Scholarly article on topic 'Treatment of Vinasse Employing Ultrafiltration Combined with Aerobic Bioreactor with Membrane and Post–treatment with Nanofiltration Allowing it to Reuse'

Treatment of Vinasse Employing Ultrafiltration Combined with Aerobic Bioreactor with Membrane and Post–treatment with Nanofiltration Allowing it to Reuse Academic research paper on "Agriculture, forestry, and fisheries"

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{Stillage / Ultrafiltration / "Membrane bioreactor"}

Academic research paper on topic "Treatment of Vinasse Employing Ultrafiltration Combined with Aerobic Bioreactor with Membrane and Post–treatment with Nanofiltration Allowing it to Reuse"

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Procedía Engineering 44 (2012) 1923 - 1924

Procedía Engineering

www.elsevier.com/locate/procedia

Euromembrane Conference 2012 [P3.111]

Treatment of vinasse employing ultrafiltration combined with aerobic bioreactor with membrane and post-treatment with nanofiltration allowing it to reuse

N.C. Magalhaes\ A.L.D. Silva1, M.C.S. Amaral1, L.C. Lange*T L.F. Neta2

'UFMG-MG, Brazil, zCEFET-MG, Brazil

INTRODUCTION

The vinasse was established as a major challenge for the growth of Brazil's alcohol industry. The generation of this waste reaches values around 15 liters of vinasse per liter of ethanol produced (VAN Haandel, 2005). In addition to the large volume of waste generated, another aggravating factor is related to the high value of COD of 30,000 mg/L, salts and nutrients. However, both organic matter and minerals contained in the stillage can be recovered, either for direct use as fertilizer, for example, or in the form of raw material for other applications as pet food or material for construction. Thus, their rational, and represents a recycling of value-added natural resources, allows us to meet more effectively the requirements of environmental legislation.

Several studies have been done to take routes that allow the recovery treatment in a secure way of nutrients and salts contained in the slop. The use of the separation process of micro or ultrafiltration membranes may be used as a pretreatment of stillage before forwarding it to a treatment to reduce its load. In micro/utrafiltragao joins the concentration of stillage recovery of water that can be treated and reused. The process of micro/ultrafiltration generate two streams called permeate and concentrate. The concentrated current is evaluated for use as fertilizer in the sugarcane fields and the permeate stream is routed to a specific treatment to reduce its load. The membrane bioreactor (BRM) is presented as a promising processes for the treatment of the permeate stream generated in the pretreatment. The BRM is the association of biological process with membrane separation processes. The use of membranes can increase the concentration of microorganisms in the bioreactor and thereby improve the quality of the effluent.

The phenomenon of membrane fouling is still a limitation to the growth of large-scale applications of these systems involve the use of membranes, since it causes a significant decline in flux, require cleaning and replacement of membranes often resulting in a rise in the cost of the treatment process. The use of aeration in both the bioreactor and in the membrane module, aims to remove the accumulation of material (cake) caused by fouling, thus allowing them to operate with sustainable permeate flux throughout the processing of stillage. Given this context, the objective of this study is to evaluate the use of micro / ultrafiltration for the concentration of vinasse as a pretreatment, as well as investigate the operating conditions for a new module submerged, followed by evaluation of the use of BRM aerobic aeration between fibers and its final polish using nanofiltration aimed at reuse.

MATERIALS AND METHODS

The vinasse treated in this study was provided by Irmaos Malosso plant localized in Itapolis/Sao Paulo in Brazil. The Irmaos Malosso plant currently produces an average of 42,000 m3 of hydrous ethanol.

