Abstract
Dimethyl phthalate (DMP), belonging to the family of Phthalate esters (PAEs), is a plasticizer and has been widely used in the world for many years. Nowadays, it has become a ubiquitous environmental pollutant and is listed as an environmental priority pollutant by China’s Environmental Monitoring Center. The purpose of this study is to estimate the responses of the bacterial community and enzyme activity to DMP contamination in three vertical flow constructed wetlands (VFCW), namely the constructed wetland A (planted with Pennisetum sinese Roxb), constructed wetland B (planted with Pennisetum purpureum Schum.), and constructed wetland C (unplanted), respectively. The results showed that the relative percentages of some genera associated with nitrogen metabolism and the function of degrading aromatic hydrocarbons were increased by DMP contamination, such as Dechloromonas agitata, Pleomorphomonas sp., Denitratisoma oestradiolicum, Plasticicumulans lactativorans, Novosphingobium sp., Alicycliphilus denitrificans, and Thauera sp. Meanwhile, principal coordinate analysis (PCA) analysis showed that the addition of DMP divided 12 samples into two groups as followed: one was the DMP group containing a-1, a-2, b-1, b-2, c-1 and c-2 while the other was no DMP group including A-1, A-2, B-1, B-2, C-1 and C-2. It indicated that DMP was the main reason for this change. In addition, by monitoring the activity of substrate enzymes, the activity of urease, phosphatase, catalase, and invertase in the wetlands before and after the experiment, these were significantly higher in the upper layer than in the lower layer and maintained high activity. Ultimately, the average influent concentration of DMP in three VFCWs was 8.12 mg/L and the average removal efficiency of the effluent was over 90%. Our results suggested that DMP was an important factor affecting the microbial community structure of wetland and the upper layer of the VFCW was the main site for the degradation of DMP. VFCW has great potential for the removal of the high concentration of DMP and it can be a good choice for the treatment of PAEs.
Highlights
Constructed wetland (CW) is a low-cost, eco-technology and a prospective wastewater treatment technology, which relies on biological, physical, and chemical processes to remove various pollutants [1]
Liao et al [20] reported that Dimethyl phthalate (DMP), dibutyl phthalate (DBP), and DEHP were the main components of Phthalate esters (PAEs) pollutants in the soil of West Lake Scenic Spot that in Hangzhou city, Zhejiang Province, China, and the contribution rate of total content ranged from 95.65% to 99.22%
When the substrate adsorption tends to saturation, the DMP removal rate decreased sharply, and the ability of the wetland to remove DMP will not be restored until the microorganisms in the wetland reach a stable state
Summary
Constructed wetland (CW) is a low-cost, eco-technology and a prospective wastewater treatment technology, which relies on biological, physical, and chemical processes to remove various pollutants [1]. In the past few years, vertical flow constructed wetland (VFCW) has become a preferable choice for wastewater treatment [2]. It showed good performance in removing nitrogen [3] and organic compounds [4,5] due to their excellent oxygen transfer characteristics and small area. The main objectives of this study are: (1) study the effect of DMP on the microbial diversity and composition in VFCW; (2) understand the dominant bacterial in processing DMP and to determine enzyme activity for assessing the potential of DMP removal in VFCW
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