Hospital Wastewater Screening for Pharmaceutical Compounds and Removal of Selected Drugs by Solid-Phase Extraction

Abstract

Hospital waste poses a significant impact on health and environment. Many pharmaceuticals, some with endocrine disrupting functions, enter sewage systems and can pass through the sewage treatment system to be discharged to the wider environment if not fully removed in the treatment process. Sources include domestic residences and hospitals, the latter being a potential point source of contaminants. Generally, hospital wastewater is differentiated as hospital sewage, infective and potentially infective wastewater, chemical wastewater, and radioactive wastewater. Pharmaceuticals residue in sewage and in the aqueous environment has begun to attract attention several scientists world over. There are several reports on the persistence of pharmacceutially active compounds (PhACs) in water streams around the globe. However, no such study is conducted in Pakistan; therefore this thesis was aimed to investigate persistence of PhACs and possible removal solutions. Study area for persistent PhACs was hospital in city of Hyderabad, Pakistan. Following were the aims and objectives of current research 1. Surveying local hospitals to identify frequently prescribed pharmaceuticals. 2. Monitoring hospital wastewater for screening of PhACs. 3. Selection of PhACs on the basis of above study and studies reported in literature. 4. Performance of adsorption experiments to estimate adsorption capacity, kinetics of selected natural adsorbents for selected PhACs. 5. Utilization of modified natural adsorbents for removal of selected PhACs. To address the objectives set above, local hospitals in Hyderabad, Sindh and its vicinity were surveyed to collect the information about frequently prescribed drugs. On the basis of surveyed data and reported literature, highly persistent PhACs were selected. From surveyed and reported literature, five antibiotics (cefuroxime, cefotaxime, cefradine, ofloxacin and ciprofloxacin) and two analgesics (ibuprofen and diclofenac sodium) were shortlisted for further studies. Initial screening of ofloxacin, ciprofloxacin and diclofenac from hospital wastewater was performed by LC-MS methods. Concentration of these drugs was found within the following 8 ranges: OFL 17-53 μg L-1, CIP 70-164 μg L-1 and DFS 78 - 118 μg L-1. IBP was determined to be in the range of 0.052-0.080 μg L-1. The presence of OFL, CIP and DFS were found in μg L-1level in nearly all of the samples. Cephalosporins type antibiotics are widely used to treat infectious diseases. A new high performance liquid chromatographic method for the determination of three cephalosporins (cefradine, cefuroxime and cefotaxime) was developed. Under optimised conditions, all three cephalosporins were baseline separated within 5 min. Linear responses for cefradine 5-20 g mL-1, cefuroxime 0.5-15 g mL-1 and cefotaxime 1.0-20 g mL-1 were established. LOD of 0.05-0.25 μg mL-1 after preconcentration was achieved. The method was applied to screen the selected cephalosporins from hospital wastewater samples. Moreover, method was applied to study stability of aqueous solutions and acid/base induced degradation of all three drugs. Ibuprofen (IBP) is one of the most used active pharmaceutical ingredients globally. Due to its extensive use and resistance to biodegradation it is considered as environmental pollutant and included in the list of pharmaceutically active compounds (PhACs). A GC-MS method was developed along with Solid-phase extraction (SPE) for clean-up and enrichment of samples. The instrumental calibration range for IBP was found 0.8 to 70 μg mL-1. After preconcentration LOD of 0.8 ng mL-1 and LOQ of 2.6 ng mL-1 was achieved. The method was applied to determine IBP in synthetic, hospital and municipal wastewaters and river water. It may be concluded that GC/MS is useful tool for quick identification and determination of IBP in aqueous environmental samples. Screening data reveals persistence of DFS, IBP, CIP and OFL in hospital wastewater of Hyderabad. Therefore sorptive removal methods using biobased sorbents were tested for their sorption activity. Sawdust, peanut shell and hydrothermal carbonized Ziziphus mauritiana L. fruit were used in this study to prioritize sorbent. Processes of sorbents are surmised below. Sawdust is waste generated in woodworks, due to its fine particle size and easy availability makes it attractive to be used as sorbent. Sawdust water, acid and base washed was tested for its sorption efficiency towards ofloxacin. HCl treated sawdust was found to have maximum removal efficiency (96%) with the sorption capacity of 47 μmol g-1 as compared to other treated sorbents. Amount of sorbent have significantly positive impact on the removal for all three treated sorbents whereas concentration of sorbate has non-significant positive effect for HCL 9 treated sawdust. Further, sorption isotherms, kinetics and thermodynamics studies onto HCL treated sawdust showed that reaction is exothermic and spontaneous in nature and psuedosecond order is predominant route. Complex sorption mechanism with simultaneous intra - particle diffusion as well as surface adsorption phenomena is responsible for sorption of ofloxacin onto sawdust. Peanuts shells (PS) were treated with acid and alkali wash for CIP sorption. Langmuir isotherm model was dominant for acid treated PS, however for alkali treated PS Freundlich isotherm model is well fitted but the obtained mean sorption energy (E) by D-R isotherm, is under the magnitude of the physisorption process. Possibly, the treated PS showed heterogenous sorbent surface behavior trend due to different interaction strengths and adsorption energy of CIP onto treated PS. The maximum sorption capacities were observed by Langmuir isotherm were 42.2 μmol g-1 and 10.12 μmol g-1 onto acid treated PS and alkali treated PS, respectively. The acid treated PS shows better adsorption capacity than the alkali treated PS. CIP adsorption shows a maximum at pH 8 because of the electrostatic interaction between positively charge CIP and negatively charged acid treated PS. Hydrothermal carbons are new generation of sorbent materials obtained through carbonization of cellulosic or lignocellulosic biomass under hydrothermal conditions and endogenous pressures. Wild variety of Ber fruit abundantly available in Sindh region of Pakistan was used as source material to prepare HTC. The IBP and DFS simultaneous removal were done onto HTC-ZM. Set of 18 experiments was used and factors as pH, amount of sorbent, contact time and concentration of sorbate were considered the critical factors to be studied for removal. Maximum sorption occurred at pH 4.0 for both PhACs. From linear plot of D-R isotherm, capacity was found 2030 μmol g-1 for DFS and 2540 μmol g-1 for IBP onto HTC-ZM. The mean free energy for both, DFS and IBP was 8.1 KJ mol-1 and 8.3 KJ mol-1 respectively, specifying a physiosorption process. Kinetics equations predicted a complex nature yet efficient sorption process. It may be concluded that natural sorbents like sawdust and peanut shell with acid treatment could be employed as sorbent for removal of selected quinolones as compared to alkali treatment of sorbents. HTC-ZM was found to be good sorbent for removal of PhACs.