design of bioreactor landfill for allahabad city

8/12/2019 Design of Bioreactor Landfill for Allahabad City

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Project Progress Report

Design of Bioreactor Landfill for Allahabad City

Submitted in partial fulfillment for the award of B. Tech. DegreeUnder the supervision of

Dr. Nekram Rawal

&

Dr. Sumedha Chakma

Department Of Civil Engineering

Motilal Nehru National Institute of Technology Allahabad

Allahabad

Submitted By:

Avaneesh Kumar Yadav 20101067

Nirbhay Narayan Singh 20106038

Akhilesh Kumar Pal 20101050


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OBJECTIVES

To estimate future production of Municipal Solid Waste at every 10 years interval To analyze leachate by collecting samples To estimate the settlement rate To select the bioreactor type and size from the existing study To design the bioreactor landfill components

Results From previous studies

Population in 2045 using Incremental Increase MethodP2045= 1594871

Total per day MSW generation considering 0.45 kg/capita/day= 717.691 Tons

Leachate Pollution Index is determined and found to be equal to 19.896 which is higher thanrecommendation of Municipal Solid Waste Rules, 2000.

Parameters Details

Parameter Sample

1

Sample

2

Sample

3

Sample

4

Mean S.D. Max Min Limit

Arsenic (mg/l) 0.01 0.025 0.025 0 0.015 0.010607 0.025 0 0.2

BOD (mg/l) 203.2 294.3 467 480.5 361.25 117.1172 480.5 203.2 30

Chloride

(mg/l)

1079.45 2272.5 3374.84 3710.23 2609.255 1031.016 3710.23 1079.45 600

COD (mg/l) 307.69 474.67 689 804.3 568.915 191.6684 804.3 307.69 250

Copper (mg/l) 1.5486 0.0731 1.7492 0.183 0.888475 0.764713 1.7492 0.0731 1.5

Iron (mg/l) 0.5114 0.5671 2.3182 1.9321 1.3322 0.804855 2.3182 0.5114 3

KjeldaNirogen

(mg/l)

18.62 33.2 42.5 43.7 34.505 10.03125 43.7 18.62 100

MPN per 100

ml

75 210 460 1100 461.25 393.8016 1100 75 5000


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pH 7.82 7.63 9.63 8.72 8.45 0.796021 9.63 7.63 5.5-9

Sulphate

(mg/l)

5.16 6.21 11.6 9.13 8.025 2.525079 11.6 5.16 1000

TDS (mg/l) 114.8 176.8 168 212 167.9 34.79813 212 114.8 2100

Settlement of MSW:

MSW settles under its own weight and as external loads are placed on the landfill.

External loads include daily soil cover, additional waste layers, final cover, and facilities such

as buildings and roads. MSW settlement is mainly attributed to-

(1)physical and mechanical processes that include the reorientation of particles, movement ofthe fine materials into larger voids, and collapse of void spaces;

(2)chemical processes that include corrosion, combustion and oxidation;(3)dissolution processes that consist of dissolving soluble substances by percolating liquids and

then forming leachate; and

(4)Biological decomposition of organics with time depending on humidity and the amount oforganics present in the waste.

MECHANISMS THAT CAUSE LARGE SETTLEMENTS

Mechanical/Primary CompressionMechanical/primary compression is due to distortion,

bending, crushing and reorientation of materials caused by the weight of overburden and

compaction. This settlement occurs rapidly and is typically complete withinapproximately

one month from the time the filling is complete. At the Landfill, mechanicaland primary

compression due to fills was estimated to range from 10 to 20 percent of newfill thicknesses

based on empirical data collected during a soil fill placement. The actual primarycompression

depends on fill geometry, density of landfill and overburden, and landfill

composition.

Biodegradation: Aerobic and anaerobic decomposition of organic material by bacteria is

theprocess known as biodegradation. For anaerobic decomposition of cellulose, which is the

primarymechanism of biodegradation, bacteria convert carbon-based solid material and water


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intoprimarily carbon dioxide and methane. This conversion results in a loss of solid mass.

Most settlement after landfill construction is due to this mechanism.

Physical Creep Compression (Including Ravelling/Void Filling): This mechanism is

caused by:

(1) Erosion and sifting of finer materials into voids between larger particles;

(2) Material moving into voids as a result of biodegradation; and

(3) Continued elastic compression.

Void filling is partly related to a weakening of the support of the solids due to such things as

biodegradation and corrosion, which causes a reduction of the rigidity of landfill materials

This form of settlement equals about2 percent of the fill height per log cycle of time. For the

landfill, physical creep compression was estimated to contribute from 0 to 7 feet of additional

settlement over the next 90 years.

