Optimizing Constructed Wetlands for Safe Removal of Triclosan: A Box–Behnken Approach

Abstract

Traditional constructed wetland designs typically result in variable efficiencies for trace organic contaminant removal. In this work, we used a Box–Behnken experimental design for optimizing the conditions of pH, nitrate concentration, and dissolved organic carbon (DOC) concentration that would maximize the rate of triclosan phototransformation while minimizing the accumulation of toxic byproducts. Triclosan is a frequently detected and toxic antimicrobial agent present in many consumer and industrial products. The results showed that high pH values (9.9) and low DOC concentration (11 mg/L–) would maximize triclosan phototransformation rate while minimizing the accumulation of toxic byproducts. As long as DOC concentrations were larger than 33 mg/L, nitrate concentration did not show a significant effect on triclosan phototransformation rate. The major transformation products detected were 2,4-dichlorophenol and compounds with chemical formulas C12H8Cl2O2 and C12H9ClO3, resulting from a chlorine loss or replacement by a OH group. In addition, 4-chlorocatechol was mainly detected during direct photolysis and 2,8-dichlorodibenzo-p-dioxin was only found during direct photolysis at pH 8. This study showed that wetland efficiency at removing triclosan can theoretically be increased by limiting DOC-contributing factors, e.g., emergent vegetation, and supporting pH-increase processes, e.g., via algae growth or by incorporating alkaline geomedia.

Continuous Flow Synthesis of Ethyl Diazoacetate and CFD Analysis of Micromixing Efficiency in a Microreactor

“…Response surface methodology (RSM) is an experimental design method that employs quadratic regression equations to identify optimal process parameters by analyzing the functional relationship between experimental factors and response values. The use of the method is extensive across a wide range of fields. − The advantage of RSM over single-factor and orthogonal designs lies in its efficiencyit requires less time and a shorter experimental period while delivering more accurate results. Among the common RSM designs, the BBD and central composite design are prominent.…”

Scale-Up and Development of Synthesis 2-Ethylhexyl Nitrate in Microreactor Using the Box–Behnken Design

“…The response surface method is an experimental design method that uses various quadratic regression equations to analyze the regression equation through the functional relationship between the experimental data relevant factor and the response value to find the best process parameters. It is widely used in many fields. − Compared with single-factor design and orthogonal design, it has the advantages of a shorter design time, a shorter period, and a higher accuracy of a regression equation. There are many design schemes in experimental RSM design, among which the Box–Behnken design and the central composite design are the most common design models.…”

Wetlands for environmental protection

“…Steroid hormones [androsta‐1,4‐diene‐3,17‐dione (ADD), 4‐androstene‐3,17‐dione (AED), 19‐nortestoserone (19‐NT), testosterone (T), and progesterone (P)] and biocides [DEET, triclosan (TCS), carbendazim (CBD), and medroxyprogesterone (MP)] were effectively removed while treating rural wastewater in an integrated CW (Chen, Deng, et al, 2019). High pH values (9.9) and low dissolved organic carbon concentration (11 mg/L) has maximized the triclosan phototransformation rate and minimized the accumulation of toxic byproducts while optimizing the CW for the safe removal of triclosan (Lam, Nélieu, Benoit, & Passeport, 2019).…”