Pesticides and its associated risk on ecology and environment

Pesticides and its associated risk on ecology and environment:

A pesticide is any chemical or mixture of chemicals intended for preventing, destroying, repelling or mitigating any pest. They include herbicides, insecticides and fungicides as well. The advantageous part of a pesticide is they can kill potential disease-causing organisms and control insects, weeds, and other pests. It is used for agricultural purpose to a great extent. A lot of people are exposed to pesticides within their working environment. Farmers, pesticide applicators and workers in pesticides manufactures are most susceptible to pesticide poisoning. Farm women, who are exposed to some commonly used pesticides in farm work, are at a greater risk of developing allergic asthma, according to a new study.

Pesticides are used in modern farming on fruit and vegetables to increase yields and are thought to increase produce quality. However, pesticides are toxic chemicals designed to kill agricultural pests but can also cause problems with human health if exposed to in large amounts. Pesticides can cause harm to humans, animals or the environment because they are designed to kill or otherwise adversely affect living organisms.

Therefore, as per rule, Govt. agencies register or license pesticides for use in any country. Before a pesticide can be used Govt. agencies conducts ecological risk assessments to determine what risks are posed by a pesticide and whether changes to the use or proposed use of that pesticide are necessary to protect the environment. The Govt. agencies and laboratories are required to conduct and submit a wide range of environmental laboratory and field studies. These studies examine: (i) The ecological effects or toxicity of a pesticide and its breakdown products (degradation products) to various terrestrial and aquatic animals and plants; (ii) The chemical fate and transport of a pesticide (how it behaves and where it goes) in soil, air, and water resources.

Finally, Govt. agencies and laboratories integrate the toxicity information with the exposure data to determine the ecological risk from the use of the pesticide, or whether it is safe for the environment and wildlife.

To reduce the risk from pesticides eat organically and ecologically grown food, wash and peel vegetables and fruit, grow your own food, avoid fatty foods or trim fat from meat as persistent pesticides are stored in fatty tissue. Cook vegetables rather than eat them raw all the time, cook meat and chicken thoroughly, garden in a non-chemical way without pesticides.

Environment-friendly Corex process of iron and steel making:

Environment-friendly Corex process of iron and steel making:

The highlight of the process is it does not require coking coal. The process differs from the conventional blast furnace route; where un-treated non-coking coal can be directly used for ore reduction and melting work, eliminating the need for coking plants. The use of lump ore or pellets also dispenses with the need for sinter plants.

The ability to operate without coke gives this process two environmental advantages over the conventional blast furnace. First, because coke ovens are not needed, all of the problems associated with the generation of benzene and other coal tar byproducts are eliminated. Second, the dust problems associated with blast furnaces are also eliminated because the off-gas is used as fuel. This process along with direct reduction of iron (DRI) process is being implemented in many countries. The off-gas obtained being used to fuel the adjoining DRI plant.

Viewing the process from the coal-route perspective, non-metallurgical coal is directly charged into the melter gasifier. Due to the high temperatures predominating in the dome of the melter gasifier (in excess of 1000 °C), a portion of the hydrocarbons released from the coal during devolatilization are immediately dissociated to carbon monoxide and hydrogen. Undesirable by-products such as tars and phenols, etc. are destroyed and therefore cannot be released to the atmosphere. Combustion with oxygen injected into the melter gasifier results in the generation of a highly efficient reduction gas. Hot metal and slag tapping are carried out as in conventional blast furnace practice. The quality of the hot metal is equivalent to that produced in a blast furnace.

Environmental Aspects: In this system emissions contain only insignificant amounts of NOx, SO2, dust, phenols, sulphides and ammonium. Emission values already exceed by far future European standards. Also, waste-water emissions from are far lower than those in the conventional blast-furnace route. These environmental features are additional key reasons for the attractiveness of the present system.

Carbon emission from bio-fuels:

Carbon emission from bio-fuels:

Bio-fuels are the fuels of solid, liquid or gaseous in nature, which has been derived from bio-mass – recently living organisms or their metabolic byproducts. Thus, it could be oils from plants, manure from cows, wood from trees etc. For example, bio-gas (i.e., gas produced by the biological breakdown of organic matter in the absence of oxygen); bio-ethanol; bio-diesel; straight vegetable oil etc., are the bio-fuels. It is a renewable energy source, mostly have agricultural based, unlike other natural resources such as petroleum, coal and nuclear fuels.

It has been seen that certain social and environmental benefits bio-fuels has as compare to use of fossil fuels, such as reduction of greenhouse gas emission, increased national energy security, increased rural earnings and development and above all, reduction of use of fossil fuel.

Bio-fuels and other forms of renewable energy are thought to be ‘carbon neutral’ or ‘carbon negative’. Carbon neutral or carbon negative is the difference of quantum of carbon produced and emitted to the atmosphere when these are used as fuels and the quantum of carbon absorbed in the process of their growth. If both are same, is called carbon neutral or if quantum of carbon absorbed through photo-synthesis is more than the emission is called carbon negative. Both the cases are advantageous towards environment point of view and reduction of global warming.

Strictly speaking, bio-fuels are neither carbon neutral nor carbon negative. This is because extra energy is required to grow crops and process them into fuel. This extra energy releases extra carbon to atmosphere as emission. For example, plants require fertilizer to grow, requires energy for transportation and processing; this extra energy releases carbon to the atmosphere as emission. Therefore, this emission aspect is to be debated, whether we are really gaining in respect of carbon emission, by using bio-fuel. However, the arid lands can be better utilized if people shift towards bio-fuels; so the rural earnings. The poorly irrigated land mass also can be taken up for cultivation.

Noise barriers are to mitigate highway noise pollution:

Noise barriers are to mitigate highway noise pollution:

High level noise is a disturbance to the human environment. Because of urbanization, noise in all areas in a city has increased considerably. One of the most pervasive sources of noise in our environment today is those associated with transportation. People reside adjacent to highways, are subjected to high level of noise produced by trucks and vehicles pass on the highways. Prolonged exposure to high level of noise is very much harmful to the health of mankind.

