Name-Abhishek Banerjee

Faculty-Science

Department- Chemistry

Reg. No.-AU/BSC/2015/426

Rain water harvesting

Introduction

It was very difficult to imagine few decades before that you will require to buy drinking. The use value of water was never undermined, but its about time that even its exchange value is given due importance. Fresh water today is a scarce resource, and it is being felt the world over. More than 2000 million people would live under conditions of high water stress by the year 2050, according to the UNEP (United Nations Environment Programme), which warns water could prove to be a limiting factor for development in a number of regions in the world. About one-fifth of the world’s population lacks access to safe drinking water and with the present consumption patterns; two out of every three persons on the earth would live in water-stressed conditions by 2025. Around one-third of the world population now lives in countries with moderate to high water stress—where water consumption is more than 10% of the renewable fresh water supply, said the GEO (Global Environment Outlook) 2000, the UNEP’s millennium report. Pollution and scarcity of water resources and climate change would be the major emerging issues in the next century, said the report. These issues would be followed by problems of desertification and deforestation, poor governance at the national and global levels, the loss of biodiversity, and population growth, said the report - The Observer of Business and Politics, 12 October 1999

Water is the most common or major substance on the earth, covering more than 70% of its surface. Out of the total volume of water

available on the surface of the earth, only 2 percent (over 28,000,000 km3) is fresh water. The fresh water is used for the purpose of human use, industries and agriculture. The

different forms of fresh water in which it is available on earth are given in Table-1. In India, the water availability per capita is declining. The per capita availability of water at the national level is reduced from about 5,177 m3 in the year 1951 to the present level of 1,869 m3.

Rainwater harvesting, in its broadest sense, is a technology used for collecting and storing rainwater for human use from rooftops, land surfaces or rock catchments using simple techniques such as jars and pots as well as engineered techniques. Rainwater harvesting has been practiced for more than 4,000 years, owing to the temporal and spatial variability of rainfall. It is an important water source in many areas with significant rainfall but lacking any kind of conventional, centralised supply system. It is also a good option in areas where good quality fresh

surface water or groundwater is lacking. The application of appropriate rainwater harvesting technology is important for the utilisation of rainwater as a water resource.

Causes & effects

Global Population GrowthGlobal population has more than doubled since 1950 and reached six billion in 1999. The most recent population forecasts from the United Nations indicate that, under a medium‐fertility scenario, global population is likely to peak at about 8.9 billion in 2050.Given that many natural resources (such as water,soil, forests and fish stocks) are already beingexploited beyond their limits in some regions,significant effort will be required to meet the needsof an additional three billion people in the next 50 years.

In parallel with these changes, there have beenprofound demographic shifts as people continue tomigrate from rural to urban areas in search of workand new opportunities. Since 1950, the number ofpeople living in urban areas has jumped from 750million to more than 2.5 billion people.Urban environmental impacts and demands are alsodifferent. By 2025, the total urban population is projected to double to more than five billion, and 90 per centof this increase is expected to occur in developing countries.

The Global Water Crisis Rapid population growth, combined with industrialisation, urbanisation, agricultural intensification andwater-intensive lifestyles is resulting in a global water crisis. About 20 per cent of the population currentlylacks access to safe drinking water, while 50 per cent lacks access to a safe sanitation system. Falling watertables are widespread and cause serious problems, both because they lead to water shortages and, in coastalareas, to salt intrusion. Both contamination of drinking water and nitrate and heavy metal pollution of rivers,lakes and reservoirs are common problems throughout the world. The world supply of freshwater cannot beincreased. More and more people are becoming dependent on limited supplies of freshwater that arebecoming more polluted. Water security, like food security, is becoming a major national and regionalpriority in many areas of the world.Other Reasons

The replenishment of ground water is drastically reduced due to paving of open areas. Indiscriminate exploitation of ground water results in lowering of ground water table (GWT) rendering many bore-wells dry, which has led to drilling of bore wells of greater depth. This further lowers the water table such frequent fluctuations in GWT results in presence of higher concentration of salts in ground water. In coastal areas, over exploitation of ground water results

in seawater intrusion thereby rendering fresh ground water bodies’ saline.

In rural areas also, government policies on subsidized power supply for agricultural pumps and piped water supply through bore and open dug wells are resulting into decline in GWT. The solution to all these problems is to replenish ground water bodies with rainwater by man made means .

