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Original article
12 2022
:15;
104344
doi:
10.1016/j.arabjc.2022.104344

Performance evaluation of constructed wetland for removal of pharmaceutical compounds from hospital wastewater: Seasonal perspective

, , , , , , , ,
a Department of Civil Engineering, King Khalid University, Abha, Saudi Arabia
b Department of Geography, LADES, FLSH-M, Hassan II University of Casablanca, Mohammedia, Morocco
c Department of Civil Engineering, Mewat Engineering College, Nuh, Haryana, India-122107
d Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh, India
e Department of Chemistry, Integral University, Lucknow, India
f Department of Information System, Rijal Ilma, King Khalid University, Saudi Arabia
g Civil Engineering Section, University Polytechnic, Faculty of Engineering and Technology, Aligarh Muslim University, India
h Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
i Student Research Committee, Iran University of Medical Sciences, Tehran, Iran

⁎Corresponding authors. rakhan@kku.edu.sa (Roohul Abad Khan), mahmood_yousefi70@yahoo.com (Mahmood Yousefi)

Received: , Accepted: ,
© The Author(s) 2022
Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Peer review under responsibility of King Saud University.

Abstract

Constructed wetland employs vegetation as a natural medium to remove pollutants from wastewater for this treatment. It is eco-friendly, sustainable, economical, low maintenance, low running cost, and easy to use. This has prompted several studies to investigate its performance in treating pollutants from the conventional to emerging contaminants category, including pharmaceutical compounds. However, there is still a lack of work on the impact of monsoons on the removal efficiency of pharmaceutically active compounds from wastewater. This study evaluated constructed wetland performance during the premonsoon, monsoon, and post-monsoon seasons. A pilot-scale constructed wetland setup was established to conduct this study. The target compound included paracetamol, ibuprofen, carbamazepine, lorazepam, ciprofloxacin, sulfamethoxazole, and Fluvastatin. In the constructed wetland, for paracetamol and ibuprofen, NSAIDs concentration was observed to be 1503–6307 ngL−1 and 564–808 ngL−1. The concentrations of antibiotics, sulfamethoxazole, and ciprofloxacin were 16532–21635 ngL−1 and 734–1178 ngL−1, respectively. The carbamazepine, lorazepam, and Lutvastatin concentration range was 616–906 ngL−1, 2742–3775 ngL−1, and 694–2068 ngL−1, respectively. The hazard quotient approach was adopted to evaluate potential environmental risk from target compounds. The increase of paracetamol 33 %, ibuprofen 94 %, ciprofloxacin 242 %, Sulfamethoxazole 64 %, and carbamazepine 77 % validated the study hypothesis. However, a decrease of 15 % lorazepam and 43 % Fluvastatin inferred that dilution was inversely proportional to the removal of these compounds. The seasonal removal efficiency was in order pre-monsoon < post-monsoon < monsoon. Hospital wastewater had HQ values of 90, 100, and 130 for premonsoon, monsoon, and post-monsoon, respectively. After treatment from the constructed wetland, the wastewater effluent had reduced HQ value to 53, 35, and 70 for premonsoon, monsoon, and post-monsoon periods respectively. The HQ values were further reduced in tubesettler to 22, 11, and 28. Ciprofloxacin posed no significant risk. However, sulfamethoxazole posed a high risk during premonsoon, monsoon, and post-monsoon season. Further works are required to analyze the removal mechanism through plant uptake, sediment bed, and biodegradation for a different season or climatic condition to present the real-time performance of constructed wetlands for treating wastewater loaded with pharmaceutical compounds.

Keywords

Constructed wetland
Hospital wastewater
Season
Pharmaceutical compounds
Hazard quotient
Removal mechanism
1

1 Introduction

Constructed wetlands have been employed for wastewater treatment since the’90s (Abad et al., 2023). Its use was restricted due to its size, which did not fit with the urban landscape's development. But the recent shift toward policies to mitigate climate change and global warming impact has called for increased green landscape in urban areas. Its easy use, operation, and maintenance have rendered it a popular treatment method (Hu et al., 2021; Parde et al., 2021). Over 700 emerging pollutants, including active pharmaceutical compounds (PhACs), have been a concern globally (Alsubih et al., 2021; Geissen et al., 2015). The better lifestyle and access to facilities have contributed to increased population and healthcare facilities (hospitals, clinics, pathology labs, etc.) (R.A. Khan et al., 2022; Hu et al., 2021). Domestic and municipal wastewater is enriched with pharmaceutical compounds from the patients' excreta (Humans and Animals) (N. A. Khan et al., 2022). Table S1 presents wastewater generation in hospitals from various activities directly responsible for pharmaceutical compound enrichment in hospital wastewater. There have been several studies for evaluating treatment performance of constructed wetlands for the removal of pharmaceutical compounds from wastewater (Ávila et al., 2021b; Cheng et al., 2021; Gerardo and Barquero, 2022).

