Simultaneous removal of ibuprofen, organic material, and nutrients from domestic wastewater through a pilot-scale vertical sub-surface flow constructed wetland with aeration system

Highlights

• Performance of vertical sub-surface flow constructed wetland (VSSFCW) was assessed.

• Simultaneous removal of ibuprofen, organic material, and nutrients was performed using VSSFCW.

• Ibuprofen was removed (>99%) from real domestic wastewater using VSSFCW.

• Removal of ibuprofen and COD was dependent on the applied aeration and HRT in VSSFCW.

• Variation of aeration did not significantly affect the nutrients removal in VSSFCW.

Abstract

Pharmaceutical compounds in wastewater are currently becoming emerging concern as the utilization of drugs in anthropogenic activities. This research analyzed the effectiveness of pilot-scale vertical subsurface flow constructed wetland (VSSFCW) planted with Scirpus grossus using an aeration system for simultaneous removal of ibuprofen, chemical oxygen demand (COD) and nutrients (NH₃-N, NO₃-N, and PO₄-P) from domestic wastewater. The constructed wetland (CW) platforms (500 L capacity) filled with gravel and sand and planted with native species of S. grossus were used to treat pharmaceutical content in domestic wastewater continuously for 21 days. Three experiments were performed with hydraulic retention time (HRT) of 3, 4 and 5 days. Aeration rates of 0, 1, and 2 L/min were employed for each HRT. The combined effect of HRT, exposure period, and aeration to simultaneously remove ibuprofen, organic materials, and nutrients were examined statistically using Two-way ANOVA and Tukey HSD test. Filtration and adsorption mechanisms of ibuprofen compound by sand medium matrix were proven to occur using solid phase extraction method. The removal efficiency of ibuprofen and COD were dependent on the applied aeration and HRT (p < 0.05). A longer HRT increased the removal efficiency of ibuprofen, while it did not significantly affect the nutrient removal (p ≥ 0.05). The VSSFCW under 2 L/min aeration and HRT of 5 days has removed 99.3% of ibuprofen, 88.2% of COD, 99.1% of ammonia, 72.9% of nitrate-nitrogen, and 83.2% of orthophosphate with effluent successfully met the effluent Standard B set by Malaysian Government. Therefore, the VSSFCW planted with S. grossus becomes a technically feasible method for treating sewage containing pharmaceutical compounds.

Introduction

Pharmaceutical residues in wastewater pose a challenge for wastewater treatment technology. Domestic sewage, pharmaceutical industries, hospital, and landfill leachate are several sources for pharmaceutical compounds found in the environment [1]. Among that origins, anthropogenic activities played major role in the release of pharmaceutical compounds [2,3]. Human is the main contributor to the availability of the pharmaceutical compounds in domestic wastewater. Residual pharmaceutical compounds, normally taken by human as medicine, will be released as metabolic products with urine and feces [[4], [5], [6]]. The utilization of herbicides and insecticides also contributes to the existence of pharmaceutical components in surface water [[7], [8], [9]].

Pharmaceutical components in environment may spark several problems [3]. Some pharmaceutical compounds exhibit chronic effect and even acute/lethal effect to certain organisms [8,10]. Antibiotics, one type of pharmaceutical compounds, are also considered as emerging concern in the field of environmental pollution [11,12]. The existence of antibiotics in the environment poses harmful effect for organisms. Antibiotics existence can generate new gene of antibiotic-resistant expression [13] that subsequently may create new antibiotic-resistant strain of microorganisms [14]. Antibiotic-resistant microorganisms can cause further problem, especially for human health. Diseases caused by antibiotic-resistant microorganisms will be harder to be cured as compared to the commonly disease-related microorganisms [15].

Ibuprofen is one type of pharmaceutical compounds found in the wastewater [16]. It is a common painkiller used to treat aches, fever and pains [17], and also reduces inflammation. Ibuprofen and any other pharmaceuticals in domestic wastewater are originated from human excreta and disposal of expired/unused drugs into sewerage systems [18,19]. The other sources may come from landfills for expired drugs and improper effluent treatment in pharmaceutical industries. Combination of ibuprofen is also being used in remediating cold and influenzas. Commonly, ibuprofen is sold without prescription under several trademarks [19,20]. Several researchers reported the negative impacts of ibuprofen existence in environment. Geiger et al. [21] reported the decreasing algal population density caused by the exposure of ibuprofen. Similarly, Moro et al. [22] also claimed the alteration of structure and ultra-skeleton of Scenedesmus rubescens after 30 days exposure of ibuprofen. In addition, a significantly decreasing number of eggs of Daphnia manga was noticed only after 6-hour exposure to 50 μg/L of ibuprofen [23].

