The solid waste management is one of the most important problems for most cities around the world. Solid waste landfill must be designed to protect the environment from contaminants which may present in waste. Over 100 million tires are generated annually in India. But, only 10 to 20% of tires are beneficially and environmental safely reused or recycled (Kaushik et al., 2013). The tire causes harmful effects due to their non-biodegradable nature. So the reuse of tire in civil engineering application is as a drainage material, fill material in embankments and pavements etc. Moreover the MSW landfill leachate is generated as a consequence of precipitation, surface run-off and infiltration of groundwater percolating through a landfill, biochemical processes and the inherent water content of wastes themselves. Leachate is generated within the landfills from the percolation of water (precipitation) through the waste, release of moisture in the waste, and the biodegradation of organic waste. The leachate mound in the LCS is a function of the spacing of pipes, bottom slope, infiltration rate, and the hydraulic conductivity of the drainage layer material. Leachate mounding within the landfill will also increase possibilities of leachate leakage through the bottom liners. This leachate may percolate into the ground and causes the contamination of ground water and soil. To minimize this effect due to leachate generation in landfill, the leachate collection and removal system is provided. The materials used in the drainage layer of leachate collection and removal system are gravel and sand but these materials are not easily available in the region. A modern municipal solid waste (MSW) landfill typically includes two components (Rowe 2005) (i) a bottom liner system with low permeability to prevent leachate migration and (ii) a highly permeable leachate collection system (LCS) to reduce the hydraulic head on the bottom liner and hence to minimize the driving force for leachate flow. The leachate head in LCS is required to be less than thickness of drainage layer i.e. between 0.3-0.5 m for granular drainage layer. The leachate mound in the LCS is a function of the rate of infiltration, pipe spacing, bottom slope, and the hydraulic conductivity of the drainage layer.
The studies showed that the permeated with MSW landfill leachate the granular drainage material experiences a growth of biomass, deposition of suspended particles, and precipitation of minerals (Cooke et al., 2001). In this study tire shreds will be used as a drainage material because to the high cost of gravel. They have shown relatively high hydraulic conductivity (Rowe and McIsaac 2005) and are a better thermal insulator than conventional materials. Tire shreds are the landfill construction material having similarities as the natural aggregates typically utilized as drainage media. Tyre shreds have properties that civil engineers generally need. The suitability of tyres as landfill drainage material have approved by several researches (Hudson et al. 2003; Van Gulck, Rowe 2004). Using these tyre shreds can significantly reduce construction cost. Tyre shreds are capable of providing free draining and are good insulator (Reddy et al. 2010). Tyre chips/shreds may be used around buried pipes and potentially keep both the pipe and tyre safe for the long term, keeping the rubber in an environmentally beneficial end application away from direct exposure of sunlight/UV radiation which may cause the possible degradation /deterioration in its quality/shape etc. (Rowe et al., 2012).
High permeability of tyre shreds make them suitable for several landfill applications like leachate collection at the base, operations layer, foundation layer and drainage layer in the landfill cap but the most likely application is to use as drainage material for construction of drainage layer of leachate collection and removal system (Kaushik et al., 2014). These tyre shreds had been used as a substitute for granular material in landfill construction. Tyre shreds can be used in the most applications with negligible effects on ground water quality but a long term service life and durability (to provide long term functioning) of the drainage material is still unknown( ASTM D6270-98). The failure of landfill leachate collection system to control the leachate head due to decrease in hydraulic conductivity of the granular layer is due to biological and mineral clogging.
