The Activated Sludge Process(ASP) exhibits highly nonlinear properties. The design of an automatic control system that is robust against disturbance of inlet wastewater flow rate and has short process settling times i...The Activated Sludge Process(ASP) exhibits highly nonlinear properties. The design of an automatic control system that is robust against disturbance of inlet wastewater flow rate and has short process settling times is a challenging matter. The proposed control method is an I-P modi fied controller automatic control system with state variable feedback and control canonical form simulation diagram for the process. A more stable response is achieved with this type of modern control. Settling times of 0.48 days are achieved for the concentration of microorganisms,(reference value step increase of 50 mg·L-1) and 0.01 days for the concentration of oxygen(reference value step increase of 0.1 mg·L-1). Fluctuations of concentrations of oxygen and microorganisms after an inlet disturbance of5 × 103m3·d-1are small. Changes in the reference values of oxygen and microorganisms(increases by 10%, 20% and 30%) show satisfactory response of the system in all cases. Changes in the value of inlet wastewater flow rate disturbance(increases by 10%, 25%, 50% and 100%) are stabilized by the control system in short time. Maximum percent overshoot is also taken in consideration in all cases and the largest value is 25% which is acceptable. The proposed method with I-P controller is better for disturbance rejection and process settling times compared to the same method using PI controller. This method can substitute optimal control systems in ASP.展开更多
In this work,38 different organic emerging contaminants(ECs),belonging to various chemical classes such as pharmaceuticals(PhCs),endocrine-disrupting chemicals(EDCs),benzotriazoles(BTRs),benzothiazoles(BTHs),and perfl...In this work,38 different organic emerging contaminants(ECs),belonging to various chemical classes such as pharmaceuticals(PhCs),endocrine-disrupting chemicals(EDCs),benzotriazoles(BTRs),benzothiazoles(BTHs),and perfluorinated compounds(PFCs),were initially identified and quantified in the biologically treated wastewater collected from Athens’(Greece)Sewage Treatment Plant(STP).Processes already used in existing STPs such as microfiltration(MF),nanofiltration(NF),ultrafiltration(UF),UV radiation,and powdered activated carbon(PAC)were assessed for ECs’removal,under the conditions that represent their actual application for disinfection or advanced wastewater treatment.The results indicated that MF removed only one out of the 38 ECs and hence it was selected as pretreatment step for the other processes.UV radiation in the studied conditions showed low to moderate removal for 5 out of the 38 ECs.NF showed better results than UF due to the smaller pore sizes of the filtration system.However,this enhancement was observed mainly for 8 compounds originating from the classes of PhCs and PFCs,while the removal of EDCs was not statistically significant.Among the various studied technologies,PAC stands out due to its capability to sufficiently remove most ECs.In particular,removal rates higher than 70%were observed for 9 compounds,22 were partially removed,while 7 demonstrated low removal rates.Based on our screening experiments,future research should focus on scaling-up PAC in actual conditions,combining PAC with other processes,and conduct a complete economic and environmental assessment of the treatment.展开更多
文摘The Activated Sludge Process(ASP) exhibits highly nonlinear properties. The design of an automatic control system that is robust against disturbance of inlet wastewater flow rate and has short process settling times is a challenging matter. The proposed control method is an I-P modi fied controller automatic control system with state variable feedback and control canonical form simulation diagram for the process. A more stable response is achieved with this type of modern control. Settling times of 0.48 days are achieved for the concentration of microorganisms,(reference value step increase of 50 mg·L-1) and 0.01 days for the concentration of oxygen(reference value step increase of 0.1 mg·L-1). Fluctuations of concentrations of oxygen and microorganisms after an inlet disturbance of5 × 103m3·d-1are small. Changes in the reference values of oxygen and microorganisms(increases by 10%, 20% and 30%) show satisfactory response of the system in all cases. Changes in the value of inlet wastewater flow rate disturbance(increases by 10%, 25%, 50% and 100%) are stabilized by the control system in short time. Maximum percent overshoot is also taken in consideration in all cases and the largest value is 25% which is acceptable. The proposed method with I-P controller is better for disturbance rejection and process settling times compared to the same method using PI controller. This method can substitute optimal control systems in ASP.
文摘In this work,38 different organic emerging contaminants(ECs),belonging to various chemical classes such as pharmaceuticals(PhCs),endocrine-disrupting chemicals(EDCs),benzotriazoles(BTRs),benzothiazoles(BTHs),and perfluorinated compounds(PFCs),were initially identified and quantified in the biologically treated wastewater collected from Athens’(Greece)Sewage Treatment Plant(STP).Processes already used in existing STPs such as microfiltration(MF),nanofiltration(NF),ultrafiltration(UF),UV radiation,and powdered activated carbon(PAC)were assessed for ECs’removal,under the conditions that represent their actual application for disinfection or advanced wastewater treatment.The results indicated that MF removed only one out of the 38 ECs and hence it was selected as pretreatment step for the other processes.UV radiation in the studied conditions showed low to moderate removal for 5 out of the 38 ECs.NF showed better results than UF due to the smaller pore sizes of the filtration system.However,this enhancement was observed mainly for 8 compounds originating from the classes of PhCs and PFCs,while the removal of EDCs was not statistically significant.Among the various studied technologies,PAC stands out due to its capability to sufficiently remove most ECs.In particular,removal rates higher than 70%were observed for 9 compounds,22 were partially removed,while 7 demonstrated low removal rates.Based on our screening experiments,future research should focus on scaling-up PAC in actual conditions,combining PAC with other processes,and conduct a complete economic and environmental assessment of the treatment.