Artificial noise barriers are solid obstructions built between the highway and the residential areas along a highway. They block major portion of noise produced by passing vehicles on a highway. Effective noise barriers typically reduce noise levels by as much as half or more. The construction of noise barrier may be built in the form of earth mounds, vertical wall along the highways for creation of blockage of sound generated by heavy vehicles. The effectiveness of mitigation of sound depends upon the height of the mounds or walls. Function of noise barriers are: (1) it can reduce the loudness of traffic noise by as much as half; (2) It may not completely block all traffic noise, but gives certain relief to the residents; (3) It may be effective, regardless of the material used; (4) It must be tall and long with no openings for making it more effective; (5) It must be designed to be visually appealing looking into the aesthetic value of the site.

Apart from constructing artificial noise barriers, creation of greenbelt, by plantation of trees along the highways. The space between the residences and highways may be utilized for creation of greenbelt. As more and more noise pollution problem is being cropped-up, city planners are increasingly adopting various methods to

Environmental pollution in coal mining and its mitigation measures:

Environmental pollution in coal mining and its mitigation measures:

The environmental related issues in coal mines (both in opencast and underground) have been discussed. As coal is very important fossil fuel and its importance has been more prominent after tremendous increase in international price of crude oil; coal mining is now essential part of civilization.

A. In number of ways coal mining projects pollute environment. Environment problems related to coal mines are discussed below:

(1) Air pollution: Air pollution in coal mines is mainly due to the fugitive emission of particulate matter and gases including methane (CH4), sulphur dioxide (SO2) and oxides of nitrogen (NOx). The mining operations like drilling, blasting, movement of the heavy earth moving machinery on haul roads, collection, transportation and handling of coal, screening, sizing and segregation units are the major sources of such emissions. Under-ground mine fire is also a major source of air pollution in some of the coal fields.

High levels of suspended particulate matter increase respiratory diseases such as chronic bronchitis and asthma cases while gaseous emissions contribute towards global warming besides causing health hazards to the exposed population.

Methane emission from coal mining depends on the mining methods, depth of coal mining, coal quality and entrapped gas content in coal seams.

(2) Water pollution: The major source of water pollution in the coal mines is the carry over of the suspended solids in the drainage system of the mine sump water and storm water drainage. In some of the coal mines, acidic water is also found in the underground aquifers. In addition, waste water from coal preparation plant and mine water are other sources of water pollution.

(3) Land degradation: The opencast coal mines are developed at the surface, because of that these mines are also called surface coal mines. The overburden, i.e., the rock or soil overlaid the coal seam, are removed before extraction of coal. This overburden is dumped on surface, preferably on mined-out or decoaled area. Therefore, this type of mining requires quite large area on surface. Many a times, large forest areas are transferred for coal mining purpose. The land degradation is the result of creation and expansion of opencast coal mines. The aspect of land degradation in underground coal mines is due to subsidence over the underground cavity resulted from underground caving.

(4) Noise pollution: Main sources of noise pollution are blasting, movement of heavy earth moving machines, drilling and coal handling plants etc.

(5) Solid waste: Major source of solid waste in a coal mine is the overburden. Segregation of the stones in the coal handling plants and the coal breeze also contribute to the solid waste generation. Over-burden to coal ratio in the open cast mining is about 2 m³/tonne of coal or sometime more. Therefore, the quantum of overburden generated and its proper management is the main concern area in dealing with the environmental issue of opencast coal mines.

(6) Deforestation: As explained, the requirement of land for a big opencast coal projects are quite large. Many of the forest area, many a times, are converted to mining field. Therefore, large forest areas are deforested to make a way for large opencast coal mines.

B. The unscientific mining practices undertaken result in large degradation of land in the form of subsidence, underground goaf filled with water, mine fires, destruction of vegetation, generation of wind blow dust etc. To mitigate above environmental problems several control measures, generally, are adopted. Some of the control measures are discussed below:

(1) Subsidence: Subsidence of surface takes place due to extraction of coal by underground mining. Subsidence is exhibited by cracks on surface and lowering of land in the worked out areas compared to surroundings. The surface is rehabilitated by dozing and sealing of cracks followed by plantation of trees. The subsided areas with medium-sized depressions are ideal for developing water pools and sustain green vegetation and also to meet the water needs of local people.

(2) Abandoned mines: The mined-out areas are to be backfilled and then rehabilitated for development of vegetation. In the quarried areas water reservoir is developed for water harvesting. The big voids created by open-pit mining cause land degradation. These voids can be gainfully utilized to serve as water reservoirs. This water provides moisture for vegetation in the surroundings areas. The water is used for domestic supply after necessary treatment. Irrigation to nearby agricultural land also may be thought off.

(3) External overburden dump: The external dump area presents an unaesthetic appearance unless rehabilitated. Vegetative rehabilitation of these dumps prevents erosion and also improves aesthetics.

(4) Mine fire: The measures for controlling the mine fires, include dozing, levelling and blanketing with soil to prevent the entry of oxygen and to stabilize the land for vegetal growth.

(5) Water and air pollution control: Mine water is pumped to a lagoon, which acts as a sedimentation pond. The overflow water, which is fairly clean, is drained out to natural drain or used for dust suppression activities. Similarly, washery effluent is re-circulated through thickener and slime ponds. For reducing air pollution, water spraying and sprinkling is done on the haul /transport roads to suppress the dust generation.

Fludised Bed Combustion (FBC) technology uses coal washery rejects / fines for power supply

Fludised Bed Combustion (FBC) technology uses coal washery rejects / fines for power supply - An eco-friendly system eases pressure of disposal problem.