The performance of the LCS is critical for a well-designed modern landfill and there is a need to be able to predict the service life of a given system. The considerable care is required to design the drainage layer by replacing gravels with tire derived aggregates. Gravels should be used in the critical zones of higher mass loading (McIsaac R. and Rowe R. 2005). In case of the continuous drainage layer, a suitable filter/separator layer between waste and underlying drainage layer is placed which will extend the service life of LCS by minimizing the migration of fines and other particulars (Fleming I. R. and Rowe R. K. 2004). Tire derived aggregates should be used in less critical zones and increased thickness of compressed tires is required to give a service life somewhat equal to that of given thickness of gravels. In order to determine the serviceability of the drainage layer, practical approach is used to estimate the service life of the drainage layer. The estimation of the service life of LCSs with different design configurations requires an understanding of the clogging mechanisms and the effects of the different factors on the clogging. The clogging process is caused by the removal of certain constituents from the incoming leachate. Clogging of these materials occurs in these drainage layers due to saturated and unsaturated zones. Clogging includes the accumulation of material in the voids of the drainage medium which decreases the effective porosity in the granular drainage medium. Thus reduces the hydraulic conductivity of the drainage medium and will eventually impair effective drainage. The clogging of drainage medium may also be due to leachate. The composition of the leachate has a critical effect on the rate of clogging. High levels of organic acids, inorganic cations, and suspended solids have all been shown to increase the rate of clogging. Greater clogging will also occur with higher mass loading (a product of the chemical concentration and flow rate). The clogging rate of the drainage layer is increased with: (1) increasing the mass loading (i.e., increasing the leachate strength, increasing the flow rate, or both); (2) decreasing the grain size or uniformity of the drainage material; and (3) increasing the landfill temperature. Thus, for a given leachate, a higher flow rate will produce greater clogging than a lower flow rate (Rowe and Yu 2010). The clog that develops, will decrease the pore space available to permeate leachate, reduces the hydraulic conductivity of the granular layer and reduced the efficiency of the leachate collection system. It is important in the initial stage of design to assess the likely service life of each component in the system, and to predict how the breakdown of any one component will affect the overall performance of the landfill system (Rowe et al., 2005, Rowe et al., 2011, Rowe and Yu, 2012). These systems are required to collect and remove leachate for extended periods of time and it is important that they be designed to optimize their long term performance and service life.
Thus service life is defined as the time period from start of the use of a structure or of part of it, during which the intended performance is achieved. The time which is required for the leachate mound to increase to the point at which it is about to exceed the permitted head on the liner (usually the drainage layer thickness) is the service life of the drainage system. The service life of the LCS is said to correspond to the time when it can no longer control the leachate head below the specified design value, which is usually taken to be the layer thickness. Therefore, the service life may be extended by increasing the drainage layer thickness. The hydraulic conductivity of the drainage layer is usually specified to be greater than 1 Ã 10-5 m/s, but the best performance will occur when it as high as possible, and it should be at least 1 Ã 10-2 m/s (Rowe et al. 2004). So, in order to determine the service life of drainage layer made up of tyre chips/shreds, mathematical approach can be used. The service life of the drainage layer generally varies from a few years to over 100 years depending on the design of the system. In order to determine the service life of drainage layer made up of TDA (tyre chips/shreds), a mathematical practical approach based upon the characteristics, properties (hydraulic conductivity, compressibility) and permeate (COD, TSS, Ca+ Conc.) under test condition of continuous flow of active MSW landfill leachate in compressed condition may be performed. A simplified form of BioClog was presented by Yu (2012), allowing a more site-specific estimate of service life. The simplified model considers linearly decreasing source concentrations of calcium, chemical oxygen demand (COD), and TSS. CHAPTER III
MATERIAL AND METHODS
Gravels are used as a conventional drainage material in landfill drainage layer. A common gravel size is 38 mm, with coarser and more uniform gravel providing a longer service life (Rowe 2009a). Although gravel has excellent drainage properties but is a scared natural resource. The availability of this drainage material is reducing day by day. Many projects in Punjab are delayed because of this reason. Moreover the MoEF, Government of India under the guidance by Supreme Court of India has banned the mining of natural aggregates from most of the rivers of the Punjab state. So, to continue with the processes, it is necessary to find an alternative for this conventional material which can be act as an efficient drainage material.
The drainage material used for the study is tire derived aggregates in place of gravels. So there are some parameters which differ from one another.
