Characterisation of Hospital Wastewater: the Case of the CHUV

The aim of this study was to characterize hospital effluents in investigating the CHUV importance as source of pollutants, the range and amounts of pharmaceuticals that are used in the hospital and the need of source treatment of the hospital sewage. The CHUV is the biggest hospital of Lausanne (Switzerland), and 71% of its beds are in a building named “BH” (Hospital Building). The BH treats around 609 patients a day and releases an important volume of water (735 litres per patient per day), potentially highly concentrated in pharmaceuticals. The drugs the most delivered to the BH patients are the analgesic Paracetamol (787 g/day) and two anti-inflammatory substances: Ibuprofen (106 g/day) and Mefenamic acid (78 g/day). Among the 39 analysed pharmaceuticals, the most concentrated in the BH effluents are Paracetamol (423 ng/l) and Ciprofloxacin (22 ng/l). The CHUV effluents plus many other wastes from Lausanne city (homes, other health centres, etc.) are treated in Vidy wastewater treatment plant (WWTP). The treated water is then released into Lake Geneva. The load of pharmaceuticals from the CHUV was found to be relatively small, compared to the total load entering in Vidy WWTP. Maximal percentages of the WWTP inputs from the BH effluents were shown by two antibiotics: Ciprofloxacin (2.8%) and Sulfamethoxazole (4.3%). This indicates that many drugs are excreted in domestic wastewater. Although the drug levels in the water from the hospital are low compared to the total levels reaching the WWTP, they still represent a significant point source and wastewater treatment at the hospital or in the WWTP is necessary. But Vidy WWTP was shown to be particularly inefficient in treating some of the pharmaceuticals that entered it. Therefore, the risk for the environment has been assessed. Diclofenac, Ibuprofen, Paracetamol, Propranolol, Ciprofloxacin, Clarithromycin, Sulfamethoxazole and 17α-Ethinylestradiol were from 2 to 601111 times more concentrated in Vidy WWTP effluents than acceptable in terms of calculated risk quotient (RQ) values. So, in some cases, a very important risk for the environment has been demonstrated here. Improvements of the WWTP efficiency are now in progress as a response to this. Treated water leaving Vidy WWTP is further diluted (at least 84.7 times) when it enters Lake Geneva, however this study revealed detectable levels of some pharmaceuticals in the lake itself, albeit below the predicted no effect concentration (PNEC) in all cases measured in this study.

Recyclage des eaux usées en irrigation

Yeli Mariam Sou

The present study takes place in Ouagadougou (Burkina Faso), a typical Sub-Saharan city where water shortage and food crisis necessitate wastewater reuse in urban agriculture. Different issues linked to this practice were studied in two components separated in two experimental sites. The first part treats about agronomic and sanitary aspects and take place in the 2iE (International Institute for Water and Environmental Engineering) experimental site of Ouagadougou. The second component was emphasised on industrial effluents impacts on irrigated soil quality and takes place in Kossodo, an industrial suburb of Ouagadougou. The 2iE site is supply with treated wastewater from domestic origin. The effluent was used to realise the following objectives: (1) managed wastewater fertilizers to fit the plant needs; (2) assess different crops sanitary quality and the effectiveness of methods used for this assessment. Three treatments were tested: (i) irrigation with the treated wastewater (ii) irrigation with the treated wastewater and fertilizers management, adjusted to plant needs and (iii) conventional treatment i.e. fresh water irrigation and total doses of commercial fertilizers. Each treatment was tested on three different crops: lettuce (Lactuca sativa), carrot (Daucus carota) and eggplant (Solanum melongena). The first objective was achieved by comparing crops yields (on basis of wet and dry matter) obtained with the different treatments. The three crops, irrigated with only wastewater, led to yield reduction between the first and the second year. At the contrary, the adjusted treatment showed higher yield for lettuce, with comparable values to conventional treatment yield. However, the effects on carrot and eggplant did not demonstrate better results; indicating that further investigations must be completed for crops with longer growing periods. Most likely, the fertilizers management should better correspond to the crop period demand. The sanitary assessment (second objective) was performed by measuring the heavy metals concentration (Cd, Cu, Pb, Ni, Cr) and the faecal levels (faecal coliform, Escherichia coli and four pathogens among which Salmonella typhimirium and Vibrio cholerae). Chromocult Coliform Agar medium was used for simultaneous detection of faecal coliform and Escherichia coli whereas pathogens were analysed by Polymerase Chain Reaction (PCR). From methodological point of view, faecal coliform were not sufficiently discriminatory in the case of this study since they were naturally present in the soil as well as in the fresh water. At the contrary, Escherichia coli were better linked to wastewater contamination. However, some "false positive" results were detected meaning that each presumptive colony of Escherichia coli must be confirmed. Nevertheless, microbial quality assessment indicated no Escherichia coli on edible parts of carrot or eggplant irrigated with wastewater. Carrots were expected to have the poorest microbiological quality. Therefore carrot root bacterial quality must be further examined. Results on eggplant are not surprising as these vegetables are somewhat far from the ground and they receive significant solar radiation which acts like a disinfectant. Lettuce from wastewater treatment plots, however, exhibited presence of Escherichia coli, meaning that lettuce is likely to be contaminated by pathogens. However, no pathogens were detected neither on crops irrigated with fresh water nor on those irrigated with wastewater. Heavy metals results demonstrated that the crop's consumption did not involve higher risk for consumers when the vegetables were irrigated with domestic wastewater, in comparison with fresh water irrigation. Kossodo treatment plant receives mainly industrial wastewater, which are characterized by high levels of sodium and bicarbonates. The treated wastewater supplies a market garden in which space has been defined for the study of this second component. The main objective was to assess the impact of treated wastewater on soil quality during two years of irrigation. Early in the second year, the presence of black spots, suspected to be black alkali (dissolved organic matter), appeared at the surface of plots irrigated with treated wastewater. These indications led to put forward the hypothesis of alkalinisation/sodisation on soil receiving wastewater. The methodological approach used was based on in situ measurement of infiltration at the end of the second year of irrigation, supplemented by shrinkage curve modelling and chemical analysis. The hypothesis of an alkalinization/sodisation and dissolved organic matter (black alkali) presence in plots irrigated with treated wastewater were validated by the chemical analysis. Shrinkage curve modelling showed a reduction of the structural porosity on wastewater irrigated plots. The reduction was more marked in the subsurface horizons than in surface, which is probably caused by dispersed clay leached in depth. These structural changes were confirmed in situ by an infiltration capacity greatly reduced on plots irrigated with treated wastewater, compared to control plots (irrigated with fresh water) where the infiltration capacity is higher and comparable to that of non-irrigated soil. The study confirmed the fertilizing value of domestic wastewater while emphasizing the need to concentrate future investigations on sustainable effluent/fertilizers management. The sanitary assessment with different crops regarding their respective distances to the soil was very useful since it showed the strong interaction of soil microbial community on the crop microbial quality. It also revealed the importance to determine a faecal indicator for the crop, specifically related to wastewater contamination. Soil quality assessment reiterated the necessity to verify wastewater quality before its reuse in agriculture. In the case of this study, the sodic and alkaline properties of the industrial effluents make them definitively unfit for irrigation.

