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Investigating The Toxicity Of Hospital Wastewater

Congress: 2015
Author(s): Colin Hunter (Glasgow, UK)

Keyword(s): Sub-theme 2: Surface water and groundwater,



One of the major challenges facing the wastewater treatment industry is the prevalence of micro-pollutants. These organic substances occur in the range of a few ng or µg/l and include pharmaceutically active compounds. While some micro-pollutants are effectively removed by traditional wastewater treatment plants (WWTP) many are not biodegraded or adsorbed onto sludge enabling them to pass unchanged into the rivers and other watercourses with the treated wastewater. Contamination of surface and ground waters by these compounds has been recognised in a number of countries as of environmental concern.

Pharmaceuticals and pharmaceutically active compounds enter the environment through different pathways, Snyder et al.2 stated that the main pathways for entry into the environment can be categorised as the following two routes: hospital/health care sources and domestic/industrial sources. As point sources effluents from hospitals, care homes and other health care provider institutions are of interest to the wastewater treatment industry as they are easier to control, regulate or manage. The first stage in any consideration of the requirement to instigate control measures is the quantification of the problem, this in terms of pharmaceuticals could be done chemically using sophisticated techniques however this is time consuming, expensive and yields information about a handful of compounds. Ecotoxicological assessment has advantage over the traditional chemical methods by allowing, for example, the interactive effects of complex mixtures to be evaluated.

As part of the PILLS (Pharmaceutical Input and Elimination from local Sources) project Glasgow Caledonian University attempted to characterise wastewater ecotoxicologically from hospitals in urban and rural setting along with the associated WWTP's.

Materials & Methods

Samples were taken between Aug 2010 and Feb 2012 from four hospitals and two WWTPs. The urban hospitals were a 318 bed general hospital and a 120 bed geriatric hospital. A 300 bed general hospital and a small 16 bed geriatric hospital were monitored as rural locations. Chemical characterisation of the effluent was carried out using standard parameters (pH, COD, BOD, etc). Samples were pre-concentrated, prior to ecotoxicological evaluation, with the use of Strata-X columns with the final volume of the tested sample concentrated 200 fold. Toxicity of serial diluted samples was evaluated using inhibition of bioluminescence produced by Aliivibrio fischeri measured at regular intervals up to 30 min exposure and measurement of the effective quantum yield of photosystem II of Raphidocelis subcapitata after 4.5 hour exposure using the saturation pulse method (Genty et al.1). IC50 values were determined by the least -- squares method and converted into toxic units (TU).

Results & Discussion

In total 171 samples were analysed from the three locations: 54% were from general hospitals; 27% from geriatric hospitals and 19% from WWTPs. For A. fischeri evaluated samples IC50 were determined for all samples but for R. subcapitata around 19% were found, even at the most concentrated, not to cause fluorescence inhibition of >50%. Of these 50% were reported at the WWTPs and only 10% from general hospitals.

Over the incubation period the inhibition of the bioluminescence remained relatively the same for all samples and after 30 minutes the mean TU value for WWTP and geriatric hospitals were comparable; the toxicity for general hospitals was between 1.8 and 3.2 times more toxic than the other two locations. When all samples were combined into either rural or urban locations the mean TU for rural samples was 487 and for urban samples it was 252.

Similar results were obtained with R. subcapitata, as was observed with A. fischeri, with the WWTP and geriatric hospitals having similar levels of toxicity and the general hospitals again yielding toxicity levels well in excess of the other locations. The maximum TU for general hospitals was 194; for geriatric hospitals it was 19 and 36 for WWTP's.

The distinct difference in toxicity between the two hospital types is probably linked to the increased range of medical procedures, and thus pharmaceutical usage, occurring in the general hospitals that provide facilities for the entire population whereas the two geriatric hospitals focus on rehabilitation services for older patients. Centralising procurement within the UK national health service has restricted the range of cleaning and disinfecting products available to individual hospitals and thus it is likely similar products are used in the four hospitals monitored reducing the potential that the difference in toxicity might be due to the choice of cleaning products. While the level of phosphates (a marker for cleaning products) in the general hospitals was slightly higher than geriatric hospitals (average 8.1 mg/l vs 5.7 mg/l) the correlation with A. fischeri toxicity was moderate (R2 0.438) but weak (R2 0.136) for R. subcapitata.


While this study demonstrated that raw hospital wastewater is more toxic to environment organisms than community wastewater it was found that not every hospital is the same as general hospitals in our study were more toxic than geriatric hospitals. The blanket approach requiring tertiary treatment at micro-pollutant hot spots, suggested by some EU countries, needs to be reviewed in light of this observation that usage of the hospital or the functions carried out within the hospital clearly affects the toxicity of the wastewater.

1. Genty B, Briantais JM and Baker NR (1989) The relationship between the quantum yield of photosynthetic electron transport and quenching of chlorophyll fluorescence. Biochim Biophys Acta 990:87-92

2. Snyder S, Lue-Hing C, Cotruvo J, Drewes JE, Eaton A, Pleus RC and Schlenk D (2009). Pharmaceuticals in the water environment. [Online]. Available from: [Accessed on 3.4.2014].

2011 IWRA - International Water Resources Association - - Admin