In developing countries, most of energy is generated by coal fired power plants. For quality purpose, coals are washed. Disposal of huge rejects and fines obtained from coal washery are a problem everywhere. Fludised Bed Combustion (FBD) technology as the renewable source of energy generates eco-friendly power supply using washery rejects and washery fines.

The objectives of coal-fired power generation is to have (1) power generation at a economical cost; (2) to improve thermal efficiency; (3) to comply with current and future environmental standards. Many of these objectives may be gained by the FBC technology based plants, with incorporation of supercritical steam cycles together with some form of flue gas desulphurisation and low NOx measures.

Advanced FBC system represents significant advantages over conventional coal combustion system. This technology uses a more compact boiler and very high rate of heat transfer to the tube surfaces in the bubbling bed; thus, level of NOx and SOx generated is much less, which is a good indication of pollution control. Generation of particulates is also less as compare to the conventional system.

Above all, it can utilize effectively coal washery rejects, coal washery fines, lignite etc. Utilizing coal washery rejects and coal washery fines means easing pressure for disposal problem of these materials.

Pollution associated with coal washeries for beneficiation of coal:

Pollution associated with coal washeries for beneficiation of coal:

Coal seam in some of the countries has drift origin, resulted in intimate mixing of mineral matter with coal, giving rise to more ash content. Coal washeries are to reduce ash content in coal. For coking coal and non-coking / thermal coal quality improvement, coal washeries are used. Coal having drift origin, coal-ash distribution in the coal matrix is so interwoven that coal is essentially required to crush to smaller sizes for better liberation of coal and ash particles. Coal washing is a process of separation mainly based on difference in specific gravity of coal and associated impurities like shale, sand and stones etc so that we get relatively pure marketable coal without changing the physical properties of the coal. Coal beneficiation largely depends on gravity difference of coal and ash particles after passing through sizing.

Pollution and its control: During various operations in coal washeries, a lot of particulate matters and gaseous pollutants are generated causing a serious air pollution problem in the area. Besides, coal washeries release very large amount of solid and liquid waste causing serious environmental problems. The washeries reduce the ash content of coal to 17.5% or less. This process consumes clear water in the range of 0.2 to 0.25 m3/tonne of raw coal input. The washeries are operated in the closed water circuit system but still about 12-18% of raw water is discharged as effluent. Though, effluent is treated in settling tank but sometimes overloading results into failure of closed circuit system. The rejects (15 to 25% of input) are dumped near available land without caring for stability of dump, as a result dumps near the river bank cause erosion of coal particles during rainy season and accumulation of fine coal particles on the bottom of river / lake bed.

In general, typical coal washery effluents characteristics are:

1. Physical appearance - Blackish brown to deep black in colour

2. pH – 7.1 to 7.8

3. Suspended solids – 800 to 4000 mg/L

4. Particle size – 0 to 150, 150 to 200, 200 to 300 micron

5. Dissolved solids – 300 to 1500 mg/L

6. Oil & grease – 15 to 200 mg/L

Though many of the washeries have adequate settling tanks but disposal of solid waste required to be accelerated, specially in developing countries to check with the pollution. Proper the reject dump management is required to minimise soil erosion.

Another very useful process of generating electricity with the help of washery rejects by using eco-friendly Fludised Bed Combustion (FBC) technology. By adopting technology which uses washery rejects, the disposal of fines and rejects can be utilized properly and economically; as coal of drift origin require to grind coal before beneficiation and thereby generation of fines are more.

Example of plantation done in mined out site – A case study

Example of plantation done in mined out site – A case study

A site at Southern India – running opencast lignite mines (more than 20 million tones of annual capacity) cum coal-fired power plants (capacity about 2500MW). The mines used to generate huge quantity of overburden apart from generating fly-ash from coal-fired power plant. One of the major challenges it has to develop rich cover of green belt.

In fact, excavating more than 20 million tones of lignite annually involves a removal of about 135 million cubic meters of overburden. The overburden excavated is backfilled in mined out areas and the modified slope as per stability, by conventional mining equipments. The dumped overburden is devoid of any nutrients to support plant growth. Adopting indigenously developed techniques, selecting locally available species of plants as per the local climate and establishing organic farming in order to enrich the wastelands created by dumps. While selecting the plant, species of dense foliage have been used for plantation. One of the criteria for selecting the plants was of high growth nature. Planting about 4000 different varieties of plants including fruit bearing trees, herbal cultivation has been undertaken in the reclaimed area. The herbal cultivation is to cater to the needs of the local ayurvedic dispensary.

Advantages:

(a) Dense foliage of green belt created around the mines serves as a barrier, to prevent dust penetration from operation of heavy earth moving machineries and movement of off-the-road vehicles in the mines into nearby dwelling is negligible;

(b) the noise pollution from these sources has been checked quite substantially, because of creation of this green cover. It has been observed that noise level reduces by 10 decibels per every 10m wide green belt development;

(c) Trees reduce mean temperature of the area by 2 degree Celsius;

(d) Trees in an acre of land have the potential to absorb six tones of sulphur dioxide, thus reducing air pollution.

Ship-breaking industry: One of the most hazardous and polluted industry

Ship-breaking industry: One of the most hazardous and polluted industry needs to be rectified soon.

Ship breaking is a type of recycling industry, involving in recovering scraps out of used and old ships. It is a very complex process involves many environmental, labour, safety and health issue. Ship breaking is the process of dismantling an obsolete vessel’s structure for scrapping and disposal. In other words, old and unserviceable ships are demolished in this industry for business of scraps. It allows material from old ships to be reused. Ship breaking operation is conducted at a beach, pier, drydock, or dismantling slip include variety of operations like removing all gears and equipments to cutting down and recycling the ship’s infrastructure.

It is a highly labour intensive industry, and due to that, most of the ship breakers located earlier at developed countries either have stopped the breaking operation or shifted to developing countries like India, Bangladesh, and China etc. The braking of ships is considered to be a dirty and hazardous occupation. Naturally, as of any business, the feasibility of ship-breaking is also largely determined by the market force, i.e., price of scrap metal.

