Submerged membrane adsorption hybrid system (SMAHS): process control and optimization of operating parameters

This study is to investigate the effect of operating parameters of submerged membrane adsorption hybrid system (SMAHS) such as preadsorption and powdered activated carbon requirement, aeration, filtration flux; There is an optimum value for each of the operating parameters and they are specific to the wastewater used. The duration and frequency of backwashing are vital parameters for successful long-term operation of a membrane system. The backwash duration and frequency required to remove the reversible component of the foulant layer increased with time during the operation of membrane and is not fixed. A new methodology introduced in this study to decide the appropriate duration and frequency of backwash based transmembrane pressure during the membrane operation. This method led to significant saving on the amount of backwash water and energy requirement.

The preadsorption, PAC dose, aeration rate, and filtration flux had effects both on organic matter removal efficiency and TMP development. Thus, there is a need of optimizing these parameters with the specific water to be treated and the characteristics of PAC chosen. The preadsorption of 1 h prior to the membrane operation was important in mitigating the membrane fouling. The suitable aeration rate, filtration flux, and initial PAC dosing were 16 L/min, <24 L/m2 h, and 5 g/L, respectively, for the wastewater used in this study. The preadsorption of organics onto PAC could help to reduce the membrane fouling and to maintain a consistent permeate flux. The PAC replacement in PAC-MF reactor could stimulate both biological activity and adsorption, as well as optimize the operation of the hybrid system. With the PAC replacement, the system could keep TOC removal efficiency over 90% after 15 days run. The duration of the backwash is a vital parameter for successful long-term operation of a membrane system. The backwash duration required to remove the reversible component of the foulant layer increased with time during the operation of the membrane and is not fixed. Using a backwash after 15 min of permeate production, the backwash duration required increased linearly from 44 to 55 s over the 20 h of the experiment. This reduced the required amount of permeate for backwash by 25%. The organic matter removal was consistently high, in the range of 80–85%, irrespective of the variation in backwash duration. The backwash frequency is a vital parameter for successful long-term operation of a membrane system. Under the experimental conditions used in this study, a 40% reduction in backwash water by automating the backwash initiation based on TMP control. Thus, with a selection of an optimum PAC dose and operational parameters such as filtration rate, PAC replacement rate, backwashing frequency, and duration, the adsorption membrane hybrid system has significant potential for longterm application in wastewater treatment for reuse.