COMBINED TREATMENT OF VINASSE BY AN UPFLOW ANAEROBIC FILTER-REACTOR AND OZONATION PROCESS

Influence of Solid Retention Time on Membrane Fouling and Biogas Recovery in Anerobic Membrane Bioreactor Treating Sugarcane Industry Wastewater in Sahelian Climate

Sugarcane industries produce wastewater loaded with various pollutants. For reuse of treated wastewater and valorization of biogas in a Sahelian climatic context, the performance of an anaerobic membrane bioreactor was studied for two solid retention times (40 days and infinity). The pilot was fed with real wastewater from a sugarcane operation with an organic load ranging from 15 to 22 gCOD/L/d for 353 days. The temperature in the reactor was maintained at 35 °C. Acclimatization was the first stage during which suspended solids (SS) and volatile suspended solids (VSS) evolved from 9 to 13 g/L and from 5 to 10 g/L respectively, with a VSS/SS ratio of about 80%. While operating the pilot at a solid retention time (SRT) of 40 days, the chemical oxygen demand (COD) removal efficiency reached 85%, and the (VSS)/(TSS) ratio was 94% in the reactor. At infinity solid retention time, these values were 96% and 80%, respectively. The 40-day solid retention time resulted in a change in transmembrane pressure (TMP) from 0.0812 to 2.18 bar, with a maximum methane production of 0.21 L/gCOD removed. These values are lower than those observed at an infinite solid retention time, at which the maximum methane production of 0.29 L/gCOD was achieved, with a corresponding transmembrane pressure variation of up to 3.1 bar. At a shorter solid retention time, the fouling seemed to decrease with biogas production. However, we note interesting retention rates of over 95% for turbidity.

Critical State of the Art of Sugarcane Industry Wastewater Treatment Technologies and Perspectives for Sustainability

The worldwide pressure on water resources is aggravated by rapid industrialization, with the food industry, particularly sugar factories, being the foremost contributor. Sugarcane, a primary source of sugar production, requires vast amounts of water, over half of which is discharged as wastewater, often mixed with several byproducts. The discharge of untreated wastewater can have detrimental effects on the environment, making the treatment and reuse of effluents crucial. However, conventional treatment systems may not be adequate for sugarcane industry effluent treatment due to the high organic load and variable chemical and mineral pollution. It is essential to explore pollution-remediating technologies that can achieve a nexus (water, energy, and food) approach and contribute to sustainable development. Based on the extensive literature, membrane technologies such as the membrane bioreactor have shown promising results in treating sugarcane industry wastewater, producing treated water of higher quality, and the possibility of biogas recovery. The byproducts generated from this treatment can also be recovered and used in agriculture for food security. To date, membrane technologies have demonstrated successful results in treating industrial wastewater. This critical review aims to evaluate the performance of traditional and conventional processes in order to propose sustainable perspectives. It also serves to emphasize the need for further research on operating conditions related to membrane bioreactors for valuing sugarcane effluent, to establish it as a sustainable treatment system.

Chemical and biological combined treatment for sugarcane vinasse: selection of parameters and performance studies

Sugarcane vinasse has been reported as a high strength industrial wastewater that could cause severe environmental pollution due to its complex and bio-refractory compounds. Thus, the combined coagulation and sequencing batch biofilm reactor (SBBR) system was employed for the sugarcane vinasse treatment. This study aims to determine the recommended conditions of various parameters under coagulation and SBBR and investigate the effectiveness of combined processes. First, the approach of the coagulation process could achieve the maximum COD reduction and decolorization efficiencies of 79.0 ± 3.4% and 94.1 ± 1.9%, respectively, under the recommended conditions. Next, SBBR as an integrated biofilm reactor showed excellent synergistic biodegradability, removing 86.6 ± 4.3% COD concentration and 94.6 ± 3.8% color concentration at 3.0 g·COD/L of substrate loading concentration. The kinetic studies of SBBR revealed that the first-order kinetic model was the best fit for COD reduction efficiency. In contrast, the second-order kinetic model was the best fit for decolorization efficiency. The SBBR reaction was further investigated by ultraviolet-visible spectrophotometry (UV-Vis). In the combined processes, SBBR followed by the coagulation process (SBBR-CP) showed greater COD reduction and decolorization efficiencies (97.5 ± 0.3 and 99.4 ± 0.1%) when compared to the coagulation process followed by SBBR (CP-SBBR). This study demonstrated the removal performance and potential application of the combined sequential process to produce effluent that can be reused for bioethanol production and fertigation. This finding provides additional insight for developing effective vinasse treatment using combined chemical and biological processes.

