Optimal conditions for chlorothalonil and dissolved organic carbon in horizontal subsurface flow constructed wetlands

Abstract

The most efficient system of horizontal subsurface flow constructed wetlands (HSSFCW) for removing dissolved organic carbon (DOC) in the presence of chlorothalonil pesticide (CLT) present in synthetic domestic wastewater was determined using the macrophyte Phragmites australis. Two concentrations of CLT (85 and 385 μg L) and one concentration of glucose (20 mg L) were evaluated in four pilot scale horizontal surface flow constructed wetlands coupled with two sizes of silica gravel, igneous gravel, fine chalky gravel (3.18-6.35 mm), coarse gravel (12.70-25.40 mm) and two water surface heights (20 and 40 cm). For a month, wetlands were acclimated with domestic wastewater. Some groups of bacteria were also identified in the biofilm attached to the gravel. In each treatment periodic samplings were conducted in the influent and effluent. Chlorothalonil was quantified by gas chromatography (GC-ECD m), DOC by an organic carbon analyzer and bacterial groups using conventional microbiology in accordance with Standard Methods. The largest removals of DOC (85.82%-85.31%) were found when using fine gravel (3.18-6.35 mm) and the lower layer of water (20 cm). The bacterial groups quantified in the biofilm were total heterotrophic, revivable heterotrophic, Pseudomonas and total coliforms. The results of this study indicate that fine grain gravel (3.18-6.35 mm) and both water levels (20 to 40 cm) can be used in the removal of organic matter and for the treatment of agricultural effluents contaminated with organo-chloride pesticides like CLT in HSSFCW.

Enhanced nitrogen and phosphorus removal by natural pyrite–based constructed wetland with intermittent aeration

“…Pseudomonas is a genus of denitrifying bacteria, which is the dominant group of nitrifying bacteria in CWs and plays an important role in heterotrophic denitrification (Nicomrat et al 2006, Okada et al 2005, Rìos-Montes et al 2017. Pseudomonas contributes to removing both CODCr and TN, and may also be the dominant genus for TP removal (Ge et al 2019).…”

A Mechanistic Model for Simulation of Carbendazim and Chlorothalonil Transport through a Two-Stage Vertical Flow Constructed Wetland

“…There are various types of CWs that have been studied over the years for the treatment of agricultural runoffs [12,13]. The use of vertical flow constructed wetlands for pesticide treatment has been studied recently [14][15][16][17], which has shown great promise towards efficient removal of pesticides.…”

Biological Visual Detection for Advanced Photocatalytic Oxidation toward Pesticide Detoxification

“…1,7−9 It is considered that the displacement of chlorine into the hydroxyl group (−OH) 1 and the oxidation/hydration of the cyano group (−CN) 10 produce 4-hydroxychlorothalonil, which is more stable and more toxic than its parent compound. 9,11…”

“…Chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbo-nitrile, CTL), a broad-spectrum organochlorine pesticide, is extensively used in agriculture, horticulture, and other applications as a protectant, bactericide, and mildewcide. − However, it is known as an acute and chronic toxic carcinogen and teratogen according to World Health Organization classification of hazards. ,,, In China, the production of CTL reaches 8.0 × 10 6 kg/year, whereas in the United States, it is approximately 5.0 × 10 6 kg/year and growing year by year. ,, The half-life of CTL ranges from several days to 1 year in soil and 8 to 220 days under different concentrations in water and seasonal conditions . Upon degradation, it produces a series of metabolites such as 2,4,5-trichloroisophthalonitrile, 2,5,6-trichloro-4-methoxyisophthalonitrile, 4-hydroxychlorothalonil, 1-carbamoyl-3-cyano-4-hydroxy-2,5,6-trichlorobenzene, and 1,3-dicarbamoyl-2,4,5,6-tetrachlorobenzene. ,− It is considered that the displacement of chlorine into the hydroxyl group (−OH) and the oxidation/hydration of the cyano group (−CN) produce 4-hydroxychlorothalonil, which is more stable and more toxic than its parent compound. , …”

“…1,7−9 It is considered that the displacement of chlorine into the hydroxyl group (−OH) 1 and the oxidation/hydration of the cyano group (−CN) 10 produce 4-hydroxychlorothalonil, which is more stable and more toxic than its parent compound. 9,11 Thiram (tetramethylthiuram disulfide, TMTD), a dimethyl dithiocarbamate compound, is widely used as a pesticide in crop protection. It is also used as an animal repellent to protect ornamental plants and fruit trees from animal foraging.…”