Table 3.1 Comparison between parameters of Gravel and Tire Shreds
Parameters Gravels Tire Derived Aggregates
Hydraulic conductivity (m/sec)
10-2 to 10-3
Void Ratio 0.3-0.5 0.55-0.75
Porosity 0.25-0.40 0.45- 0.60
Compressibility Not compressible 40-60%
Specific gravity 2.62-2.72 1.1-1.28
Unit weight (Kg/m3) compacted 1520 522-690
Density (Kg/m3) 1500-1800 450-900
3.2 Tire Derived Aggregate (TDA):-
Tire derived aggregate (TDA) is an engineered product made by cutting scrap tires into 25 to 300-mm pieces. TDA provides many solutions to geotechnical challenges since it is lightweight (0.8 Mg/m3), produces low lateral pressures on walls (as little as 1/2 of soil), is a good thermal insulator (8 times better than soil), has a high permeability (greater than 1 cm/s for many applications), and absorbs vibrations (D. N. Humphery). So due to their light weight, tires had been considered as an alternative for soil/mineral aggregates for civil engineering applications, as a drainage layer for landfill leachate collection systems. TDA has the excellent drainage properties, maintains its structural integrity. TDA reduces the weight makes the material easier to handle and results reduction in transportation costs. Thus the drainage material used in the leachate collection system is tire derived aggregates. Tire derived aggregates of thickness 900mm needed to achieve equal thickness of 300 mm of gravel, due to high compressibility of the tire shreds (44-48%). Thus the leachate collection system is considered to be failed when thickness of leachate mound exceed design thickness of drainage layer. Hydraulic conductivity of the tire rubber under various overburden pressures and confinement becomes important parameter if these scrap tires required to be utilized for drainage application.
Fig. 3.1 Tire Derived Aggregate used as a Drainage Layer Material
3.2.1 Determination of hydraulic conductivity of tire derived aggregates:
Permeameter mould (internal dia.=30 cm)
Fig. 3.2 Schematic Drawing of Constant Head Permeameter
First of all take a permeameter and apply a little grease on the sides of the mould.
Weight the permeameter and measured the internal diameter and effective height of
Connect the valve of the permeameter with water system and allow water to flow out
so that all the air in the permeameter is removed.
When all the air has escaped, close the stop cock.
Take tire derived aggregates and put 60 cm of TDA in the permeameter and place the
plate over TDA, thus the height is reduced.
Then allow the water to flow the through tires and establish a steady flow.
The head of water is kept 5 cm. When steady state flow was reached, collect the water
in the measuring cylinder for a conventional time interval (10 seconds).
Increase the head with the increment of 5 cm up to 15 cm. To determine the permeability of the tire derived aggregates.
Repeat this procedure thrice, quantity of water collected must be same, otherwise observations were repeated.
The formula used for calculating permeability is,
Where k = permeability of tire chips/shreds (cm/sec)
Q = quantity of water collected in time, t
L = length of sample, cm
A = cross sectional area of sample, cmÂ²
h = constant hydraulic head, cm
3.2.2 Determination of Compressibility of tire shreds:-
The compressibility of tire derived aggregates is typically obtained in a compression test. The TDA particles are placed in a rigid, cylindrical mold, and then an increasing vertical stress is applied and the vertical strain or deformation is measured. The tire shreds are highly compressible due to high porosity. The compressibility of tire shreds can be measured by placing the tire shreds in containers having diameters ranging from 15 to 75 cm. The vertical compression (or strain) caused by an increasing vertical stress is then measured. The compressibility of tire derived aggregates can be measured by stress applied on the sample and the change in the height of the sample. The dial gauge is placed near the end of the container. The load applied on the tire derived aggregates by means of hydraulic jack.
Fig. 3.3 Compressibility test set up for Tire Derived Aggregates
Fig. 3.4 Tire Derived Aggregates Fig. 3.5 Application of load on the
in the permeameter. TDA by hydraulic jack
Fig. 3.6 Compressibility of TDA after application of load.
The container of 30 cm diameter and 92 cm is filled with tire derived aggregates of average dimension 17×9 cm.
The hydraulic jack was placed on the sample and is connected to the loading assembly.
The container was connected to the hydraulic jack.
Loads were applied incrementally on top of sample using the steel plate of thickness 2 cm.
The stresses at the top of the sample were measured using a load gauge attached to the compression apparatus.
The sample was loaded up to 50 KN and the unloaded to zero stress.
Based on the average stress, a load of 150 KN is applied for 1 minute.
As the load reached maximum stress, deformation is taken and then pressure is released to zero.
