|Title of Invention||
"AN IMPROVED PROCESS FOR DECOLOURISATION OF AGRO-INDUSTRY EFFLUENTS TO PRODUCE COLOURLESS EFFLUENT"
|Abstract||This invention relates to an improved process for decolourisation of treated agro-industry effluents to produce colorless effluent. It relates to a catalytic process which increases the adsorption capacity for colouring matter from treated agro-industry effluent by activated charcoal. The process of the present invention thus aims at bringing about cost effectiveness in the tertiary treatment of distillery effluent or spent wash. By using cheap oxidation catalysts in ppm levels (which will not add to the cost of carbon powder) the adsorption capacity of the activated charcoal with respect to colouring matter has been enhanced in the present invention.|
|Full Text||This invention relates to an improved process for decolourisation of treated agro-
. industry effluentsto producte colowlen efflunt. More particularly it relates to a catalytic process which increases
the adsorption capacity for colouring matter from treated agro-industry effluent by activated charcoal. The process of the present invention thus aims at bringing about cost effectiveness in the tertiary treatment of distillery effluent or spent wash. One of the highly toxic and malodorous industrial effluent is the spent wash emanating from distillery. For every liter of the alcohol about 8-15 liters of spent wash is generated depending upon the nature of molasses fermentation processes, continuous or batch. Thus from a typical 30 KL capacity distillery about 240 - 450 cubic meters of spent wash is generated everyday which will create great damage to the ecosystem if it is not treated properly. In the primary treatment of spent wash comprising of biomethanation, the exit effluent will get rid of about 85 % BOD and
75 % COD. The treated spent wash still contains organic loads, which can be treated by an aerobic process called activated sludge treatment, and /or by chemical precipitation of charged organic particles. Even after employing the above mentioned secondary treatment steps, the exit water contains colouring matter consisting mainly of caramel and melanoidins which are bio-refractory and cannot be flocculated completely using flocculants and / or coagulants. Depending upon the concentration of the biopolymers present in the treated spent wash, its colour ranges from pale brown to yellow. This colouring matter is responsible for high COD value of the treated spent wash even after giving it
secondary treatments consisting of activated sludge process (aerobic biocatylitic process) and subsequent charge neutralization of colloidal particles of colouring components (consisting melanoidins) using chemical flocculants as suggested by Gokam et al, (Gokam A. N. Joshi, A. P. Sankpal, N.V. and Kulkarni B. D. Indian Patent Application No. 203/DEL/96), and Rao et al., (Rao A. V. S. P., Karthikeyan, J. and lyenger, L. in 44th Purdue industrial waste conference proceedings, 1990, Lewis Publishers, Inc. Chelsea, 1990, p.787). In recent years regulatory agencies have become more stringent with respect to the discharge of coloured effluents to the surface waters. Hence there have been some concrete efforts in the direction of colour removal from the spent wash both treated and untreated. A noteworthy effort in this direction is by Berchmans et al., (Berchmans, L. J. and Vijayavalli, R. In Indian J. Environ. Hlth, 31 (4) 1989, p. 309). They adopted electrochemical oxidation technique to decolorize raw spent wash diluted to 10 times with water and incorporating about 2 % sodium chloride. The colourless treated effluent had negligible BOD/ COD values but the cost of treatment is very high. Additional daunting factor is the presence of high amount of dissolved solids in the treated effluent, which is several times higher than 0.21 % (maximum limit of d.s. is 2100 ppm) as stipulated by central pollution control board. A cheap method for colour removal from the spent wash has been suggested by Hashinu et al (Hashinu, K and Yabuki, M.r Japanese patent No. 80, 130696 dt. 15-10-1980). Treating 2.5 times diluted spent wash with C-37 bacteria (Thiotritium) they obtained about 83 %
colour removal in 12 days time. Considering the enormous volume of spent wash to be handled by a distillery, the slow process of this bacterial treatment may not be suited to practical use. Hutteri et al, (Hutteri, Y., Kawabala, S. and Matsuda, T. M. Chemical Abstract, 88:176714, 1977) have subjected spent wash containing colouring material to the tertiary treatment using activated charcoal granules to remove caramels by adsorption. By using about 2.5 % of activated charcoal (based on spent wash), they were able to remove upto 90 % of colour from the treated spent wash. This seems to be a very costly process since the requirement of costly carbon granules will be about 25 kilograms per KL of the spent wash and the caramel adsorbed will not have an economic outlet. With an objective of colour removal recently Patil and Kapadnis (Patil, N. B. and