EPFL2009

Origines et flux de biocides et de filtres UV dans les stations d'épuration des eaux usées

Cécile Plagellat

Adverse effects on the environment have become a matter of increasing concern considering the increase of industrialization and of the amount of commercialized chemicals. At present, approximately 100'000 substances are on the market, 3000 are sold at high volumes. In Europe, 200 to 300 new substances are authorized every year (in Switzerland, approximately 50). Contamination is induced by consumption of numerous products frequently applied by private or professional users. Persistence and ecotoxicity of certain organic compounds contained in these products might have impacts on the quality of our environment. Knowledge on potential sources of these substances is the first step in order to limit their release. The project developed within the present PhD thesis aims at determining the sources of certain compounds by applying material flux analysis on the basis of sewage sludge. Presently, a large number of anthropogenic organic compounds originating from private households, craft industry, industry and stormwater is disposed of into the collector system and ends up in sewage sludge. Carbendazim, diuron, Irgarol 1051®, octhilinone, permethrin, tributyltin (TBT) and triphenyltin (TPT) comprise numerous applications as biocides and pesticides whilst methylbenzylidene camphor (4-MBC), octyl methoxy cinnamate (OMC), octocrylene (OC) and octyl triazone (OT) are used as UV-screens (type UVB) in a large number of cosmetic products. Their toxic effects on non-target organisms and their potential for bioaccumulation give rise to environmental concern. These substances are used as ingredients in products of daily use and are disposed of into wastewater. Due to their physico-chemical properties they are more or less lipophilic and are likely to persist in sewage sludge. On the basis of the analysis of sewage sludge samples from well characterized sites (catchments and wastewater treatment plants, WWTPs) it is possible to determine the sources (private households, craft industry, industry and stormwater). The first step of this study was the development of analytical methods which allow for quantification of these compounds in sewage sludge. Due to their different physico-chemical properties, four different methods were required. These methods have recovery rates ranging between 75 and 106 % and limits of detection in the order of μg/kg dry matter. The analysis of sludge from 12 sites obtained within 2 sampling periods show that most of the substances are present in all samples. Mean concentrations were 6,8 μg/kg dm (dry matter) for carbendazim, 9,5 μg/ kg d.m. for diuron, 98,1 μg/kg d.m. for permethrin, 148 μg/kg d.m. for TBT, 1777 μg/kg d.m.for 4-MBC, 110 μg/kg d.m. for OMC, 4834 μg/kg d.m. for OC and 5517 μg/kg d.m. for OT. Octhilinone was not detected whilst Irgarol 1051® and TPT were found in 7 and 11 samples, respectively. The transfer of these compounds from wastewater into sludge is an important parameter for material flux analysis on the basis of sewage sludge. A study on the fate of carbendazime and permethrin during wastewater treatment has been carried out on two WWTPs. Whilst removal of permethrin was high (>94%) up to 70% of carbendazime present in sewage were found in treatment plant effluents. Adsorption is an important process for removal of permethrin. However, only 4 to 15 % of the load in wastewater was transferred to sewage sludge. Carbendazim is mainly associated to the aqueous phase and thus, a very small quantity ends up in sludge (approximately 1%). Therefore, the loads found in sewage sludge are more or less representative for consumption of the compounds in the catchments according to their physico-chemical properties. Additionally, it has been shown that the part of permethrine ending up in sludge depends on the treatment techniques of the WWTPs. Thus, for comparison of the pollutant loads in sewage sludge between different sites their fate in the WWTPs has to be known. The loads per inhabitant of the three well characterized types of sites have been calculated in order to determine the sources of the substances. Type A comprises sites with a separate sewer system and a catchment where mainly private households are present. Type B has a combined sewer system collecting sewage from private households, craft industry and stormwater whilst type C comprises a combined sewer system which includes effluents from private households and industry as well as stormwater. The results are as follows: Stromwater is considered as main source of carbendazim in wastewater whilst diuron originates mainly from stormwater and from industrial effluents. Private households contribute significantly to the loads of permethrine and TBT in sewage. For UV-screens the loads from private households are also important but stormwater and industrial effluents are likely to be potential sources as well. A difference in consumption between rural (type A) and more urban sites (type B and C) is possible which might hamper a proper estimate of the sources of UV-screens.

