral pollution, in the hospital effluents is to correlate
to that of other viruses. Besides, the HIV, causal agent of the AIDS, was isolated from biological liquids and excretions
of infected persons. These liquid effluents, directly rejected in the network drainage of research laboratories and
hospitals, can contribute under certain physico-chemical conditions to the presence of the virus in the urban sewer
networks and in the WWTP (Wastewater Treatment Plant). Indeed, Casson et al. (1997) mention the presence of
infectious particles (IP) of HIV in natural and wastewater. Lue-Hing et al.  found a concentration of PI of HIV by
liter included between 1.4 x 10-2 and 8.6 x 10-1 (lower than 1 IP of HIV by liter of effluent) for the city of Chicago.
Hospital wastewater reveals the presence of molecules chlorinated in high concentrations and in a punctual way the
presence of heavy metals such as mercury and silver. Concentrations in AOX superior to 10 mg/L were proved in the
effluents of the hospitalization services of a university hospital center (Gartiser et al., 1996). The AOX have a bad
biodegradability and a bad behavior of adsorption (Sprehe et al., 1999). The application of Ames and Hamster cell tests
on hospital wastewater indicate that these effluents are potentially mutagenic (Gartiser et al., 1996). The origin of this
mutagenic potential remains to be investigated. The value of the total hospital wastewater showed a high toxicity as
determined using the daphnia and luminescent bacteria tests. (Leprat, 1998; Emmanuel et al., 2001 ; Jehannin, 1999).
The dosage of pollutants of hospital origin shows that certain substances, particularly organohalogens and
pharmaceutical partially metabolised, leave mostly WWTP without any degradation (Richardson and Bowron, 1985;
Gartisser et al., 1996 ; Kümmerer et al., 1997 ; Halling-Sorensen, 1998 ; Sprehe et al., 1999). Indeed, since the 1980s.
Data about the occurrence of pharmaceuticals in natural surface waters and the effluent of sewage treatment plants have
been reported (Richardson and Browron, 1985 ; Kümmerer et al., 1997). Stan et al. (1994) have measured
pharmaceuticals in ground and drinking water. Pharmaceutical drugs given to people and to domestic animals --
including antibiotics, hormones, strong painkillers, tranquilizers, and chemotherapy chemicals given to cancer patients --
are being measured in surface water, in groundwater, and in drinking water at the tap. Large quantities of drugs are
excreted by humans and domestic animals, and are distributed into the environment by flushing toilets and by spreading
manure and sewage sludge onto and into soil (Montague, 1998). Investigations in the United Kingdom as reported by
Waggott (1981), Watts et al. (1983) and Richardson and Browron (1985) revealed that drugs were present in the aquatic
environment at concentrations up to approximately 1 µg/L. On Iona Island (Vancouver/Canada) the two antiphlogistics,
ibuprofen and naproxen have been identified in sewage (Rogers et al., 1986). Hignite and Azarnoff (1977) detected
loads of salicyclic acid up to 28.7 kg/d and of clofibric acid up to 2.7 kg/d in the effluents of the municipal sewage
treatment plant of Kansas City (USA). Earlier investigations of drug residues in WWTP effluents were focused on
clofibric acid, the major metabolite of three lipid regulators (etofibrate, etofyllinclofibrate and clofibrate) (Ternes, 1998 ;
Stumpf et al., 1999). Garrisson et al. (1976) detected clofibric acid in the lower µg/L-range in treated wastewater in the
United States. Waggot (1981) found clofibric acid in the River Lee (Great Britain) at concentration levels below 0.01
µg/L and in Spain clofibric acid was detected in ground water samples (Galceran et al., 1989). In Germany the clofibric
acid has been identified in river and ground water and even in drinking water with concentration levels ranging up to
165 ng/L by Stan et al. (1994), Heberer and Stan (1996).
ENVIRONMENTAL PROBLEMS WITH HOSPITAL WASTEWATER
One of the main environmental problems putting by the hospital effluents is their discharge, in the same way as the
urban classic effluents, towards the urban sewer network without preliminary treatment. The figure 1 illustrates the
environmental problem with the hospital effluents.
