Abstract
Membrane Bio Reactors (MBRs) are mainly used for industrial wastewaters applications where their costs can be more easily afforded. High costs are basically due to energy consumption and membrane cleaning or replacement. Membrane fouling is responsible for reducing treated water production and increasing maintenance as well as operation costs. According to previous researches, the addition of Powdered Activated Carbon (PAC) in high dosages could reduce membrane fouling; but such concentrations are economically unsustainable for operative conditions. A MBR pilot plant, fed by mixed liquor of a full-scale activated sludge process from a municipal wastewater treatment plant, was operated dosing low PAC concentrations (0, 2, 5, 10 and 20 mg·L−1, respectively). Experiments were also carried out at two different temperatures corresponding to summer and winter conditions. Results indicated that PAC addition was effective at the low dosages (2 and 5 mg·L−1) by reducing the permeate flux loss (from 16 up to 27%, respectively) while higher PAC concentrations turns out in a useless cost increase.
Highlights
Membrane bioreactor (MBR) applications allow several advantages with respect to conventional activated sludge [1,2]
Energy consumptions span from 0.50–0.80 kWh·m−3 for flat sheet membrane to around
All membrane bioreactor experiments were carried out in a pilot plant fed with mixed liquor coming from the activated sludge tank of a full scale wastewater treatment plant (WWTP)
Summary
Membrane bioreactor (MBR) applications allow several advantages (e.g., higher performances, lower space requirements, lower sludge production) with respect to conventional activated sludge [1,2] Their extensive application to urban wastewater treatment is still restrained due to the capital as well as the operation and maintenance (O&M) costs (e.g., energy and membrane replacement). 43–47€ Equivalent inhabitant−1 for flat sheet and 42–43€ Equivalent inhabitant−1 for tubular) decreased over the past 10 years as a result of their increased diffusion, improvements in process design, more sophisticated control of the operating parameters and backwashing operation strategy. Their life time has been expanded [3]. Frequent membrane cleaning is required, increasing significantly the operating costs as a result of cleaning agents and production downtime
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