Kapadnis, B. P. Indian J. Environ. Hith, 37(2) 1995, p. 84) have subjected post biomethanated spent wash to chemical and biological treatments. The high cost involved in 0.5-5% hydrogen peroxide and large residence time of 72 hours required for biochemical treatment are disturbing factors for adoptation of this work in colour removal of spent wash. In a recently patented three stage process for secondary treatment of spent wash, Gokarn et al, (Gokarn A. N., Joshi, A. P., Sankpal, N.V. and Kulkarni B. D. Indian Patent Application No. 203/DEL/96) have suggested use of activated charcoal powder to the extent of 0.1 to 0.5 % W/ V for the final stage of colour removal with a view to obtain a colourless effluent which satisfies the norms laid down by the statutory bodies except that with respect to dissolved salts. Activated charcoal powder because of its large specific area and internal area demands lesser quantities than its granular variety for the same specific job. The requirement of 0.1 to 0.5 %
W/ V of active charcoal for the final stage treatment is also an economic burden considering high cost of activated charcoal (powder and granules) which is not less than Rs. 50 per kilogram. One way of reducing the high cost of activated charcoal treatment is to regenerate and reuse it several times for colour removal. The thermal method of regeneration is popular in developed countries only, but the overall efficiency of charcoal after several regeneration cycles is reported to be less than 60 % (Carbon adsorption handbook, Ed, P. N. Cheremisinoff and F. Ellerbusch, Ann. Arbor Science Publisher, 1980, p 895). Moreover the thermal processing cost is about 75 % of the cost of the activated charcoal itself (Leng, C. C. and Pinto, N. S. In. Ind. Eng. Chem. Res, vol. 35, 1996, p. 2024).
The only alternative to reduce the high cost of active charcoal treatment seems to be looking for the ways and means to enhance the adsorption capacity of carbon with respect to colouring matter consisting of caramel and melanoidins. Hence any attempt in achieving the enhanced capacity of the carbon should reflect in bringing down the cost of overall treatment of spent wash which is an end-of pipe process. Cost effectiveness can be achieved if the methodology for enhancing the effectiveness of the carbon (activated charcoal) capacity for colouring matter is very cheap. By using cheap oxidation catalysts in ppm levels (which will not add to the cost of carbon powder) the adsorption capacity of the activated charcoal with respect to colouring matter has been enhanced in the present invention.
The object of the present invention is to provide an improved cost effective process fro the decolourisation of agro-industry effluents in activated charcoal treatment (tertiary treatment) using catalysts.
Accordingly, the present invention provides an improved process for the decolourisation of agro-industry effluents to provide colourless effluent which comprises: treating treated yellow coloured spent wash 25-50 ml having COD 1000-3000 mg I"1 with activated charcoal 25-100 ml for a period ranging between 0.25 to 2 hrs, repeating the above step with 4 to 5 times weight of the active charcoal as in the preceding step in presence of oxidation catalyst, separating carbon by conventional methods to obtain the colourless effluent.
In an embodiment of the present invention, the catalyst to be used may be selected from hydrogen peroxide, perchloric acid, bleaching powder, and ammonium persulfate or alike.
In an another embodiment of the present invention, the quantity of catalyst to be used may very from 100to900mgr' of the spent wash (It may be noted that this
much small quantity of catalyst alone can bring about only very negligible reduction in colour of the spent wash).
In a feature of the present invention the amount of activated charcoal used for decolourisation is determined by establishing the popular Freundlich adsorption isotherm, which relates the amount of adsorbate (colouring matter) in the solution phase to that in the adsorbed phase by expression:
x / m = KCn wherein,
x - amount of colouring matter adsorbed (in terms of measurable parameters
like optical density) m - weight of carbon,
C - equilibrium concentration of adsorbate in solution after adsorption, K- Freundlich affinity parameter for a heterogeneous disperse system, n - related to the magnitude of the adsorption driving force and for
distribution of energy sites on the adsorbent.
In another feature the adsorption capacity of activated charcoal is calculated using the formula(Formula Removed)
Vc0 = theoretical volume of the liquid treated per unit weight of the carbon (x/m)co = capacity per unit weight (gram) of carbon at the influent
V = volume of the liquid used in the isotherm test
Co= influent concentration (optical density)
(Carbon Handbook. Eds. P.N. Cherimisenoff and F. Ellerbush, Ann Arbor Publisher, Michigan. 1980)
In yet another feature of the present invention, the spent wash after biomethanation
and /or subsequent flocculation may be used.
