Soft computing techniques are very much needed to design the environmental related systems these days. Soft computing (SC) is a set of computational methods that attempt to determine satisfactory approximate solutions to find a model for real-world problems. Techniques such as artificial neural networks, fuzzy logic, and genetic algorithms can be used in solving complex environmental problems. Self-organizing feature map (SOFM) model is proposed in monitoring and collecting of the data that are real time and static datasets acquired through pollution monitoring sensors and stations in the distilleries. In the environmental monitoring systems the ultimate requirement is to establish controls for the sensor based data acquisition systems and needs interactive and dynamic reporting services. SOFM techniques are used for data analysis and processing. The processed data is used for control system which even feeds to the treatment systems.
The wastewater coming from distillery generally known as spent wash is dark brown in color, carries high organic load, and causes severe fouling of the atmosphere. Waste water discharged by distillery from sugarcane molasses poses problems of disposal to acceptable standards due to their high BOD, COD, and color. About 12–15 liters of spent wash is produced per liter of alcohol produced. After fermentation of molasses, alcohol is separated by distillation and the residual liquor is discharged as spent wash. The effluent as such discharged from the plant is hot, dark brown colored, acidic and possesses objectionable odor. The biological oxygen demand (BOD) value are extremely [
This massive quantity, approximately 40 billion liters of effluent, from the distilleries are associated with very high organic load with BOD and COD levels in the range of 35,000 to 60,000 and 60,000 to 1, 20,000 mg/liter respectively. In India the population equivalent of distillery waste to organic pollution is approximately seven times more than the entire population of India [
A number of conventional treatment technologies have been considered for treatment of wastewater contaminated with organic substances. Among them, adsorption process is found to be the most effective method. Adsorption as a wastewater treatment process has aroused considerable interest during recent years. Commercial activated carbon is regarded as the most effective material for controlling the organic load [
It is felt that the shells can be used for producing an adsorbent for treating distillery spent wash from sugar industry using adsorption process [
In most of the coastal cities and towns across the globe,
Steam activation and chemical activation are the two commonly used processes for the manufacture of activated carbon. However coconut shell based activated carbon units are adopting the steam activation process to produce good quality activated carbon [
Lowering of pH value of the stream, increase in organic load, depletion of oxygen content, destruction of aquatic life, and bad smell are some of the major pollution problems due to distillery wastewater. One of the main advantages of COD [
The distillery spent wash sample was taken from Niphad Sahakari Sakhar Karkhana, Niphad, Dist. Nashik, and Maharashtra India. Once a sample is taken, the constituents of the sample should be maintained in the same condition, as when collected. When it is not possible to analyze collected samples immediately, samples should be preserved properly in such a way that the biological activity (microbial respiration), chemical activity (precipitation or pH change), and physical activity are the minimum. Methods of preservation [
Required containers, preservation techniques, and holding times for samples.
Maximum holding time | Preservative | Container | Parameter |
---|---|---|---|
14 days | Cool 4°C | P.G. | Acidity |
14 days | Cool 4°C | P.G. | Alkalinity |
48 hours | Cool 4°C | P.G. | BOD |
28 days | Cool 4°C, |
P.G. | COD |
28 days | Cool 4°C |
G. | Phenols |
0 hours | None required | P.G. | pH |
0 hours | None required | G. | DO |
48 hours | Cool 4°C | P.G. | Nitrate |
7 days | Cool 4°C | P.G. | Residue volatile |
7 days | Cool 4°C | P.G. | TSS |
The coconut shells derived from various waste sources were cleanly shaved to remove all the fibers on its surface. Cleaned shells were cut into 3 mm to 8 mm pieces. These pieces were washed with distilled water to remove surface dust and dried in sunlight for two to three days.
The cleaned and dried coconut shells were then broken into small pieces to allow insertion into a muffle furnace {KW = 0.3, AMP = 13, TYPE = MFRA, PHASE = Single} and subjected to destructive distillation in the absence of air. The temperature of the furnace was maintained at 400°C for three hours to avoid reactions with atmospheric oxygen, thereby preventing formation of ash. This resulted in the formation of black carbonized matter. The carbonized matter was washed [
Characteristics of adsorbents.