Adsorption [24] and filtration [23] are the common technology used for treating ibuprofen as water contaminant, while electrocoagulation, ozonation and photocatalytic has also emerged as alternative technology [[24], [25], [26]]. Physical treatment like filtration removed the ibuprofen by its particle size, while adsorption and electrocoagulation removed ibuprofen by its charge. Chemical coagulation and flocculation is also evident to treat ibuprofen in water/wastewater [27]. Despite the reliable efficiency of the above-mentioned technologies, there is a concern on the used chemicals and treatment residues that might cause further pollution to the environment [[28], [29], [30]]. In addition, chemical treatment also generates abundant amount of sludge which requires further handling [27,31]. The high consumption of energy and high operational cost by applying these technologies also need to be considered [27,32]. To comprise these issues, biological treatment using wetland becomes a very promising technology to treat ibuprofen contaminated water.

Among biological treatment methods, constructed wetland (CW) is the most promising technology to be applied in treating ibuprofen contaminated water [16,33,34]. CW mimics the natural phenomenon of filtration, degradation, and uptake of pollutants [35,36]. A horizontal sub-surface CW planted with Thypa angustifolia showed the efficiency of ibuprofen removal up to 70% through complex plant-microbes-medium interactions, with aeration supply had promoted the removal of ibuprofen by enhancing the aerobic bacteria growth which played important roles in the degradation of ibuprofen in wastewater [10]. In addition, Zhang et al. [37] also mentioned that different hydraulic retention time (HRT) affected the removal kinetics of pharmaceutical components in CW. Based on many conducted studies [[38], [39], [40]], the results showed that HRT between 2 and 7 days is the most applicable depending on the pollutant concentrations/loading and the capability of plant species. The utilization of plants showed a significant increment of ibuprofen removal as compared to the non-planted system, indicating the importance of plants for the degradation of ibuprofen in wetland [16]. Another study showed the performance of vertical free-flow CW planted with Eichhornia crassipes and Heliconia rostrata in treating ibuprofen in wastewater with removal value up to 89% [17].

Following the emergence of the pharmaceutical compounds inside wastewater originating from atherogenic activities [41], research conducted on the simultaneous removal of nutrients and ibuprofen from domestic wastewater is not widely conducted yet. Scirpus grossus is a native plant species in tropical countries which exhibits great performance of organic and nutrient removal in domestic wastewater using CW [36,[42], [43], [44]]. This species was chosen based on its great performance in removing pollutant in domestic wastewater. It was able to remove up to 90% of COD from domestic wastewater [43], while another research [45] mentioned its capability to achieve an average of 69% for BOD removal. This species also had demonstrated good performance for nutrient removal from domestic wastewater with values reaching 84.7% of NH₄-N, 38.3% NO₃-N, 71.0% of PO₄-P, and 61.2% PO₄³⁻ [42,45]. Looking at the performance of this species, and the emerging of pharmaceutical compounds, especially ibuprofen, in domestic wastewater, an opportunity to conduct a research of ibuprofen-containing domestic wastewater using CW planted with S. grossus is considered applicable. Hence, its performance in treating pharmaceutical compound especially ibuprofen is awaiting to be explored further. Moreover, most of the current treatment of ibuprofen in wastewater is through adsorption and filtration, and yet they are conducted at laboratory scale [23,24], while the utilization of pilot-scale CW planted with native plants under different HRT and aeration systems is currently still limited. Understanding the potential of CW, this research aimed to analyze the simultaneous removal of ibuprofen, chemical oxygen demand (COD), and nutrients (NH₃-N, NO₃-N, and PO₄-P) from domestic wastewater using pilot-scale vertical subsurface flow constructed wetland (VSSFCW) planted with S. grossus under different HRT and aeration rates. This setup was also used to analyze the capability of S. grossus in treating ibuprofen, since research on ibuprofen treatment using S. grossus is currently limited. The presented result is targeted to contribute to the knowledge of alternative environmentally friendly technology to treat pharmaceutical containing wastewater.