Laura Hamdan de Andrade

Internal versus external submerged membrane bioreactor configurations for dairy wastewater treatment

AbstractTwo submerged membrane bioreactor (SMBR) configurations, one with the membrane module internal (SMBRi) and the other one external (SMBRe) to the biological tank, were used for the treatment of dairy industry effluent and evaluated in terms of pollutant removal capacity and fouling, focusing on the production of soluble microbial products (SMP) and extracellular polymeric substances (EPS). Both the MBRs presented excellent chemical oxygen demand (COD) removal efficiency (98% average), color (98%), and nutrients (86% for total nitrogen and 86–89% for total phosphorus); however, it was shown that shearing caused by the sludge recirculation pumps in the SMBRe reduced biomass growth considerably. The SMBRe presented better performance in terms of fouling than the SMBRi, which was associated with the higher concentration of suspended solids and SMP and EPS in the SMBRi. The SMP concentrations (mgSMP/gMLVSS) were superior in the SMBRe, showing that the friction from recirculation pumps leads to the break...

Microfiltration of vinasse: sustainable strategy to improve its nutritive potential.

The purpose of this article was to evaluate and establish microfiltration (MF) operating conditions for vinasse (ethanol industries wastewater also known as stillage, slop, distillery effluent or dunder) concentration aiming to improve the use of its nutritive potential. The operating conditions influence permeate flux that has been evaluated by monitoring the flow rate profile during the operation on bench scale in different conditions (feed pH, aeration condition and recovery rate). From the results found, the process scale up was then effected. The bench scale findings showed that the vinasse microfiltration under air flow of 0.5 m(3).h(-1) between membrane fibers, with no pH adjustment, and recovery rate of 93% produced two flows, one of permeate that may be used to wash the sugarcane during the ethanol production processing, and the other of concentrate that contains a high organic compounds and nutrients concentration. This concentrate has additional potentiality of being used as organic compound supplement in contaminated soil bioremediation, and as a supplier of microbial biomass or substrate for biosurfactant production.

Integration of two-stage nanofiltration with arsenic and calcium intermediate chemical precipitation for gold mining effluent treatment

ABSTRACT The aim of this study was to evaluate an innovative treatment route for gold-mining effluents rich in calcium, arsenic, and sulfate. This treatment route comprised two nanofiltration (NF) stages and a two-step intermediate precipitation. Arsenic and iron coprecipitation (first step) and calcium carbonate precipitation (second step) were assessed aiming to treat the first-stage NF concentrate and increase the permeate recovery rate in a second-stage NF. The pH, the molar ratio of Fe/As (first step), and the molar ratio of CO3/Ca (second step) were optimized by using rotational central composite design. Under optimal conditions, the arsenic removal was 99.8% (at pH = 7.0 and Fe/As = 4.0), and the calcium removal was 99.5% (at pH 11.5 and CO3/Ca = 3.5). The supernatant of Ca precipitation had very basic pH and had to be acidified before the second-stage NF. The pH 8.5 proved to be the best one regarding retention efficiency and flux. The flux decay of the second-stage NF was attributed to both osmotic pressure increase and reversible fouling resistance. It was concluded that the proposed treatment system is efficient for the treatment of gold-mining wastewater, ensuring higher production of treated effluent and an easy disposable of the final concentrate.

Avaliação do emprego de microfiltração para remoção de fibras do efluente de branqueamento de polpa celulósica

The bleaching process is the stage where there is the greatest loss of fibers during the pulp production. Besides being a waste of product, these fibers increase the concentration of organic matter in the effluent and make the treatment of effluent more difficult. The aim of this study was to evaluate the use of microfiltration (MF) in the removal of fiber of effluent of alkaline bleaching pulp mill. The membrane employed was hollow fiber poly (ether imide), with average pore size of 0.5 µm and filtration area of 0.05 m2. The effect of operating conditions on the permeate flux was evaluated by monitoring the flux profile during operation in different conditions of flow velocity (Reynolds 1,226, 1,653 and 2,043), pH of feeding (7, 10 and 10.6), temperature (28, 43, and 48°C) and pressure operation by evaluating the critical pressure. The results showed that MF is an efficient process for removal of fiber, with 99% removal efficiency of suspended solids. The best performance of the operation of MF was obtained using pH 7, 1 bar and Reynolds number of 1,653. The results show that the flow reduction is mainly due to cake formation.

Integrated ultrafiltration-nanofiltration membrane processes applied to the treatment of gold mining effluent: Influence of feed pH and temperature

ABSTRACT This study aimed to evaluate the effect of feed pH (2.2 - original effluent pH – up to 6.0) and temperature (20 up to 40°C) on the performance of integrated ultrafiltration (UF) and nanofiltration (NF) applied to gold mining effluent. pH increase led to a significant decrease in UF permeate flux. NF showed high retention efficiencies of ions when temperature was below 30°C. Retention of high-valence counter-ions to balance the charge of retained co-ions seemed to be the strongest NF mechanisms. Process performance at feed pH of 5.0 was superior in terms of fouling, retention efficiency, and investment cost.

Long-term use of the critical flux for fouling control in membrane bioreactors treating different industrial effluents: bench and pilot scale

AbstractThis paper presents an evaluation, in the long term, of the critical flux test as a tool to monitor and control fouling in membrane bioreactors (MBRs). The critical flux was assessed in this work on bench- and pilot-scale MBRs treating different kinds of effluents. The results showed that the critical flux test is important for the indication of the optimal operational flux and serves as a tool to compare propensity to fouling in several systems, independent of the characteristics of the feed or the operational conditions. The results also show that the improvement in the quality of the sludge or the improvement in the hydrodynamic conditions is an effective example of alternatives to increase the critical flux. As an example, these improvements can be achieved by dosing powder activated carbon, improving specific membrane permeability or increasing aeration rate.

Distribuição de massa molar em um biorreator com membrana para tratamento de efluente de laticínios

The membrane bioreactor (MBR) is one of the most promising processes for the treatment of high organic load wastewaters, as dairy effluent, providing the generation of an effluent with high quality, which could be reuse directly or after tertiary treatment. The aim of this study was to evaluate a MBR to treat effluent from the dairy industry and to use molecular weight distribution of the feed, permeate and the soluble fraction of the sludge as a tool for investigating the mechanisms of pollutants removal in the system. The MBR has proven to be a viable system for the treatment of the effluent in question, with removal efficiencies of chemical oxidation demand (COD) and color of 98 and 99% respectively. Through the molar weight distribution it was possible to observe the high biodegradation capacity and stability provided by the MBR, as even in situations of constant change in feed characteristics, the mixed liquid always showed low concentrations of pollutants. It is also highlighted the importance of the membrane in the system, which, besides allowing the complete retention of biomass and operation with high solids retention time and suspended solids concentration, it can provide the retention of compounds which were not biodegraded, contributing to the generation a treated effluent with high quality.

Avaliação da biotratabilidade do efluentede branqueamento de polpa celulósicapor processos aeróbios e anaeróbios

The bleaching pulp mill effluent presents, in addition to high concentrations of organic matter in terms of Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) and color, compounds with high toxicity, which makes the treatment of these effluents difficult. The aim of this article is to evaluate the biotreatability of acid and alkaline bleach effluents from kraft pulp by aerobic and anaerobic processes through characterization using conventional and collective parameters. The results of inert COD, aerobic and anaerobic biodegradability, molecular weight distribution, soluble microbial products and extracellular polymeric substances showed a low biotreatability of the effluents