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Waste Treatment Options for Molasses and Grain based Distilleries. By Dr.B.Subba Rao, President: International School in Environmental Management Studies Opp. Sahayog Nagar, “Arundhati Banglow” Vishrambag -416415 , Sangli.
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Waste Treatment Options for Molasses and Grain based Distilleries By Dr.B.Subba Rao, President: International School in Environmental Management Studies Opp. Sahayog Nagar, “Arundhati Banglow” Vishrambag -416415, Sangli. E-mail: bssubbarao@yahoo.com Tel. (M) 9372109522, (L) 0233-2301857
INTRODUCTION • Molasses based Distillery waste known as spentwash is highly polluting with a population equivalence of 250. • The present recommended treatment technologies are • "Anaerobic Digester followed by controlled land application“. • "Anaerobic Digester followed by anaerobic filter, two stage aerobic treatment and dilution with fresh water and applied on land as “ferti-irrigation“.
"Concentration and Incineration in Boiler" • “Anaerobic Digestion followed by evaporation & composting” • Anaerobic Digestion followed by controlled land application/ferti-irrigation are not encouraged by the CPCB/SPCB as these technologies are found to pollute land and ground water sources.
SUGGESTIONS • “Controlled land application” appears to be one of the viable alternatives if it is practiced scientifically. • The protocol developed by CPCB is based on the practices followed in other parts of the world with a great success and also studies carried out by Agricultural Universities in India. • However, the Regulating Agencies feel that “Controlled Land Application” is not practicable as monitoring and controls are very difficult, even though the task was entrusted to Agricultural Universities
The Industry, Regulating Agencies and Experts may once again review the ways and means by which a proper mechanism can be developed for monitoring and controls. • Adoption of ferti-irrigation may not be a feasible alternative as the secondary treatment is not able to yield the desired results. • The dilution water requirements are huge to meet irrigation standards.
“Concentration and Incineration in Boiler” • The condensates from evaporators have high COD and require treatment before discharged into Environment or recycled as process water. • Sludge from spentwash is to be removed before it is sent to evaporators for concentration. • The sludge requires treatment such as "composting" which is not permitted as per the present protocol.
The operation and maintenance problems of Boilers, especially the clogging of Boiler tubes appear to be very frequent. • Some suppliers recommend stand- bye Boilers which makes the project very expensive. • Complaints regarding techno-economic viability of these plants are not properly assessed. • The Industry and also the suppliers of these plants are not willing to share the success of the process. • The sustainability of this technology needs to be established
SUGGESTIONS • The condensates after reducing the temperature recycled as process water for dilution of molasses. • If any extra condensates present, may be used as makeup water for cooling towers after treatment. • Sludge may be permitted to be used as manure. • The material selection of Boiler tubes shall have to be perfected to avoid clogging problem. • The technology of “Concentration and Incineration” should be transparent
"Composting" • The filler material pressmud is not available in required quantity • The ratio of pressmud to spentwash of 1:2.5 appears to be impracticable. • Needs revision depending on the moisture content of pressmud. • It appears that ratio of 1:1.5 to be practicable with 70% moisture content in pressmud. • The disposal of compost as manure also appears to be difficult in some parts of the Country.
The land requirement is around 0.25 hectares per KL of spirit production which is huge area. • Due to the large requirement of pressmud, the technology may not be suitable for large capacity Distilleries. • "Composting" process is not permitted for standalone Distilleries as per the present guidelines. • May be due to non-availability of filler materials in required quantities. • Technology is not allowed for raw spentwash due to the fear that leachate concentrations may be high when raw spent wash is used.
Whenever "composting" process is adopted, the Distillery should not operate during rainy season. • Thus 270 days of operation in a year is only permitted.
SUGGESTIONS • The recommended solution to match pressmud to digested spentwash is to reduce effluent quantity through Multiple Effect Evaporators/Reverse Osmosis. • The digested effluent have inorganic dissolved solids in the range of 25,000-30,000 mg/l. • When the effluent is concentrated the inorganic solids concentration would go around 50,000-60,000mg/l, if fifty percent concentration is adopted.