The application of micro/ultrafiltration of stillage treatment targets both primary treatment of the same, to reduce the organic load that will be sent to secondary treatment, as well as the use of the current concentrated stillage for use in fertigation. The tests were performed pre-treatment modules using microfiltration and ultrafiltration membranes of type hollow fiber membranes provided by PAM Selective Membranes LTDA. Before performing each test membrane was subjected to cleaning in a solution of sodium hypochlorite 200 mg/L for 20 minutes in an ultrasonic bath. The vinasse was then submitted to two tests of concentration by the following

1877-7058 © 2012 Published by Elsevier Ltd. doi:10.1016/j.proeng.2012.08.1006

N.C. Magalh'e3es et al. /Procedia Engineering 44 (2012) 1923 - 1924

operating conditions: suction pressure of 40 kPa (ultrafiltration) and 20 kPa (microfiltration) and flow aeration in the base module 0.2 Nm3/h both processes. Both the concentration process using ultrafiltration and microfiltration were the one using fed-batch made with replacement of vinasse equivalent to the volume of permeate removed and permeate flux and permeate quality in terms of COD were monitored. For the first ultrafiltration, the degree of recovery achieved was 93% and for microfiltration, the degree of recovery was 80%. Regarding the solid concentration, there was an increase in total and volatile solids in the concentrate and reduce them in the permeate. The same was observed for the process with microfiltration. Probably due to increased cake formation on the membrane surface (fouling), resulting in greater retention. We also observed a concentration of 175 and 250% in terms of COD and solids, respectively, for the ultrafiltration and concentration of 437 and 216% of COD and solids, respectively, for microfiltration. The highest concentration of COD in microfiltration and ultrafiltration for may be associated with a higher concentration of solids in the stilläge fed microfiltration over the slop ultrafiltration. The sharp reduction of the organic load of the permeate will contribute to an efficient process that will follow the treatment of vinasse, thus raising the degree of removal enabling the reuse of water. This permeate can be directed to a secondary treatment at the BRM, aiming at the reuse of effluent. To monitor the operation of the BRM pressure was monitored and recorded daily, aliquots of effluent stilläge ultrafiltrate (feed) and permeate the BRM were collected daily and characterized in relation to concentration of COD and the sludge aliquots for analysis of solids. All these observations were performed in accordance with the recommendations of Standard Methods for the Examination of Water and Wastewater (APHA, 2005). During testing of degradation of vinasse using membrane bioreactor were used microfiltration membranes inside the bioreactor. The estimated residence time was 48 hours with a sludge age of 30 days. According to the results, the permeate from the bioreactor showed average COD around 619 mg/L (less than 106 mg/L and a maximum of 1250 mg/L with a standard deviation of 343 mg/L). Thus, the COD removal of slop at the BRM was maintained with mean values around 96.6% and COD removal efficiency overall system (MF/UF in conjunction with BRM) was 98.8%.

For final polishing of the effluent after passage through the BRM, we used the nanofiltration process, whose critical flow was not observed. The hydraulic permeability of the NF membrane with distilled water was 1.32 L/h.m2.bar, while the permeate of the BRM permeability was 0.99 L/h.m2.bar. The approximation of these values can be explained by the absence of scale as evidenced by test results of critical flow. We evaluated two feed flow rates (4.0 and 7.2 L / min) to see which one could obtain a permeate quality. It was observed that when using a flow rate of 4.0 L / min, a reduction of 98.8% of organic matter in the final permeate and using the flow rate of 7.2 L / min, the reduction of COD reached 100 %. In addition, conductivity and color of the NF permeate obtained using a flow rate of 4.0 L / min was 36.38 UH and 0.43 mS / cm, respectively, and a flow rate of 7.2 L / min, the values obtained were 0.52 HU and 17.01 mS / cm, respectively, and using as the nanofiltration permeate for final polishing of the BRM, there was obtained 100% removal of organic matter in relation to the effluent, allowing therefore the reuse of the remaining water.

REFERENCES

APHA Standard Methods for the Examination of Water and Wastewater, 20th Edition. American Public Health Association, Washington, DC, 2005.

Van Haandel, A. C. Integrated energy production and reduction of the environmental impact at alcohol distillery plants. Water Science and Technology. 2005;52(1-2):49-57.

Keywords: Stillage, Ultrafiltration, Membrane bioreactor