When ship is brought for dismantling, it carries lot of hazardous items, chemicals etc. Breaking them without taking adequate care of human safety, pollutants, and ways for safe disposal of wastes, are quite hazardous job. Hazardous factors involved in Ship breaking operation are: Asbestos; Lead; Chromates; Mercury; Fumes of welding & cutting; Radiation; Noise; Vibration; Air pollution; Low-level radium sources; Organic liquids ( Benzene etc.); Battery, Compressed gas cylinders, firefighting liquids, etc.; Chemical materials; Work using plasma and gas torches; Explosives; Work using cranes and lifting equipment; Saws, Grinders and Abrasive cutting wheels; Accident factors: falling, upsetting, electric shock, etc.

To make the entire operation cheaper, wherever the ship breaking operation is conducted at developing country, there is extremely high rate of exploitation of workers exists with no formal education with them, no / less availability of protective equipments to maintain any safety standard and above all, high rate of corruption among regulators made the situation at a dire state. There exists high level of accidents, occupational diseases among workers; with limited or no medical provisions.

In order to enhance the standard of safety and environmental issue, Government departments of several countries have initiated lot of research; and several proposals and recommendations have been forwarded for implementation. Some of them are: (a) Design improvement of vessels that would not only make scrapping ships less labour intensive, but also environmentally friendly and profitable; (b) Consideration of international duration limitations on vessel life cycles; (c) The establishment of a "Global Scrapping Endowment Fund" in which Shipbuilders would include as part of the construction costs a cash payment to the fund in the amount of the expected costs for the ships eventual demolition; (d) A 'Global Scrapping Tax `Fund' in which taxes would be levied on every ship (according to size and weight) in operation across in globe; (e) Require ship builders to reacquire control of a vessel when it is due to be demolished and to accept responsibility for the safe and environmentally sound scrapping of each ship.

Governments of developing countries required to implement stricter regulations towards safety, health and environmental issues and implementation of them are to be followed. It may be noted, at present iron and steel prices have gone up; so the price of scraps; this financial benefit, should be extended to the personnel engaged for ship breaking operation. Moreover, environment-friendly entrepreneurs are to be encouraged for this re-cycling industry.

As ship breaking industry is re-cycling industry; environmentally it has to be upgraded and it would be everybody’s interest to make this operation as green as possible. Nevertheless, keep continuing recycling industry like sheep breaking is beneficial for the society, as it reduces not only pressure on mineral ore mining, the disposal problem is taken care of as well. Therefore, we have to make this ship breaking industry greener, exploitation & accident free.

Dust control systems in coal handling plant

Dust control systems in coal handling plant:
Thermal power plants (coal-fired power plants) use coal as their fuel. To handle the coal, each power station is equipped with a coal handling plant. The coal has to be sized, processed, and handled which should be done effectively and efficiently. The major factor which reduces the staff efficiency in operation of coal handling plant is the working environment i.e. a dusty atmosphere and condition. Lots of care is always needed to reduce dust emission. In developing countries, all most all systems used in power station coal handling plants are wet dust suppression systems.

A. After dust is formed, control systems are used to reduce dust emissions. Although installing a dust control system does not assure total prevention of dust emissions, a well-designed dust control system can protect workers and often provide other benefits, such as

(a) Preventing or reducing risk of dust explosion or fire;

(b) Increasing visibility and reducing probability of accidents;

(c) Preventing unpleasant odors;

(d) Reducing cleanup and maintenance costs;

(e) Reducing equipment wear, especially for components such as bearings and pulleys on which fine dust can cause a "grinding" effect and increase wear or abrasion rates;

(f) Increasing worker morale and productivity;

(g) Assuring continuous compliance with existing health regulations. In addition, proper planning, design, installation, operation, and maintenance are essential for an efficient, cost-effective, and reliable dust control system.

B. There are two basic types of dust control systems currently used in minerals processing operations are:
(a) Dust collection system - Dust collection systems use ventilation principles to capture the dust-filled air-stream and carry it away from the source through ductwork to the collector. A typical dust collection system consists of four major components, such as (1) An exhaust hood to capture dust emissions at the source; (2) Ductwork to transport the captured dust to a dust collector; (3) A dust collector to remove the dust from the air; (4) A fan and motor to provide the necessary exhaust volume and energy.
(b) Wet dust suppression system - Wet dust suppression techniques use water sprays to wet the material so that it generates less dust. There are two different types of wet dust suppressions: (i) wets the dust before it is airborne (surface wetting) and (ii) wets the dust after it becomes airborne. In many cases surfactants or chemical foams are often added to the water into these systems in order to improve performance. A water spray with surfactant means that a surfactant has been added to the water in order to lower the surface tension of the water droplets and allow these droplets to spread further over the material and also to allow deeper penetration into the material.
i. Surface wetting system: The principle behind surface wetting is the idea that dust will not even be given a chance to form and become airborne. With this method, effective wetting of the material can take place by static spreading (wetting material while it is stationary) and dynamic spreading (wetting material while it is moving). For static wetting, more effective dust suppression arises by increasing the surface coverage by either reducing the droplet diameter or its contact angle. For dynamic spreading, more factors come into play such as the surface tension of the liquid, the droplet diameter, the size of the material being suppressed, and the droplet impact velocity.
ii. Airborne dust capture system - Airborne dust capture systems may also use a water-spray technique; however, airborne dust particles are sprayed with atomized water. When the dust particles collide with the water droplets, agglomerates are formed. These agglomerates become too heavy to remain airborne and settle. Airborne dust wet suppression systems work on the principle of spraying very small water droplets into airborne dust. When the small droplets collide with the airborne dust particles, they stick to each other and fall out of the air to the ground. This collision between the particles occurs due to three factors involving both the water and the dust particles. As a dust particle and water particle approach each other, the airflow could move the particle around the droplet, have a direct hit on the droplet, or barely graze the droplet. It is this factor that leads us to the second factor, which is that droplets and particles that are of similar sizes have the best chance of a collision. If a droplet is smaller than the dust particle or vice versa, then they may never collide and instead just be swept around each other. The last factor is the dependence of an electrostatic force on a droplet and how the path is affected by this force. Just like with magnets, similarly charged particles repel each others. Thus it is advantageous to have the particles either both neutrally charged (so that they neither repel nor attract one another) or oppositely charged (so that they attract one another) in order to increase the likelihood of a water and particle collision.