However, a research gap was identified in these studies as none of the research work used hospital wastewater for analysis. J. Chen et al. (2021) and Li et al. (2020) have investigated simulated wastewater in the laboratory to evaluate the performance of constructed wetlands for pharmaceutical removal. Ávila et al. (2021) have used septic tank effluent for pharmaceutical compounds removal efficiency analysis. Stroski et al. (2020) have analysed the receiving waters of the arctic for pharmaceutical compound occurrence. Cheng et al. (2021), Delgado et al. (2020) and Guedes-Alonso et al. (2020) have investigated constructed wetlands efficiency for GIG community wastewater, domestic wastewater, and university wastewater, respectively. Additionally, the point source of pharmaceutical compounds besides pharmaceutical industries are hospitals and health care facilities, which have been overlooked in most studies. This presents the research gap in terms of constructed wetland being evaluated for removal of pharmaceutical compounds from hospital wastewater. Also, constructed wetland being an open landscape wastewater treatment system is directly affected by local weather and climatic conditions. This perspective again is lacking in terms of available literature especially for hospital wastewater. Also, constructed wetland being an open landscape is susceptible to be affected from climate change especially rainfall. Table 1 presents some of the constructed wetlands investigated in recent years and type of wastewater used for its performance evaluation in removal of PhACs.

Table 1 Constructed wetlands type of wastewater treated and pharmaceutical compounds studied.
Constructed wetland Type of wastewater Pharmaceutical compound Reference
Horizontal sub-surface flow constructed wetland Synthetic wastewater Acetaminophen, diclofenac, ketoprofen, carbamazepine lorazepam sulfamethoxazole etc. (Ávila et al., 2021b)
Tidal flow constructed wetland with baffle & plants Synthetic wastewater Ciprofloxacin, sulfamethoxazole, etc. total of 24 PPCPs (Cheng et al., 2021)
Horizontal sub-surface flow constructed wetland Cauca river and wastewater treatment plant Carbamazepine and 2 personal care products (Delgado et al., 2020)
Horizontal sub-surface flow constructed wetland coupled with ozonation Domestics wastewater Ibuprofen and naproxen (Lancheros et al., 2019)
Mesocosm constructed wetland Synthetic wastewater Carbamazepine, ibuprofen etc. in total 7 PhACs (He et al., 2018)
Small-scale constructed wetland Synthetic wastewater Ibuprofen, naproxen, and gemfibrozil (Zhang et al., 2018)
Horizontal constructed wetlands Synthetic wastewater Carbamazepine, diclofenac, atenolol (Ravichandran and Philip, 2022)
Vertical flow constructed wetlands Municipal wastewater Ciprofloxacin, sulfamethoxazole, carbamazepine, etc. in total, 27 PhACs (Venditti et al., 2022)
Vertical flow constructed wetlands Synthetic wastewater Furosemide, gemfibrozil, triclosan, triclocarban, hydrochlorothiazide, chloramphenicol (Hu et al., 2022)

Zhang et al. (2020) have investigated constructed wetland treatment efficiency in the dry season with low influent volumes. Zhao et al. (2020) analysed the performance of floating constructed wetlands in dry and cold seasons for nitrogen removal. Zhang et al. (2021) investigated the evolution of constructed wetlands during the monsoon season. Bojcevska and Tonderski (2007) evaluated tropical wetlands in terms of season, load, and type of plant. Zhao et al. (2018) examined constructed wetlands during the cold season for nitrogen removal. Ma et al. (2017) have considered the impact of low temperature on cadmium removal from wastewater using the constructed wetland. It can be inferred from the literature that the impact of climate on the performance of constructed wetlands for removing pharmaceutical compounds is yet to be explored.

