A Study on Effect of Leachate on Different Filter Materials

A Study on Effect of Leachate on Different Filter Materials

Mr. Midhun M L1 Dr. Mariamma Josepp

1Student 2Assistant Professor

1Department of Geotechnical Engineering

1,2Kerala Technical University St. Thomas Institute for Science and Technology, Trivandrum, India

Abstract – Landfill leachate is defined as any contaminated liquid which is usually generated principally by precipitation percolating through the waste deposited in the landfills. Once the rain water comes in contact with the solid waste, the rain water becomes contaminated and it flows out of the waste called leachate. It usually consists of many organic, inorganic and suspended particles. The composition of leachate varies widely depending on the age of landfill, type of waste, climatic conditions and the landfilling technology. Usually landfill leachate is characterized by high value of BOD, COD, ammonia, methane, sulphides, and heavy metals as well as strong colour and bad odour. Leachate from municipal solid waste landfills can cause serious threat to surface water, ground water, soil and environment. The risk of leachate leakage is mainly due to the inappropriate material in the liner system of landfill. Underdesingned landfill liner allow the leachate to easily pass through the soil strata and mix with the groundwater. The main goal of this project is to find out the most effective material for the liner system of the landfills. For this purpose, leachate samples were collected and analysed for various physico- chemical parameters to estimate its pollution potential. Then this leachate is passed through different filter medias such as tyre chips, coir pith and sand and the effects of leachate on different filter medias was estimated.

I INTRODUCTION

Due to rapid urbanization and population growth, our environment is degrading day by day. Waste generation has been increasing rapidly due to the rise in population. In developing countries, the wastes are generally deposited in low lying areas called landfills. One of the major pollution problems caused by the municipal solid waste landfill is leachate. The rainwater which percolates through the landfill and dissolves the organic and inorganic substance of solid waste produces leachate. The landfill leachate dischage may lead to severe environmental problems. Leachate may percolate through landfill liners and subsoil causing groundwater pollution. The leachate may also migrate into surrounding soil and changes the geotechnical properties of soil. The pollutants in MSW landfill leachate can be grouped into four namely; dissolved organic matters, inorganic components, heavy metals and particular organic components. When leachate passed through the landfill liners, the insoluble organic and inorganic materials may get accumulated within the pore space of the drainage media. This will results in decrease in porosity and hydraulic conductivity. Moreover, the leachate components may combined with the microbial activity results in chemically and biologically induced clogging. As a result the the period of effective funtioning of the leachate drainage system will reduces. One of the

main objectives in the design of the landfill should be the proper management of leachate migration. Modern landfills are highly engineered that utilize liners to minimize the negetive impact of the solid waste. Liner systems are usually designed to be reliable and robust, remaining active for years.

The use of tyre chips, coir pith and sand in bottom drainage layer of landfill has been given global attention. This paper presents the study on the use of tyre chips, coir pith and sand mixed with coarse grained rubbles as the drainage material in the liner system of the landfill.

1. OBJECTIVES

   • To study the effect of leachate on various filter medias.

   • To identify the most suitable and effective material for drainage layer.

   • To identify the most suitable material which reduces the clogging of leachate on drainage layer.

   • To check whether the usage of natural drainage materials can be reduced.

2. MATERIALS

   The following are the materials used for this study;

   1. Course grained rubbles

   2. Tyre chips

   3. Coir pith

   4. Sand

   5. Leachate

   1. COURSE GRAINED RUBBLES

      Here we are using course grained rubbles in which gravel and sand predominates. Rubbles are broken stones of irregular size, shape and texture. Coarse grained rubbles were collected from Thonnakkal.

      Fig 1 course grained rubble

      Table 1 properties of course grained rubbles

      PROPERTY	VALUE
      Specific Gravity	2.66
      Maximum Dry Density	1.734g/cm3
      Minimum Dry Density	1.463g/cm3
      Hydraulic conductivity	0.07cm/s
      Angle of internal friction	380
      Size	4 to15mm

   2. TYRE CHIPS

      Tyre chips or scrap tyre is a solid waste that includes any unwanted or discarded tyre has been removed from its original use. This means that tyres which are no longer suitable for use on vehicles due to wear or damage can be recycled to serve a new economic purpose. Tyre chips were collected from automobile workshop, near Attingal.

      Table 2 Properties of tyre chips

      PROPERTIES	VALUE
      Density	56gm/cc
      Specific Gravity	1.12
      Hydraulic conductivity	15cm/s
      Angle of internal friction	300
      Cohesion	Negligible

   3. COIR PITH

      Coir pith is a by-product of the coir fibre processing industry. The composition and properties of coir pith vary depending on maturity of coconut, method of extraction and disposal, period between extraction and use and environmental factors. Coir pith was collected from Murukumpuzha.