C. System Efficiency: Over the years, water sprays has established the following facts: (1) For a given spray nozzle, the collection efficiency for small dust particles increases as the pressure increases; (2) At a given pressure, the efficiency increases as the nozzle design is changed so as to produce smaller droplets. The efficiency of spray dust capture increases by increasing the number of smaller sized spray droplets per unit volume of water utilized and by optimizing the energy transfer of spray droplets with the dust-laden air.

D. Sophisticated system like ‘Ultrasonic Dust Suppression’ systems uses water and compressed air to produce micron sized droplets that are able to suppress respirable dust without adding any detectable moisture to the process. Ideal for spray curtains to contain dust within hoppers. The advantages of using Ultrasonic Atomizing Systems for dust suppression can therefore be summarized as:

(a) reduced health hazards;

(b) decrease in atmospheric pollution;

(c) improved working conditions;

(d) efficient operation with minimum use of water.

Measures taken to mitigate environmental impacts while concreting for construction

Measures taken to mitigate environmental impacts while concreting for construction

With the large scale construction activities going on everywhere, the potential environmental impact in cement works for concreting are to taken care of. Air quality, noise nuisance, water quality and visual impact induced by concrete batching plant operated for construction working.

A. Fresh concrete and cement-related mortars are toxic to marine life. Therefore, Concrete run-off from washing or leaking equipment or from disposing of these materials to the street gutters and stormwater drains eventually finds its way into waterways, which has the potential to cause pollution. It not only does serious environmental degradation, but also against law.

Concrete run-off blocks stormwater drains, pollutes our creeks, lakes and rivers and has a major impact on water quality, aquatic plants and animals. Appropriate measures must be taken to control concrete run-off.

Understanding few environmental best management practices should significantly reduce the likelihood of pollution from typical day-to-day concreting activities; some of these are:

(a) Establishing a concrete wash-down area on-site. (b) The wash-down area must be located with appropriate sediment controls. These should be inspected and maintained regularly and be repaired or replaced as necessary; (c) minimize the amount of wash-down water generated, scrape excess concrete off the equipment before it is washed; (d) Place excess concrete into a site receptacle designated for concrete and masonry; (e) A high pressure, low volume water spray nozzle conserves water and reduces maintenance of sediment controls; (f) Wash-down water is best managed by draining it into a container, allowing the water to stand until the solid particles settle at the bottom. After adjusting the pH of the water to neutral, it can then be siphoned off and reused, and the residue in the bottom can be allowed to set, then recycled with other excess concrete and masonry material; (g) No wash-down water may be disposed of to the sewerage system without prior agreement of the local water authority; (h) Do not allow equipment wash-down water to flow directly into a stormwater drain or system.

B. Ensure that concrete washed from trucks and mixer units on site is contained and does not leave the site or enter the stormwater system.

C. For modern commercial skyscraper building development projects, the works involved piling, concreting and eventually superstructure construction. Many, being in the heart of busiest commercial central district, noise arising from the concreting work were the major concern. Measures to be adopted: (a) Quieter Method - A purposely-built acoustic enclosure was built to screen the operation of concrete pump and the concrete lorry mixer. The mixer is a Specified Powered Mechanical Equipment which demands a more stringent acceptable noise level; (b) No concreting work was allowed beyond 11 p.m.; (c) Administration - To ensure good communication, the contractor was required to submit a 48-hour-advance notification before commencement of concreting work of those identified bore piles and diaphragm walls necessitating major concrete pour; (d) With the incorporation of the purpose-built acoustic enclosure, the construction noise from the subject site was reduced to a level below the relevant Acceptable Noise Level.

D. General precautions: All such rules and legislations relevant to reduction of impact of concreting are to be adhered to by all the personnel engaged at the job site. Proper training procedures are also to be followed in order to impart training for adoption of all the procedure laid down.

Dust in cement industry: Its prevention

Dust in cement industry: Its prevention and collection enhances environment standard:

The manufacturing of cement involves mining; crushing and grinding of raw materials (mostly limestone and clay); calcinating the material in rotary kiln; cooling the resulting clinker; mixing the clinker with Gypsum; and milling, storing and bagging the finished cement. The cement manufacturing process generates lot of dust, which is captured and recycled to the process. Gasses from clinker cooler are used as secondary combustion air. The process, using pre-heaters and pre-calciners, is both economically and environmentally preferable to wet process because of techno-economic advantages of the energy saving dry system over wet. Certain other solids such as pulverized fly ash from power plants, slag, roasted pyrite residue and foundry sand can be used as additives to prepare blended cement.

A. Dust generation: Generation of fine particulates and dust are inherent in the process; but most are recovered and recycled. The sources of dust emission include clinker cooler, crushers, grinders and material-handling equipments. Material-handling operations such as conveyors result in fugitive dust emission.

B. Prevention and control of dust: The priority in the cement industry is to minimize the increase in ambient particulate levels by reducing the mass load emitted from the stacks, from fugitive emissions, and from other sources. Collection and recycling of dust in the kiln gases in required to improve the efficiency of the operation and to reduce atmospheric emissions. Units that are well designed, well operated, and well maintained can normally achieve generation of less than 0.2 kilograms of dust per metric tonne (kg /t) of clinker, using dust recovery systems. For control of fugitive dust:

(a) ventilation systems should be used in conjunction with hoods and enclosures covering transfer points and conveyors;

(b) Drop distances should be minimized by the use of adjustable conveyors;

(c) Dusty areas such as roads should be wetted down to reduce dust generation;

(d) Appropriate stormwater and runoff control systems should be provided to minimize the quantities of suspended material carried off site.

