FIELD OF INVENTION;
The present invention relates to an improved module for studying leaching
characteristics of fly ash generated from Thermal Power stations individually
and in combination of soil without using any pumping device. More
particularly, the invention propose a design module that can be used effectively
to study leaching behavior of any solid material.
BACKGROUND AND PRIOR ART:
Leaching is the process by which soluble constituents are dissolved from a
solid material (such as rock, soil or waste) into a fluid by percolation or
diffusion. Thus, when fill materials comes into contact with liquid (including
percolating rainwater, surface water, groundwater and liquids present in the fill
material) constituents in the solid phase will dissolve leach into the liquid
forming a leachate. The extent to which the constituents dissolve into the
contact liquid will depend upon site and material specific conditions (chemical,
physical, and biological factors) and the length of time involved. The
composition of the leachate generated from the material and its potential to
impact water quality are key factors in evaluating the suitability of the material
for use as filing material.
In India, Thermal Power Generation which contributes to about 72% of overall
power generation, occupies a predominant place in the power sector, bulk of
which is coal based. It has been estimated that currently about 80-100 million
tones of fly ash is being generated every year. Only about 20% of it is ustilised
in the manufacturer of bricks and cement. For the disposal of rest, nearly
28,000 hectares of land has already been converted into ash dumps. India
coals are typically high ash coals and the ash content of coals supplied to
power stations is of the order of 40-50%. About 80% of the ash produced from
pulverized fuel power plants is in the form of fly ash which may cause air,
water and land pollution. The primary factors that influence the mineralogy of
a coal fly ash are the minerals present in the coal. Ash can pollute the water in
several ways, such as direct carryover of ash or carry over of increased
dissolved solids from ash to natural water sources, leaching form ash dumps

finding way to water source or percolation to effect ground water quality. Ash
may also sometimes contain heavy metals or radioactive or toxic substances,
which may find way to natural water sources including underground water.
Leaching characteristics are studied generally using the readily available glass
columns. In our previous study glass columns of 90cm was used to carry out
these studies. The quantity of fly ash used was very low and after running for
some time the water coming out of the column was not adequate for the
analysis. The time cycle of the experiment was also high. The experiment has to
be conducted using standard glass column which restricts any change in the
design parameters as a result of which the results obtained through
experimentation did not indicated true picture of the leaching behavior of solid
materials. Handling of glass columns was also found to be difficult.
Further, the experimentation conducted used glass columns which could not
be used for soil and fly ash studies. The glass columns could not withstand
bulk weight of soil and fly ash. Scanty literatures are available for
experimentation of leaching experiments using soil and fly ash mixture for
longer duration. Almost in all the experimentation pumps were used to regulate
flow rate.
OBJECT OF THE INVENTION;
It is therefore, an object of the present invention is to provide a design module
for leaching studies using soil and fly ash mixture that can be used for
experimentation for longer period of time.
Another object of the present invention is to propose a design module for
leaching studies that is simple, economic and capable of studying leaching
characteristics of soil along with fly ash for longer duration which could also
minimize the disadvantages of prior art.
Another object of the present invention is to propose a design module for
leaching studies to propose a module that can be used for similar kind of
studies at laboratory scale.
Another object of the present invention is to provide a module that can also be
used to study leaching characteristics of industrial and hazardous waste.

Another object of the present invention is to provide a module for
experimentation the results of which can be used to predict short term and
long term impact of these waste materials used in the experimentation.
Another object of the present invention is to provide relatively accurate
estimates of the parameters of interest to study leaching characteristics.
Yet another object of the present invention is to propose a columns apparatus
that is designed and constructed of materials chosen to enhance the leaching
of low concentrations of semi volatile and nonvolatile organic constituents as
well as to maximize the leaching of metallic species from the solid.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a method of determination of
leachability aspects of soil and fly ash with a device, the device comprising of:
a plurality of heavy duty polyvinyl chloride column or pipe;
a plurality of mild steel support stand;
a plurality of clamp;
a plurality of layers of stainless steel wire mesh;
a collection stand;
a support stand;
a flask with a funnel;
the method of determination of leachability comprising the steps of:
filing the heavy duty polyvinyl chloride columns or pipes with soil
collected from thermal power station;
pouring fly ash slurry above the soil bed in the columns or pipes;
addition of fly ash to the soil bed each days for 25 days;

collection of leachate in every 24 hrs at the bottom of the polyvinyl
chloride columns or pipes in the conical flask with funnel; and
analysis of the leachate to analyse its various physiochemical
constituents.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS;
Fig 1 shows module of conducting leaching studies.
1- PVC Heavy Duty Pipe
2- Clamps
3- SS Wire Mesh 0.5 (2 Layers)
4- Collection Stand
5- Flask 1000 CC & Funnel Φ 170
6- Support Stand
7- Fly Ash slurry
8- Mild steel support stand
9- Soil Bed