Sr. no. | Characteristics | CSC | CAC |
---|---|---|---|
1 | Moisture, % | 16.26 | 6.37 |
2 | Ash content, % | 0.33 | 4.51 |
3 | Bulk density, g/cc | 0.67 | 0.57 |
4 | Matter soluble in water, % | 1.32 | 1.31 |
5 | Matter soluble in acid, % | 2.25 | 1.39 |
6 | pH | 2.40 | 8.50 |
7 | Decolorizing power, mg/g | 39 | 78 |
8 | Surface area, m2/g | 1.69 | 337 |
To study the effect of important parameters like initial pH, adsorbent dose (gm), contact time
The kinetics of adsorption was determined by analyzing adsorptive [
Columns are mounted vertically one above the other. It is often good practice to operate columns in upflow as this reduces the opportunity for channeling. It is also preferred where suspended solids create a high-pressure drop. For downflow or percolation system an influent line should be installed at the top of column with effluent line at bottom. To develop reasonably good data from scaleup to full plant design, it is important to have operation of the pilot column system as near as possible to the anticipated conditions. The most critical factors, flow rate and feed impurity concentration, must be constant for the entire test run. The adsorbent bed should be at least 60 cm deep with a 4 cm internal diameter. A smaller column is not recommended as the wall effect becomes significant. The adsorbent bed can be supported by glass wool, wire cloth, and so forth. Columns and fixtures can be constructed from glass, plastic, reinforced fiberglass, or metal. Borosilicate glass is commonly used. It is essential that all columns used in the pilot system have at least the same diameter [
A bed volume is the volume occupied by the adsorbent including adsorbent volume and void volume. The quantity of effluent is expressed in the number of adsorbent volumes passing through the column per hour. As the flow rate and quantity of liquor are the most important controllable variables in developing design data, a feed pump suitable for accurate and continuous flow is required. Depending on the size of the pilot column system, the use of peristaltic, diaphragm, piston type, and centrifugal pumps is recommended if the effluent is viscous.
When loading the column care should be taken to avoid entrapping air in the adsorbent bed. Entrapped air can cause channeling during operation preventing complete contact of the process effluent with the adsorbent. In small columns entrapped air can be avoided by pouring out the adsorbent in the boiling water just before loading of most of the excess water can be poured off, along with most of the adsorbent particles. Before starting the test the complete system should be checked by running on water for several hours. After setting the appropriate flow rate, the effluent to be treated can be fed to the columns and this will displace the water. Samples of effluent after each column should be taken at regular intervals of time. When the effluent from the parallel columns or last column in series exceeds the purity requirement, the test should be stopped [
Characteristics of spent wash vary widely depending upon the quality of raw material, process technology, energy conservation, and effluent treatment strategies. The typical composition of spent wash from Niphad Sahakari Sakhar Karkhana, Niphad, Tal Niphad, Dist. Nashik, is given in Table
Typical composition of distillery spent wash.
Sr. no. | Parameter | Spent wash analysis |
---|---|---|
1 | pH | 7.87 |
2 | Suspended solids | 56,891 mg/lit |
3 | Total dissolved solids | 2,41,066.6 mg/lit |
4 | B.O.D. at 27°C for 3 days | 24,000 mg/lit |
5 | C.O.D. | 39,840 mg/lit |
6 | Oil and grease | 23.0 mg/lit |
7 | Sulphate | 4,000 mg/lit |
8 | Potassium | 1,3000 mg/lit |
9 | Chloride | 1,00,000 mg/lit |
10 | Sodium | 1,200 mg/lit |
11 | Calcium | 2,600 mg/lit |
12 | Magnesium | 2,700 mg/lit |
13 | Iron | 61 mg/lit |
14 | Total nitrogen | 1,350 mg/lit |
15 | Colour | Dark brown |
16 | Odor | Smell of burnt sugar |
17 | Temperature | 90–95°C |
The composition of the effluent is a reflection of the composition of the molasses. A bad molasses produces a bad effluent. Thus, the poor quality of the cane molasses produced by the sugar mills is responsible for the complex character of the distillery effluent. The composition of the molasses from different sugar mills used in different distilleries in India also varies, due to different processes of sugar manufacture.
In matter of characteristics, effluent is normally a diluted replica of the molasses pressed in the production of alcohol. If molasses differ in composition, as a natural corollary it would yield an effluent, which would also differ in composition and as a consequence the extent of BOD reduction during primary treatment of the effluent would also differ [
Usually, the adsorption reactions are exothermic; high temperature or slow adsorption would seem to inhibit, but this is not usually found to be a factor in most systems. Adsorption rate is limited by diffusion; variable that influences diffusion has significant effect on adsorption rate. Higher temperatures may obstruct adsorption sight, but they significantly speed up the pace of diffusion, offending any negative temperature effect. The temperature dependence of adsorption process is of a very complex nature. Thermodynamic parameter like heat of adsorption and the energy of activation plays an important role in predicting the adsorption behavior and both are strongly temperature dependent. Heat of adsorption influences the equilibrium absorption capacity and also indicates that the nature of interaction taking place between the adsorbate and adsorbent is dependent of the energy of activation.