C. Mechanical systems for controlling dust: Several mechanical equipments are used in cement manufacturing plant to control / collect dust. These are:

• Dust collector - A dust collector (bag house) is a typically low strength enclosure that separates dust from a gas stream by passing the gas through a media filter. The dust is collected on either the inside or the outside of the filter. A pulse of air or mechanical vibration removes the layer of dust from the filter. This type of filter is typically efficient when particle sizes are in the 0.01 to 20 micron range.
  

• Cyclone - Dust laden gas enters the chamber from a tangential direction at the outer wall of the device, forming a vortex as it swirls within the chamber. The larger articulates, because of their greater inertia, move outward and are forced against the chamber wall. Slowed by friction with the wall surface, they then slide down the wall into a conical dust hopper at the bottom of the cyclone. The cleaned air swirls upward in a narrower spiral through an inner cylinder and emerges from an outlet at the top. Accumulated particulate dust is deposited into a hopper, dust bin or screw conveyor at the base of the collector. Cyclones are typically used as pre-cleaners and are followed by more efficient air-cleaning equipment such as electrostatic precipitators and bag houses.
  

• Electrostatic Precipitator - In an electrostatic precipitator, particles suspended in the air stream are given an electric charge as they enter the unit and are then removed by the influence of an electric field. A high DC voltage (as much as 100,000 volts) is applied to the discharge electrodes to charge the particles, which then are attracted to oppositely charged collection electrodes, on which they become trapped. An electrostatic precipitator can remove particulates as small as 1 μm (0.00004 inch) with an efficiency exceeding 99 percent.

“Coal Dust Explosion” in Coal fired Cement plant – Its prevention

“Coal Dust Explosion” in Coal fired Cement plant – Its prevention is necessary for safety and enhancement of environment standards.

The numbers of coal fired industrial systems, particularly cement plants, is rapidly increasing, because of high cost and uncertainty in availability of fuel oil and natural gas. Many of the countries do not have access to sufficient quantity of petroleum products; there by, worldwide growth in coal-fired cement plant is tremendous. There is inherent risk associated with coal pulverizing, drying, blending, transportation and storing.

To understand fully the hazard potential of using pulverized coal as a fuel in a cement plant, one should be familiar with the factors responsible for development of coal dust explosion. A typical pulverized coal fuel system process bulk coal into a form that can be efficiently utilized as a fuel to heat the kiln for calcining the raw material of cement, i.e., clay, limestone, etc., into clinker. This is usually accomplished by grinding and drying the bulk feed in a pulverizer so that coal emerging from pulverizer consist 70 to 80% particulate that passes through 200 mesh screen. High temperature air from clinker cooler is often used to dry the coal and convey it from pulverizer to the burning pipe of the kiln. Coal pulverizing is one of the most hazardous jobs from fire and explosion point of view, as both fuel and oxygen are present at the pulverizer. A coal dust explosion is described as rapid burning of combustible particulate within a confined area; which generates a considerable heat and corresponding pressure rise. The factors responsible for coal dust getting exploded:

• presence of dust in suspension at a concentration above flammability limit,
  
• presence of sufficient oxygen to enable the combustion,
  
• source of ignition of the coal dust air mixture,
  
• a certain degree of confinement to the mixture.

Most coal used in firing system have tendency for spontaneous ignition (Spontaneous heating is an inherent property of coal to get heated on oxidation, when it is kept for prolonged time with air or oxygen. Oxidation of coal is an exothermic process, hence the self-ignition) in the pile. Therefore, care should be taken in storage, handling within firing system and prevention of accumulation of coal dust during system operation.

Special precautions are necessary to ensure safe operation:

• use oxygen-deficient air in the pulverizers under normal operating condition,
  
• use of rock dust, carbon dioxide, water systems in the pulverizers and dust collectors when shutdown occurs,
  

• inerting with water sprays or steam when over-temperature conditions are observed,

• care must be taken to prevent development of coal dust cloud,
  
• use of magnet or metal detection to remove foreign iron substance in the system to prevent occurrences of sparks,
  
• cutting & welding operation should be carried out as per the safety norms,
  
• electric components used in the system should be of non-inflammable type,
• hot coal, if any, should be avoided to charge into pulverizers,
  
• proper control measures should be adopted to prevent spontaneous ignition of coal,
  
• prevention of static electricity discharge into the system should be adopted by grounding dust collector bags,
  
• by properly designing of several coal handling equipments in order to prevent accumulation coal dust at various idle spots of locations.

As coal dust explosion in coal-fired industrial systems (whether in a cement plant or in a thermal power plant) is very much serious in nature and may cause damage to the property and personnel, utmost care should be taken to prevent such occurrences. Last but not least, proper training the personnel is most important to handle such situation most effectively.

Environment-friendly Blended cement – Eases pressure on Industrial waste disposal

Environment-friendly Blended cement – Eases pressure on Industrial waste disposal and reducing emissions per unit weight of cement manufactured

Portland Cement, an essential component of concrete, hardens and become strongly adhesive after application; used for various engineering and building construction activities. It is a mixture of Calcium silicate (CaO, SiO2), Calcium aluminate (CaO, Al2O3) in varying proportion, with small amount of magnesium, iron compounds etc. To slowdown the hardening process of cement, sometime Gypsum is also used.

Production of Portland cement is highly gas pollutant; emits considerable amount of Carbon dioxide (CO2) in the atmosphere, polluting air. CO2 is well known for its ill-effects towards Global warming as greenhouse gas. In cement manufacturing plant alone, CO2 produces (a) during de-carbonation of limestone, (b) during kiln fuel combustion, (c) during transportation by vehicles in the cement plant & for cement distribution.

