A Process For The Decolorization Of Molasses Based Distillery Effluent

Abstract

This invention relates to a process for the decolourisation of molasses based distillery effluent after secondary treatment. The process is environment friendly for color removal from the sugarcane based alcohol distillery effluent after biomethanation and activated sludge process. The ozone treatment processes are generally combined with UV, H2O2 microbial, fixed bed biofilm reactors, and coagulation treatments, to enhance the performance of decolorization. The wastewater is from industries like, Pulp and Paper, dye industry, municipal drainage, secondary effluent from a paper mill treatment plant. Spent wash is an unique effluent primarily composed of varied amount of caramel, melanoidins and lignins of uncertain characteristics. The carmels and melanoidins, which are of uncertain characteristics, pose difficulties for removal or treatment efficiently using the present treatment methods. In the present invention this effluent has been treated with ozone.

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This invention relates to a process for the decolourisation of molasses based distillery effluent after secondary treatment. Particularly it relates to an environmental friendly process for color removal from the sugarcane based alcohol distillery effluent after biomethanation and activated sludge process. More specifically it relates to the treatment of the distillery effluent containing primarily of lignin, caramels, melanoidins, and dissolved inorganics using ozone.
Distillery effluent or spent wash is generated after molasses fermentation to ethyl alcohol and its recovery by distillation. Normally the process produces about 15 liters of the spent wash per liter of the alcohol. This discharged effluent has obnoxious odor, dark brown color, acid pH and COD of about 1,20,000 and is difficult to treat to satisfy the environmental norms. Biomethanation is the first treatment, wherein some organics are converted into methane rich gas, which is used as fuel for boiler. Biomethanation of the effluent reduces the COD upto 60 to 80% and the wastewater after biomethanation needs further treatment. This effluent still has COD about 25,000 to 30,000 mgl"1. Activated sludge is the secondary treatment, which generates the bacterial sludge using organic matter as a carbon source to give an effluent with COD ranging from 6,000- 8,000 mgl"1 and has a dark brown color. To meet the environmental compliance the dark brown colour has to be reduced before discharge of the effluent. Conventionally, the coloured effluent is passed over active charcoal where the coloured material is adsorbed. But the frequent regeneration of the active charcoal and its reusability is the limitation to use it as an adsorbent. Eventhough the colour matter is removed from the effluent on active charcoal (using elution method), its eluted discharge need further treatment before its discharge. Reactivation using heat treatment leads to loss of material and its activity upto 30 %, as well as it increases its ash content. Reactivation using heat treatment it is possible to regenerate the charcoal at the most three to four times. Therefore an efficient and cost effective process for decolorisation of distillery effluent is highly desired.
The color of the effluent is an important visible parameter needs to be reduced to the required level to meet the environmental norms before discharging it to the main public drainage.
Ozone is one of the strongest commercially available oxidizers, making it popular for primary disinfection of potable water as well as for color removal and organic removal in

wastewater applications. For example, The paper industry has long used chemical methods of bleaching pulp for paper. The oxidants used help to create a clean, white paper pulp for processing into paper.
Use of ozone technology provides advantages that include:
1. Ozone is not typically associated with byproducts or contamination, and naturally
reverts to oxygen, so no taste or odor is associated with its use.
2. Ozone is generated on-site, so no dangerous storage or handling is required.
3. Ozone requires no chemical additives, so there are no waste products to dispose of
after use.
4. Ozone can be generated on site and does not require storage.
5 Ozone is less corrosive than chlorine in water.
Ozone is created in a number of different ways, including ultra violet (UV) light, corona discharge of electricity through an oxygen stream (including air), and several others. In treating small quantities of waste, the UV ozonators are the most common, while large-scale systems use either corona discharge or other bulk ozone-producing methods. The ability of ozone to effectively treat wastewater is dependent on the nature of contaminant. Differences in ozone effectiveness are directly due to the chemistry involved in the ozone induced degradation process. Other agents, such as peroxides, ultraviolet (UV) light, and/or high pH are often used in conjunction with ozone to enhance the destruction of pollutants.
Ozone readily reacts with most species containing multiple bonds (such as C=C, ON, N=N, etc.) and simple oxidizable ions such as S2", to form oxyanions such as SOs2" and SO42". Some of the pollutents are highly stable and difficult to oxidize, in such saces ozone can be used as enhancer of oxidation.
To assist ozone in reacting with difficult to oxidize pollutants, other agents such as hydrogen peroxide (H2O2), high-energy light (ultraviolet range or UV), and/or high pH (hydroxyl ion or HO") are often used. Processes utilizing one or more of these agents to assist ozone are called advanced oxidation processes (AOP). These chemical aids are each capable of breaking down, at least partially, pollutants. Consequently, when used in