Hence, hospital wastewater treatment is gaining focus attributed to its pharmaceutical constituent. Khan et al. (2019) evaluated the performance of extended aeration for treating hospital wastewater. Alsubih et al. (2021) employed an aerobic fluidized bed bioreactor to evaluate its treatment efficiency. Nadeem A. Khan et al. (2020) have compared hospital wastewater treatment efficiency of membrane bioreactor and sequencing batch bioreactor. Nadeem Ahmed Khan et al. (2020) have used horizontal flow constructed wetlands to treat hospital wastewater. Nevertheless, these studies have focused on conventional pollutant removal from hospital wastewater, primarily the removal of nutrients (NO3– & PO43-) and organic matter (COD & BOD5). The objective of this study is to evaluate the performance of constructed wetland for removing pharmaceutical compounds (PhACs) from hospital wastewater (HWW) and to assess the impact of premonsoon (PRM), Monsoon (M), and Post monsoon (POM) on CW performance and to evaluate efficiency of tubesettler in reducing PhACs concentration from CW effluent to render it as an efficient and effective polishing unit or replacement of secondary clarifier.

2

2 Data and method used

2.1

2.1 Target compounds in this study

The detail of targeted pharmaceutical compounds in this study were selected from inventory of hospital and the risk quotient (Table 2.). This study investigated the fate and removal of seven pharmaceutical compounds, and their classes are as follows:

  1. Antibiotics: sulfamethoxazole (SMZ) and ciprofloxacin (CIP)

  2. Nonsteroidal anti-inflammatory drugs (NSAIDs): paracetamol (PCM) and Ibuprofen (IBF)

  3. Anticonvulsants: carbamazepine (CAB)

  4. Neural suppressant: Lorazepam (LZM)

  5. Statin: Fluvastatin (FUT)

Table 2 Studied pharmaceuticals category, chemical formula molecular weight, and molecular structure.
Pharmaceuticals Category Chemical Formula Molecular Weight (g/mol)
2D
Paracetamol Non-Steroidal

anti-inflammatory Drug		 C8H9NO2 151.163 g/mol
Ibuprofen anti-flammatory C13H18O2 206.28 g/mol
Carbamazepine ANTICONVULSANT C15H12N2O 236.27 g/mol
Lorazepam BENZODIAZEPINE C15H10Cl2 N2O2 321.2 g/mol
Ciprofloxacin antibiotics C17H18 FN3O3 331.34 g/mol
Sulfamethoxazole antibiotics C10H11N3 O3S 253.28 g/mol
Fluvastatin LOWER BAD CHOLESTEROL C24H26FNO4 411.5 g/mol

2.2

2.2 Wetland configuration

The constructed wetland consisted of a 1 m long steel tank, 0.70 m wide and 0.60 m high was constructed in Mewat Engineering College, Nuh. The slope was 1 %, which Delgado et al. (2020) adopted. The wetland bed comprised gravels of 0.1 m and a sand bed of 0.1 m. The outlet of constructed wetland was connected to a tubesettler. Phragmites australis were planted in constructed wetlands. The plantation was left to mature and adapt in the first four weeks before actual wastewater feeding. Wastewater collection sampling and Laboratory analysis are explained in detail in previously published work Nadeem Ahmed Khan et al. (2020). Fig. 1 presents the constructed wetland flow diagram used in this study.

Location of constructed wetland fig (a) and constructed wetland experimental study setup fig (b).
Fig. 1
Location of constructed wetland fig (a) and constructed wetland experimental study setup fig (b).

2.3

2.3 Water sampling and collection

Wastewater samples were obtained from 500 bedded nearby hospital drain i.e. SHKM Government Medical College, Nuh . The sample was accepted as a composite sample over a period of 24 h. Samples were collected at an interval of 4 h to make a composite sample representative of 24 h average. The collection bottles were sterilized and dried prior to sample collection. The sample was collected in amber glass to inhibit interference from light water interaction. The samples were analyzed upon immediate arrival at the lab. If immediate analysis cannot be done, samples were tested within 24 h upon storage. The collected water samples were stored at 4 °C before being used as an inlet in the constructed wetlands (Pi et al., 2022). The sampling was done from March-April 2021 for pre the monsoon season, July-August 2021 for the monsoon season, and October to November 2021 during the post-monsoon season. Three replicas for each sample were collected, and an average of the three were taken as the final target compound concentration. The effluent samples were collected from the outflow of constructed wetland and tubesettler effluent to evaluate the performance of each unit. The samples were filtered using a 0.45 µm filter to ensure the separation of TSS from the sample (Chen et al., 2022).

2.4

2.4 Chemicals and reagents

The laboratory standards concerning pharmaceuticals and their associated reagents for sample preparation were obtained from Sigma-Aldrich. The reagent water for blank determination and analyte fortification was deionized water obtained from the lab-installed deionized machine. The SPE (solid phase extraction) cartridges were of configuration: 500 mg, 3 ml, and 200 mg, 6 ml. Standard stock (500 µg/ml) was prepared in methanol and stored at 4 °C. Filter paper of 47 mm (Whatman) with a pore size of 0.45 µmetre was used. 500 ml wastewater sample was filtered through 0.45 µmeter filter paper and acidified to pH=2 using hydrochloric acid. Filtered water samples were extracted on SPE cartridges packed with 0.5 g OASIS HLBTM.