Considering CO2 associated with electric energy consumed by a cement plant, we have observed, for production of 1 tonne of Portland cement 1 tonne of CO2 is produced and emitted to the atmosphere. This is a quite large quantity of CO2 which a Portland cement unit pollutes. To mitigate this extent of pollution menace, many of the steps have been taken by cement industries - production and use of environment-friendly blended cement, i.e., use of alternate or supplementary cementitious materials such as fly ash and slag, is among such steps taken to bring down emission per unit weight of cement manufactured. In addition to reduction of emission per unit weight of cement manufactured, it eases problem of Industrial waste disposal; as both fly-ash and slag are the waste from thermal power and steel making industry respectively, available abundantly almost at free of cost.

Fly-ash blended cement: Fly ash is the waste generated by thermal power units, resulting from combustion of powdered coal. Fly ash consists of mostly Silicon dioxide (SiO2), Aluminum oxide (Al2O3) and Iron compounds. It is pozzolanic, i.e., it reacts with calcium hydroxide and alkali to form cementitious materials.

Activated Fly ash can replace up to 50% by mass in blended cement. It is less expensive and it is advantageous in a host of applications. Fly ash can be used to improve workability and pumpability of concrete. Due to its generally slower rate of hydration, fly ash also lowers the heat of hydration and is important in mass concrete structures, such as large foundations, bridges, and piers. High fly ash concrete shows less bleeding and shrinkage than straight cement mixes. Fly ash is also used as a component in the production of flowable fill, which is used as self-leveling, self-compacting backfill material in lieu of compacted earth or granular fill.

Due above advantages of fly ash blended cement, more and more fly ash is being used beneficially as a recycled material.

Slag blended cement: Slag is the waste product of iron making industry. These are the impurities present in iron ore and obtained from blast furnace while processing for pig iron. It was found that ground granulated slag reacts with water to produce cementitious properties. Therefore it is used in concrete in combination with Portland cement as part of blended cement. Concrete containing ground granulated slag develops strength over a longer period, leading to reduced permeability and better durability properties. Slag cement concrete is less vulnerable to alkali-silica and sulfate attack.

As with fly ash, processing blast furnace slag into slag cement or slag aggregate eases the burden on environment. Apart from reducing the burden of waste disposal, it reduces the air emissions at the cement kiln as well as the material in landfills. Most significantly, slag decreases Portland cement usage by as much as 50 percent, thereby diminishing CO2 emissions, the amount of energy required to produce concrete, and the quantity of virgin land extraction through mining raw materials for Portland cement.

Concrete made with blended cement has generally higher density than concrete made with Ordinary Portland Cement. Hence it improves the impermeability and durability. All these make for better long-term strength, dense and impermeable concrete and improved corrosion resistance and longer service life with reduced cost for repairs and maintenance.

Thus, the Blending cement is not only environment-friendly, but also make improved concrete performance.

Cleaner Coal-fired ‘Supercritical Power plants’

High performance Coal-fired ‘Supercritical Power plants’ – Promotes cleaner environment

As name suggests, Coal-fired Supercritical power plants operate at very high temperature and pressure (580 degree centigrade temp. and at a pressure of 23 MPa) resulting much higher heat efficiencies (46%), as compare to sub-critical coal-fired plants which operates at 455 degree centigrade temp., and efficiency of within 40%. Some of the benefits of advanced supercritical power plants include:

• Reduced fuel costs due to improved plant efficiency;

• Significant improvement of environment by reduction in CO2 emissions;

• Plant costs comparable with sub-critical technology and less than other clean coal technologies;

• Much reduced NOx, SOx and particulate emissions;

• Can be fully integrated with appropriate CO2 capture technology.

In other words, supercritical power plants are highly efficient plants with best available pollution control technology, reduces existing pollution levels by burning less coal per megawatt-hour produced, capturing the vast majority of the pollutants. This increases the kWh produced per kg of coal burned, with fewer emissions.

Because of the above techno-economic benefits along with its environment-friendly cleaner technology; more and new power plants are coming-up with this state-of-the-art technology. As environment legislations are becoming more stringent, adopting this cleaner technology have benefited immensely in all respect. As LHV (lower heating value) is improved (from 40% to more than 45%); a one percent increase in efficiency reduces by two percent, specific emissions such as CO2, NOx, SOx and particulate matters.

"Supercritical" is a thermodynamic expression describing the state of a substance where there is no clear distinction between the liquid and the gaseous phase (i.e. they are a homogenous fluid). Water reaches this state at a pressure above 22.1 MPa. The efficiency of the thermodynamic process of a coal-fired power describes how much of the energy that is fed into the cycle is converted into electrical energy. The greater the output of electrical energy for a given amount of energy input, the higher the efficiency. If the energy input to the cycle is kept constant, the output can be increased by selecting elevated pressures and temperatures for the water-steam cycle.

There are various operational advantages in case of supercritical power plant:

• There are several turbine designs available for use in supercritical power plants. These designs need not fundamentally differ from designs used in sub-critical power plants. However, due to the fact that the steam pressure and temperature are more elevated in supercritical plants, the wall-thickness and the materials selected for the high-pressure turbine section need reconsideration. The supercritical plant needs once-through boiler, where as drum type boiler is required by sub-critical power plant. In fact, once-through boilers are better suited to frequent load variations than drum type boilers, since the drum is a component with a high wall thickness, requiring controlled heating.

• The performance of supercritical plant depends on steam condition. Steam conditions up to 30 MPa/600°C/620°C are achieved using steels with 12 % chromium content. Up to 31.5 MPa/620°C/620°C is achieved using Austenite, which is a proven, but expensive, material. Nickel-based alloys, would permit 35 MPa/700°C/720°C, yielding efficiencies up to 48%. Lot R&D inputs and allying with suppliers are required to achieve higher performance.

• Moreover, fuel Flexibility is not compromised in Once-Through Boilers. A wide variety of fuels have already been implemented for once-through boilers. All types of coal as well as oil and gas have been used.

