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Recovery of materials from the wastewater from wine distilleries by drying the mixture of solid and liquid wastes
Water Research Pergamon Press 1973. Vol. 7, pp. 595-598. Printed in Great Britain
RECOVERY OF MATERIALS FROM THE WASTEWATER FROM WINE DISTILLERIES BY DRYING THE MIXTURE OF SOLID AND LIQUID WASTES* G. DUCELLIER~ Regional Board of Management for the Water Supplies of Languedoc-Roussillon. (Received 7 June 1972)
INTRODUCTION THE PRODffCT[ONof 1 million hectolitres of wine gives 20,000-25,000 tons of by-products, an average of 6000 tons of wine dregs and 16,000 tons of "marc" (pressed grapes), containing 55-60 per cent of moisture. One ton of marc is composed of 249 kg of "rafles",~. 225 kg of grape stones and 425 kg of grape pellicles. After distillation the pressed grapes are in general dried and the grape stones are separated from the stalks and pellicles, then ground to extract their content of edible oil, about 10 per cent of their weight. The dry stalks and pellicles constitute the "mould". Distillation of pressed grapes and of wine dregs separates alcohol from wastes. When 1 ton of pressed grapes is treated by a diffusion process, the volume of effluent reaches 1-1.300 m 3 but by repeated recycling (15-20 times) the volume of spent wine is much lessened and does not exceed 50-70 1. ton-1 of marc. The wine dregs are first dried in order to separate the tartar, then diluted to facilitate their flow through the distillation pipes; the volume of water is one and a half or two times that of the dregs distilled. From 1 ton of pressed-grapes 200 kg of mould dried to a percentage of 10 per cent humidity are obtained. The mould and dregs in the waste are in the relative proportion0f 1:5 to 4:5. Until recently the effluent of wine dregs distillation was disposed of by lagooning or discharging it to a water-course. Undiluted waste has a BOD5 of more than 100,000. A wine distillery discharging 100 m 3 effluent per day produces a level of pollution equal to that of a town of 200,000 inhabitants. RESISTANCE TO PURIFICATION Spent wine is more difficult to purify than domestic sewage. After chemical and biological treatment, the diluted spent wine still has a BOD5 of 600-3000, which is much more than the 40 mg 1- ~ limit permitted by law. During the biological treatment the degradation rates vary greatly according to the size and complexity of the molecules, starchy matters, waxes, polyphenols and cellulose disintegrate more slowly than sugars. Some of their derivatives may even be antiseptics, antibiotics or sterilizing agents, for example: in the anaerobic state, 2 g 1-~ of volatile fatty acids stop all fermentation (particularly of valerianic acid). With less than the toxic dose of several centigrammes per litre, fermentation is momentarily accelerated; then the growing acid concentration stops all activity; this state of inertia may last for weeks, or even months. * Experiments carried out for the Regional Board of Managementfor the Water Supplies of Languedoc-Rousillon. t National Superior School of Agriculture, Montpellier, France. Grape stalks. 595
596
G. DUCELLI~R
Moreover, the purification process frequently decelerates with high loads. The bacterial population which is self-selected in lightly loaded media is, in richly-loaded media, infested by parasitic agents which interfere with the chain of degradation. With too concentrated a feed, the flora becomes fibrous and ciliated, thus making the sludge spongy and difficult to separate. It is therefore necessary to dilute the waste water with purified effluent by recycling. The length of time taken and the difficulties arising in the reactions, and the need for the dilution required in this process explain why the results are always incomplete and why it is impossible to obtain a satisfactory BOD reduction except by using expensive plants. NEW PROCESSES In the U.S.A. after experiments in biological, chemical and physical methods (such as filtration and centrifuging) research was carried out with concentration using multiple effects. It then appeared that reclaiming fertilizer or cattle-feed from the waste products, would be more economical than purification. For French wine distilleries of limited means, the process of evaporation may seem expensive. Still, with the use of certain apparatus, it may become economical. Fuel costs can be lowered by 1/20th according to the aim in view and the means adopted. The Regional Board of Management for the Water-Supplies of LanguedocRoussillon had to investigate and solve the problems of pollution in agricultural industries. Data on the subject were collected and several classic processes of purification were tried. In 1970, the author was asked to investigate the possibility of drying in the open air and of heating in a rotating furnace of a mixture of spent wine dregs and mould. The experiment was continued in 1971 by the B.C.E.O.M.* From the author's encouraging results of the proposed process one notes the following considerations: To obtain 1 ton of dry matter, the weight of water to evaporate are (according to the water content of the mixture dregs-mould).
