Effectiveness of combined tools: adsorption, bioaugmentation and phytoremediation for pesticides removal from wastewater

Abstract

The aim of this study was the comparison of two process in pentachlorophenol (PCP: 100 mg L⁻¹) removal by combined process bioaugmentation-adsorption and bioaugmentation-phytoremediation in secondary treated wastewater (STWW). The phytoremediation procedure was conducted by using two plants such as Typha angustifolia and Schoenoplectus acutus, and the bioaugmentation procedure was operated by Pseudomonas putida HM 627618 as a plant growth promoting bacteria (PGPR). The adsorption process was performed by palm date activated carbon. The PCP monitoring was assessed by high performance liquid chromatography (HPLC) and the optical density determination at 600 nm (OD₆₀₀). The performance of the two processes was observed by the determination of total bacteria, chlorophylls and physical and chemical analysis (COD, pH, conductivity, chloride, and organic carbon). The alfalfa seed germination test was conducted to assess the two operational performance procedures. According to the results obtained from the physical and chemical analysis of the treated STWW, there was no significant differences in the pH and in the EC content of the bioaugmentation-phytoremediation treatment, while a significant increase of the EC content was observed in the bioaugmentation-adsorption to 5.08 mS cm⁻¹. The COD value significantly decreased up to 1320 mg L⁻¹ in bioaugmentation-adsorption treatment (control value 2400 mg L⁻¹) and 98 mg L⁻¹ in bioaugmentation-phytoremediation treatment (control value 98 mg L⁻¹). Microbial biomass monitoring of P. putida shows significant greater in both processes in the order of 9.18 and 7.01 Log CFU mL⁻¹ for bioaugmentation-adsorption and bioaugmentation-phytoremediation, respectively. The chlorophyll content in Typha angustifolia and Schoenoplectus acutus significantly decreased after 144 h with the exception of the chlorophyll a content of Schoenoplectus acutus in which the content increased up to 3.31 mg mL⁻¹. Comparing the performance of these two treatments, it was found according to HPLC analysis that the bioaugmentation-adsorption process was more efficient in removing about 97% of PCP after 48 h, against around 90% of PCP after 72 h for the phytoremediation-bioaugmentation. The alfalfa seeds showed a germination rate after the 5th day of incubation of 100% and 95%, respectively for the PCP-non-contaminated and treated STWW, while for wastewater containing PCP the germination was totally inhibited.

Graphical abstract

NOVELTY STATEMENT

This paper describing sensitive methods of combined bioaugmentation-phytoremediation and bioaugmentation-adsorption for pentachlorophenol (PCP) depletion in wastewater. The novelty is the choice of a macrophyte Typha angustifolia and Schoenoplectus acutus in constructed wetland fixed in clay matrix. The two-selected plants are still used for the elimination of heavy metals but not for pesticide in wastewater. Also, the combined process bioaugmentation-adsorption was not tested in other researches. On the other side, in this study, the phytoremediation technique combined with bacteria positively affected the plants activity in order to promote pollutant remediation. Hence, the Pseudomonas putida HM 627618 in wastewater with the macrophyte presence or date stone adsorbent have a great capacity to reduce this pollutant (PCP) by improving the bioremediation process.

Keywords:

• Activated carbon
• pentachlorophenol
• pseudomonas putida
• schoenoplectus acutus
• typha angustifolia

Acknowledgments

The authors thank all the coauthors for their technical support and their manuscript editing.

Additional information

Funding

This research was funded by Water Treatment and Recycling Laboratory member lab (CERTE), Eremology and Combating desertification, Arid Regions Institute of Medenine, Tunisia and National Agency of Scientific Research Promotion (Mobidoc Promotion 2019).