• Current designs of supercritical plants have installation costs that are only 2% higher than those of sub-critical plants. Fuel costs are considerably lower due to the increased efficiency and operating costs are at the same level as sub-critical plants. Specific installation cost i.e. the cost per megawatt (MW) decreases with increased plant size.

Because of the high performance, efficiency and preservation of much cleaner environments than sub-critical coal-fired power plants, more than 400 supercritical coal-fired power plants are operating in the developed countries like US, Europe, Russia and in Japan. Most of the new power plants coming up now-a-days are of supercritical coal-fired technology.

Guidelines for making City Green

As cities are keep on growing because of urbanization, more and more cities are becoming congested. To make cities livable for the citizen and to make their life beautiful, it has been the constant endevour of the Government to encourage for green building, keep city pollution within the limit and to create sufficient green belt.

A. Green Building is a philosophy of design and construction that integrates natural resources more effectively, preserves and restores the natural and human resource base while creating healthier, more efficient “high-performance” structures, homes and communities. This philosophy incorporates the following guiding principles:

• Using natural and manmade resources efficiently;

• Considering the impact of buildings and development projects on the local, regional and global environment;

• Reducing building footprint and development size;
  

• Allowing ecosystems to function naturally;

• Conserving and reusing water; treating storm water on-site;

• Maximizing the use of local materials;

• Optimizing energy performance by installing energy efficient equipment and systems;
  

• Optimizing climatic conditions through site orientation and design;
  

• Integrating natural day-lighting and ventilation;

• Minimizing the use of mined rare metals and persistent synthetic compounds and volatile organic compounds;
  

• Minimizing construction waste by reducing, reusing and recycling materials during all phases of construction and deconstruction.

Sustainability is the practice of using resources to provide for the needs of today’s citizens while preserving the use of those same resources for the needs of future generations. Generally, objectives of green buildings are: (a) Improve work and learning environments, thus increasing worker productivity and student performance; (b) Mitigate health risks such as asthma and childhood lead poisoning; (c) Create local green building jobs within every existing industrial sector; (d) Reduce energy consumption and costs; (e) Affirm the City’s commitment to environmental conservation.

B. The creation of green-space in cities is often spoken of as if it were the result of orderly planning or regulation. Most of the cities have a plan to conserve green-space on the urban fringe. Generally, planning for creation of city green zones includes:

• Greening Commercial Corridors – This focus on landscape enhancements along strategic streets that can serve as a neighborhood's economic lifeline.

• City Parks Revitalization – This focus on maintaining and beautification of existing parks in a city.

• Setting-up of New Community Gardens;
  

• Street Beautification Projects- creation of "Garden Blocks".

· Education and Training Opportunities - Courses and workshops help city dwellers beautify their communities through horticulture.

C. Apart from setting up green buildings, green covers, strategy for implementing proper solid waste management, restricting generation of air / water pollutants and strict implementation of local emission control codes. Thus, guidelines should include:

• Utilize sites to capture environmental benefits and preserve or create new open space;
  

• Develop programs and policy to conserve potable water use, improve stormwater management and “green” the city sewage waste water system;
  

• Address city and regional transportation issues by encouraging transit-oriented development, improve public transit services and reduce dependency on individual automobile use;

• Implement citywide energy conservation programs and incentives, encourage use of renewable, non-fossil fuel energy sources and improve city performance on meeting regional clean air standards;
  

• Promote the development of local, green manufacturing industries and the use of recycled content materials or renewable materials for building, operations, and supplies for city work. Also establish more extensive recycling program to include construction and demolition waste recycling;
  

• Maintain city’s sustainable development by integrating programs, such as in workforce development, economic redevelopment, and the public school system.

D. Citywide ban on smoking in all enclosed public spaces and public vehicles, also to be imposed for long term benefit of its citizen.

Planned city development emphasizes value of environment and heritage:

Transformation of rapid urbanization in developing world due to industrialization has necessitated to the planned city development. In general, the planned city development include environmental sustainability, heritage conservation, appropriate technology, infrastructure efficiency, place making, "social access," transit oriented development, regional integration, human scale, and institutional integrity. Some of these points are discussed below:

Balance with nature: Balance with nature emphasizes the distinction between utilizing resources and exploiting them. It focuses on the thresholds beyond which deforestation, soil erosion, aquifer depletion, siltation and flooding. The principle promotes environmental assessments to identify fragile zones, threatened eco-systems and habitats that can be enhanced through conservation, density control, land use planning and open space design. Balance with nature do not support any act against nature, which include cutting of hillside trees, quarrying on slopes, dumping sewage and industrial waste into the natural drainage system, paving and plinthing excessively, and construction on steep slopes.

Balance with tradition: Balance with tradition integrate plan interventions with existing cultural assets, respecting traditional practices and precedents of style. It calls for respect for the cultural heritage of a place. It also promotes architectural styles and motifs designed to communicate cultural values. Aesthetic sense of the area should be maintained.

Appropriate Technology: Appropriate technology emphasizes the employment of building materials, construction techniques, infrastructural systems and project management which are consistent with local contexts.

Cordiality: It is well known that, vibrant societies are interactive, socially engaging and offer their members numerous opportunities for gathering and meeting one another. Therefore modern society calls for cordiality among everybody. Design should follow promotion of interactive behaviour of society. It leads to creation of places of solitude for individual; spaces for “beautiful, intimate friendship” where unfettered dialogue can happen; place where the individual socializes into a personality; creation of city level domains like plazas, parks, stadium, transport hubs, gallerias etc.

Efficiency: The principle of efficiency promotes a balance between the consumption of resources such as energy, time and fiscal resources, with planned achievements in comfort, safety, security, access, tenure, and hygiene. It encourages optimum sharing of public land, roads, facilities, services and infrastructural networks reducing per household costs, while increasing affordability, access and civic viability.