The decrease in adsorption with the rise in temperature may be due to weakening of adsorptive forces between the active sites of the adsorbent and adsorbate species and also between the adjacent molecules of the adsorbed phase [
Effect of temperature on COD removal,
It may be observed that the (COD) removal rate for activated carbon is higher and slightly lower for coconut shell ash. But due to the easy availability of coconut shells it is more suitable adsorbent than commercial activated carbon. It may be concluded that, at higher temperature, the decrease in the adsorption could be due to the possible exothermic nature of the adsorption process. In the present study, the optimum (COD) removal was found near at room temperature (25–35°C).
The effect of flow rate on removal of COD is shown in Figures
Effect of flow rate on COD removal (CSC),
Effect of flow rate on COD removal (CAC),
During adsorption both anions and captions have been removed from waste water with adsorbent. Researchers have found that carbon exhibits preferential adsorption for ionic species in an order of preference as Al+3 > Ca+2 > Li+ > Na+ > K+. For anions, the NO3 ion is preferred over the Cl− ion. It is not surprising that pH plays an important role in the adsorption characteristics of these ions as the low pH provides large quantities of the preferred H+ ion, which may take the space of other ions on potential adsorption sites. Even without pH variations inorganic compounds exhibit a wide range of absorbability on adsorbents. The adsorption by using coconut shell ash and commercial activated carbon was studied at different pH values from 3 to 11. Figure
Effect of pH on COD removal (CAC),
The effect of adsorbent dose on removal of COD is shown COD in Figure
Effect of contact time on COD removal (CAC),
In column adsorption the rate of adsorption goes on decreasing with the passage of time which is shown in Figure
Colorization of distillery effluent has been a cause of major concern and even after the primary treatment and two-stage biological treatment (anaerobic followed by aeration) the color is not destroyed. Adsorption experiments were carried on distillery effluent using coconut shell ash and commercial activated carbon. Color removal of 40–50% was observed in case of coconut shell ash while in case of activated carbon as adsorbent (dose of 20 gm/L) color removal of 70–75% was observed.
From Figure
Effect of agitation speed on COD removal (CAC),
The effect of concentration on adsorption is shown in Figure
Effect of concentration on COD removal, adsorbent dose = 2 gms.
The effect of adsorbent bed depth on adsorption, that is, COD removal in this case, was studied by packing the adsorption column with different depths of the adsorbent (20 cm, 30 cm, and 45 cm). The results are shown in Figure
Effect of adsorbent bed height on rate of COD removal
In continuous flow experiments, it is essential to predict the exhaustion rate of adsorbent bed on how long the bed will last before regeneration is necessary. In this method the service time of a fixed bed adsorbent, treating a solution of single adsorbate, can be expressed as a function of operational variables as shown by (
The straight line plots of breakthrough time versus bed height were obtained as shown in Figure
Bohart Adam’s model.
The breakthrough time is found to increase with increase in the adsorbent bed height. Thus, column test shows the applicability of BDST model [
The effect of using various particle sizes of CSC on COD removal was studied by using CSC adsorbent of three different particle sizes, namely, 425 microns, 610 microns, and 750 microns for the column experiments. The Co was kept constant at 20480 mg/lit. and all the experiments were carried out at natural pH of 7.87 and temperature 30°C.
From the results (Figure
Effect of particle size on COD removal (CAC),
Figure
Effect of CSC column in series with CAC bed on COD removal,
The equilibrium data for removal of COD by using CSC and CAC in the present investigations were analyzed using Langmuir adsorption model. The linear plots of
Langmuir adsorption isotherm
For CSC,
For CAC,
A plot of
The Tempkin isotherm plots for CSC and CAC are shown in Figure
Tempkin adsorption isotherm
From Figure
Now,
From Figure
For CAC,
The rate of adsorption of organic matter on to CSC and CAC was studied and the rate constant
Lagergren plot
At equilibrium, COD removal is Nil. So,
One of the most challenging elements in a design will be estimating the cost to build and operate the wastewater treatment facility that is designed. Cost estimation is also an important element when selecting between alternative designs [
For treating 1 liter of distillery spent wash, using CAC as adsorbent, time required = 22.22 minutes, amount of CAC required = 32 gms, cost of adsorbent CAC = Rs. 300 per kg, and cost of adsorbent CAC required to treat 1 liter of distillery spent wash = Rs. 9.60.