MECHANISMS THAT CAUSE SMALL SETTLEMENTS

Interaction: Examples of interaction include methane supporting combustion, spontaneous

combustion and organic acids causing corrosion. This mechanism is closelyassociated with

the occurrence of the other mechanisms. By itself, interaction is not expected torepresent a

significant amount of settlement over a large areal extent. It could result in largelocalized

settlements; although with a properly maintained and operated LFG collection systemand

cover in place, the source of oxygen to support combustion will be significantly reduced.

Consolidation: Consolidation settlement is caused by excess water squeezing from pore

spaces inlow permeable soil formations. If landfill is not saturated then settlement due to

consolidation is not expected.

Methodology for Primary and Mechanical Compression

The waste mass consists of layers of refuse of finite thickness. Addition of a new waste layer

causes settlement, attributable theweight of the overlaying layers, and stress increases

instantaneouslybecause of construction of a new layer.The strain [(t)] resulting from an

instantaneous response to surcharge loading can be expressed by

(t) = C log((0+ )/0) (1)


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where C = compression ratio (coefficient of compressibility);

0= initial vertical stress; and

= change in vertical stress

Because the unit weight of a solid waste deposit in a landfillincreases with depth, the

overburden pressure at different heightsHi is computed by

(2)

Thus, the strain in each lift of the multilayer fill can be expressed bythe equation

(3)

where C = coefficient of compressibility;

Hi = initial thickness ofthe compacted lift (assumed initially same for all the lifts);

i= unit weight of lift i; and

j = incrementof unit weight imposed by lift j on lift i; and pi and mi stand for primary and

mechanical strain, respectively.

The primary compression (S(t)pi) can be obtained by

S(t)pi= Hj pi(t) (4)

Similarly, the mechanical compression (S(t)mi ) attributable to creep, is obtained by

S(t)m= H mi(t) (5)

where H = initial height of the landfill after primary compression.

Eqs. (4) and (5) give the temporal change of primary andmechanical compressions

attributable to overlaying layers. Theseequations can be used to compute primary and

mechanical settlementwhile assuming constant density, or spatial and temporal

variation of density.

Model Parameters:

Coefficient of Compressibilityand DensityIn Eq. 3, the coefficient of compressibility (C) is

used for bothprimary and mechanical strain. The value C is found from the relationship

(6)


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where C= compressive index; eo= initial void ratio of the solidwaste; and t = time after

landfill closure (years).The compressive index Cis primarily dependent on the voidratio and

is obtained from the slope of the void ratio versus log-timecurve. The following range is

provided for estimating the compressiveindex:

C= (0.15 to 0.55)eofor primary compression;

(0.03 to 0.09)eofor secondary compression

The value of C is different for primary and mechanical compression. The coefficient of

compressibility for primarycompression lies in the range 0.10.5, whereas secondary

compressionlies in the range 0.0120.08.

The variation of refuse density with depth (z) is computed by the method of Manna et al.

using Eq. (7)

Pz= Pm+(PmP0) ((z/z + )) (7)where Po= starting value of the density;

Pm= maximum density value corresponding to infinite load; and

= numerical coefficient.

Once the density is known by Eq. (7), the unit weight of thesolid waste is calculated by

multiplying the acceleration due togravity (g) with density. The temporal variation of the unit

weightis then obtained by

(8)

Where (t) = required unit weight at time t (days) and

i= initial unit weight of the refuse.

Density varies from 600694 kg/m3during activefilling, whereas the maximum density

observed is in the range11861653 kg/m3.

Computation of Primary and Mechanical CompressionPrimary and mechanical compression were computed considering two cases: assuming (1)

constant density throughout the landfill and (2) spatial and temporal variation in landfill

density. In the first scenario, primary compression, density is assumed to be the same

throughout the cell and taken as the starting value of 600 kg=m3; the coefficient of

compressibility (C) is taken as 0.2. For mechanical compression, considering t = 15 years in

Eq. 8,spatial variation of density is computed using Eq. 7 and assumed not to vary temporally

throughout computation; the coefficient of compressibility (C) is taken as 0.02. In Eq. 7, the


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starting value of the density Pois taken as 600 kg/m3; the maximum density Pmis taken as 1;

350 kg/m3; and a numeric coefficient is taken as 12.4. These values were taken after

thorough sensitivity analysis and are used by many researchers, as shown in following tables.

In the second scenario, primary compression, Eq. 8 is used to calculate temporal variation of

density. Furthermore, for mechanical compression, spatial and temporal variation of density

is calculated using Eqs. 7 and 8. The values C, Po, Pm, are the same as in mechanical

compression, as previously describedResults are shown in following table


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Year Settlement (m)variable density

Settlement (m)

constant density

Difference2 0.104 0.104 05 0.6275 0.6035 0.02410 1.8423 1.7269 0.115415 3.291 3.0466 0.244419 4.5604 4.1958 0.364623 5.904 5.4087 0.495327 7.3078 6.6741 0.633730 8.3945 7.6527 0.7418Settlement (%) 27.98 25.51

design of bioreactor landfill for allahabad city

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