Clogging is the most significant challenge limiting the application of constructed wetlands. Application of a forced resting period is a practical way to relieve clogging, particularly bioclogging. To reveal the alleviation mechanisms behind such a resting operation, evapotranspiration and oxygen flux were studied during a resting period in a laboratory vertical-flow constructed wetland model through physical simulation and numerical model analysis. In addition, the optimum theoretical resting duration was determined based on the time required for oxygen to completely fill the pores, i.e., formation of a sufficiently thick and completely dry layer. The results indicated that (1) evapotranspiration was not the key factor, but was a driving force in the alleviation of bioclogging; (2) the rate of oxygen diffusion into the pores was sufficient to oxidize and disperse the flocculant biofilm, which was essential to alleviate bioclogging. This study provides important insights into understanding how clogging/bioclogging can be alleviated in vertical-flow constructed wetlands.
Evapotranspiration versus oxygen intrusion in alleviating bioclogging in vertical flow constructed wetlands
Two sample preparation methods were introduced and compared in this paper to establish a simple, quick and exact analysis of geosmin and 2-methylisoborneol. LC-18 column was employed in solid phase extraction (SPE), 1.0 mL of hexane was adopted in liquid-liquid extraction (LLE), and the extracts were analyzed by gas chromatograph mass spectrum (GCMS) in selected ion mode. Mean recoveries of SPE were low for 2-methylisoborneol (2-MIB) and geosmin (GSM) with values below 50%. For LLE, the recoveries were satisfyingly above 50% for 2-MIB and 80% for GSM. Detection limits of the LLE method were as low as 1.0 ng/L for GSM and 5.0 ng/L for 2-MIB. A year-long investigation on odor chemicals of drinking water in Shanghai demonstrated that in the summer, there was a serious odor problem induced by a high concentration of 2-MIB. The highest concentration of 152.82 ng/L appeared in July in raw water, while GSM flocculation was minimal with concentrations below odor threshold. 相似文献
Two sample preparation methods were introduced and compared in this paper to establish a simple, quick and exact analysis
of geosmin and 2-methylisoborneol. LC-18 column was employed in solid phase extraction (SPE), 1.0 mL of hexane was adopted
in liquid-liquid extraction (LLE), and the extracts were analyzed by gas chromatograph mass spectrum (GCMS) in selected ion
mode. Mean recoveries of SPE were low for 2-methylisoborneol (2-MIB) and geosmin (GSM) with values below 50%. For LLE, the
recoveries were satisfyingly above 50% for 2-MIB and 80% for GSM. Detection limits of the LLE method were as low as 1.0 ng/L
for GSM and 5.0 ng/L for 2-MIB. A year-long investigation on odor chemicals of drinking water in Shanghai demonstrated that
in the summer, there was a serious odor problem induced by a high concentration of 2-MIB. The highest concentration of 152.82
ng/L appeared in July in raw water, while GSM flocculation was minimal with concentrations below odor threshold. 相似文献
