Distillery Waste Treatment Research Articles

Optimization of distillery-sourced wastewater anaerobic digestion for biogas production

Distillery industries in Ethiopia produces large volumes of high-strength, acidic, recalcitrant, and colored wastewater from sugarcane molasses-based alcohol distilleries. Interestingly, distillery wastes are high in organic nutrients that facilitate microbial growth and serve as substrates for renewable energy production. Conversely, energy insecurity is a major issue in the country, as access to modern energy services is limited in many parts of the country, particularly in rural areas. To address both challenges simultaneously, this study investigated the effects of temperature, pH, and retention time on distillery-sourced wastewater anaerobic digestion for biogas production. A Box-Behnken design confirmed that retention time influenced biogas production and biomethane yield largely. The numerical optimization of the process determined that the optimal conditions for specific biogas production (SBP) and biomethane yield were 31.21 °C temperature, 7.35 pH, and 16.85 days retention time. At this optimal point, the predicted values of SBP and biomethane yield were 0.469 l/g-COD removed and 57.87, respectively. The error percentages between experimental and predicted values were 1.71 % for SBP and 1.57 % for biomethane yield, suggesting the accuracy and predictability of the models. The study findings imply that simultaneous distillery waste treatment and energy production could be a viable option for providing affordable and clean energy to rural communities and small businesses in Ethiopia.

Evaluation of the physiology of miniature pig fed Shochu distillery waste using mRNA expression profiling

Shochu distillery waste is the discarded material generated during Shochu production, and it has been used as feed for livestock. In this study, we evaluated the applicability of Shochu distillery waste as a livestock diet. Shochu distillery waste diet was fed to Clawn miniature pigs. At the end of the dietary period, blood samples were collected for biochemical examination and microarray analysis. No significant differences were observed between the control and Shochu distillery waste treatment groups based on physical and biochemical examination. Gene expression patterns were also similar. In addition, gene profiling of these two groups was compared with those of hyperlipidemia and toxicant model groups. Expression profiling of the two groups was different from those of the hyperlipidemia and toxicant model groups. In conclusion, the Shochu distillery waste diet did not affect pig physiology and it is a suitable substitute for standard feed. Moreover, these results promote the potential for microarray analysis use in the evaluation of food safety.

High biohydrogen yielding Clostridium sp. DMHC-10 isolated from sludge of distillery waste treatment plant

A mesophilic high hydrogen producing strain DMHC-10 was isolated from a lab scale anaerobic reactor being operated on distillery wastewater for hydrogen production. DMHC-10 was identified as Clostridium sp. on the basis of 16S rRNA gene sequencing. Various medium components (carbon and nitrogen sources) and environmental factors (initial pH, temperature of incubation) were optimized for hydrogen production by Clostridium sp. DMHC-10. The strain, in late exponential growth phase, showed maximum hydrogen production (3.35 mol-H 2 mol −1 glucose utilized) at 37 °C, pH 5.0 in a medium supplemented with organic nitrogen source. Butyric acid to acetic acid ratio was ca. 2.3. Hydrogen production declined when organic nitrogen was replaced with inorganic nitrogen.

Tertiary treatment of distillery wastewater by nanofiltration

Tertiary treatment of aerobically treated distillery wastewater by nanofiltration was carried out in a spiral wound nanofiltration membrane module under different operating conditions. The results show that the percentage separation of organic and inorganic compounds was quite high, as reflected by the reduction of chemical oxygen demand (COD) and total dissolved solids (TDS) in the range of 96–99.5%, and 85–95% respectively. The color removal was in the range of 98–99.5%. The results of the effect of variation of the inlet concentration, feed circulation rate and pH conform to the mechanism of gel layer formation. Gel layer formation and Concentration polarization was found to play a major role in the treatment of distillery waste using nanofiltration (NF) membrane. It was observed that as concentration of feed solution increases the permeate flux was reduced. This change was higher compared to the separation of COD and TDS. The result indicates that the NF membrane showed very high performance efficiency for organic components (96–99.5%), as indicated by COD removal. In comparison, the separation of inorganic compounds was found to be in the range of 25–90% as estimated from relative separation of COD and TDS. The present study shows that nanofiltration is a promising technique for recovery of water from distillery waste, which could be used to achieve zero discharge status and solve a major environmental problem.

Evaluation of UASB reactor performance during start-up operation using synthetic mixed-acid waste

A start-up experiment was performed in a laboratory-scale, upflow anaerobic sludge blanket (UASB) reactor using seed sludge from a domestic waste treatment plant at 3.8–33.3 gCOD l −1 day −1 loading rates. Analysis over the height of the reactor with time showed that the VSS in the reactor was initially differentiated into active and non-active biomass at increasing gas production and upflow velocities, and specific update rates of the volatile fatty acids (VFA) components were pronounced at the bottom 10% of the reactor. During start-up, specific methanogenic activity and chemical oxygen demand (COD) uptake rate increased from 0.075 to 0.75 gCOD–CH 4 (gVSS) −1 day −1 and from 0.08 to 0.875 gCOD removed (gVSS) −1 day −1, respectively. When seed sludge from a distillery waste treatment plant was used, improved performance due to a predominance of active biomass was evident when the loading rate was increased from 9.4 to 28.7 gCOD l −1 day −1. The proposed start-up evaluation is an effective tool to successfully monitor performance of UASB reactors.