      Table 3 properties of coir pith

      PROPERTIES	VALUE
      Specific gravity	0.87
      Water Absorption	10%
      Aspect Ratio	105
      moisture retention capacity	600% – 800%
      Density	0.8g/cc
      C:N Ratio	24:1

   4. LEACHATE

      Leachate is the liquld residue resulting from the various physical, chemical, and biological processes taking place within the landfill. Leachate sample for the study were collected from Attingal. Various physico-chemical parameters were analysed to determine the pollution potential of leachate sample.

      Table 4 Properties of leachate

      PROPERTIES	VALUE
      Chloride	625mg/l
      Dissolved oxygen	40 mg/l
      Sulphides	88 mg/l
      Nitrites	12.5 mg/l
      pH	8.42
      Electrical conductivity	1.956Ms/cm
      Total dissolved solid	450g/l

   5. SAND

      Experiments were carried out on locally available cohesionless soil collected from Trivandrum district, Kerala.

      Fig 2 sand

      Table 5 Properties of sand

      PROPERTIES	VALUE
      Specific Gravity	2.616
      Liquid Limit	48.2%
      Angle of Internal Friction	350
      Maximum Dry Density	1.82g/cc
      Minimum Dry Density	1.45g/cc
      Optimum Moisture Content	24%
      Hydraulic Conductivity	0.04cm/s

3. METHODOLOGY

   Leachate samples are collected from MSW plant. In this study, the leachate samples were collected from Attingal municipal treatment plant. Laboratory tests were conducted on the leachate and analyse the various physico-chemical parameters of the leachate samples. Then the leachate sample is passed through different filter medias and estimate the effects of leachate on different filter medias. Filter medias includes tyre chips, coir pith and sand.

   Table 6 Weight of material in each layer

   PROPERTY	GRAVEL	SAND	COIR PITH	TYRE CHIPS
   SPICIFIC GRAVITY	2.66	2.55	0.87	1.12
   MAX DRY DENSITY (g/cm3)	1.734	1.82	1.15	1.02
   RELATIVE DENSITY (%)	75.7	52.96	61.9	60
   WEIGHT (gm)	1211.2	847.36	990	960

   FIG 3 Experimental setup

4. RESULT AND DISCUSSION

The following results were obtained from the study.

1. Properties of leachate in different filter medias.

   PROPERTIE S OF LEACHATE	CONDITIONS
   	TYRE CHIPS IS SANDWICHE D BETWEEN GRAVELS	COIR PITH IS SANDWICHE D BETWEEN GRAVELS	SAND IS SANDWICHE D BETWEEN GRAVELS
   Chloride	524.98mg/l	399.988mg/l	474.98mg/l
   Dissolved oxygen	38 mg/l	36 mg/l	376mg/l
   Sulphides	84 mg/l	78 mg/l	80 mg/l
   Nitrites	12 mg/l	10 mg/l	11.5 mg/l
   pH	8.41	8.39	8.40
   Electrical conductivity	0.583Ms/cm	0.439Ms/cm	0.719Ms/cm
   Total dissolved solid	311g/l	236g/l	387g/l

2. Permeability of drainage layer in different filter medias.

   CONDITION	COEFICIENT OF PERMEABILITY (cm/s)
   Tyre chips is sandwiched between gravels	K= 3.83×10-4
   Coir pith is sandwiched between gravels	K= 2.81×10-4
   Sand is sandwiched between gravels	K= 3.4×10-4

   IV CONCLUSION

   • This study revealed the possibility for the use of tyre chips, coir pith, and sand as a reliable material in the drainage layer of the liner system.

   • It has been concluded that the leachate sample contains high concentration of organic and inorganic consistuents. It also have high alkalinity, TDS and conductivity.

   • Both tyre chips and coir pith were found as effective material in reducing the amount of organic, inorganic and suspended patricles in the leachate. They also improves the physico- chemical parameters of the leachate.

   • Tyre chips have high hydraulic conductivity than coarse grained rubbles and sand which makes them suitable material for drainage layer.

   • Coir pith have a very high water holding capacity and thus it reduces the quantity of leachate generation.

   • Coir pith has the least permeability value. Thus it also helps to reduce the migration of leachate into the soil.

   • Thus coir pith is more effective than sand and tyre chips and sand as drainage material in the liner system.

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