2.5

2.5 Instrumental analysis of pharmaceuticals

All particulate matter was removed from samples using hexane-washed Whatman filters. Sample extraction was done by employing HLB SPE (solid phase extraction) cartridges, as explained by Zhang et al. (2011). The extracts were analyzed for antibiotics, NSAIDs, neural, and diuretic categories. The target pharmaceutical compounds were analyzed using UPLC (Ultra-performance liquid chromatography) in combination with a mass spectrophotometer. Multiple reaction mode was selected for analysis. The details of the analysis are described by J. Chen et al. (2021). Table 3. Provides descriptive statistics of hospital wastewater concentration, influent on a constructed wetland.

Table 3 Influent concentration (ngL−1) in hospital wastewater (HWW) statistic description for constructed wetland.
PhAC compound Premonsoon Monsoon Post monsoon
Range Average Range Average Range Average
PAR 4889–8569 6307 ± 1138 1503–8036 2061 ± 1329 4385–6345 5453 ± 479
IBF 711–948 808 ± 71 564–853 716 ± 95 844–1253 1042 ± 117
CAB 714–1079 906 ± 120 616–866 758 ± 80 933–1299 1132 ± 103
LOR 3069–4310 3774 ± 399 2742–4143 3317 ± 431 3837–5241 4602 ± 471
CIP 734–1484 1178 ± 202 818–1109 958 ± 81 1428–1842 1659 ± 117
SMZ 16532–26547 20365 ± 2291 17885–27027 21635 ± 2813 22182–30297 26604 ± 2723
LUT 1709–2583 2068 ± 269 694–1734 1019 ± 253 1333–2381 1876 ± 324

The removal efficiency of pharmaceuticals was determined as:

(1)
RE ( % ) = ( 1 - C in C out ) x 100 %

Further Removal Efficiency was divided into three categories Low (≤50 %), Medium (50–80 %), and high (RE > 80 %).

2.6

2.6 Environmental risk assessment

The hazard quotient approach, risk assessment, or environmental risk assessment are the same method with different terminologies (Lancheros et al., 2019; Vymazal et al., 2017), which employs Measured environmental concentration (MEC) and predicts no effect concentration (PNEC) of the target compound to assess potential risk. The risk is presented as a Hazard quotient (HQ) or risk quotient (RQ). (Chen et al., 2016) Equation (2) assesses the potential risk from targeted compounds (Guedes-Alonso et al., 2020). The hazard quotient was categorized as: very high risk > 1; medium risk 0.1 to 1, low risk 0.01 to 0.1, and negligible risk < 0.01 (Vymazal et al., 2017).

(2)
H Q = MEC PNEC

3

3 Results and discussion

3.1

3.1 Target pharmaceutical compounds removal

Constructed wetland performance was evaluated concerning premonsoon, monsoon, and post-monsoon season. Large, rooted plant such as Phragmites australis was employed as it grows more slowly than plants will less leaf area. The target compounds concentration in influent and effluent of constructed wetland is presented in Fig. 2.

Influent and effluent average concentration of targeted compounds in hospital wastewater during premonsoon (PRM), Monsoon (M), and post-monsoon (POM) period in constructed wetland.
Fig. 2
Influent and effluent average concentration of targeted compounds in hospital wastewater during premonsoon (PRM), Monsoon (M), and post-monsoon (POM) period in constructed wetland.

Paracetamol among NSAIDs was higher in concentration as compared to Ibuprofen. The removal efficiency of PCM was 66 %, 88 %, and 54 % for 6307 ngL−1, 2061 ngL−1, and 5453 ngL−1 influent concentration during premonsoon, monsoon, and post-monsoon seasons respectively. The premonsoon season was chosen to evaluate change in removal efficiency as it is among the driest season of the three. NSAID, IBF removal efficiency increased by 33 % during the monsoon season while decreased by 18 % during the post-monsoon season. This corresponds to a 67 % and 14 % decrease in average influent concentration and 23 reductions and a 16 % increase in effluent concentration for monsoon and post-monsoon season, respectively. Ninety-eight percent removal of paracetamol has been achieved in a study using spirodela polyrhiza (duckweed) (Li et al., 2017). 47–99 % removal efficiency has been reported in horizontal subsurface flow CW when used as secondary wastewater treatment (Li et al., 2014). In another study of full-scale CW in Ukraine, the paracetamol removal efficiency was between 50 and 80 % (Vystavna et al., 2017). PCM removal in CW combines plant uptake, adsorption, and biodegradation. Plant uptake degrades paracetamol into non-toxic compounds (Vo et al., 2019). Mohammed et al. (2021) identified plant uptake as a significant paracetamol removal process, which reported >85 % removal efficiency.