Evaluation of inverse anaerobic fluidized bed reactor for treating high strength organic wastewater

The aim of this work is to evaluate the feasibility of an inverse fluidized bed reactor for the anaerobic digestion of distillery effluent, with a carrier material that allows low energy requirements for fluidization, providing also a good surface for biomass attachment and development. Inverse fluidization particles having specific gravity less than one are carried out in the reactor. The carrier particles chosen for this study was perlite having specific surface area of 7.010 m 2/g and low energy requirements for fluidization. Before starting up the reactor, physical properties of the carrier material were determined. One millimeter diameter perlite particle is found to have a wet specific density of 295 kg/m 3. It was used for the treatment of distillery waste and performance studies were carried out for 65 days. Once the down flow anaerobic fluidized bed system reached the steady state, the organic load was increased step wise by reducing hydraulic retention time (HRT) from 2 days to 0.19 day, while maintaining the constant feed of chemical oxygen demand (COD) concentration. Most particles have been covered with a thin biofilm of uniform thickness. This system achieved 84% COD removal at an organic loading rate (OLR) of 35 kg COD/m 3/d.

Evaluation of a laboratory-scale stabilization pond for tertiary treatment of distillery waste previously treated by a combined anaerobic filter–aerobic trickling system

Distillery waste tertiary treatment in a laboratory stabilization pond was evaluated. Effluents from a combined laboratory-scale anaerobic filter–aerobic trickling filter process were used as the influent. The effect of the hydraulic retention time (HRT) in the range of 5–30 days was evaluated at influent total chemical oxygen demand (TCOD) in the range of 271–5286 mg/l (BOD 5 in the range of 66–1212 mg/l). TCOD and BOD 5 removals of up to 54% and 74%, respectively, were obtained for the most concentrated influent used at 30 days of HRT. The effect of the HRT on TCOD and BOD 5 removal efficiencies followed an exponential relationship. An empirical equation adequately described the effect of the organic surface-loading rate on the process efficiency. The pond acted as an intermediate flow pattern between completely mixed flow and plug-flow. It was found that a second-order model fit in well with the experimental results of organic matter removal rate and effluent substrate concentration. The second-order kinetic constant was found to be K S = 0.23 mg BOD 5/mg TSS day. The proposed model accurately predicted the behaviour of the pond showing deviations between the experimental and theoretical values of effluent substrate concentrations equal to or lower than 11%.

Biological treatment of distillery waste for pollution-remediation.

The biological treatment of spent wash from molasses distilleries was investigated. Analysis of raw spent wash showed it to be a recalcitrant waste, with a high COD of 85,170 mg/l and containing inhibitory phenolic compounds. Reverse phase thin layer chromatography identified gallic and vanillic acid present in spent wash. The fungi Geotrichum candidum, Coriolus versicolor, Phanerochaete chrysosporium and Mycelia sterilia were screened for their ability to decolourize spent wash and to reduce the COD level. A 10 day pretreatment with Geotrichum candidum at 30 degrees C resulted in reducing the COD by 53.17% and total phenols by 47.82%, enabling other bioremediating organisms to grow. Coriolus versicolor immobilized in a packed-bed reactor reduced the COD of spent wash by a further 50.3%, giving an overall reduction in COD of 77% to 15,780 mg/l. A small amount of decolourization was achieved (4.2%), although the spent wash was still coloured. Present studies are encouraging and indicate that it is possible to bioremediate spent wash using a multi-stage treatment process involving an initial pretreatment step with Geotrichum candidum.

Production of biomass, carbon dioxide, volatile acids, and their interrelationship with decrease in chemical oxygen demand, during distillery waste treatment by bacterial strains

The products of the biodegradation of distillery waste with certain bacteria have been found to be biomass, carbon dioxide, and volatile acids. Volatile acid production levelled off after 48 to 72 h and correlated with the reduction in COD values. Carbon dioxide production did not exhibit such a correlation. The relationship of biomass to carbon dioxide production showed a biphasic pattern, indicating the preferential utilization of some substrates over others. Carbon dioxide production in the later phase may be due to the metabolism of secondary metabolites which do not differ much in their COD values.

