The influence of dissolved oxygen on growth and degradation of Cypermethrin by Pseudomonas using a biosimulator

Abstract

Cypermethrin, a least water soluble pesticide, was selected because such compounds are very difficult to remove from environmental systems by conventional means. In this study, Pseudomonas strain (IES-Ps-1) was used to assess its potential for Cypermethrin degradation. Continuous agitation of a wastewater sample in biosimulator was found to be suitable for growth as well as the metabolism of Cypermethrin by Pseudomonas. At optimum temperature (28-30ºC) using 8-9 mg/L dissolved oxygen (DO), >85% degradation of Cypermethrin was achieved after 48 hours when the initial added concentration was 80 mg/L. In contrast, at 5-6 mg/L DO, only 38% degradation occurred. When the concentration of DO further increased from 9 to 12mg/l, no pronounced effect on the removal efficiency was observed. Results were confirmed by COD and HPLC analysis. Moreover, during treatment, no significant effect of pH change was observed and the pH remains between 7.3 and 8.8. The findings suggest that IES-Ps-1 strain could effectively be used for the removal of pesticide waste.

Presence of Organic Pesticides in Commercial Rainbow Trout Farms

“…In addition to pH, it is well known that temperature and salinity also influence the degradation time of the pesticides. In the present study, temperature was below the optimum degradation range, -25 0 C (PPDB, 2009) [19]. In this sense, the degradation of Organophosphorus chlorpyrifos (in freshwater at 10 0 C) occurred in 18.7 days, while in sea water (10 0 C), it suffered degradation up to 49.4 days (Bondarenko et al, 2004) [13].…”

“…Table 2: Means (± standard deviation) of the physiochemical parameters (pH, temperature, dissolved oxygen and alkalinity) evaluated on collection points (A1, A6, B1, B9) during rainbow trout cultivation in raceway in periods of rain and drought (2014 and 2015) in two commercial trout farms (A and B). Some pesticides may be more recalcitrant to hydrolysis at pH 7, such as carbamate aldicarb (189 days), pyrethroids cypermethrin (179 days) and organophosphate phosalone (321 days) (PPDB, 2009) [19]. In addition to pH, it is well known that temperature and salinity also influence the degradation time of the pesticides.…”

“…In the same pH as mentioned, for carbaryl (carbamate) the half-life may be 45 days at 6 0 C and for 2 days, if the temperature = 22 0 C [20]. Increases in dissolved oxygen in water can influence the microbiological degradation of pesticides, such as pyrethroids at pH (7.3-8.8), temperature (28-30 0 C) and dissolved oxygen between 8-9 mg/L, degradation rate is rapid after 48 h [19]. …”

“…However, physicochemical parameters, such as pH, temperature, dissolved oxygen and alkalinity, may influence the rate of pesticide degradation ( Table 2). These parameters can degrade Organophosphorus pesticides, carbamates Zamy et al [18]; Hui et al [5] and pyrethroids [19] in the aquatic environment. Due to the influence of alkalinity on the average values of pH and considering the results of this study in the two trout farms, it is verified the tendency of alkaline pH, as a factor that can influence the degradation of some pesticides due to the more pronounced hydrolysis.…”