OCCUPATIONAL HEALTH AND SAFETY

Occupational Health and Safety (OHS) is also referred as workplace health and safety or occupational health. It is a multi disciplined field dealing with the health, safety and welfare of people at work. 

The purpose of OHS is to maintain a safe and healthy work environment for workers. 

The World Health Organization (WHO) defines the Occupational Health and Safety as occupational health deals with all aspects of health and safety in workplace and main focus is on the prevention of hazards.

Three main objectives of OHS are:

• Maintenance of workers health and working capacity
• Improvement of working environment and work to become conductive for health and safety
• Development of work organizations and working culture in direction that supports health and safety

This painting shows that during World War II a woman is working in factory on a lathe  in Britain. Her eyes are not protected but today these practices are not allowed according to occupational health and safety standards for workers. 

Harry McShane, of 16 years age was pulled  into machinery of a  factory in Cincinnati. His arm was cut off and his leg was broken. All this is due to  no health and safety measures. 

CORE PRINCIPLES OF OHS

All workers have rights. Their rights must be protected. 

• Work must take place in healthy and safe environment
• Work conditions must be consistent with worker well being.
• Work should offer personal achievements.

Occupational Health and Safety policies must be established.

National system of occupational health and safety must be established.

Stakeholders and social partners must be consulted.

These safety programmes and policies must aim at prevention and protection.

Health is major and central element in Occupational Health.

Compensation, rehabilitation and cure measures must be available for workers who face  occupational injuries, accidents and work related diseases.

IMAGE REGARDING OHS

These measures must be adopted by workers for maintenance of their health.

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HOW TO QUIT SMOKING

When any one is addicted to smoking, it is very difficult for him to quit smoking. By adopting different methods smoking could be avoided. These are as follows:

1. Making a Quit Plan

If someone made a quit plan than it is easier for him to quit smoking. A smoking plan makes a person more determined, confident, focused and motivated. According to the own need the plan depends.

2. Remain Busy

By keeping busy yourself in some work your attention is diverted from smoking and you can easily quit that.This can be done by performing various activities such as:

• Go for walk outside
• Go for dinner in smoke free restaurants
• Spend time with non smoking friends and families
• Relax by deep breath
• Keep busy your hand with pen or play game
• watch movie

3. Avoid Smoking Triggers

Triggers are the people, places, things, and situations that set off your need to smoke. 

There are some tips to avoid triggers:

• Throw away your cigarettes, lighters and ash trays etc.
• Go to places where smoking is not allowed
• Spend time with non smokers
• Take healthy diet and have plenty of rest
• Change your routine that link you with smoking

4. Stay Positive

Quitting is difficult task. It can take a minute, day or year to quit smoking at one time. Try to think not to quit forever but for a day. Think about today not the next day or future. Thus the days will be added up and it keeps you positive.

5. Ask for Help

Ask friends for help to quit smoking. It is not necessary to deal alone with smoking. Ask family and friends to help you out of this habit. 

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GAS AND LECHATE MOVEMENT AND CONTROL IN LANDFILL

GAS MOVEMENT

Mostly 90 % of gas produced from decomposition of solid waste includes methane and carbon dioxide. The methane in air in the concentration of 5 to 15 % is explosive. In case of high concentration of methane in landfill, there is no oxygen present so there is no danger of explosion. Most of the methane releases into the atmosphere. Both methane and carbon dioxide are found in concentrations of 40 % at lateral distances of 400 ft from the edges of landfill. 

If proper venting is applied than methane does not create any problem. Carbon dioxide is problematic because of its density. Carbon dioxide is 1.5 times denser than air and 2.8 times denser than methane. It tends to move at the bottom of landfill. The concentrations of carbon dioxide in the bottom is thus high.

CONTROL OF GAS MOVEMENT BY PERMEABLE METHODS

The lateral movement of gas could be controlled by installing the vents that are made of materials that are more permeable than surrounding soil. Normally gas vents are made of gravel. The spacing of vents depends upon width of waste cells, mostly it varied between 60 to 200 ft. The thickness of gravel layer should be continuous and recommended between 12 to 18 in.  Barrier vents and well vents are also use to control lateral movement of gases. 

When well vents are used, waste gas burners are also installed often. It is recommended well penetrates in the upper waste cell. The height of waste burner varied between 10 to 20 ft. The burner can be burned by hand or by pilot flame. 

The downward movement of gases can be controlled by perforated pipes in gravel layer at the bottom of landfill. 

LECHATE MOVEMENT

Lechate is generally found in the bottom of landfills. It movement is by underlying strata. Lateral movement can also occur depending on properties of surrounding materials. 

Darcy's Law: 

The rate of seepage of lechate from the bottom of landfill can be estimated by this law. It is written as:

Q= -KA dh/dL

Q= lechate discharge per unit time

K= coefficient of permeability

A= cross sectional area by which lechate flow

dh/dL= hydraulic gradient

The - sign comes from the fact that head loss dh is always negative. Coefficient of permeability is also termed as hydraulic conductivity, effective permeability or seepage coefficient. 