conjunction with ozone, the breakdown of an organic pollutant to CO2 and H2O is facilitated.
In the prior art the wastewater treatment of the agro-industry has been described and claimed in Indian patent No. 193284, wherein a three step process for the treatment of distillery effluent after biomethanation and activated sludge process has been described. But the high capital and operating costs of the three stages of the treatment process may limit its application in plant scale.
In an advanced effluent treatment in the Pulp and Paper Industry with a combined process of ozonation and fixed bed biofilm reactors (Helble, Alfred; Schlayer, Wolfgang; Liechti, Pierre-Andre; Jenny, Rudolf,; Mobius, Christian H. Water Sci. Technol., 40(11-12), 343-350, 1999). The combination of ozone with fixed bed biofilm reactors is used for tertiary effluent treatment processes to give maximum elimination of COD, color and AOX with a min. of ozone dosage.
A combined chemical coagulation-ozonation process has been tried to treat high strength wastewater from dye manufacturing plant (Hsu, Yung-Chien; Pong, Robert Y.; Yen, Chao-Hsi; Huang, Hsing-Chao Huanjing Baohu 21(1), 33-46 1998. In this report, Chemical coagulation was placed before ozonation to coagulate majority of organics in first step, then the filtered wastewater was treated by ozonation to eliminate most of the coloring matters, and to destroy those unexcluded by coagulation. The ozonator, which is a newly developed vortex-forming reactor, acted efficiently to eliminate the majority of COD and coloring matter.
In a pilot-scale study on ozone/hydrogen peroxide process for the treatment of the secondary effluent from a wastewater treatment plant is reported (Shishida, Kenichi; Tabasaki, Masayuki; Yamada, Harumi; Matsui, Saburo Gesuido Kyokaishi, 36(443), 123-134 1999). In a multistage injection of ozone and hydrogen peroxide reactor, hydrogen peroxide doses are controlled in a appropriate ranges for the reduction of TOC and COD.
Improvement of wastewater coagulation using ozone is reported (Orta de Velasquez, M. T.; Altamirano Corro, J. M.; Monje Ramirez, I.;Manero Brito, 0. Ozone: Sci. Eng., 20(2), 151-162. 1998). For a municipal drainage, 3.32 ± 0.20 mg/L of ozone

dosage and coagulant level from 50 mg/L to 40 mg/L was used without affecting the effluent quality.
In another technique, biologically treated paper mill effluents is treated by using ozone and ozone along with UV radiations (Oeller, H.-J.; Demel, I.; Weinberger, G. Water Sci. Technol., 35 (2-3, Forest Industry Wastewaters V), 269-276. 1997, Wastewater samples were subjected to ozonization or a combined ozone/UV treatment at varied temperatures and pH. Ozone consumption was considerably higher for a combined ozone/UV treatment or treatment at pH >9 or at elevated temperatures (40°C).
Removal of phenols, cyanides, toxicants, and color from wastewater are reported to permissible levels from wastewater generated in manufacture of dyes and textile processing by passing Oj through a column (Bhatt, Shailesh Rasikchandra; Parikh, Bharat Siddharth; Thakkar, Rejendra kumar D.; Patel, Jayanthibhai P.; Patel, Jayshreeben C.; Dave, Milan Suresh Chandra. Indian Patent, IN 172895).
In all the cited prior art, the ozone treatment processes are generally combined with UVj H2O2, microbial, fixed bed biofilm reactors, and coagulation treatments, to enhance the performance of decolorization. Further the wastewater in the reported literature is from industries like, Pulp and Paper, dye industry, municipal drainage, secondary effluent from a paper mill treatment plant. Spent wash is an unique effluent primarily composed of varied amount of caramel, melanoidins and lignins of uncertain characteristics. The above processes are aiming to decolorize the lignins from paper mill effluent or dyes, which are of known composition. The carmels and melanoidins, which are of uncertain characteristics, pose difficulties for removal or treatment efficiently using the present treatment methods. In the reported literature, there is no attempt to decolorize spent wash (primary, secondary or tertiary) originated from alcohol distillery.
Accordingly the present invention provides a process for the decolorization of molasses based distillery effluent; which comprises; reducing COD of the molasses based alcohol distillery effluent containing colour contributing lignin, caramel and melanoidins by known method such as biomethanation or activated sludge, charging the above treated effluent in a

