Fate of pharmaceuticals in advanced biological wastewater treatment plant, removals by membrane processes and transitions to soil and plants through different agronomic practices

Production of pharmaceuticals in very high quantities in the world and their widespread use in different sectors causes that these compounds to be released continuously into the environment and to be present simultaneously in many different environmental matrices. In recent years, wastewater has become very critical, with the emergence of a wide variety of pharmaceutical compounds in very high concentrations due to industrial discharges, livestock, agricultural practices and anthropogenic activities. Since domestic and urban wastewater treatment plants (WWTPs) are not specifically designed to treat pharmaceuticals, they are shown as one of the most important sources for the release of pharmaceutical compounds into the environment. With the performed thesis study, first of all, the occurrence and fate of 45 pharmaceutical compounds, 27 parent compounds from 10 different pharmaceutical groups and 18 important metabolites of these main compounds, were investigated in detail both in wastewater and sludge lines of Konya advanced biological WWTP. In addition, the removal performances of pharmaceutical compounds in treated wastewater by ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membrane processes were investigated with the pilot scale membrane plant installed at the outlet of Konya WWTP. Treated wastewater discharged from Konya WWTP to the main discharge channel is intensively reused as irrigation water in agricultural production. In this context, the changes in pharmaceuticals after discharge from the plant were followed at different irrigation points determined in the main discharge channel. Then, the transitions of pharmaceuticals to soil and plants were investigated seasonally in fields where barley, corn and sunflower are grown by using treated wastewater from the main discharge channel. The treatment sludge stabilized in Konya WWTP is used as soil amendment in agricultural lands by the farmers who request it in a licensed and controlled manner. Finally, within the scope of the thesis, the pharmaceutical transitions and seasonal changes were investigated both on the agricultural lands where stabilized sewage sludge was applied and, on the corn and sugar beet plants grown in these lands. As a result, the full cycle of pharmaceuticals in a metropolitan city was investigated with the thesis carried out. Wastewater, treatment sludge, soil and plant samples were collected from determined sampling points within the scope of the thesis seasonally during the year of 2020 for 1 year. Within the scope of the thesis study, a total of 119 different samples were collected, including 64 wastewater, 25 treatment sludge, 20 soil and 10 plant samples. Appropriate extraction methods were applied for all sample types collected before analysis. While the solid phase extraction (SPE) method was applied to the collected liquid samples, the ultrasonic extraction method was applied to the solid samples. The analyzes of the extracts obtained as a result of the applied extraction methods were performed by liquid chromatography tandem mass spectrometry (LC-MS/MS) according to the EPA 1694 method. Antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs), anticonvulsants and nerve stimulants have been detected in raw wastewater in all seasons among the investigated pharmaceutical groups. However, compounds in the other steroid hormones, antidepressants, anticancer drugs, lipid regulators, receptor antagonists and antiseptics groups investigated within the scope of the thesis were rarely detected in the plant. The compound, which was detected with the highest concentration values in the raw wastewater of Konya WWTP, was determined as caffeine (CAF) in the nerve stimulant group, up to 180 µg/L. The results obtained in both wastewater and sludge lines of Konya WWTP revealed that the effective removal mechanisms in WWTP for the investigated pharmaceutical compounds are biodegradation, biological transformation and sorption onto treatment sludge. Apart from the determination of different removal efficiencies for compounds in the different pharmaceutical groups in Konya WWTP, highly variable removal efficiencies were determined even for compounds in the same group depending on the physicochemical properties of the investigated compounds. In general, it was observed that, apart from diclofenac (DCF), the compounds in the NSAID group and the compounds in the nerve stimulants group were easily treated in the wastewater line of Konya WWTP, while the compounds in the anticonvulsant group, on the contrary, could not be treated at all or treated at negligible levels. It has been determined that the pharmaceutical group most affected by seasonal periods is antibiotics, and it is not possible to generalize about the total removal ratios in Konya WWTP for this group, similar to other groups. Apart from these, another important finding is the determination of the potentials of the main compounds and their metabolites to behave quite differently from each other in terms of both their occurrence concentrations in raw wastewater and the total removal determined in the plant. In the sludge line of Konya WWTP, it has been determined that the tendency of the compounds to pass into the primary and secondary treatment sludges is different depending on the physicochemical properties of the investigated pharmaceutical compounds. It was determined that paracetamol (PAR), ibuprofen (IBU), naproxen (NAP) compounds from the NSAID group and CAF and nicotine (NCT) compounds in the nerve stimulants group had a higher tendency to pass into the primary sludge. On the other hand, it was determined that the tendency of ciprofloxacin (CIP) and azithromycin (AZI) compounds from the group of antibiotics to pass into the secondary sludge was much higher compared than the primary sludge. In the study, the highest concentration values detected in the primary and secondary sludges were determined as 274.4 and 23.5 µg/kg for CAF and CIP compounds, respectively. In addition, although almost all of the pharmaceutical compounds detected in raw wastewater were determined at different rates, sorption onto treatment sludge was found to be a valid removal mechanism for pharmaceuticals. It has been determined that compounds such as carbamazepine (CBZ) and DCF show serious resistance to the treatment processes in the sludge line as in the wastewater line, while compounds such as PAR and NCT are easily eliminated in the treatment sludge. Although different removal rates are obtained for pharmaceutical compounds and their metabolites in the sludge line of the plant, the compounds detected in the treatment sludge in all seasons after sludge dewatering, which is the last unit of the sludge line, were determined as clarithromycin (CLA), DCF, NAP, CBZ and CAF. The annual average concentration values of these compounds determined in the decanter sludge varied between 2.8 and 6.3 µg/kg. Within the scope of the thesis study, pharmaceutical pollution has been determined in agricultural lands due to agricultural irrigations with treated wastewater discharged from Konya WWTP for many years. Detection of CAF up to 14.2 µg/kg and CBZ up to 1.2 µg/kg in soils irrigated with treated wastewater in all seasonal studies indicates that these compounds may be permanent in these lands. At the same time, on the condition that it is limited, transitions of pharmaceutical compounds in different groups to agricultural products grown on these lands have also been determined. Different pharmaceutical compounds were detected up to 910, 1320 and 90 ng/kg concentration values, respectively, in barley, sunflower and corn plants grown in fields irrigated with treated wastewater. In addition, the difference in the pharmaceutical compounds detected in different plant species grown reveals that the specific properties of the plants are also very important in their pharmaceutical transition, apart from the fact that the agricultural lands where they are grown are irrigated with treated wastewater. On the other hand, the common pharmaceutical compounds detected in the products grown in the lands irrigated with treated wastewater were determined as CBZ together with the metabolites of the main compound IBU. As a result, it has been determined that pharmaceutical compounds are included in the food chain through the agricultural products grown in the fields irrigated with treated wastewater. Similarly, in agricultural lands where stabilized treatment sludge supplied from Konya WWTP are applied as a soil amendment, some pharmaceutical compounds have been detected, much more limited than in the fields irrigated with treated wastewater. Also, no pharmaceutical compounds were detected that tended to persist in treated sludge applied farmland. The detection of different pharmaceuticals in different agricultural products grown in the fields where treatment sludge was applied, revealed that the plants behave differently in taking the pharmaceuticals from the fields into their bodies. On the other hand, the common pharmaceutical compounds detected in plants grown in treatment sludge applied fields were determined as CAF together with the metabolites of IBU. Pharmaceutical compounds were detected up to the concentration values of approximately 100 and 515 ng/g, respectively, in corn and sugar beet plants grown in agricultural lands where treatment sludge was used as soil amendment. As a result, it has been determined that pharmaceuticals can be introduced in the food chain through the plants grown in the fields where treatment sludge is applied. Within the scope of the thesis, the pharmaceutical removal performances of different membrane processes were also investigated within the context of the treatment of treated wastewater discharged from Konya WWTP to the main discharge channel by membrane processes, which is one of the advanced treatment methods. The results showed that the removal rates for pharmaceutical compounds in the UF membrane were generally quite low. However, it has been determined that the negative or positive removal rates determined in the UF membrane are largely due to the physicochemical properties of the investigated pharmaceutical compounds and the specific interactions of the compounds with the UF membrane surface. With the NF membrane process, it was determined that all the investigated pharmaceutical compounds were treated at very high rates of 95% and above, or completely, especially through the size exclusion removal mechanism. Therefore, it was determined that the treatment of pharmaceutical compounds was mainly carried out with NF membrane. In very exceptional cases, it was determined that pharmaceutical compounds whose NF membrane effluent still has concentration values above the limit of quantification (LOQ) value were completely treated with the RO membrane. As a result, it has been seen that operating UF and NF membranes together is sufficient to provide effective pharmaceutical removals before discharge in the treated wastewater of Konya WWTP.