Removal of organic micropollutants from wastewater : treatment in selected health care facilities and energy considerations

• Entfernung von organischen Mikroverunreinigungen aus Abwasser - Behandlung in ausgewählten Einrichtungen des Gesundheitswesens und Betrachtungen zum Energiebedarf

Mousel, Danièle; Pinnekamp, Johannes (Thesis advisor); Hansen, Joachim (Thesis advisor); Wintgens, Thomas Josef (Thesis advisor)

1. Auflage. - Aachen : Gesellschaft zur Förderung des Instituts für Siedlungswasserwirtschaft an der RWTH Aachen e.V. (2023)
Book, Dissertation / PhD Thesis

In: Gewässerschutz, Wasser, Abwasser 255
Page(s)/Article-Nr.: XIV, 198 Seiten : Diagramme

Dissertation, RWTH Aachen University, 2022

Abstract

The use of numerous pharmaceuticals and other chemicals in daily life leads to a discharge of these substances into the aquatic environment. Since these anthropogenic substances are found in very low concentrations in the range of ng L-1 to ug L-1 in the aquatic environment, they are called organic micropollutants. Despite their low concentrations, toxic effects on the ecosystem cannot be excluded. As organic micropollutants are generally not or only partly removed in state-of-the-art wastewater treatment plants, a lot of investigations on installing advanced treatment processes at wastewater treatment plants have been performed throughout the last years. Especially processes based on ozonation and adsorption with powdered or granular activated carbon have proven suitable for removal of organic micropollutants. Moreover, other treatment processes such as advanced oxidation processes or membrane processes have been the objects of several studies. These previous investigations have led to more open questions of whom two are assessed in the present thesis. Since hospital wastewaters can contain high concentrations of organic micropollutants, especially of pharmaceutically active compounds, numerous studies have already also been performed on treating hospital wastewater. On-site treatment can help lessen the load of pharmaceutically active compounds emitted into water bodies. The studies performed on hospital wastewater have shown the suitability of the same processes for hospital wastewater than for municipal wastewater. Yet, implementation of such a treatment step is generally more complicated and more expensive for hospitals than for municipal wastewater treatment plants. Besides hospitals, other institutions in the health care system such as specialized clinics or nursing homes can also potentially emit high loads of organic micropollutants into water bodies and have not been thoroughly investigated so far. Thus, an in-depth study on removal of pharmaceutical residues from specialized health care facilities is one of the objects of the present thesis. Wastewater from three healthcare facilities (a nursing home, a clinic with orthopaedic focus and a psychiatric clinic) was pre-treated in a membrane bioreactor. Advanced treatment with ozonation, granular activated carbon and ultraviolet irradiation with optional dosage of hydrogen peroxide was performed. The results show the general suitability of all three technologies for removal of organic micropollutants. Specific settings and dosages depended on the respective wastewater matrix. A more in-depth analysis of ozonation of the nursing home wastewater was also performed. The investigated pharmaceutically active compounds showed a similar behaviour compared to previous studies on ozonation, but the investigations on nursing home wastewater are a novelty compared to preceding studies that focused on municipal or general hospital wastewater. Implementing a decentralised treatment step in health care facilities induces however, some challenges such as higher costs, possibly needed post-treatments and questions of plant operation, so that an in-depth cost-benefit analysis must be performed beforehand. Moreover, no general recommendation for treating wastewater of health care facilities can be stated since the three investigated facilities did not show a significantly higher input of organic micropollutants into the sewer system than municipal wastewater. As a result, a holistic evaluation in specific case studies must be performed to assess the possible benefit of on-site treatment in health care facilities. The second open question assessed in the thesis is the energy demand of micropollutants removal. An additional treatment steps induces a higher energy demand both at and outside the wastewater treatment plants. So far, data has been collected at some treatment plants but a collection of the most important influencing parameters has not been performed to the author’s knowledge. Thus, the data of ten wastewater treatment plants was evaluated in the present thesis and calculations on cumulative energy demand were performed. Electrical energy demand of ozonation at the plant depends on ozone dosage and is significantly higher than energy demand of adsorption processes. It is shown that the cumulative energy demand of adsorption steps is significantly higher than the energy demand at the wastewater treatment plant in spite of uncertainties regarding the data on carbon production. Using reactivated granular activated carbon saves energy compared to using fresh granular activated carbon and powdered activated carbon and should hence be preferred. The gained results are aligned with literature data, yet energy demand is always plant-specific and depends on different factors (delivery heads, existing filtrations/post-treatment etc.). Future optimization can however decrease both the electrical and thermal energy demand of treatment processes. To conclude, the present thesis is able to prove the suitability of treatment processes used in municipal and hospital wastewater treatment plant for other specific health care facilities. Further research on this topic can lead to optimized processes and help decision makers to choose between decentralised and centralised treatment. The data presented for energy demand should allow for optimized planning of future micropollutant removal steps. However, future developments are also strongly dependent on the future legal background. If removal rates or maximum concentrations for certain substances are fixed, the priorities of the treatment processes will evaluate. Since numerous studies are still ongoing on removing organic micropollutants removal, optimized and even new treatment possibilities can be expected.