Water Journal : Water Journal July 2012
refereed paper wastewater water JULY 2012 85 in 2008 were 95m3 day-1 and 627m3 day-1 respectively. QEII discharges its effluent to the Oxley Creek STP, which in 2008 treated on average 55,336 m3 day-1. RBWH discharges its effluent to the Luggage Point STP, with an average of 148,622 m3 of wastewater treated per day in 2008. Prediction of the contribution of a hospital to the loads of pharmaceuticals in municipal wastewater Annual pharmaceutical consumption audit data collected from public hospitals in Queensland (Source: Medication Services Queensland, Queensland Health, Clinical and Statewide Services Division, Queensland Government) and pharmaceutical consumption by the Australian population (Source: Drug Utilisation Sub-Committee (DUSC), Department of Health and Ageing, Australian Government) were used to predict the contribution of a hospital to the loads of pharmaceutical in influent of the corresponding STP. The consumption of a pharmaceutical in a catchment of an STP was estimated by calculating an average per capita consumption from the national consumption data, multiplied by the number of inhabitants in the catchment. The consumption by in-patients in the hospital was added to the domestic consumption to obtain an estimate for the total STP influent load. The contribution of a hospital was then the ratio of the hospital consumption by the total STP influent load. Overall, 589 active pharmaceutical ingredients (API) were identified from the hospital audit data base for evaluation. These excluded naturally occurring substances such as hormones, sugars and enzymes as well as gaseous substances. Compounds available over the counter in Australia (TGA, 2011) were also excluded from the list since information on consumption for these substances is not available. Hospital-specific compounds: comparison of predicted concentrations with effect thresholds In order to assess if hospital-specific compounds (i.e. compounds for which a hospital contribution equals 100%) may present a hazard for human health, estimated concentrations in both hospital wastewater and influent of the corresponding STP were predicted and compared to effect thresholds (ETs). Effect threshold (ET) values were calculated based on the method used in the "Australian Guidelines for Water Recycling: Managing Health and Environmental Risks (Phase 2): Augmentation of Drinking Water Supplies" (NRMMC, 2008). A margin of exposure (MOE) was then determined to compare concentrations expected in hospital wastewaters and in influents of STPs with these ET values. A MOE > 100 implies that the pharmaceutical concentration predicted in either wastewater type (hospital effluent or STP influent) is more than 100-fold below a "concentration of no concern". This means that such a compound is unlikely to present a risk of reaching drinking water sources at elevated concentrations and to affect human health. Results and Discussion Out of 589 compounds investigated, the number of compounds returning a contribution value was 487 at QEII and CAB, 502 at IPS, 524 at PC, 541 at PA and 548 at RBWH. Overall, the six hospitals were found to contribute from 1% (in the catchment of QEII hospital) to 9% (in the catchment of PA, PC and RBWH hospitals) of the total pharmaceutical load at the corresponding STP. Reducing pharmaceutical loads in municipal wastewater through onsite treatment of these hospitals effluent would, therefore, be of limited benefit. When looking more specifically at the contributions of individual hospitals to loads of pharmaceuticals in municipal wastewater, for 63% to 84% of the API used, these contributions are likely to be Ipswich Figure 1. Location of the six hospitals investigated in SEQ and their characteristics (a = number of beds; b = population in catchment area; c = bed density; e = hospital water consumption; f = STP to which the hospital discharge its effluent; g = average raw influent flow rate to STP; proportion of STP influent wastewater coming from the hospital). Figure 2. Distribution of the contributions of the six hospitals investigated (Queen Elizabeth II (QEII), Caboolture (CAB), Ipswich (IPS), Prince Charles (PC), Princess Alexandra (PA) and the Royal Brisbane and Women's Hospital (RBWH)) towards the load of pharmaceuticals in the corresponding STP.
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