Also the strain applied at the sample can be evaluated by measuring the initial and the final height of the sample after the application of the load.
The characteristics of leachate are highly variable and depend on the composition of the solid waste, precipitation rate, site hydrology and hydrogeology, compaction, waste age, cover design, sampling procedures, interaction of leachate with the landfill design operation and environment. Leachate contains large numbers of organic, inorganic contaminants and high concentrations of total suspended solids. The age of the landfill also affects the concentration of substances in landfill leachate. Under the normal conditions, leachate is found at the bottom of the landfill and moves through the underlying strata, the lateral movement of leachate may also occur, depending on the characteristics of the surrounding drainage material. As leachate percolates through the underlying strata, its chemical and biological constituents will be removed by the filteration and absorptive action of the material composing the strata. The leachate data used in this study has performance results of a landfill site. Leachate samples were collected and analysed for various physico-chemical parameters to estimate its pollution potential. The leachate composition is typical of a mature landfill. The landfill is deposited with wastes of solid, non-hazardous, industrial, commercial and institutional waste from municipalities. The characteristics of leachate are evaluated in terms of BOD, COD and TSS etc. These characteristics are determined for the Jalandhar region (Warriana Dump Site).
Fig. 3.7 Leachate Sample Taken from Dump Site
3.4 Leachate Sampling and Analysis:
To determine the quality of leachate, integrated samples was collected from landfill location. The sites are non-engineered low lying open dumps. The landfill has neither any bottom liner nor any leachate collection and treatment system. Leachate sample was collected from the base of solid waste heaps where the leachate was drained out by gravity. The concentration of the COD, Ca2+, and TSS is evaluated in laboratory and analysed to determine pollution potential.
3.4.1 Determination of COD concentration:-
Standard potassium dichromate 0.25 N
Standard ferrous ammonium sulphate solution.
Fig. 3.8 Sample preparation for titration (COD conc.)
Place 0.4 g mercuric sulphate (HgSO4) in a reflux flask.
Take 25 ml sample or a smaller amount diluted to 25 ml in a refluxing flask.
Add 10 ml 0.25 N K_2 ãCrã_2 O_7 solution and again mix.
Add 30 ml H2SO4 containing AgSO4 and mixing thoroughly.
Attach the condenser and start the cooling water.
Add ferroin indicator to the solution.
Dilute the mixture and titrate excess of dichromate with standard ferrous ammonium sulphate.
The colour will change from yellow to green – blue and finally red.
Fig.3.9 End Result after Titration of Sample (COD conc.)
Concentration of COD: (A-B) Ã N Ã 8000
ml of sample
Where, A = blank volume of sample (ml)
B= volume of sample used (ml)
N= normality of ferrous ammonium sulphate
3.4.2 Determination of Ca2+ concentration:-
Analysis method for calcium hardness
Murexide indicator (potassium purpurate)
Standard EDTA solution 0.01 N
Fig. 3.10 Change in colour of sample before and after titration (Ca2+ conc.)
Take 25 ml in porcelain dish or conical flask.
Add 1-2 ml buffer solution.
Add a pinch of Murexide indicator and titrate with standard EDTA (0.01N) till wine red colour changes to blue.
Note down the volume of EDTA required.
Formula used = (volume of EDTA Ã D Ã 1000)
volume of sample used
3.4.3 Determination of TSS concentration:-
Analysis methods for Total Solids, Total Suspended Solids and Total Dissolved Solids:
Heater or oven
Fig. 3.11 Suspended Solids in Leachate after Heating
The crucible was cleaned and then put on an oven.
Then it was placed on the desiccators until it cools and then the weight was takenW_1.
100 ml of sample was taken in the crucible dish and it was placed in an oven for 24 hours.
Then it was taken out of the oven and the weights were noted down i.e. W_2.
Weight of total solid = ( W_2-W_1)mg/l.
Total suspended solids :
Take 100 ml sample in a beaker and filter paper were taken.
Filter paper was weighted i.e. W_f and placed in the funnel.
Pass water through filter paper.
Filter paper was placed in the oven till it dried. Then the filter paper was weighed again i.e. W_f2
Total suspended solids were calculated as :
Weight of total suspended solids = ( W_f2 – W_f) mg/l.