In yet another feature of the present invention, spent wash after its biomethanation
and followed by activated sludge process and subsequent chemical flocculation as
per our patented process (Indian Patent Application No. 203/DEL/96) can be
In another feature of the present invention, the activated charcoal used may be a
reagent grade (eg. Loba Chemie) or prepared from chemical activation of biomass
consisting sawdust, bagasse, corn residue and the like.The methodology described in this patent needs to be applied even if the granular charcoal bed in a column is used in the-final stage of spent wash treatment. The additional requirement in such cases will be maintaining of oxic condition by sparging air or oxygen in the carbon column (to bring about the effectiveness of the catalyst used). The invention has been described herein below with examples, which are
illustrative only and should not be construed to limit the scope of the present invention in any manner.
Post biomethanated spent wash having COD of about 25,000 was subjected to the physico-chemical treatment involving flocculation step. The treated sample had a yellow color and COD of 2600. The pH of the treated sample was 5.0 and it was diluted with equal volume of water to bring COD to 1300. 25 ml of the treated sample was stirred with 25 mg of Loba grade fine activated charcoal in 100 ml conical flask using magnetic stirrer for 15 minutes. The solution was filtered and analyzed for absorbence or optical density (OD). Similar experiments were carried out with 50, 75, 100, 125 mg of the activated
charcoal. A graph of log x/m vs log C was plotted and (x/m)c0 corresponding to initial OD,
C0 was noted from the plot. And using the formula for capacity of carbon or Vc0, i.e. the
volume of spent wash, which can theoretically absorb colouring matter per gram of
carbon ,Vc0 was calculated using the formula, Vc0 = ( x/m )c0 V /C0.
Vc0 was found to be 188-mg I"1.
The experimental set was repeated in the presence of:
a: 100 mgl"1 of perchloric acid,
b: 190 mgl"1 of ammonium persulfate,
c: 310 mgl"1 of bleaching powder,
d: 190 mgl"1 of hydrogen peroxide.
For the Loba grade activated charcoal having a Methylene blue value of 180., the
adsorption capacity values of colouring matter from treated spent wash are as follows: (based on adsorption isotherm)
(Table Removed)EXAMPLE: 2
Spent wash after biomethanation followed by activated sludge process had COD of about 6000. It was subjected to flocculation treatment, when COD was reduced about 1446 and the liquid had pale yellow colour. Charcoal adsorption experiments were conducted using Loba grade carbon of 25, 50, 75, 100, 125 mg per 25 ml of the effluent as described in example 1 .
The experiments were repeated in the presence of 200, 400 and 600 mgl"1 of hydrogen peroxide per liter and using 15, 30, 45, 60, 75 mg of active charcoal per 25 ml in each case.
The adsorption isotherm graph was plotted; the results are as follows.
(Table Removed)In the presence of 600 mgl"1 hydrogen peroxide in the treated spent wash, the adsorption capacity is enhanced by almost 200 %. Considering the cost of the activated charcoal at Rs.50 per kg and that of H2O2 to be about Rs. 20 per liter, the economic benefits are certainly significant.
1. An improved process for the decolourisation of agro-industry effluents to provide
colourless effluent which comprises: treating treated yellow coloured spent wash 25-50
ml having COD 1000-3000 mg I"1 with activated charcoal 25-100 ml for a period
ranging between 0.25 to 2 hrs, repeating the above step with 4 to 5 times weight of the
active charcoal as in the preceding step in presence of oxidation catalyst, separating
carbon by conventional methods to obtain the colourless effluent.
2. An improved process as claimed in claim 1 wherein the oxidation catalyst to be used is
selected from hydrogen peroxide, perchloric acid, bleaching powder, ammonium
persulfate or alike either singly or in combination.
3. An improved process as claimed in claims 1 and 2, wherein the quantity of catalyst to be
used ranges from 100 to 900 mg 1"' of the spent wash.
4. An improved process as claimed in claims 1-3 wherein, the activated charcoal used for
decolourisation derived from biomass, coal or sludge containing carbonaceous material.
5. An improved process for decolourisation of agro-industry effluent to produce colourless
effluent as substantially described herein before with reference to examples.
|Indian Patent Application Number||1490/DEL/1999|
|PG Journal Number||12/2008|
|Date of Filing||18-Nov-1999|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110 001, INDIA.|
|PCT International Classification Number||C02F 1/00|
|PCT International Application Number||N/A|
|PCT International Filing date|