single reactor or more in series and treating in a batch or continuous mode with an ozone gas ranging between 1 to 200 mg/1, at ozone flow rate ranging from 5 to 15 1/hrs, at a pH ranging from 6 to 9, temperature ranging from 20 to 30°C, for a period ranging from 2 to 6 hrs to obtain the desired decolorized alcohol distillery effluent.
In an embodiment of the present invention the molasses based alcohol distillery effluent used has high COD%.
In an another embodiment the molasses based alcohol distillery effluent used contains colour contributing lignin, carmel and melanoidins.
In yet another embodiment the ozone gas used for effluent treatment is achieved by using an ultra violet (UV) light, corona discharge of electricity through an oxygen stream and / or air and several other known methods.
In yet another embodiment the ozone gas dose used is preferably in the range of 2 to 100 mg/L for a period preferably in the range of 3-5 hrs.
In yet another embodiment the ozone consumption can be increased by using series of reactors, agitated reactors, high performance nozzles, or modified reactors.
In still another embodiment the treatment of distillery effluent is also effective in continuous mode and treated effluent can be recycled for next batch.
The methodology described in this patent need to be applied if the final treated water is to be odorless and colorless, and in this respect, within the limits of specification of the central pollution control board.
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.

Example 1
Batch treatment method using single reactor
500 ml effluent sample of COD 3104 mg/L was taken in a reactor. Ozone was passed at the rate of 10 liters per hrs through a sparger for 75 mins. temperature and pH of the effluent was 34 °C and 8.54 respectively. The treated sample was analyzed for COD, color, TS and pH. Data is presented in Table 1.
Table 1
(Table Removed)

Example 2 Batch treatment method using single reactor
500 ml effluent sample of COD 14,000 mg/L was taken in a reactor. Ozone was passed at the rate of 10 liters per hrs through a sparger for five hrs. Temperature and pH of the effluent was 33.4 °C and 8.98 respectively. The treated sample was analyzed for COD, color, TS and pH. Data is presented in Table 2.
Table 2
(Table Removed)

Temp 33.4-36.9

Example 3
Batch treatment method using single reactor
500 ml effluent sample of COD 12,000 mg/L was taken in a reactor. pH of the samples were varied at 5, 6, 7, 8, 9 and 10. Ozone was passed at the rate of 10 liters per hrs through a sparger for three hrs. Temperature and pH of the effluent was 33.4 °C and 8.98 respectively. The treated sample was analyzed for COD, color, TS and pH. Data is presented in Table 3.
Table 3
(Table Removed)

Example 4
Batch treatment method using three reactor (in series)
1500 ml effluent sample of COD 14,342 mg/L was taken in three reactors arranged in series. Exit ozone gas of first reactor was passed through second and so on. Ozone was passed at the rate of 10 liters per hrs through a sparger for five hrs Temperature and pH of the effluent was 34 °C and 8.54 respectively. The treated sample was analyzed for COD, color, TS and pH. Data is presented in Table 4.

Table 4
(Table Removed)

Temperature: A-36.9 °C; B-37; °C - 37 °C
Example 5 Continuous treatment method
In a reactor 360 ml sample was taken having COD 18,000 mg/L. In this system effluent and ozone was added at the rate of 2 ml /min and 10 lit /h. Residence time for the effluent was 3 hrs.
Table 5
(Table Removed)

Temperature: 33°C-36UC

We Claim:
1. A process for the decolorization of molasses based distillery effluent; which
comprises; reducing COD of the molasses based alcohol distillery effluent
containing colour contributing lignin, caramel and melanoidins by known method
such as biomethanation or activated sludge, charging the above treated effluent in a
single reactor or more in series and treating in a batch or continuous mode with an
ozone gas ranging between 1 to 200 mg/1, at ozone flow rate ranging from 5 to 15
1/hrs, at a pH ranging from 6 to 9, temperature ranging from 20 to 30°C, for a period
ranging from 2 to 6 hrs to obtain the desired decolorized distillery effluent.
2. A process as claimed in claim 1, wherein the molasses based distillery effluent used
has high COD %.
3. A process as claimed in claim 1-2, wherein the ozone gas used for effluent treatment
is achieved using ultra violet (UV) light, corona discharge of electricity through an
oxygen stream and / or air.
4. A process as claimed in claims 1-3, wherein the ozone gas dose used is preferably in
the range of 2 to 100 mg/L for a period preferably in the range of 3-5 hrs.
5. A process as claimed in claims 1-4, wherein the ozone consumption can be
increased by using series of reactors, agitated reactors, high performance nozzles, or
modified reactors.
6. A process for the decolourisation of molasses based distillery effluent substantially
as herein described with reference to the examples.

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