Water content of the mixture (%) 95 90 85 80 75 70
19 9 6 4 5 2.33
65 60 55 5O 45
1"86 1.50 1-22 I
40 30 20 * Burea
Water to evaporate
0-82 0-67 0-42 0"25
Central d.EquipementOutre Mer a French Research Bureau.
(tons)
Recovery of Materialsfrom the Wastewaterof Wine Distilleries
597
To tranfform wine dregs waste with a 90 per cent moisture content into a ton of dry powder requires the evaporation of 9 tons of water in a rotating furnace and a consumption of 820-900 kg of fuel. But a mixture of 4 parts spent dregs and 1 part of mould with a 74 per cent moisture content necessitates the evaporation of only 2.75 tons of water. Fuel consumption will not exceed 260--265 I. To obtain a fertilizer with 50 per cent moisture which can be stacked, only 1.85 tons of water has to be evaporated and the fuel consumption will be reduced to 170-180 kg. With pre-drying in the open air, which lowers the humidity from 74 to 65 per cent, and a further drying in a rotating furnace from 65 to 50 per cent, I ton of water is evaporated in the open air and 0-86 tons by heating, thus reducing the fuel consumption to 78-85 kg of ton- ~ of fertilizer. The results may be even more favorable if strong drying winds lower the water content to below 60 per cent. This inexpensive and rapid process underwent experimentation during first half of 1970 and investigations were completed in 1971. The 1970 tests consisted of putting into a concrete-mixer a mixture of mould and distilled dregs waste; the proportions were varied from I/4 mould and 3/4 waste to 1/10 mould and 9/10 waste. The matter obtained was granular and more or less fluid (FIGs. 1-3). It was poured into large flat cases, each holding 250-300 kg of this paste. The cases were then set on the high brick heater of the rotating drum oven which was already at work desiccating the pressed grapes, prior to extracting the grape stones. Thus, by making use of heat which was formerly wasted the mixture lost 50 per cent of its water. It was then spread in the open air over a cemented drying-floor (20 kg m-2) where the drying was completed. Dried that way, the mixture was reddish brown and granular: 100 kg of moist mixture gave about .20-26 kg of granules with 10 per cent water. Drying over the oven took 48 h, and in the open air 3 or 4 days. Experiments on complete drying in the open air alone showed that cold dry northern winds could evaporate 2/3 of the water in 24 h. Besides, owing to the waxes on the pellicles, the granules spread in the open air, absorbed very little moisture from the rain, and regained their former state of dryness in 48 h. The dry product thus obtained may be kept for more than I year. The granules contain 2.8-3 per cent nitrogen and some tannin; they can be used as sheep-feed. The last of the 1970 experiments were as follows: A mixture of 200 kg of dregs and 70 kg of mould passed through the rotating oven at the rate of 5.5 tons h- ~ (FzGs. 4--6). Blackish brown granules were obtained with 40-50 per cent water. Piled into 3--4 m high stacks (FIG. 8) the granules underwent fermentation which raised the temperature at some points to 80°C. This temperature can be maintained for 3 or 4 months without causing noticeable loss of nitrogen. At the end of the experiments the process which turned out to be the least costly consisted of the preparation of a fertilizer by: first a pre-drying in open air from a 75-65 per cent water content, then oven drying to 65-50 per cent water content. In 1971 the following points were identified in working out of the proportions of the mixture: (1) time of malaxing; (2) efficacy of drying in open air; (3) aspect of the product; (4) analysis of the product; (5) cost of the process.
598
G. DUCELLIER
Time o f malaxing Mixture : 1/3-2/3 Time(rain) : 5
: 1/4.3/4 : 10
: 1/5.4/5 : 15
: 1/6-5/6 : 20
: 1/7-6/7 : 20
: i/8-7/8 : 30
Drying by heating is easy, as the wet mixture is more or less granular. Pre-drying in the open air facilitates desiccation in the oven while sparing fuel. But if the moisture content is over 70 per cent, the mixture sticks to the sides o f the oven and the granules may exceed 15 m m in diameter.
9
9=0
8 I800
5
500
\
"OF" F E R T I L I Z E R
4
400
3
30C ; . k ,
2
23: ~
1
13C
\
90 85
',~,~. d,y,o~,
[
I d,~;.g;. ')
80 75 70 65 60 55 .50 45 40 35 30 2S 20 15 lu M0~STURE %
F[o. 9.
The particlescoming out of the oven are smaller and dryer when the initialmoisture content is lower. The most economical moisture content is 65 per cent when the mixturc is fed into the oven and 50 per cent when taken out. From the results of analysis the following conclusions arc obtained: the quantities of nitrogen, phosphorus and potassium do not seem to be noticeably modified whatever the mode of drying; the dried mixture contained an average of 3.3 per cent nitrogcn, 1 per cent phosphorus, 1.5 per cent potassium; the percentage of nitrogen varies between 2-5 and 4.3 per cent.