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REACTIONS OCCURRING IN COMPLETED LANDFILL

Solid waste in sanitary landfill is undergone by many chemical, biological and physical changes. The most important changes are as follows:

• Biological decay of organic material either aerobically or anaerobically with the emission of gases and liquids
• Chemical oxidation of materials
• Release of gases from the landfill and lateral diffusion of gases
• Movement of liquids by differential heads
• Leaching and dissolving of organic and inorganic materials by water and lechate movement through the fill
• Movement of dissolved material by concentration gradient
• Irregular settlement of materials by merging of materials in spaces

1) DECOMPOSITION IN LANDFILL

The waste that is placed in the landfill is undergone by bacterial decomposition. At first the decomposition occurs in aerobic condition because air is soon lost. Long term decomposition occurs in anaerobic conditions. The source of aerobic and anaerobic organisms that deals with decomposition is soil that is used as final cover material daily.

The rate of decomposition of organic material depends upon their properties and to much extent on the moisture conditions. The organic material in solid waste is classified into 3 categories:

• those containing cellulose and derivatives of cellulose
•  those not containing cellulose and their derivatives
• plastics, rubber and leather

Cellulose is major part of organic waste e.g. paper, straw, string and plant tissues. Non cellulose organics are proteins, carbohydrates and fats. Mineral salts in less amount and moisture are attached with these materials. 

The end result products from anaerobic decomposition are intermediate volatile organic acids, partially stable organic materials and many gases. 

2) GASES IN LANDFILL

Gases in landfill consist of air, ammonia, carbon dioxide, carbon monoxide, hydrogen, hydrogen sulphide, nitrogen, methane and oxygen. The main gases evolved from anaerobic decomposition of organic material are carbon dioxide and methane. The high carbon dioxide concentration is due to aerobic decomposition. It occurs until the oxygen in air is depleted. After this anaerobic decomposition occurs. After 18 months the composition of gas varies. If the landfill is not vented the percentage of methane increases. 

The total volume of gas released during anaerobic decomposition is estimated by various methods. One is for example if all the organic materials have the formula CaHbOcNd then total volume could be estimated with the assumption of its complete conversion into carbon dioxide and methane.   

3) LECHATE IN LANDFILLS 

Lechate is defined as liquid that percolates through solid waste and has extracted dissolved or suspended materials from it. In landfills the liquid is produced from decomposition of waste and from external sources such as groundwater, rainfall, surface drainage and water from underground springs. 

When lechate percolates through solid waste that undergoes decomposition, both biological and chemical materials are picked up.

Quantity of lechate is direct function of the amount external water entering the landfill.  If landfill is constructed properly then production of lechate could be eliminated. 

COMPLETE LANDFILL

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LANDFILLING METHODS AND OPERATIONS

The methods used for landfilling dry areas are classified into area, trench and depression.

1) AREA METHOD

Area method is used when the land is not suitable for the excavation of trench where solid waste is placed. In this method the waste is unloaded and spread in the long narrow strips in layers that vary in depth from 16 to 30 in. Each layer is compacted in day's operation until its height reaches the 6 to 10 ft. At the end of each day's operation 6 to 12 in layer of cover material is placed over the completed fill. The cover material is hauled from the nearest borrow pit or adjacent land from trucks or earth moving equipment. 

The filling operation is started by building an earthen lavee against which wastes are hauled and compacted. The length of unloading area is based on site conditions and size of operation. The width of compacted waste varies from 8 to 20 ft depending on the terrain. A complete lift having cover material is called a cell. Successive lifts are placed on top of one another until the final grade is reached that is called ultimate development plan. The length of unloading area used every day should be such that final height of fill is achieved at the end of days operation.

2)TRENCH METHOD

The trench method is used when there is enough amount of cover material available at the site and the water table is near the surface. The solid waste is placed in trenches that vary in length from 100 to 400 ft, depth from 3 to 6 ft and width from 15 to 25 ft. In the beginning of the process some part of trench is dug and waste is piled to form an embankment behind the first trench. Wastes are placed there and thin layers of 18 to 24 in are made and compacted. This process continued until the required height is achieved. The length of trench should be such that at the end of days operation final height is achieved. The cover material is gained from the excavation of nearest trench or continuing the trench that is being filling.

3) DEPRESSION METHOD

In the areas where artificial or natural depressions are present, they can be used for landfilling operations. Canyons, Ravines, quarries and dry borrow pits all can be used for this. The technique of placing and compacting the waste depends upon the geometry of the site, properties of cover material, hydrology and geology of site and access to the site. 

In canyon the floor is flat and the first filling is done here by the method of trench. After this the filling is done at the head end of canyon than at the mouth of canyon. This avoids the water accumulation behind the landfill. Wastes are deposited at canyon floor and pushed against canyon face at the slope of 2 to 1 . High compaction is achieved. The compacted density achieved as high as 1,200 Ib/yd3 was seen. 