For treating 1 liter of distillery spent wash, using CSC as adsorbent, time required = 22.22 minutes, amount of CSC required = 36 gms, and cost of adsorbent CSC = Rs. 100 per kg.
Cost of adsorbent CSC required to treat 1 liter of distillery spent wash = Rs. 3.60. On comparing the cost of treatment of distillery spent wash using both CSC and CAC, it can be observed that treatment using CSC as adsorbent is much cheaper than that using CAC as adsorbent.
However, as far as the production of sugar is concerned, 0.4–0.45 tone of molasses is produced per ton of sugar. About 90% of the total molasses produced is utilized for production of alcohol. For producing 1 liter of alcohol about 10–15 liters of spent wash is produced. Hence for producing 1 liter of alcohol, treatment cost of spent wash is about Rs. 96 by using commercial activated carbon as adsorbent and Rs.36/- by using coconut shell as adsorbent. Thus it can be observed that for treating 1 liter of distillery spent wash, there is a difference of Rs. 6 between the treatments by two adsorbents {CSC and CAC}.
Coconut shell activated carbon was synthesized and characterized for comparison of adsorption capacities with commercial activated carbon. The results revealed that CAC gives the best result between the two adsorbents, that is, coconut shell carbon {CSC} and commercial activated carbon {CAC} tested for COD reduction from distillery spent wash. However, CSC also showed quiet effective adsorbent capacities. Though the adsorption capacity of CSC is lower than that of commercial grade activated carbon, the low material cost makes it an attractive option for the treatment of effluents. The treatment of distillery spent with CSC becomes highly effective, as it is a readily and locally available low cost absorbent which needs not be regenerated.
With the increase in adsorbent dosage there is an increase in percentage COD removal from the distillery spent wash. Change in natural pH of the distillery spent wash caused color removal due to the structural changes being affected in the adsorbent molecules. COD removal by both adsorbents, that is, CAC and CSC, is the maximum at a pH between 3 and 5. Effect of initial concentration on COD removal by both CSC and CAC shows that the percentage COD removal increases with increase in initial concentration (above 8580 mg/lit) for initial contact time intervals and decreases with increase in initial concentration as the saturation of adsorbent is reached. Adsorption capacity decreases with increase in temperature for both the adsorbents. Breakthrough time increases with increase in bed height and decrease in flow rate for the column adsorption. By operating CSC column in series with CAC column the efficiency of carbon utilization is increased.
The equilibrium time was nearly one hour for both CAC and CSC adsorbents. The correlation for equilibrium adsorption data were well fitted by the Langmuir and Tempkin adsorption isotherm for both the adsorbents. Bohart Adam’s equation was found to be applicable for the column study. The adsorption kinetics was well in agreement with the Lagergren plots revealing first order rate.
From the results obtained it can be stated that though CAC is more efficient adsorbent than CSC, but due to high cost and 15 to 20% loss of CAC during regeneration CSC is more preferable than CAC for COD removal from sugar-distillery spent wash. However, for evaluation of the technical and economical feasibility, more research is required on pilot plant scale, so that this low cost adsorbent can be used on larger commercial scale for removal of COD from distillery spent wash.
Expansion of this technology to large-scale applications should be encouraged. As used coconut shells find their way as urban and rural refuse; exploitation of this waste for waste water treatment will dispose this waste in a safer manner.
Besides the gold mining industries, the breweries, and soft drink industries that currently use activated carbon, other potential users such as the textile industries, soap manufacturing industries, vegetable oil nulls, and the Water and Sewerage Corporation can also be sensitied to use this commodity, thereby creating more market for the product. The pilot studies to develop a national capability for the production of activated carbon form coconut shells will, among several benefits, contribute to measures for abating the environmental degradation caused by dumping of agricultural wastes. Improved public education to ensure awareness of the technology and its benefits, both environmental and economic, is recommended.
More experimental work on removal of organic matter from other industrial effluents by using coconut shell ash as adsorbent should be encouraged in order to prove the suitability of this low cost adsorbent for waste water treatment.
Adsorption column studies should be carried out for different column configurations to get the characteristic dependence of the adsorption capacity and other parameters. Design parameters for scaled up adsorption column should thereafter be fixed for the removal of COD from distillery spent wash. Costing of the adsorption based on industrial scale treatment system should be carried out to popularize the adsorption technique. Computing, modeling, and simulation will be carried out for the large-scale plants based on the computations proposed.
The authors declare that there is no conflict of interests regarding the publication of this paper.