3.5 Method to determine the service life of drainage layer:
Rowe and Yan (2013) developed a sophisticated numerical model to determine the characteristics of leachate and service life of drainage layer. It was a complex numerical model not suited to routine design application. Thus based on the findings from field studies of Flemming et al.,(1999), Brune et al., (1991) and Cooke et al., (2001), Rowe and Flemming (1998) developed a practical approach for estimating service life of LCS.
To calculate the service life of LCS following steps were used (Rowe and Yu 2013):
Select the bulk density of clog material, Ïc (Kg/m3).
Select the peak and residual COD concentration cL1,COD (Kg/m3) and cL2,COD (Kg/m3).
Select the peak and residual Ca concentration cL1,Ca (Kg/m3) and cL2,Ca (Kg/m3).
Select the peak and residual TSS concentration cL1, TSS (Kg/m3) and cL2,TSS (Kg/m3).
Select infiltration rate of qo (m/year)
Select size of tire derived aggregates (maximum length).
Select the drainage length of LCS, L meter.
Select average porosity reduction, É³c,avg. required to cause clogging.
Select drainage layer thickness, B.
Select leachate mound thickness at upstream end, Bu (Bu = B-0.1).
Select L.M.T at downstream end Bd. Select drainage length between upstream end and location with the maximum leachate mound thickness, Lm.
Separator layer should be placed between waste and drainage layer.
Calculate reduction in total void volume within the drainage layer .The total void volume occupied by clog mass, Vtot (m2), is equal to the volume of clog material accumulated in the drainage material and is given by:
VTot = â«_0^Lâ’É³_(c avg.) h_(x ) d_x
= É³_(c avg. ) [1/3 L_(m ) (2B+B_(u) )+ 1/5 (L-L_m )(4B+ B_d)]
For calcium concentration cL1,Ca = 2.3 kg/m3 and COD concentration cL1,COD = 26 kg/m3, the condition cL1,Ca > 0.041 cL1,COD is satisfied.
Additional TSS concentration
cL1,ADD = 0.018 cL1,COD
Modified TSS concentration,
cL1 = cL1,ADD + fFS cL1,TSS
Calculate service life tc (years) of LCS from eq.
tc = (Ï_(c f_TSS ) (t) V_Tot)/q_(oC_(L1 ) L)
where tc is service life of LCS estimated from the practical model.
Thus the service life predicted by using the practical model can be used for the engineering applications where it is difficult to approach BIOCLOG model (Rowe and Yu 2013).
RESULTS AND DISCUSSION
4.1 Tire Derived Aggregates:
Tire derived aggregates have the hydraulic conductivity value in range of 1x 10-2 to 1×10-3 m/sec. This value of the hydraulic conductivity is suitable for the efficient drainage in leachate collection systems. The tire derived aggregates used in the drainage layer of leachate collection system should have higher hydraulic conductivity. Thus in comparison to the gravels used in drainage layer, tire derived aggregates can be used. The hydraulic conductivity values observed from the test results are given as:
Table 4.1 Hydraulic conductivity values for Tire Derived Aggregates
Sr. No. Hydraulic conductivity
Hydraulic gradient, i Head, cm
1 4.7 x 10-3 0.09 5
2 2.9 x 10-3 0.19 10
3 2.1 x 10-3 0.28 15
Fig. 4.1 Variation in Hydraulic Conductivity of Tire Derived Aggregates
Gravels have the hydraulic conductivity varying in range of 10-2 to 1. Gravels have the hydraulic conductivity more than that of the tire derived aggregates.
Hydraulic conductivity of Gravels:-
Table 4.2 Hydraulic conductivity values of Gravel
Sr. No. Hydraulic conductivity
Hydraulic gradient, i Head, cm
1 2.9 x 10-2 0.09 5
2 2.59 x 10-2 0.19 10
3 2.4 x 10-2 0.28 15
Fig. 4.2 Variation in Hydraulic Conductivity of Gravel
Gravels are not compressible even under the load. So the effect loading was not considered on the gravel. Although the tire derived aggregates has a great effect of the loading. The tire derived aggregates are much more compressible than that of the gravels. The strain value of the tire derived aggregates was measured with applied stress. The stress strain curve of TDA was plotted.