While for Ibuprofen, the influent concentration was reduced to 808 ngL−1, 716 ngL−1, and 1042 ngL−1, along with the reduction in removal efficiency of 34 %, 66 %, and 54 % during premonsoon, monsoon, and post-monsoon season respectively. For IBF, 11 % and 34 % decreases were observed during the monsoon season, and a 29 % and 27 % increase during the post-monsoon season for influent and effluent concentration, respectively. During the monsoon season, a 94 % increase in IBF was observed. In comparison, removal efficiency variation was observed as zero despite a variation of 27 % in influent concentration. Five to ten percent of the variation in removal efficiency has been observed based on the cold and warm seasons in CW for the removal of PhAC compounds (Chen et al., 2016). The removal efficiency of 56 % was achieved in vertical subsurface flow constructed wetland for Ibuprofen but with filtration mechanism of sand bed (AL Falahi et al., 2021). Chen et al. (2016) have reported 75–99 % Ibuprofen and 95–100 % removal efficiency in monitored horizontal sub-surface flow CW. Bacteria in the rhizosphere can oxidize ibuprofen. After undergoing a redox environment, ibuprofen byproducts are readily removed through uptake by plants in CW (AL Falahi et al., 2021). Aerobic and anaerobic bacteria in CW can assimilate PhACs and render biodegradation as an established mechanism for PhACs removal from wastewater (Vo et al., 2019). Ibuprofen biodegradation has been identified to be better in sediment beds than in the aqueous phase (Ravikumar et al., 2022).

A similar influent concentration difference was observed in the case of antibiotics. In the case of CIP, CW achieved 24 %, 82 %, and 53 % for the average influent concentration of 1178 ngL−1, 958 ngL−1, and 1659 ngL−1 during premonsoon, monsoon, and post-monsoon season. Antibiotics' CIP removal efficiency increased significantly during the monsoon and post-monsoon season. During monsoon season, influent and effluent concentrations were reduced by 19 % and 29 %, but removal efficiency increased by 242 %. While during the post-monsoon season, there was an increase of 41 % and 23 % in effluent concentration against a rise of 121 %. In a vertical flow, CW removal efficiency of 89 % has been reported using synthetic wastewater (Sun and Zheng, 2022). In another study of vertical flow, CW removal efficiency of 77 % was achieved in treating synthetic wastewater (Ávila et al., 2021a). It has to be noted that vertical CW performs better as compared to horizontal CW (Prochaska et al., 2007).

SMZ had influent concentrations of 20,365 ngL−1, 21,635 ngL−1, and 26,604 ngL−1 in CW, which achieved removal efficiency of 42 %, 64 %, and 56 % for pre-monsoon, monsoon, and post-monsoon seasons respectively. There was an increase in removal efficiency of SMZ during monsoon and post-monsoon season, but not like CIP. There was an increase in influent concentration by 6 % and 31 % for SMZ during the monsoon and post-monsoon season, respectively, against a rise of 52 % and 33 %. The increase in removal efficiency decreases SMZ concentration in effluent by 34 % and 87 %, respectively, in the post-monsoon season. SMZ is primarily responsible for the rise in sulphonamide resistance genes (Ávila et al., 2021b). Ma et al. (2022) have reported a removal efficiency of 57–80 % for sulfamethoxazole for treating synthetic wastewater. CW has achieved 80 % efficiency in SMZ removal from treated and untreated urban wastewater (Verlicchi and Zambello, 2014). SMZ has been removed with an efficiency of <50 % in treatment plants in lower-income countries (Dalahmeh et al., 2020). Removal of antibiotics in CW is affected by the type of plant, substrate, and microorganisms. The removal mechanism involves plant uptake, biodegradation, and substrate adsorption (Ma et al., 2022). Plant uptake significantly affects the removal of CIP and SMZ from wastewater. Ciprofloxacin conversion to ofloxacin and enrofloxacin for plant uptake has been observed in a study (Ravikumar et al., 2022). Diffusion of antibiotics is the main mechanism for plant uptake, which is affected by water solubility, the concentration of antibiotics, and hydrophobicity (Ma et al., 2022). Removal of antibiotics is directly proportional to plant growth (Sun and Zheng, 2022).

