AI SearchPotential of constructed wetlands for toxic organic waste treatment
Call Number: AIT Thesis no.EV-93-23 Material type:
SeriesSeries: Asian Institute of Technology. Thesis ; no. EV-93-23Publication details: Bangkok : Asian Institute of Technology, 1993Description: 126 leaves + 1 online resourceSubject(s): Online resources: Dissertation note: Thesis (M.Eng.) - Asian Institute of Technology, 1993 Summary: This study was conducted to evaluate the capability of a wetland system for treatment of phenol. One pilot-scale and 3 lab-scale units of an free water surface system (FWS), a type of constructed wetland, were set-up. Cattails (Typha sp.), an emergent plant, were planted on the lab-scale and pilot-scale wetland units. Commercial-grade phenol was mixed with the AIT campus wastewater to achieve influent phenol concentrations of 25 - 700 mg/L, corresponding to organic loading rate (OLR) of 40 - 400 kg SCOD/(ha-day). The experiment results revealed that the FWS system with cattails could effectively remove phenol, SCOD, SS, VSS at the OLRs of 40 - 270 kg SCOD/(ha-day); the optimum hydraulic retention times (HRT) were 5 - 7 days. At these operating conditions, the overall SCOD and phenol removal were 97.2 - 99.9% and 99.9 - 100%, respectively (in which SCOD and phenol removal by volatilization were 12.2 - 18.9% and 25.5 - 22.2%, respectively). The phenol concentrations of 400 mg/L and above inhibited the photosynthetic and transpiration capacity of the cattails. However, the bacteria were still able to decompose the organic matter under these conditions. Phenol was found to be present in the cattail-cells about 1.4 mg/kg of wet weight of the harvested cattails, equivalent to 1.9 kg phenol/ha. Harvesting by cutting aerial portion of the cattail plants could remove a large amount of nutrients of 970 kg N/ha/year and 330 kg P/ha/year. At the outdoor conditions, the average removal rate constant by volatilization for phenolic wastewater, Kv was 0.0573 day-1 {u2022} The removal rate constant by biodegradation, adsorption and plant uptake, Kb, increased as the initial phenol concentration increased, then reached to peak at the phenol concentrations of 250-350 mg/L and decreased as phenol toxicity dominated (above 350 mg phenol/L). The Kb reached to maximum at the HRTs of 5-7 days.
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A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering
Thesis (M.Eng.) - Asian Institute of Technology, 1993
This study was conducted to evaluate the capability of a wetland system for treatment of phenol. One pilot-scale and 3 lab-scale units of an free water surface system (FWS), a type of constructed wetland, were set-up. Cattails (Typha sp.), an emergent plant, were planted on the lab-scale and pilot-scale wetland units. Commercial-grade phenol was mixed with the AIT campus wastewater to achieve influent phenol concentrations of 25 - 700 mg/L, corresponding to organic loading rate (OLR) of 40 - 400 kg SCOD/(ha-day). The experiment results revealed that the FWS system with cattails could effectively remove phenol, SCOD, SS, VSS at the OLRs of 40 - 270 kg SCOD/(ha-day); the optimum hydraulic retention times (HRT) were 5 - 7 days. At these operating conditions, the overall SCOD and phenol removal were 97.2 - 99.9% and 99.9 - 100%, respectively (in which SCOD and phenol removal by volatilization were 12.2 - 18.9% and 25.5 - 22.2%, respectively). The phenol concentrations of 400 mg/L and above inhibited the photosynthetic and transpiration capacity of the cattails. However, the bacteria were still able to decompose the organic matter under these conditions. Phenol was found to be present in the cattail-cells about 1.4 mg/kg of wet weight of the harvested cattails, equivalent to 1.9 kg phenol/ha. Harvesting by cutting aerial portion of the cattail plants could remove a large amount of nutrients of 970 kg N/ha/year and 330 kg P/ha/year. At the outdoor conditions, the average removal rate constant by volatilization for phenolic wastewater, Kv was 0.0573 day-1 {u2022} The removal rate constant by biodegradation, adsorption and plant uptake, Kb, increased as the initial phenol concentration increased, then reached to peak at the phenol concentrations of 250-350 mg/L and decreased as phenol toxicity dominated (above 350 mg phenol/L). The Kb reached to maximum at the HRTs of 5-7 days.
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