Table 4.3 Compressibility of the Tire Derived Aggregates under loading
S. No. Stress (kPa) Initial thickness of sample (cm) Final thickness of sample (cm) Strain%
1. 14 60 56 6.0
2. 28.16 60 54.5 9.16
3. 42.2 60 51.2 14.7
4. 70.42 60 49 18.33
5. 84.50 60 46.5 22.5
6. 112.67 60 42.3 29.5
7. 140.84 60 40.2 33.0
8. 154.92 60 36.8 38.6
9. 211.26 60 31.2 48.0
Fig. 4.3 Compression behaviour of the TDA
Leachate from active MSW landfill has high concentration of COD, Ca2+ and TSS. As the landfill is still in operating condition, so concentration of leachate is high.
Chemical Oxygen Demand:
COD represents the amount of oxygen required to completely oxidize the organic waste constituents chemically to inorganic end products. The COD values for leachate samples of the landfilling site after number of titrations are 25360 mg/l, 26450 mg/l, 26355 mg/l, 25480 mg/l, 26220 mg/l.
Total Suspended Solids:
The total suspended solids in the leachate have high concentrations. The values of TSS obtained are 2680 mg/l, 2720 mg/l, 2715 mg/l, 2690 mg/l, 2755 mg/l.
The conc. of Ca -hardness for the sample is obtained as 2275 mg/l, 2335 mg/l, 2345 mg/l, 2284 mg/l, 2330 mg/l.
Thus the characteristics of leachate obtained in the laboratory. The average concentration of COD, TSS and Ca2+ is given as
Table 4.4 Characteristics of leachate in Jalandhar dump site (Warriana)
Sr. No. Parameters Concentrations
1 COD 26000 mg/l
2 Ca2+ 2300 mg/l
3 TSS 2700 mg/l
4.3 Initial characteristics values for service life calculation:-
The concentration of the leachate of Jalandhar region is obtained. The leachate in the leachate collection system causes clogging of drainage material over a period of time.
The concentration of COD into leachate varies from 25350 to 26400 mg/litres. The values are obtained from number of titrations done for the leachate. So the average concentration of leachate taken is 26000 mg/lit.
The effluent average calcium concentration of leachate is about 2300 mg/litres.
The calculated TSS concentration is about 2700 mg/litres.
The concentration of these parameters is found very high because of continuous dumping of the waste in the area.
The properties of TDA are evaluated under test conditions. The permeability of the TDA obtained is 3.1 Ã10-3 m/s. The compacted unit weight of tire derived aggregate is 553.85 kg/m3 but generally varies from 525 Kg/m3 to 690 Kg/m3. Thus the calculated average porosity reduction within the leachate mound is 0.20 (the initial porosity was 0.60).
The bulk density of the clog mass (Ïc) is 1480 Kg/m3. The average annual infiltration rate is 0.2m/year.
The thickness of drainage layer opted is 0.9 m and the compresses thickness for tire shreds is 0.54 which is to be used for service life calculation. The length of the drainage layer is taken as 20m, 30m, 32.5m and 100m. The separator layer provided waste and drainage layer. The filter separator coefficient for silt film is fFS = 1.0
Based upon these parameters the approximated service life is calculated for the tire derived aggregate. This evaluated service life is used in practical application of estimating service life as it is not suited to use the sophisticated numerical model.
4.4 Service life calculated using practical application for TDA drainage layer:-
Using the above data the service life for the drainage layer can be evaluated.
Consider a 0.9 m thick drainage layer at the different drainage length. The compressed thickness of drainage layer is 0.54 which is used. The average porosity reduction within leachate mound is 0.20.The bulk density of clog material is Ïc = 1480 kg/m3. The average infiltration rate is taken to be 0.2 m/year. The strength of leachate is assumed to be constant with time having average COD concentration cL1, COD = 26000 ppm = 26 kg/m3, average calcium concentration cL1,Ca= 2300 ppm = 2.3 kg/m3, average TSS concentration, cL1, TSS = 2700 ppm= 2.7 kg/m3. The drainage length between upstream end and the location with maximum leachate mound thickness is Lm = (0.6 x L). The leachate mound thickness at downstream Bd = 0.1 and at upstream Bu = Bcompressed-0.1 = 0.44 m. The separator used may be taken as slim film separator placed between waste and TDA having filter separator coefficient fFS= 1.0.