Anticonvulsant CAB was removed up to 26 %, 46 %, and 53 % for the influent concentration of 906 ngL−1, 757 ngL−1, and 1132 ngL−1 during premonsoon, monsoon, and post-monsoon periods respectively. CAB's removal efficiency in CW increased by 77 % and 104 % during monsoon and post-monsoon seasons, respectively. However, during the monsoon season, there was a decrease in influent concertation by 16 %, while an increase of 25 % was observed for the post-monsoon season. Removal efficiency in CW has been reported in earlier studies as <50 % (Auvinen et al., 2017). Also, in another study for varying hydraulic loads, CAB removal was observed to be <50 % for treating synthetic wastewater (Zhang et al., 2012). CAB has been identified as a natural recalcitrant PhAC, which renders it distinct from others. Its high hydrophobicity results in lower removal efficiency as its primary removal mechanism involves sorption to available organic matter (Zhang et al., 2011). Dalahmeh et al. (2020) have observed accumulation of CAB up to 9 ngL−1 in wetland soil. He et al. (2018) reported phytodegradation of CAB by detecting two intermediate 11-epoxycarbamazepine and 10,11-dihydro, which also suggests uptake by the plant as another removal mechanism. CAB has been observed at a rate of 0.51 µg/g growth of the plants in CW (Delgado et al., 2020).

Neural suppressant LOR with influent concentration of 3774 ngL−1, 3317 ngL−1 and 4602 ngL−1 53 %, 45 % and 49 % respectively. In the monsoon season, there was a decrease in the influent concentration of LOR by 12 %, while in the post-monsoon season, there was an increase in the influent concentration by 22 %. However, when removal efficiency is concerned, it decreased by 15 % and 8 % for monsoon and post-monsoon seasons, respectively, compared to pre-monsoon season. Ávila et al. (2021b) has observed the removal efficiency of LOR in horizontal sub-surface flow CW of 56 % in continuous and intermittent aeration. Adsorption to solids in wastewater can be said to be a primary removal mechanism. Statin compound FUT was removed in CW with an efficiency of 69 %, 58 %, and 79 % in the premonsoon, monsoon, and post-monsoon periods. During the monsoon season, there was an increase of 27 % in removal efficiency compared to the pre-monsoon sampling period.

3.2

3.2 Pharmaceutical compounds removal in tubesettler

Influent and effluent concentration of pharmaceutical compounds in hospital wastewater in tubesettler is presented in Fig. 3. PAR showed an accumulation in the monsoon season and an increase in engagement.

Influent and effluent average concentration of targeted compounds in hospital wastewater during premonsoon (PRM), Monsoon (M), and post-monsoon (POM) period in constructed wetland.
Fig. 3
Influent and effluent average concentration of targeted compounds in hospital wastewater during premonsoon (PRM), Monsoon (M), and post-monsoon (POM) period in constructed wetland.

In tubesettler removal, the efficiency of 50 %, −13 %, and 58 % were achieved for paracetamol in the respective three seasons. While for ibuprofen, it was 27 %, 19 %, and 51 %, respectively, for premonsoon, monsoon, and post-monsoon seasons. PAR removal was decreased by 26 % during monsoon against a reduction of 3 % in influent concentration, while it increased by 16 with an increase in influent concentration by 46 % during post-monsoon season. In the case of IBF, a 30 % decrease was observed with a 34 % decrease in influent concentration.

CIP was removed in tubesettler with an efficiency of 24 %, 32 %, and 40 %. CIP removal performance in tubesettler was increased by 33 % and 67 % during monsoon and post-monsoon seasons, respectively. This indicates a high biodegradation rate against dilution. SMZ removal efficiency of 31 %, 36 %, and 42 % was achieved for premonsoon, monsoon, and post-monsoon seasons respectively. A similar variation in removal efficiency for SMZ was observed compared to CIP. During monsoon removal, efficiency was enhanced by 16 % and 35 % during the post-monsoon season, signifying dilution for enhancing biodegradation.

CAB, LOR, and FUT were removed with an efficiency of 75, 71 %, 10 %, 21 %, 31 %, 50 %, 69 %, 58 %, and 79 % during premonsoon, monsoon and post-monsoon season, respectively. There was a decrease of 18 % and 89 % in CAB removal efficiency in monsoon and post-monsoon season, indicating no particular influence of rainfall on the performance of tubesettler. In the case of LOR, tubesettler performance was enhanced by 48 % and 138 % during monsoon and post-monsoon seasons, respectively, inferring that dilution may enhance LOR removal efficiency decreased by 16 % and increased by 14 % during monsoon and post-monsoon seasons, respectively, removal from hospital wastewater.