RECOVERY OF MATERIALS FROM THE WASTEWATER FROM WINE DISTILLERIES BY DRYING THE MIXTURE OF SOLID AND LIQUID WASTES* G. DUCELLIER~ Regional Board of Management for the Water Supplies of Languedoc-Roussillon. (Received 7 June 1972)
INTRODUCTION THE PRODffCT[ONof 1 million hectolitres of wine gives 20,000-25,000 tons of by-products, an average of 6000 tons of wine dregs and 16,000 tons of "marc" (pressed grapes), containing 55-60 per cent of moisture. One ton of marc is composed of 249 kg of "rafles",~. 225 kg of grape stones and 425 kg of grape pellicles. After distillation the pressed grapes are in general dried and the grape stones are separated from the stalks and pellicles, then ground to extract their content of edible oil, about 10 per cent of their weight. The dry stalks and pellicles constitute the "mould". Distillation of pressed grapes and of wine dregs separates alcohol from wastes. When 1 ton of pressed grapes is treated by a diffusion process, the volume of effluent reaches 1-1.300 m 3 but by repeated recycling (15-20 times) the volume of spent wine is much lessened and does not exceed 50-70 1. ton-1 of marc. The wine dregs are first dried in order to separate the tartar, then diluted to facilitate their flow through the distillation pipes; the volume of water is one and a half or two times that of the dregs distilled. From 1 ton of pressed-grapes 200 kg of mould dried to a percentage of 10 per cent humidity are obtained. The mould and dregs in the waste are in the relative proportion0f 1:5 to 4:5. Until recently the effluent of wine dregs distillation was disposed of by lagooning or discharging it to a water-course. Undiluted waste has a BOD5 of more than 100,000. A wine distillery discharging 100 m 3 effluent per day produces a level of pollution equal to that of a town of 200,000 inhabitants. RESISTANCE TO PURIFICATION Spent wine is more difficult to purify than domestic sewage. After chemical and biological treatment, the diluted spent wine still has a BOD5 of 600-3000, which is much more than the 40 mg 1- ~ limit permitted by law. During the biological treatment the degradation rates vary greatly according to the size and complexity of the molecules, starchy matters, waxes, polyphenols and cellulose disintegrate more slowly than sugars. Some of their derivatives may even be antiseptics, antibiotics or sterilizing agents, for example: in the anaerobic state, 2 g 1-~ of volatile fatty acids stop all fermentation (particularly of valerianic acid). With less than the toxic dose of several centigrammes per litre, fermentation is momentarily accelerated; then the growing acid concentration stops all activity; this state of inertia may last for weeks, or even months. * Experiments carried out for the Regional Board of Managementfor the Water Supplies of Languedoc-Rousillon. t National Superior School of Agriculture, Montpellier, France. Grape stalks. 595
596
G. DUCELLI~R
Moreover, the purification process frequently decelerates with high loads. The bacterial population which is self-selected in lightly loaded media is, in richly-loaded media, infested by parasitic agents which interfere with the chain of degradation. With too concentrated a feed, the flora becomes fibrous and ciliated, thus making the sludge spongy and difficult to separate. It is therefore necessary to dilute the waste water with purified effluent by recycling. The length of time taken and the difficulties arising in the reactions, and the need for the dilution required in this process explain why the results are always incomplete and why it is impossible to obtain a satisfactory BOD reduction except by using expensive plants. NEW PROCESSES In the U.S.A. after experiments in biological, chemical and physical methods (such as filtration and centrifuging) research was carried out with concentration using multiple effects. It then appeared that reclaiming fertilizer or cattle-feed from the waste products, would be more economical than purification. For French wine distilleries of limited means, the process of evaporation may seem expensive. Still, with the use of certain apparatus, it may become economical. Fuel costs can be lowered by 1/20th according to the aim in view and the means adopted. The Regional Board of Management for the Water-Supplies of LanguedocRoussillon had to investigate and solve the problems of pollution in agricultural industries. Data on the subject were collected and several classic processes of purification were tried. In 1970, the author was asked to investigate the possibility of drying in the open air and of heating in a rotating furnace of a mixture of spent wine dregs and mould. The experiment was continued in 1971 by the B.C.E.O.M.* From the author's encouraging results of the proposed process one notes the following considerations: To obtain 1 ton of dry matter, the weight of water to evaporate are (according to the water content of the mixture dregs-mould).
Water content of the mixture (%) 95 90 85 80 75 70
19 9 6 4 5 2.33
65 60 55 5O 45
1"86 1.50 1-22 I
40 30 20 * Burea
Water to evaporate
0-82 0-67 0-42 0"25
Central d.EquipementOutre Mer a French Research Bureau.