EPFL2004

Presence of sub-inhibitory concentrations of quaternary ammonium compounds in water: effects on bacteria and their inactivation by ozone and monochloramine

Margaux Océane Voumard

Disinfection agents have been present in our daily lives for several decades in detergents or in personal care products, where their role is to prevent the spread of pathogenic microor-ganisms. One of the largest class of disinfection agents is quaternary ammonium compounds (QACs). Within this class, cetyltrimethylammonium chloride (CTMA) and benzalkonium chlo-ride (BAC) are widely used. QACs have a broad-spectrum effect on bacteria, where they pri-marily target the membrane. After use, QACs are partially discharged to municipal wastewaters, where they are diluted to concentrations in the sub-inhibitory range. These low concentrations of QACs can trigger resistance mechanisms in bacteria, including membrane modifications and the expression of efflux pumps.The aim of this thesis was to investigate the consequences and the impact of the presence of low concentrations of QACs in wastewater and surface water on the survival of bacteria. It could be demonstrated that strains of P. aeruginosa long-term exposed to constant sub-inhibitory concentrations of either BAC or CTMA showed decreased susceptibility to both QACs, regardless of which QAC the bacteria had been exposed to. However, no resistance to selected antibiotics was found after this exposure. Investigations of the membrane using atomic force microscopy showed an increase in surface roughness following exposure to both BAC and CTMA, demonstrating that QACs affect bacterial membranes.QACs are poorly biodegradable and their presence, even at constant sub-inhibitory concen-trations, affect bacteria. QACs are poorly reactive with chemical oxidants commonly used for water disinfection, which aims to inactivate microorganisms. Therefore, QACs remain present during water and wastewater treatment. Several methods of disinfection exist, where ozona-tion and monochloramination are widely applied worldwide. The effect of a pre-exposure of E. coli to CTMA and of the presence of CTMA during disinfection with ozone (O3) and mono-chloramine (NH2Cl) were investigated. The pre-exposure to CTMA led to contrasting results: inactivation of E. coli was enhanced when using ozone but decreased when using monochlo-ramine. This result demonstrates the different modes of inactivation of bacteria for ozone and monochloramine. Moreover, the role of efflux pumps during inactivation was tested with two strains of E. coli, expressing different efflux pump systems. These two strains showed contrasting behaviors when treated with either ozone or monochloramine. Nevertheless, we were unable to resolve the role of efflux pumps in this system. The presence of CTMA en-hanced the inactivation when concentrations were higher than 2 mgL-1 for ozone and 2.25 mgL-1 for monochloramine.Standard methods to determine the minimum inhibitory concentration use ideal conditions for bacterial growth, which do not occur in natural water. Therefore, the susceptibility of E. coli to CTMA in PBS, lake water (Lake Geneva, Switzerland) and a wastewater effluent was investigated and compared to nutrient broth. It could be shown that E. coli was significantly more susceptible to CTMA in dilute aqueous solutions compared to broth. These results are relevant to assess the effect of CTMA and potentially other biocides on bacteria under realis-tic conditions, as it is probably overestimated using the current standard methods for MICs determination.

EPFL2021