Physical and economical evaluation of laboratory-scale membrane bioreactor by long-term relative cost–benefit analysis

Abstract

<jats:title>Abstract</jats:title> <jats:p>Two laboratory-scale single-stage submerged membrane bioreactors (MBRs) were operated in parallel to examine the effect of different flux conditions and several fouling mitigation methods. After control operation (filtration only), three fouling control methods (relaxation, standard backwash and chemical backwash) at 27 LMH flux and four different flux conditions (54, 36, 27 and 18 LMH) with standard backwash were applied. Physical performance of MBRs was evaluated based on the operational duration to reach maximum transmembrane pressure and the volume of permeate produced during the operational duration. Then relative cost–benefit analysis was carried out. Results showed that the combination of chemical backwash and standard backwash was the most effective for fouling mitigation in terms of physical improvement of MBR performance. However, the combination proved less economical (400% + α relative cost) than standard backwash alone (343% relative cost), because of the additional cost for pumps and chemical. It also showed that lower flux (18 LMH) is desirable as it showed better physical performance (1,770% improvement as compared to the highest flux, 54 LMH) and proved more economical than higher flux configuration. Therefore, it is concluded that the operation with standard backwash at the lowest possible flux is the best combination to improve MBR performance as well as long-term cost–benefit.</jats:p>

Effect of Aeration Intensity on Performance of Lab-Scale Quorum-Quenching Membrane Bioreactor

“…The result of the current study suggests that a decision should be made among the choices whether physical cleaning should be maximized by increasing aeration with a greater energy cost or the QQ effect should be maximized by adding the effort of making QQ-CIBs with bacterial cultures and the encapsulation cost. When it is assumed that a longer operational duration leads to a less extreme condition to the membrane (i.e., experience of fouling and recovery cleaning) and thus requires less replacement of the membrane when it is not possible to recover their performance at all, the long term relative cost from membrane replacement of QQ-CIBs (C3) will be inversely proportional to the relative improvement of operational duration, i.e., around 1/3 of the no bead operation (C1) [ 34 ]. However, this relative cost does not include the energy cost, the bacterial culture, or the fabrication of the QQ-CIBs.…”

“…TMP data of each membrane module was monitored with a data-logging monometer and then transferred to a PC every week for further analysis. Hydraulic retention time (HRT), solid retention time (SRT), mixed liquor suspended solid (MLSS), and flux were selected from previous researches [ 31 , 34 ] on this plant. MLSS was maintained at 8000 mg/L by withdrawing excess sludge through daily checking of the MLSS concentration, and the average mixed liquor volatile suspended solid (MLVSS) was 7080 mg/L.…”

“…To observe the pure QQ effect that is separated from the physical cleaning effect of QQ-CIBs, comparative operations (vacant bead condition) were added. To observe the effect of aeration intensity on MBR performance, three different air flow rates were selected to be low, medium, and high, i.e., 1.5 L/min, 2.5 L/min, and 3.5 L/min with reference to previous research [ 22 , 34 ]. These air flow rates are equivalent to 3.1, 5.2, and 7.3 m 3 /m 2 /h as specific aeration demand (SAD m , air flow rate per unit surface area of membrane) and estimated to provide the velocity gradient G value of 92, 119, and 140/s, respectively, using the formulas of Mueler et al [ 36 ] and Psoch and Schiewer [ 37 ].…”

Adsorption of Low-Molecular-Weight Carboxylic Acids to Anion Exchange Resins with Various Properties and the Mechanisms of Interaction

“…Currently, electronic-grade UPW is purified using multiple steps including reverse osmosis (RO) filtration, activated carbon adsorption, UV oxidation, and ion exchange resin adsorption. RO filtration and activated carbon adsorption remove most organic and inorganic components, , but they cannot efficiently eliminate neutrally charged and low-molecular-weight (LMW) organics. , For example, only a portion of methanol, isopropyl alcohol, formaldehyde, and acetone is removed by RO filtration. , The presence of these residual LMW organics makes it difficult to achieve the TOC requirements of electronic-grade UPW. Thus, subsequent treatment steps are needed, such as UV oxidation (e.g., 185 nm vacuum-UV oxidation) and anion exchange resin (AER) adsorption.…”

UV and bacteriophages as a chemical-free approach for cleaning membranes from anaerobic bioreactors

“…Current strategies to reduce membrane biofouling include the use of physical means (e.g., gas scouring, backwashing, and sonication) and chemical cleaning [e.g., citric acid and chlorine (6)]. Physical cleaning is generally more effective to remove the reversible foulant layer (11), but the use of hydraulic or mechanical forces to clean the membrane can increase energy costs depending on the cleaning frequencies and regimes (12). Current physical cleaning approaches are also used to complement chemical cleaning which is effective against irreversible foulant layers (13).…”