Anaerobic-aerobic treatment of distillery wastes

In this study an attempt has been made to find a solution to the problem of disposal of distillery effluents through anaerobic followed by aerobic treatment. Accordingly, experimental studies were planned and carried out in two phases. The first phase experimentation was conducted to study the performance of Semicontinuous Fixed Film Anaerobic Reactors (SCFFAR) which simulate Downflow Stationary Fixed Film anaerobic reactors (DSFF) for partial treatment of distillery waste. Second phase experimentation included studies on degradation of anaerobically treated effluent employing semicontinuous aerobic reactors with sludge recycle. The results indicated that the distillery waste should be diluted to bring down the COD to about 50 000 mg L−1 before the same is treated by stationery fixed film anaerobic reactors and this dilution can be achieved by circulating the treated effluent. Further the reduction of COD beyond 9000 to 10 000 mg L−1 by anaerobic treatment appears to be uneconomical. Results of second phase of the study show that the aerobic degradation of anaerobically treated effluent can achieve significant COD reduction (approx. 67%). However, reduction of COD of final effluent below 500 mg L−1 appears to be very difficult. The settling characteristics of the sludge produced in aerobic study depended on the BSRT value and improved with increase in BSRT.

Distillery wastewater treatment by high rate anaerobic filters

Anaerobic filters have been applied to distillery waste treatment at volumetric organic loading from 8 to 13.9 Kg COD/m3/day with efficiencies of 91.9% to 70.0% (Brondeau 1984, Bories 1982). Here, the efect of higher volumetric organic loading and the use of effluent recirculation are studied. The laboratory reactor used consisted of a glass column of 1 m height and 95 mm diameter, filled with ceramic Raschig rings. The specific surface area was 118 m2/m 3 and the void volume of the reactor was estimated as 83%. The hydraulic detention time was fixed at four days, and the organic loading was changea by dilution of the raw waste. Five runs were done starting with diluted distillery waste (i:iO) and decreasing the dilution. The last run was done with the raw waste using effluent recirculation with i:i ratio. During the experiments, soluble COD and HOD, solids, acidity, pH and alkalinity were determined. Biogas production and composition were also measured. In Table i, the influent characteristics and the organic volumetric loading applied for each run are summarized.

Performance of bacterial strains used for distillery waste treatment on different substrates

Six bacterial strains were isolated and acclimatized on distillery waste. The performance of these bacterial strains in respect to growth, reduction in chemical oxygen demand (COD) values, carbon dioxide production and volatile acid production were studied on five different substrates. Glucose and xylose exhibited growth patterns similar to that on spentwash. Glucose, xylose, casein hydrolysate and amino acids led to very good reduction in COD values compared with glycerol. Rate of substrate consumption was maximum in the case of glucose followed by amino acids, casein hydrolysate, xylose and glycerol. Production of volatile acids and carbon dioxide from glucose amounted to ≈ 50% of the theoretical yield based on glycolysis and the tricarboxylic acid cycle. Production of carbon dioxide followed the usual microbiological growth pattern while volatile acids did not show any such pattern. Carbon dioxide and volatile acids appear to be the major degradation products in distillery waste treatment by these bacteria.

Enzymatic studies of bacteria used for distillery waste treatment

Six bacterial strains isolated from sewage waters, acclimatized on spentwash and purified were very effective in the treatment of distillery waste. Because of their apparently extensive metabolic capabilities, eight enzymes were assayed in cell free sonicates of these strains at 8, 20, 48 and 72 h during distillery waste treatment. Hexokinase (EC 2.7.1.1) was found to be a membrane bound enzyme in all the strains. Glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12), glucose dehydrogenase (EC 1.1.1.47) and gluconate dehydrogenase (EC 1.1.99.3) were found to be more active in the later phases of growth. Glutamate oxaloacetate aminotransferase ( l-aspartate:2-oxoglutarate aminotransferase, EC 2.6.1.1), glutamate pyruvate aminotransferase ( l-alanine:2-oxoglutarate aminotransferase, EC 2.6.1.2), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and protease were active throughout the growth period.

Deamination of amino acids by Bacillus pasteurii

Resting cells of Bacillus pasteurii as employed in the treatment of distillery waste showed deamination of amino acids. The deamination of l-glutamic acid and dl-aspartic acid was found to be oxidative while that of dl-serine, dl-threonine and l-asparagine was non-oxidative. dl-Alanine and glycine were not deaminated when present individually but when incubated together showed oxidative deamination. NAD stimulated the oxidation of l-glutamic acid and α,α′-dipyridyl completely inhibited it .

Treatment of Distillery Waste by Anaerobic Digestion

In the production of distilled alcoholic beverages, malted or unmalted grains such as rye, barley, corn and wheat are milled into a fine meal which is mashed, cooked and fermented. The resultant beer or wash, is then distilled in a column still. The product of this first distillation is a distillate of low alcoholic content, called low wines. The process separates the alcohol from the liquid leaving a waste residue of yeast and unfermentable matter, commonly referred to as thin stillage. This residue is the major waste produced in a distillery.