a) 2.5
b) Φ 165
c) 400
d)750

e) 1300
f) 1500
All dimensions are in mm

DETAILED DESCRIPTION OF THE INVENTION;
DESIGN SPECIFICATION OF THE MODULE:
The module consist of two heavy duty PVC pipes (1) of internal diameter
160mm and length 1300mm (e) these pipes are clamped (2) at two places and
is mounted on mild steel support stand (8). The lower end of the pipe drains
into two layers of stainless steel wire mesh (3) having pore size of 0.5mm. For
supporting the assembly a collection stand and support stand (6), made of
stainless steel are provided. For the collection of leachate a flask with funnel (5)
of diameter 170mm are provided just below the stainless steel wire mesh (3).
The heavy duty PVC pipes (1) are filled with soil collected from thermal power
station upto 750 mm (d) from the bottom. Above the soil bed (9) fly ash slurry
(7) in the ratio of 1:10 is poured upto the level of 450mm. 150mm from the top
of the PVC pipe (1) column is kept empty in order to maintain the head
constant. The leachate water passing through entire soil column is collected at
the bottom in conical flask with funnel (5). The process of collection is repeated
every 24 hours in order to analyze its various physiochemical constituents.
In order to study the leaching behavior of Fly ash a study has been conducted
using a module considering factors like, leaching as a function of pH, effect for
liquid/ solid (L/S) ratio and water contact with waste (L/S or infiltration).
LEACHABILITY STUDIES
Evaluation of ground water pollution potential requires the conduction of
testing methods to determine constituent and concentration in leachates
produced. The leachability tests were performed on collected fly ash sample for
various contact period using batch and column tests techniques.
LABORATORY SCALE LEACHING STUDIES OF FLY ASH:
These Leaching test provides data that is used for the estimation of various
constituents that can be mobilized in short-term field leaching scenarios. The
method provides useful information as to the degree of leachability of many
major and trace elements. The effect of changes in pH the variation in relative
solubility and the subsequent inhibition of release of elements have a
considerable impact on composition of leachates from a dynamic open system.

In column tests flow through the waste can deplete readily mobilized
constituents several of which including macro and micro elements.
COLUMN LEACHING TEST:
Column leaching test study was conducted to determine leachability aspects of
Fly Ash. For this purpose Polyvinyl chloride (PVC) (1) column of height 1300
mm (e) and diameter 160mm were used. Leaching material was put in the
column. At the bottom of the column a stainless steel sieve of the size was
placed to support the fly ash etc. Sieve was put at its place using circular
clamp. The general arrangement is shown in the Figure-1.
Soil bed (9) containing 8 Kg of soil collected from the Thermal Power Station
was filled in the column. Fly ash slurry (7) was made using fly ash water ratio
1:10 (300gm fly ash and 3 liter of distilled water) and was added to the column
keeping the soil bed (9) constant. This fly ash slurry (7) was added to the soil
bed (9) each day. The experiment continued for 25 days. The leachate so
collected was analysed each day for various parameters.
The constituents of leachate of fly ash were examined and compared with the
drinking water standard. On the basis of the study conducted following results
were obtained.
During laboratory scale column experimentation the higher concentration of
some of the elements appeared on first two days is due to the solubility of
elements present in soil. After successive days of the experimentation only the
addition of fly ash slurry (7) resulted solubility of elements mainly from the
layers of fly ash which gets deposited each day on the surface of soil in the
column.
Column leaching tests conducted in the laboratory showed that the pH of the
effluent and initial effluent concentration from soil-fly ash mixtures increases
fly ash content. The initial effluent concentration depends primarily on the type
of fly ash and the retardation factor depends primarily on the type of soil that
issued to prepare the soil-fly ash mixture.

There exists relationship between the pH of the fly ash leachates and the
alkaline and acidic components of the ashes.
Different species of metal ions exhibit maximum absorbance at a specific pH
and some types of fly ash have more absorbance capacity than others.
During column experimentation using soil and fly ash combination it has been
noticed that for first 4-5 days the leachate contains soluble metals from fly ash
and soil. This is in agreement of the various factors affecting the composition of
leachate. With passage of time the values of various constituents in the
leachate gradually decreased that could be due to complete solubility of various
substances present in soil matrix.
Column leaching better simulates actual leaching from lab scale
experimentation and provides time dependent data.
The continuous addition of these constituents may result in significant change
in existing ground water quality in near future.

WE CLAIM:
1. A method of determination of teachability aspects of soil and fly ash with
a device, the device comprising of:
- a plurality of heavy duty polyvinyl chloride column or pipe (1);
- a plurality of mild steel support stand (8);
- a plurality of clamp (2);
- a plurality of layers of stainless steel wire mesh (3);
- a collection stand (4);
- a support stand (6);
- a flask with a funnel (5);
the method of determination of leachability comprising the steps of:
- filing the heavy duty polyvinyl chloride columns or pipes (1) with soil
collected from thermal power station;
- pouring fly ash slurry (7) above the soil bed (9) in the columns or pipes
(2);
- addition of fly ash to the soil bed (9) each days for 25 days;
- collection of leachate in every 24 hrs at the bottom of the polyvinyl
chloride columns or pipes in the conical flask with funnel (5); and
- analysis of the leachate to analyse its various physiochemical
constituents.
2. The device for determination of leachability as claimed in claim 1,
wherein the polyvinyl chloride pipes are of height of 1300 mm and
diameter 160mm.

3. The device for determination of leachability as claimed in claim 1,
wherein the stainless steel wire mesh have the pore size of 0.5mm.
4. The device for determination of leachability as claimed in claim 1,
wherein the collection stand and the support stand are provided for
supporting the design module.
5. The device for determination of leachability as claimed in claim 1,
wherein the flask with funnel is of diameter 170 mm.
6. The device for determination of leachability as claimed in claim 1,
wherein the flask is positioned just below the stainless steel wire mesh
for the collection of the leachate.
7. The method of determination of leachability as claimed in claim 1,
wherein the polyvinyl chloride columns or pipes are filled with the soil
up to 750 mm from the bottom.
8. The method of determination of leachability as claimed in claim 1,
wherein the fly ash slurry is made by using fly ash and water in 1:10
ratio.
9. The method of determination of leachability as claimed in claim 1,
wherein the top of the polyvinyl chloride pipe or column is kept empty
upto 150mm in order to maintain the head constant.
10. The method of determination of leachability as claimed in claim 1,
wherein the fly ash slurry is poured above the soil bed upto the level of
450 mm.