Thus using the equations (Rowe and Yu 2013), the service life for the tire derived aggregate drainage layer can be calculated
Case 1: For drainage length L= 20 m.
Maximun leachate mound thickness Lm = 0.6 ÃL = 12m.
.VTot=É³_(c avg. ) [1/3 L_(m ) (2B+B_(u) )+ 1/5 (L-L_m )(4B+ B_d)]
= o.20 [1/3 12(2Ã0.54+0.44)+ 1/5 (20-12)(4Ã0.54+ 0.1)]
For calcium concentration cL1,Ca= 2.3 kg/m3 and COD concentration cL1,COD = 26 kg/m3, the condition cL1,Ca > 0.041 cL1,COD is satisfied.
So the additional TSS concentration
cL1,ADD = 0.018cL1,COD
Modified TSS concentration,
cL1 = cL1,ADD+ fFS cL1,TSS
So service life for tire derived aggregate drainage layer is given by the equation
tc = (Ï_(c f_TSS ) (t) V_Tot)/q_(oC_(L1 ) L)
= (1480Ã0.375 Ã1.95)/(0.2Ã3.16Ã20)
tc = 86 years
Case 2: For drainage length L= 30 m.
Maximun leachate mound thickness Lm = 0.6 ÃL = 18m.
The other parameters remain same.
VTot = É³_(c avg. ) [1/3 L_(m ) (2B+B_(u) )+ 1/5 (L-L_m )(4B+ B_d)]
= o.20 [1/3 18(2Ã0.54+0.44)+ 1/5 (30-18)(4Ã0.54+ 0.1)]
So the service life, tc = (1480Ã0.375 Ã2.91)/(0.2Ã3.16Ã30)
tc = 85 years
Case 3: For drainage length L= 32.5 m.
Maximun leachate mound thickness Lm = 0.6 ÃL = 19.5m.
VTot = É³_(c avg. ) [1/3 L_(m ) (2B+B_(u) )+ 1/5 (L-L_m )(4B+ B_d)]
= o.20 [1/3 19.5(2Ã0.54+0.44)+ 1/5 (32.5-19.5)(4Ã0.54+ 0.1)]
So the service life, tc = (1480Ã0.375 Ã3.15)/(0.2Ã3.16Ã32.5)
tc = 86 years
Case 4: For drainage length L= 100 m.
Maximun leachate mound thickness Lm = 0.6 ÃL = 60m.
VTot = É³_(c avg. ) [1/3 L_(m ) (2B+B_(u) )+ 1/5 (L-L_m )(4B+ B_d)]
= o.20 [1/3 60(2Ã0.54+0.44)+ 1/5 (100-60)(4Ã0.54+ 0.1)]
So the service life, tc = (1480Ã0.375 Ã9.69)/(0.2Ã3.16Ã100)
tc = 85 years
From the above results it can be observed that the service life of tire derived aggregate drainage layer is 85 years whereas service life of gravels is found 114 years for the same condition. However the gravel is used as a drainage material worldwide but this conventional material is not easily available these days, so it is reliable to use tire derived aggregate as drainage material.
Based upon the above results it is concluded that
The dump is non-engineered low lying open dumps. There is neither any bottom liner nor any leachate collection and treatment system. Therefore, all the leachate generated finds its paths into the surrounding environment.
The concentrations of COD, TSS and Ca2+ are found to be more as the landfill is active landfill and still receiving the municipal solid waste. The concentration of these parameters depends upon the type of waste material that is dumped.
The tire derived aggregates have the high hydraulic conductivity as it can be used as the drainage material.
Tire derived aggregates are available in huge quantity as a waste material, so it is easy to use it as a drainage material, which would thus reduce the construction cost and its adverse effect on environment.
It is a simplified mathematical approach, which can be used by the engineer in practice.
The estimated service life by numerical approach was near to that of gravel. So tire shreds have enough service life so that can be used as the drainage material.
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