Figure 1-The environmental problem with hospital wastewater
This study aims at presenting both data on the biological, physico-chemical and ecotoxicological characterisation of the
hospital wastewater before their discharge in the municipal sewage system and their effects as well as those of the
pharmaceuticals and disinfectants on the urban wastewater systems and on the environment. In addition, this review on
hospital wastewater allows identifying some environmental stressors released by hospital activities. This knowledge is
important for risk assessment as well as risk management related to hospital effluents.
MATERIALS AND METHODS
The effluents of the service of infectious and tropical diseases of a hospital of the Southeast of France were collected for
the determination of the various physico-chemical, microbiological and ecotoxicological parameters. Water sampling
took place from february 22 to march 22 of 2001, and from march 1 to march 22 of 2002 (rainy season) on the effluents
of this service of 144 beds. Samples are taken in a deep well of 4 m about of the hospital ’s sewage system. The
European and French standards were applied in the determination of the different parameters with the exception of the
COD (only for samples of 2001) where the protocol HACH was used. To evaluate the toxicity of industrial effluents,
French water agencies have developed a specific unit called “équitox/m3” (which is equal to: 1/EC x 100 or 1/IC x 100).
This unit has been use in this study for the ecotoxicity tests. Table 1 supplies the parameter standards.
Administered drugs to the patients
Excretion of the patients with
pharmaceutical residues (drugs and
urban sewer network
Wastewater treatment plant
Purification water plant
Wastewater from care activities and medical
research (blood, urine, feces, gastric liquid,
…, solvents, acids, bases, miscellaneous
reagents, radio elements, disinfectants,
cleaners , …)
TABLE 1 : Selected parameters and their protocol of execution
PARAMETERS STANDARD UNIT
SSM NF EN 872 mg/L
BOD NF EN 1899-1, 05/98 mg/L
pH NF T90-008 -----------------------------------
Conductivity NF EN 27888, IS0 7888 mS/cm
COD HACH & NF T 90-101 mg/L
TOC EN 1484 mg/L
Chlorides ISO 10 304 mg/L
AOX ISO 9562 mg/L
Fecal coli. (E. coli) NF T 90-433 N/100mL
Microtox NF EN ISO 11348-3 Equitox/m3
Daphnia magna Strauuss NF EN ISO 6341 Equitox/m3
RESULTS AND DISCUSSIONS
Table 2 shows the different values obtained for the selected parameters.
TABLE 2 – Concentration of the selected parameters
PARAMETERS UNIT MEAN MINIMA MAXIMA
Conductivity mS/cm 1 0,524 1,669
PH ------------ 7,85 6,26 8,52
Chlorides mg/L 8,2 7,9 8,5
SSM mg/L 225 155,16 297,6
AOX mg/L 0,67 0,38 1,24
BOD5 mg/L 603 251 1 559
COD mg/L 1 223 604 2 590
TOC mg/L 211 160 350
BOD5/COD -------------- 0,43 0,31 0,60
Microtox Equitox/m3 30,35 24,07 40,51
Daphnia magna Strauss Equitox/m3 46,26 9,8 116,7
A concentration of bacteria flora of 2,4x103/100mL lower than that of the 108/100mL generally present in the municipal
sewage system was deducted for the hospital wastewater. These effluents present an important concentration in AOX
(1,24 mg/L), in chlorides (359,45 mg/L) and have an average report BOD5 / COD of 0,43. The average concentrations
obtained for the hospital effluents have been compared with the medium values of the municipal wastewater. The table 3
illustrates the load in pollutants, which the hospitable effluents can bring to the municipal sewage system and their
possible impact on treatment mechanisms of the WWTP.