4) CONVENTIONAL METHODS FOR WET AREAS

Swamps, marshes, tidal areas, ponds and quarries are wet areaas that could be used for landfilling. Due to the problems of odor and ground water contamination the design of landfill in wet areas is a serious concern. 

To bear mudwaves and to enhance structure stability dikes are used to divide the cells or lagoons by riprap trees, lumber demolition waste,, tree limbs and other relevant materials with clean fill material. Sometimes to avoid the malodorous lechate movement and gases in lagoons, the clay and wood sheet piling or leightweight interlocking steel are used. 

The problems could also be ressolved by first draining the site and then lining the bottom with clay liner and other sealants. 

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SITE SELECTION PARAMETERS FOR A SANITARY LANDFILL SITE

The following considerations are taken while designing a sanitary landfill site:

SITE SELECTION

Factors considered while evaluating the potential of solid waste disposal sites are:

• availability of land area
• Processing and resource recovery impacts
• Haul distance
• soil conditions and topography
• climatic conditions
• surface water hydrology
• geologic and hydrologic conditions
• local environmental conditions
• Final use of complete site

1) LAND AREA AVAILABILITY

In order to select a suitable land disposal site sufficient land area should be ensured. There are no fixed rules prescribed for area but its is needed to have the area operated for atleast 1 year at a site. For shorter times the operations become more expensive because of site preparation, provision of auxiliary facilities and final cover completion. 

2) RESOURCE RECOVERY

During the assessment of potential disposal sites the extent of resource recovery processing activities occurring in future should be predicted. These activities have impact on quantity and condition of residual materials to be disposed off. As an example for the recycling of 50 % of paper  the weight of disposed materials and requirement of landfill area must be reduced. The recovery facility presence should also be in consideration at the disposal sites.

3) HAUL DISTANCE

For selecting a disposal site the haul distance is an important parameter. The length of haul affect the design and waste management operation. It is suggested to use minimum haul distance but along with this other factors should also be considered such as: collection route location, local traffic patterns, condition of routes, traffic patterns and access conditions.

4) SOIL CONDITIONS AND TOPOGRAPHY

The characteristics of soils in the area must be provided. If the soil of proposed landfill area is used for cover material than its geologic and hydrlogic investigations must be there. If the cover material is taken from borrow pit than test borings are needed to characterize the material. The local topography must be considered.

5) CLIMATIC CONDITIONS

Climatic conditions must be considered to evaluate the potential sites. Many locations access is affected by winter season. When freezing is severe landfill cover material must be available in stockpiles. Wind and its patterns must be considered carefully. Windbreaks must be used to avoid the blowing or flying papers. Specific type of wind break depends upon local conditions.

6) LOCAL ENVIRONMENTAL CONDITIONS

To build landfill sites close to residential or industrial areas care must be taken while it is environmentally acceptable or not in terms of noise, odor, dust and vector control. Flying papers and plastic films must be controlled.

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INTRODUCTION AND ADVANTAGES, DISADVANTAGES OF SANITARY LANDFILL SITES

INTRODUCTION

For the waste that has no use after its collection and after its processing and recovery of conversion products, something must be done. There are two alternatives for the long term handling of solid waste: One is disposal on or in the earths mantle and second is disposal at the bottom of the ocean. Disposal on land is most commonly used method today. Disposal in the atmosphere provides a third alternative. It is not a good method because the discharge in atmosphere ultimately deposits the waste in earth or in the ocean by natural phenomenon (such as rainfall).    

Ocean dumping of solid waste was practiced at the end of 20 th century and it continued till 1933. Than it was prohibited by US Supreme Court. Industrial waste are also discharged at sea. Recently the ocean floors are used as waste storage sites. 

Land disposal in the form of sanitary landfill has been proved as more economical and accepted method for the disposal of solid wastes.

SANITARY LANDFILL SITES

The sanitary landfill means an operation in which waste to be disposed is compacted and covered with layer of soil at the end of each day operation. When disposal site has reached its ultimate capacity than a final layer of 2 ft or more of cover material is applied. 

ADVANTAGES

• Where land is available sanitary landfill is a good method for waste disposal.
• The initial investment is low as compared to the other disposal methods.
• It is final or complete disposal method as compared to composting and incineration that require additional treatments.
• Sanitary landfill can receive all types of waste. It avoids the need of separate collection of waste.
• A sanitary landfill is flexible, high quantity of waste can be disposed without additional equipment requirement.
• Some marginal land can be reclaimed for use such as: playgrounds, golf courses and airports.

DISADVANTAGES

• In high populated areas land might not be available within economical hauling distance.
• Proper sanitary landfill standards must be adhered to daily operation may result in an open dump.
•  A sanitary landfill in residential areas is highly opposed by people.
• A complete landfill requires the periodic maintenance.
• Special design and construction must be used for the buildings that are constructed on landfill due to settlement factor.
• Methane that is an explosive gas and other gases produced from decomposition of waste produce the hazard and interfere with the use of complete landfill.

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