Technische und ökonomische Aspekte der separaten Erfassung und Behandlung von Krankenhausabwasser

• Technical and economic aspects of the separate collection and treatment of hospital wastewater

Mauer, Christian; Pinnekamp, Johannes (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2011)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2011

Abstract

Depending on the size and equipment, the water consumption in hospitals averages between 130 and 1,200 liters per bed and day. The contamination of hospital wastewater with chemical and physical standard parameters is comparable to municipal wastewater. However, heightened AOX-concentrations have been measured, which are mainly caused by the application and excretion of iodinated X-ray contrast media. The concentrations of antibiotics and X-ray contrast media in hospital wastewater are about 10 to 100 times higher than in municipal wastewater, whereas other mainly domestically used pharmaceuticals are partially measured in higher concentrations in municipal wastewater. The literature generally considers hospitals as a main point source for the emission of multidrug resistant bacteria into the aquatic environment. Furthermore, hospital wastewater causes toxic and mutagenic effects. In the context of this dissertation, different technical and economic aspects of the separate collection and treatment of hospital wastewater have been investigated using the example of the Waldbröl county hospital. It has been demonstrated that the fraction of the overall pharmaceutical load in the inlet of the local municipal wastewater treatment plant that originates from the hospital, reaches a maximum of 8% for Carbamazepine, Diclofenac and Ibuprofen, whereas fractions from 20% to 94% have been measured for the investigated antibiotics. These relatively high values as compared to what is found in the literature may be explained by the high number of hospital beds per 1,000 P.E. (33.9 in Waldbröl compared to 6.2 in the nation-wide average). The full-scale wastewater treatment plant of the Waldbröl hospital proves that a combination of a membrane bioreactor (MBR) and subsequent ozonation can eliminate all pharmaceuticals in the wastewater except for the X-ray contrast media to below a threshold value of 100 ng/l. The biological treatment in the MBR at the hospital, which was operated at a high solids retention time, shows a better elimination of antibiotics than the treatment in the central municipal wastewater treatment plant. Furthermore, the combination of MBR and ozonation largely ensures disinfection and greatly reduces the toxic and mutagenic potential. The specific energy consumption of the treatment plant after optimization measures averages 5.0 kWh/m³. 80% of the energy are used in the MBR while 20% are used for ozonation. The specific treatment costs for the Waldbröl county hospital with its 342 beds amount to 4.92 €/m³. The major part of the costs is allotted to the investment and operational costs of the MBR. If these costs are transferred to hospitals with different sizes, scaling effects have to be taken into account. Based on data for the development of specific costs of small decentralized MBR the cost range for the separate treatment of hospital wastewater can be estimated between 3 €/m³ for large hospitals with more than 1,200 beds and 8 €/m³ for small hospitals with less than 100 beds. The costs depend on local circumstances and can differ from case to case. An economic comparison of a separate treatment of hospital wastewater with a refitting of central wastewater treatment plants with an ozonation, in order to find the most cost-effective option for eliminating pharmaceuticals, is affected by the number of beds in the respective hospital and the size of the municipal wastewater treatment plant. In case of the Waldbröl county hospital, which is connected to a small municipal wastewater treatment plant, the separate treatment is cost-effective if the concentration of pharmaceuticals in the hospital wastewater is about 40 times higher than in the municipal wastewater. As for selected antibiotics, the separate treatment of the wastewater of the Waldbröl county hospital can be assessed as cost-effective.