(tons)
Recovery of Materialsfrom the Wastewaterof Wine Distilleries
597
To tranfform wine dregs waste with a 90 per cent moisture content into a ton of dry powder requires the evaporation of 9 tons of water in a rotating furnace and a consumption of 820-900 kg of fuel. But a mixture of 4 parts spent dregs and 1 part of mould with a 74 per cent moisture content necessitates the evaporation of only 2.75 tons of water. Fuel consumption will not exceed 260--265 I. To obtain a fertilizer with 50 per cent moisture which can be stacked, only 1.85 tons of water has to be evaporated and the fuel consumption will be reduced to 170-180 kg. With pre-drying in the open air, which lowers the humidity from 74 to 65 per cent, and a further drying in a rotating furnace from 65 to 50 per cent, I ton of water is evaporated in the open air and 0-86 tons by heating, thus reducing the fuel consumption to 78-85 kg of ton- ~ of fertilizer. The results may be even more favorable if strong drying winds lower the water content to below 60 per cent. This inexpensive and rapid process underwent experimentation during first half of 1970 and investigations were completed in 1971. The 1970 tests consisted of putting into a concrete-mixer a mixture of mould and distilled dregs waste; the proportions were varied from I/4 mould and 3/4 waste to 1/10 mould and 9/10 waste. The matter obtained was granular and more or less fluid (FIGs. 1-3). It was poured into large flat cases, each holding 250-300 kg of this paste. The cases were then set on the high brick heater of the rotating drum oven which was already at work desiccating the pressed grapes, prior to extracting the grape stones. Thus, by making use of heat which was formerly wasted the mixture lost 50 per cent of its water. It was then spread in the open air over a cemented drying-floor (20 kg m-2) where the drying was completed. Dried that way, the mixture was reddish brown and granular: 100 kg of moist mixture gave about .20-26 kg of granules with 10 per cent water. Drying over the oven took 48 h, and in the open air 3 or 4 days. Experiments on complete drying in the open air alone showed that cold dry northern winds could evaporate 2/3 of the water in 24 h. Besides, owing to the waxes on the pellicles, the granules spread in the open air, absorbed very little moisture from the rain, and regained their former state of dryness in 48 h. The dry product thus obtained may be kept for more than I year. The granules contain 2.8-3 per cent nitrogen and some tannin; they can be used as sheep-feed. The last of the 1970 experiments were as follows: A mixture of 200 kg of dregs and 70 kg of mould passed through the rotating oven at the rate of 5.5 tons h- ~ (FzGs. 4--6). Blackish brown granules were obtained with 40-50 per cent water. Piled into 3--4 m high stacks (FIG. 8) the granules underwent fermentation which raised the temperature at some points to 80°C. This temperature can be maintained for 3 or 4 months without causing noticeable loss of nitrogen. At the end of the experiments the process which turned out to be the least costly consisted of the preparation of a fertilizer by: first a pre-drying in open air from a 75-65 per cent water content, then oven drying to 65-50 per cent water content. In 1971 the following points were identified in working out of the proportions of the mixture: (1) time of malaxing; (2) efficacy of drying in open air; (3) aspect of the product; (4) analysis of the product; (5) cost of the process.
598
G. DUCELLIER
Time o f malaxing Mixture : 1/3-2/3 Time(rain) : 5
: 1/4.3/4 : 10
: 1/5.4/5 : 15
: 1/6-5/6 : 20
: 1/7-6/7 : 20
: i/8-7/8 : 30
Drying by heating is easy, as the wet mixture is more or less granular. Pre-drying in the open air facilitates desiccation in the oven while sparing fuel. But if the moisture content is over 70 per cent, the mixture sticks to the sides o f the oven and the granules may exceed 15 m m in diameter.
9
9=0
8 I800
5
500
\
"OF" F E R T I L I Z E R
4
400
3
30C ; . k ,
2
23: ~
1
13C
\
90 85
',~,~. d,y,o~,
[
I d,~;.g;. ')
80 75 70 65 60 55 .50 45 40 35 30 2S 20 15 lu M0~STURE %
F[o. 9.
The particlescoming out of the oven are smaller and dryer when the initialmoisture content is lower. The most economical moisture content is 65 per cent when the mixturc is fed into the oven and 50 per cent when taken out. From the results of analysis the following conclusions arc obtained: the quantities of nitrogen, phosphorus and potassium do not seem to be noticeably modified whatever the mode of drying; the dried mixture contained an average of 3.3 per cent nitrogcn, 1 per cent phosphorus, 1.5 per cent potassium; the percentage of nitrogen varies between 2-5 and 4.3 per cent.