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WATERFRIENDHUSRB/1203/221/196

2nd Training course – Industry wastewater treatment

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2nd Training course Waterfriend

TREATMENT OF DISTILLERY WASTEWATER

BY MICROFILTRATION

Vesna Vasic

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2nd Training course Waterfriend

Stillage (distillery wastewater) is the main waste product generated in distilleries. It is characterized by a high content of organics and total solids, low pH and a very large volume, increasing together with the ethanol production.

To produce 1L of ethanol, approximately 10 to 15 liters of distillery stillage are generated.

It has very high BOD, COD and BOD/COD ratio

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Starch stillage:• suspended solids• nitrogen, phosporus• proteins, aminoacids• vitamins

Molasses stillage:• coloured compounds (melanoidins, caramels)• potassium,phosporus• sulphates

Cellulosic stillage:• hard metals (Pb, Cd, Hg)• phenolic compounds, furfurals

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Comparative characteristics of differente stillages

Feedstock BOD (mg/L)

COD (mg/L)

Total nitrogen (mg/L)

Total phosphate

(mg/L)pH

Wheata ~90 ~90 550 170 4.6

Barleya 83.0 97.0 600 nd* 3.9

Sugar beet molassesb 44.9 91.1 3569 163 5.35

Sugar cane molassesb 39.0 84.3 1229 187 4.46

Cellulosic feedstockb 27.6 63.1 2787 28 5.35

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Stillage disposal in the environment can cause adverse consequences, such as:

• eutrophication

• endangerment aquatic organisms

• contamination and acidification of soil

• inhibition of seed germination

• deterioration of groundwater quality

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Different treatment approaches, based on biological and various physico-chemical methods, have been introduced for the treatment of stillage:

• centrifugation and evaporation high energy consuption• coagulation and flocculation the use of chemicals, • adsorption sludge• anaerobic and aerobic digestion high energy consuption and high labour costs

Also, it is difficult and sometimes impossible to achieve effluent discharge limits with this kind of treatment.

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Membrane separation techniques are widely used for distillery wastewater treatment, offering a possibility to improve the value of stillage and to meet environmental standards.

The most commonly used membrane processes for wastewater purification are: microfiltration, ultrafiltration, nanofiltration and reverse osmosis.

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Microfiltration

Microfiltration refers to filtration processes that use porous membranes to separate suspended particles with diameters between 0.1 and 10 μm. Thus, microfiltration membranes fall between ultrafiltration membranes and conventional filters.

Dead-end and cross-flow microfiltration

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Experimental

Scheme of laboratory apparatus for cross-flow microfiltration

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Results of analyses of stillage, permeate and retentate

Parameter Stillage Permeate Retentate

Dry matter (mg/L) 63,700 52,362 77,132

Ash (mg/L) 9,640 16,637 4,635

Organic dry matter (mg/L) 54,060 35,725 72,497

% of organic dry matter (%DM) 85 68 94

Suspended solids (mg/L) 18,340 - 33,560

Ash of suspended solids (mg/L) 1,165 - 2,237

Organic dry matter of suspended solids (mg/L) 17,175 - 31,323

% of organic dry matter of suspended solids (%) 94 - 93

COD (mgO2/L) 102,000 65,964 118,000

Total nitrogen (mg/L) 2,866 1,480 3,650

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Under performed experiments and results obtained for investigation of microfiltration efficiency for distillery wastewater treatment, it can be concluded that the satisfactory organic matter reduction degree was achieved compared to initial values in stillage. Using microfiltration membranes, organic pollution was not removed completely from wastewater. However, remarkable results can be achieved by combination of the microfiltration with other membrane processes (ultrafiltration, nanofiltration, reverse osmosis), which is crucial both from the economic standpoint and the standpoint of environmental protection.

Conclusion

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Presentation/lecture has been produced with the financial assistance of the European Union. The content of the presentation/lecture is the sole responsibility of University of Novi Sad, Faculty of Technology and can under

no circumstances be regarded as reflecting the position of the European Union and/or the Managing Authority.

Thank you for your attention