Biomethane Production from Sugarcane Vinasse in a Circular Economy: Developments and Innovations

Sugarcane ethanol production generates about 360 billion liters of vinasse, a liquid effluent with an average chemical oxygen demand of 46,000 mg/L. Vinasse still contains about 11% of the original energy from sugarcane juice, but this chemical energy is diluted. This residue, usually discarded or applied in fertigation, is a suitable substrate for anaerobic digestion (AD). Although the technology is not yet widespread—only 3% of bioethanol plants used it in Brazil in the past, most discontinuing the process—the research continues. With a biomethane potential ranging from 215 to 324 L of methane produced by kilogram of organic matter in vinasse, AD could improve the energy output of sugarcane biorefineries. At the same time, the residual digestate could still be used as an agricultural amendment or for microalgal production for further stream valorization. This review presents the current technology for ethanol production from sugarcane and describes the state of the art in vinasse AD, including technological trends, through a recent patent evaluation. It also appraises the integration of vinasse AD in an ideal sugarcane biorefinery approach. It finally discusses bottlenecks and presents possible directions for technology development and widespread adoption of this simple yet powerful approach for bioresource recovery.

Biogas production by anaerobic co-digestion of sugarcane biorefinery byproducts: Comparative analyses of performance and microbial community in novel single-and two-stage systems

Anaerobic co-digestion (AcD) of sugarcane biorefinery byproducts (hemicelluloses hydrolysate (HH), vinasse, yeast extract and sugarcane bagasse fly ashes was evaluated using new anaerobic reactors fed with organic loading rates (OLR) from 0.9 to 10.8 gCODL^-1d^-1. The best results were obtained in a two-stage system when the OLR was 5.65 gCODL^-1d^-1, leading to a total chemical oxygen demand (COD) removal of 87.6 % and methane yield of 243NmLCH₄gCODr^-1. Microbial community analyses of sludge from both systems (one and two-stages) revealed structural changes and relationship among the main genus found (Clostridium (62.8%), Bacteroides(11.3 %), Desulfovibrio (19.1 %), Lactobacillus(67.7 %), Lactococcus (22.5%), Longilinea (78%), Methanosaeta (19.2 %) and Syntrophus (18.9 %)) with processes performance, kinetic and hydrodynamic parameters. Moreover, biomass granulation was observed in the novel structured anaerobic reactor operated at single stage due to sugarcane bagasse fly ash addition.

Seasonal variation of the organic and inorganic composition of sugarcane vinasse: main implications for its environmental uses

Sugarcane vinasse is the main waste stream of the Brazilian agroindustry. The typical composition of sugarcane vinasse gives it a high polluting potential that implies the necessity to define sustainable strategies for managing this waste. Knowledge of the inorganic and organic composition of vinasse and its seasonal variation is extremely important to conduct scientific research to define alternative managements for vinasse disposal other than fertigation. This study evaluated the variability of vinasse composition throughout the same harvesting season and among three harvesting seasons of one Brazilian annexed biorefinery (2015-2017). The contents of chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), total solids (TS), suspended solids (SS), salinity (K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl^-, F^-), nutrients (N, P, S), trace metals (Al³⁺, As²⁺, Ba²⁺, Cd²⁺, Cr³⁺, Co²⁺, Cu²⁺, Fe²⁺, Pb²⁺, Mn²⁺, Hg²⁺, Mo²⁺, Ni²⁺, Se²⁺, Zn²⁺), and specific soluble organic compounds (sugars, alcohols, and organic acids), as well as pH and conductivity, were monitored in 13 samples. The results indicated that sugarcane vinasse is a suitable feedstock for biological treatments, such as anaerobic digestion processes for energy recovery, as well as substrate for biomass (e.g., microalgae, energy crops, lignocellulosic biomass) growth. The application of a previous treatment makes vinasse a more environmentally friendly natural fertilizer for land fertigation.