The inorganic solids content in terms of chlorides and sodium present in digested effluent may affect the soil characteristics, when applied on land as compost. • This aspect has not been studied. • To permit raw spentwash if “composting” is to be adopted as a method of treatment and disposal, as organic matter is beneficial. • If Energy Recovery is the only consideration suitable technologies for “Anaerobic Digestion” should be developed to treat spentwash having COD concentration as high as 2,00,000-4,00,000mg/l.
As the present practice is to adopt fermentation technologies based on Integrated evaporation systems.
Co-Incineration • Recently, the CPCB intiated a project "Co-Incineration" wherein concentrated spentwash is burnt as fuel in Cement/Steel industries along with other fuels/raw materials. • Even though, the initial trails appear to be encouraging, the effect of inorganic constituents in spentwash on the finished product are to be assessed. • The applicability of the technology for Distilleries which are located far away are to be assessed in terms of cost effectiveness.
SOME OF THE COMMON ISSUES RAISED BY THE INDUSTRY • "Concentration and Incineration" technology appears to be the only solution provided the techno-economic viability is established. • Also operation and maintenance problems are resolved along with the residual pollution issues such as condensates and sludge treatment and disposal. • Demonstration plant should be established to have transparency or one of the existing unit shall be made accessible with full transparency.
The standalone Distilleries have the only option to adopt this technology. • Success of the technology is still to be established. • Viable alternative technologies are to be found by the Experts, Industry and the CPCB. • Composting" technology would not be viable if Biomethanation followed by concentration is a prerequisite. • Whatever the energy recovered through Biomethanation shall have to be spent for concentration of Digested effluent.
Besides the capital cost of Degassifier for Biomethanated effluent and the treatment of condensates would be additional. • "Composting" may be permitted for raw spentwash. • The existing process technologies such as Integrated evaporation can reduce spentwash quantity as low as 4 to 5 liters per liter of R.S. production, which could match the availability of pressmud. • "Co-Incineration" requires further studies and may not be applicable in all situations.
The suggested and recommended technologies shall be tested for their Sustainability. • Till suitable technology is developed • “Controlled land application”, • Composting either for raw spentwash or Biomethanated effluent without concentration may be permitted, even to Standalone Distilleries. • Spentwash storage is restricted to 30days. • It is often found that wherever anaerobic digesters are used as primary treatment and when Distillery is shut down for more than 100days, when “Composting” is practiced for Biomethanated effluents.
The restart of Digester would take at least 30days to achieve full stabilization. • During this period of time spentwash is required to be stored to feed Digesters to keep reactor in active condition. • It is, suggested to provide additional storage of 30days for raw spentwash during shutdown period of the Distillery, which can be used as organic source to keep bacteria in active state. • If raw spentwash is permitted for composting, 30days storage would be sufficient as the process do not require any initial starting period.
The emerging technologies such as Anaerobic digester followed by evaporation and drying and converting it as manure. • Anaerobic digester followed by evaporation and spraying on Bagasse/Bricketting and burning in Boiler as fuel is practiced at some places. • These technologies also need to be assessed before adoption. • Gasification is another upcoming technology which is being under implementation at one place in Maharashtra. • The techno-economic viability of this process need to be studied.
Research is an ongoing process. • Sustainability of a technology is important and continuous assessment of technologies is the need of the Day for which the Associations should strive hard.
GRAIN BASED DISTILLERIES • Grain based distilleries are considered as eco-friendly with regard to waste management. • Thick and Thin slops should be converted as animal feed (DDGS). • The washings of process equipment, Backwashing of water treatment plant, Boiler Blow down, Cooling tower blow down, and excess spentlees requires treatment based on anaerobic filter, aeration, Sand filtration. • Can be recycled as make up water for Cooling tower or used for Green belt development.
A schematic water balance and the flow sheet of ETP are given for waste management and recycling for Grain based Distilleries. • The entire effluent is converted into useful bye-product. • The Grain Based Distilleries are the most preferred option in comparison to molasses based distilleries, by the Regulating Agencies and the Expert Committees constituted by the Ministry of Environment & Forests, Government of India.