TABLE 3: Comparison of the average concentrations in pollutants of hospital effluents (H.E.) and urban
classic effluents (C.U.E)
POLLUTANTS UNITS CONCENTRATIONS IN
Suspended Solid Matters mg/L 300 225
BOD5 mg/L 220 603
TOC mg/L 160 211
COD mg/L 500 855
Total Phosphorous mg/L 8 8.80
Chlorides mg/L 50 188
This high toxicity, of 116.8 équitox/m3 indicated by the application of the ecotoxicity tests Daphnia magna Strauss on
hospital wastewater samples, is due probably to the presence of organohalogen compounds resulting from the use of the
hypochlorite of sodium and some iodized substances, in considerable quantities, in the disinfection of hospital effluents
(Emmanuel et al., 2002). Made before the implemented of the processes of settling of solid substances and filtration of
the floating, this disinfection leads to an increase of the concentration of organohalogen compounds (OHC) resulting
from reactions of oxide-reduction between the organic matter and the disinfectants. OHC are mostly lipophilic,
persistent, and toxic (Carey et al., 1998). Emmanuel et al. (2002), at pH ≥ 8, are used chlorides as indicators of hospital
wastewater toxicity on daphnia. A coefficient of correlation r=0,978 was found between the concentration in chlorides
and the results of the test of ecotoxicity on Daphnia. The equation of the model is Y= -24,147 + 0,369X or equitox/m3
[Daphnia] = -24,147 + 0,369 [Cl-] mg/L. Figure 2 shows the graph of the linear regression between Daphnia and
Figure 5 – Graph of the linear regression between Daphnia and chlorides
EFFECTS OF HOSPITAL WASTEWATER ON URBAN WASTEWATER SYSTEMS - AND ECOLOGICAL
Having crossed the maximal threshold of efficiency of unitary process, the flow and the polluting load of the hospital
effluents have already provoked in the municipal WWTP the effects of saturation which allow releasing pollutants in the
natural environment (Figure 2). In theory, the flow of the liquid effluents (expressed in m3/s) and their superficial charge
or polluting charge by unit surface (expressed in m3/ m2/s) are among the main parameters which enter in the design of
almost all the reactors constituting the units of treatment of WWTP. They participate largely in the definition of the
maximal threshold of efficiency of the WWTP. For unitary systems in operation, as the reactors of WWTP, any increase
of the hydraulic load and/or the organic and inorganic loads of wastewater can entail the demonstration of a
phenomenon of excess load in the mechanisms of cleanup.
Hospital effluents +
Releasing of pollutants
Y = - 24.147 + 0.369
r = 0.978
0 100 200 300 400
X : c h l o r i d e s
Y : Daphnia
Level of cleanup of WWTP Maximal threshold of efficiency
0 Threshold Level of hospital
Figure 2– Effects of hospital effluents on WWTP
The hospital effluents have generally a very weak microbiological load resulting from the regular use of disinfectants.
These bactericides can have a negative influence on the biological processes of the WWTP. Even by considering that
these effluents are diluted after their discharge towards the municipal WWTP, it remains evident that it is not necessary
to neglect the possibility that certain substances present in the WWTP effluents can generate by cumulative effect a
biological imbalance in aquatic ecosystem. To protect the natural environment against the phenomenon of excess load in
the processes of the WWTP, it seems important to consider upstream treatments of hospital wastewater before their
discharge in the municipal sewage system (Emmanuel, 2001).
Indeed, the contact of hospital pollutants with the elements of the aquatic ecosystems puts in evidence a danger which is
bound to the existence of hazardous substances, i.e., which have the potentiality to exercise negative effects on the
environment and the living species (Rivière, 1998). In case the environmental conditions allowing the degradation of
these substances are not gathered, hospital pollutants risk to be present for a long time in the natural environment and
can represent a risk in short, middle and long term for the living species of the ecosystems.
The risk is the probability of appearance of toxic effects after the exposure of the living organisms to hazardous objects.
The existence of a possible exposure of biological, chemical and radioactive substances released by hospital effluents
conducts to take into account, the eventuality of a radioactive chemical and microbiological risk for the abiotic system
and the living species which populate them. Rivière (1998) distinguishes the hazardous products of the others by their
capacity to provoke toxic short-term effects (mortality) or in the long-term (appearance of cancers, reproduction
problems, etc.). The high results obtained for the ecotoxicological tests confirm the existence of hazardous substances in
hospital wastewater. Considering the volume of wastewater generated by the hospitals and of the extreme diversity of
physical, chemical and biological evolutions that these effluents can know it seems important to make their
ecotoxicological and sanitary risk assessment.
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