E-Beam Irradiation and Ozonation as an Alternative to the Sulphuric Method of Wine Preservation

Potassium metabisulphite is usually used for microbial stabilization in the process of vinification and wine preservation, but it is considered to be allergenic. The objective of the present study was to assess the efficiency of ozonation and ionizing radiation as alternatives to wine sulphurization. The efficiency of yeast removal and the retention of the chemical quality of wine were evaluated. Wine was subjected to 60 min of ozonation, and radiation doses were set at 1-10 kGy. Moreover, a combination of ozonation and ionizing radiation treatment was used. The ozonation of wine did not produce the expected results. That is, it did not limit the number of yeast cells. From the sixth minute, a significant deterioration in the taste and the color of the wine was found. Ionizing radiation at a dose of 1 kGy reduced the yeast count by 95.5%, and a reduction of 99.9% was seen after the application of 2.5 kGy. Moreover, these doses did not have a significant effect on the organoleptic properties or the chemical composition of wine. The total amount of polyphenols reduced from the maximum of 1127.15 to 1023.73 mg at the dose of 5 kGy. Radiation is widely used to preserve food products. Its use for finished wine preservation may be an alternative to sulphurization.

A novel anaerobic filter membrane bioreactor: prototype start-up and filtration assays

Anaerobic digestion allows efficient treatment of high loaded wastewater, and membrane technology allows obtaining high quality effluents with complete biomass retention. However, high biomass concentration interferes with membrane fouling. In the present work, a new bioreactor that integrates an attached biomass anaerobic culture on a fixed bed and a submerged membrane has been started up. The recirculation between the digestion and filtration chambers is coupled to the gas-lift effect of the bubbling employed for the scouring of the membranes, avoiding the use or electromechanical pumps that damage the suspended biomass. The support material retains the biomass in the digestion tank despite the downwards flow, avoiding the submerged membrane contacting with a high concentrated suspension. This novel system, called an anaerobic filter membrane bioreactor was immediately started up, achieving chemical oxygen demand (COD) removal efficiencies of 96% at an organic loading rate (OLR) of 7 kg COD/m³·d. In order to select filtration flux, specific gas demand and filtration cycle duration, the results of 15 short term assays, eight hours for each one, is presented for fluxes between 15.7 and 17.7 L/m²·h, cycle duration between 10 and 30 minutes, and three levels of scouring. It was checked that reversible and irreversible fouling were directly related when dTMP/dt > 2.5 mbar/min.

Anaerobic treatment of blended sugar industry and ethanol distillery wastewater through biphasic high rate reactor

This study aimed to investigate the physicochemical properties of sugar industry and ethanol distillery wastewater and the treatment of the blended wastewater through a two-stage anaerobic reactor. For this treatment, different initial chemical oxygen demand (COD) concentrations (5-20 g/L) and hydraulic retention times (HRTs) (2-10 days) were applied. The sugar industry effluent characteristics obtained in terms of organic matter (mg/L) were as follows: 5 days biochemical oxygen demand (BOD₅): 654.5-1,968; COD: 1,100-2,148.9; total solids (TS): 2,467-4,012 mg/L; and pH: 6.93-8.43. The ethanol distillery spent wash strengths obtained were: BOD₅: 27,600-42,921 mg/L; COD: 126,000-167,534 mg/L; TS: 140,160-170,000 mg/L; and pH: 3.9-4.2. Maximum COD removal of 65% was obtained at optimum condition (initial COD concentration of 10 g/L and HRT of 10 days), and maximum color removal of 79% was recorded under similar treatment conditions. Hence, the performance of the two-stage anaerobic reactor for simultaneous removal of COD and color from high-strength blended wastewater is promising for scaling up in order to mitigate environmental problems of untreated effluent discharge.