Removal of selected organic pollutants and coliforms in pilot constructed wetlands in southeastern Mexico

Abstract

The removal efficiency of selected emerging pollutants, total (TotCol) and faecal (FecCol) coliforms in surface (SF) and subsurface (SSF) flow constructed wetlands (CWs) was compared. The pilot plant (located in southeastern Mexico) consisted of eight CWs: four with SF and four with SSF. Two cells of each type were planted with Typha sp. and two were left without plant as controls. CWs were fed with water from Sordo river, which receives untreated urban sewage and industrial wastewaters. Water samples from river and outflow from each CW were collected in four sampling campaigns, they were filtered, extracted and analysed by GC/MS. Redox potential (Eh) was measured in all cells. The following pollutants were identified and quantified: Caffeine, CAF; Galaxolide, GAL; Methyl dihydrojasmonate, MDHJ; Linear alkylbenzenes, LAB; Butylated hydroxytoluene, BHT; Surfynol 104, SSURF; Alkylphenols, AP; 4-alkylphenol monoetoxylates, APE; Parsol, PAR. Typical removals of studied compounds were attained with slightly better results in SSFCW. A multiple linear regression analysis considering Eh, time, influent pollutant concentration (C₀) and the presence of plants and filtering media (Fmedia) as independent variables showed that Eh has a significant influence in the removal for almost all the studied compounds with the exception of BHT and AP. C₀ influences removal processes with the exception of coliforms. A significant influence of Fmedia in the BHT and PAR removal is observed, also positive for AP, APE, CAF, LAB and GAL in decreasing order. The effect of plants is positive for PAR (significant), GAL, CAF, BHT and MDHJ. SURF has a distinct behaviour with a negative coefficient for its C₀. For TotCol and FecCol the most significant effects are Eh and time. This may be related to the fact that predation by aerobic microbial communities may be the predominant factor in their removal and the development of these microbial communities with time.

Keywords:

• emerging pollutants
• coliforms
• removal
• constructed wetlands

Ackowledgements

Funding for this project was provided by the Mexican National Council for Science and Technology-CONACyT through the National Research System-SNI-Undergraduate project # 102122 and the basic science project # 81942. Additional support from the project 21-09-020351 of the Support Program for the State of Puebla (Secretary Rural Development) is gratefully acknowledged.