Tubesettler works on the principle of shallow sedimentation (Al-Dulaimi and Racoviţeanu, 2019). Tubesettler can achieve up to 53 % of turbidity and 98 % of bacteria removal from wastewater (Fouad et al., 2016). tubesettler, when investigated as a secondary clarifier, achieved up to 98 % removal for BOD5, COD, and TSS (Faraji et al., 2013). Similar removal efficiencies were observed while treating hospital wastewater in a combination of tubesettler and CW, has been reported by Nadeem Ahmed Khan et al. (2020). However, tubesettler removal efficiency was low in the case of LOR, CIP, and IBF. Hence, this study will suggest its application as a potential clarifier unit in wastewater treatment. From this study, it can be inferred that dilution of antibiotics concentration viz. CIP and SMZ enhance their removal through biodegradation. LOR removal also depicted a similar phenomenon. Also, the dilution range affects its removal as excessive dilution results in reduced removal efficiency, as observed in PAR, IBF, and LUT reduction. It can be said that they have a lower dilution range as compared to antibiotics. CAB removal was observed to be inversely proportional to dilution. Hence, the impact of precipitation significantly affects the performance of the tubesettler and must be considered in its design parameters for hospital wastewater treatment.

3.3

3.3 Combined removal efficiency of constructed wetland and tubesettler

Fig. 4 presents the overall removal efficiency of CW and tubesettler combined treatment of hospital wastewater. Among the targeted compound, the study setup achieved high removal efficiency in the case of CAB > 80 % for the pre-monsoon, monsoon, and post-monsoon periods. In comparison, IBF was removed with low efficiency of <50 % in monsoon and post-monsoon periods. While in the premonsoon period, IBF removal was >50 % rendering it in the medium category or efficiency. PCM had a wide range of variations, with premonsoon removal being in the medium category, monsoon period removal in the low category, and post-monsoon season in the high category of removal efficiency. Another targeted compound was found to be in the category of medium removal efficiency for this study setup of 50–80 %. Except for CIP in monsoon, which indicated low removal efficiency. Hydrophobicity, solubility, and dilution are significant factors affecting removal efficiency. However, further analysis is required to associate removal efficiency with hospital activities and associated complex compounds reaching hospital wastewater during the study period. Also, this can be validated by the fact that the concentration of targeted compounds varies on a large scale in the same class of PhAC. Table 3 presents some of the recent literature investigating hybrid constructed wetlands for pharmaceutical compound removal from wastewater. It can be inferred from the table that constructed wetland removal efficiency was high in the case of synthetic wastewater. However, when sewage, urban and domestic wastewater are treated, their performance is like this study (see Table 4).

Overall removal efficiency of pharmaceutical compounds in a constructed wetland and tubesettler for premonsoon, monsoon, and post-monsoon season.
Fig. 4
Overall removal efficiency of pharmaceutical compounds in a constructed wetland and tubesettler for premonsoon, monsoon, and post-monsoon season.
Table 4 removal efficiency of PhACs in a constructed wetland, type of wastewater treated, and type of constructed wetland used in some of the recent studies.
Influent type Type of treatment Removal efficiency Reference
Synthetic Constructed wetland CAB 90 % aerobic condition at 0.1 ppm and 20 % at 5 ppm concentration (Ravichandran and Philip, 2022)
Municipal wastewater Post-treatment vertical constructed wetland CIP 72 %
SMZ 56 %
CAB 0 %		 (Venditti et al., 2022)
Domestic wastewater Vertical subsurface flow constructed wetland IBF −47–56 % (AL Falahi et al., 2021)
Urban wastewater Vertical subsurface flow constructed wetland SMZ 94 % (influent, 33 ngL−1) (Ávila et al., 2021a)
Synthetic Aerated constructed wetland CAB 40 % (influent, 0.1 ngL−1)
LOR 75 % (influent, 470 ngL−1)		 (Ávila et al., 2021b)
Synthetic Horizontal constructed wetland CAB 10 % (Delgado et al., 2020)

3.4

3.4 Risk assessment

The potential environmental risk from pharmaceutical compounds is of concern for the environment and human health. A ratio of the measured concentration of pharmaceutical compounds against their respective predicted no affected concentration (PNEC) is used to ass the potential risk termed as hazard quotient (HQ). The measured environmental concentration was taken as the average concentration of the respective targeted compound for each season. HQ was classified on a scale of 0 to 1. HQ ≤ 0.1 indicates minimal risk; 0.1 > HQ < 1 infers moderate risk, and HQ ≥ 1 means high risk (Chen et al., 2016). In this study, the Hazard quotient was determined for a chance to invertebrates from targeted antibiotics CIP and SMZ. HQ values from antibiotics are presented in Fig. 5. SMZ was found to be posing a maximum threat to the environment. However, it is evident from Fig. 3 that hospital wastewater had HQ values of 90, 100, and 130 for premonsoon, monsoon, and post-monsoon, respectively. After treatment from the constructed wetland, the wastewater effluent had reduced HQ value to 53, 35, and 70 for premonsoon, monsoon, and post-monsoon periods respectively. The HQ values were further reduced in tubesettler to 22, 11, and 28. Even though the HQ value indicates a high risk from the effluent of this study setup, it must be noted that there was no pre-treatment or primary treatment for HWW before being used in CW. But even then, it can be observed that there is reduced risk by 4–10 times in effluent than the initial risk posed by untreated HWW. In risk assessment of rural wastewater treated with constructed wetlands, moderate to high risk was observed. With high removal efficiency, it was concluded in the study that it is safe to discharge wastewater after treatment with HSSF CW into the river (Chen et al., 2016). The high risk from SMZ is attributed to its higher concentration in HWW compared to CIP and lower PNEC value compared to CIP.

Hazard risk from hospital wastewater, the effluent of constructed wetland, and tubesettler effluent (HWW = hospital wastewater, CW = constructed wetland, and TS = tubesettler).
Fig. 5
Hazard risk from hospital wastewater, the effluent of constructed wetland, and tubesettler effluent (HWW = hospital wastewater, CW = constructed wetland, and TS = tubesettler).

4

4 Conclusion

This study was carried out to investigate the performance of CW associated with tubesettler in treating hospital wastewater during the premonsoon, monsoon, and post-monsoon periods. In the constructed wetland, NSAIDs concentration was observed to be 1503–6307 ngL−1 and 564–808 ngL−1 for paracetamol and ibuprofen. The concentrations of antibiotics, sulfamethoxazole, and ciprofloxacin were 16532–21635 ngL−1 and 734–1178 ngL−1, respectively. The carbamazepine, lorazepam, and Lutvastatin concentration range was 616–906 ngL−1, 2742–3775 ngL−1, and 694–2068 ngL−1, respectively. The removal efficiency was 20 %, 88 %, and 30–66 % for paracetamol and ciprofloxacin, respectively. In the constructed wetlands, antibiotics, ciprofloxacin, and sulfamethoxazole were removed from wastewater with a removal efficiency of 21–82 % and 39–64 %, respectively. The other three PhACs, carbamazepine, lorazepam, and Fluvastatin, were removed in the range of 22–48 %, 50–62 %, and 18–52 %, respectively.

The removal efficiency of CW and tubesettler in treating hospital wastewater was low as single unit treatment. However, the removal efficiency was satisfactory in a combination of constructed wetland and tubesettler. The low removal efficiency of CW, in contrast with published literature, is due to two reasons. First, hospital wastewater was used in this study instead of synthetic wastewater, presenting results of a real-time scenario. Also, when synthetic wastewater is employed, other factors such as biological waste, disinfectant, and other compounds from various hospital-oriented activities are not taken into consideration which can alter, inhibit, and enhance the performance of CW. Hence, this study can be a reference study for future research work.

The study was limited to the influent and effluent concentration of the study setup. However, the effluent from the hospital needs to be investigated along with the volume of water and PhACs consumption data to provide an in-depth analysis of the CW removal mechanism in CWs. Also, the study presents results for one plant species, while several other vegetation species have been investigated to be used in CWs. This necessitates further investigation of CWs, and PhACs removal efficiency using various plant species. Also, climatic factors such as temperature, sunshine hour humidity have not been included in the scope of this study which needs further attention to realize the feasibility of CW's efficient functioning in different climatic conditions globally.

It was evident that the dilution factor in monsoon was playing a significant role in the performance of CW and tubesettler. However, to confirm the dilution factor, wastewater samples need to be collected from the outlet pipe of the hospital compared with the inlet of CW to determine the extent of dilution. Further research work is required to evaluate the impact of season, and rainfall on the performance removal mechanism of CW and tubesettler, viz. sorption, uptake by plants, biodegradation, and sediment deposition.

Acknowledgment

The authors extend their appreciation to the Deanship of Scientific Research at King Khalid University for funding this work through Large Groups (G.R.P.2-95-43).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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