Advantages

Rainwater harvesting systems can provide water at or near the point where water is needed or used. The systems can be both owner and utility operated and managed. Rainwater collected using existing structures(i.e., rooftops, parking lots, playgrounds, parks, ponds, flood

plains, etc.), has few negative environmental impacts compared to other technologies for water resources development. Rainwater is relatively clean and the quality is usually acceptable for many purposes with little or even no treatment. The physical and chemical properties of rainwater are usually superior to sources of groundwater that may have been subjected to contamination.The rainwater’s environmental advantage and purity over other water alternatives makes it the sustainable option, even though the precipitation cycle may fluctuate from year to year. The collection of rain water not only leads to conservation of water but also energy since the energy input required to operate a centralized water system designed to treat and pump water over a vast service area is bypassed. Rainwater harvesting also lessens local erosion and flooding caused by runoff from impervious cover such as pavement and roofs, as some rain water is captured and stored. Rain water quality almost exceeds that of ground or surface water as it does not come into contact with soil and rocks where it dissolves salts and minerals and it is not exposed to many of the pollutants that often are discharged into surface waters such as rivers, and which can further contaminate groundwater. However, rainwater quality can be influenced by characteristics of area where it falls, since localized industrial emissions affect its purity. Thus, rainwater falling in non-industrialized areas can be superior to that in cities which are

dominated by heavy industry or in agricultural regions where crop dusting is prevalent.Some Other Advantages of Rainwater Harvesting Include:a. Rainwater harvesting can co‐exist with and provide a good supplement to other water sources and utility systems, thus relieving pressure on other water sources.b. Rainwater harvesting provides a water supply buffer for use in times of emergency or breakdown of the public water supply systems, particularly during natural disasters.c. Rainwater harvesting can reduce storm drainage load and flooding in city streets.d. Users of rainwater are usually the owners who operate and manage the catchment system, hence, they are more likely to exercise water conservation because they know how much water is in storage and they will try to prevent the storage tank from drying up.e. Rainwater harvesting technologies are flexible and can be built to meet almost any requirements. Construction, operation, and maintenance are not labour intensive.

working principle disadvantagesComponents Of Rain Harvesting System A rainwater harvesting system comprises components of various stages - transporting rainwater through pipes or drains, filtration, and storage in tanks for reuse or recharge. The common components of a rainwater harvesting

system involved in these stages are illustrated here.

1. Catchments The catchment of a water harvesting system is the surface which directly receives the rainfall and provides water to the system. It can be a paved area like a terrace or courtyard of a building, or an unpaved area like a lawn or open ground. A roof made of reinforced cement concrete (RCC), galvanised iron or corrugated sheets can also be used for water harvesting.

2. COARSE MESH At the roof to prevent the passage of debris.

3. GUTTERS Channels all around the edge of a sloping roof to collect and transport rainwater to the storage tank. Gutters can be semi-circular or rectangular and could be made using: * Locally available material such as plain galvanised iron sheet (20 to 22 gauge), folded to required shapes. * Semi-circular gutters of PVC material can be readily prepared by cutting those pipes into two equal semi-circular channels. * Bamboo or betel trunks cut vertically in half. The size of the gutter should be according to the flow during the highest intensity rain. It is advisable to make them 10 to 15 per cent oversize.

Gutters need to be supported so they do not sag or fall off when loaded with water. The way in which gutters are fixed depends on the construction of the house; it is possible to fix iron or timber brackets into the walls, but for houses having wider eaves, some method of attachment to the rafters is necessary.

4. Conduits Conduits are pipelines or drains that carry rainwater from the catchment or rooftop area to the harvesting system. Conduits can be of any material like polyvinyl chloride (PVC) or galvanized iron (GI), materials that are commonly available.

5. First-Flushing A first flush device is a valve that ensures that runoff from the first spell of rain is flushed out and does not enter the system. This needs to be done since the first spell of rain carries a relatively larger amount of pollutants from the air and catchment surface

6. FILTER The filter is used to remove suspended pollutants from rainwater collected over roof. A filter unit is a chamber filled with filtering media such as fibre, coarse sand and gravel layers to remove debris and dirt from water before it enters the storage tank or recharge structure. Charcoal can be added for additional filtration

* Charcoal water filter A simple charcoal filter can be made in a drum or an earthen pot. The filter is made of gravel, sand and charcoal, all of which are easily available.

* Sand filters Sand filters have commonly available sand as filter media. Sand filters are easy and inexpensive to construct. These filters can be employed for treatment of water to effectively remove turbidity (suspended particles like silt and clay), colour and microorganismsCalculation of Required Storage SizeWhen using rainwater, it is important to recognize that the rainfall is not constant throughout the year; therefore, planning the storage system with an adequate capacity is required for the constant use of rain water even during dry periods. Knowledge of the rainfall quantity and seasonality, the area of the catchment surface and volume of the storage tank, and quantity and period of use required for water supply purposes iscritical. For example, in Tokyo, the average annual rainfall is about 1,400 mm. Assuming that the effective catchment area of a house is equal to the horizontal line of its roof surface area, and given that that the roof surface area is 50 m2, the average annual volume of rainwater falling on the roof may be calculated as 70 m3.However, in practice, this volume can never be achieved since a portion of the rainwater evaporates from the

roof surface and a portion may be lost to the drainage system, including the first flush. Furthermore, a portion of collected rainwater volume may be lost as overflow from the storage container if the storage tank has insufficient capacity to store the entire collected volume even in a heavy rain. Thus, the net usable or available amount of rainwater from the roof surface would be approximately 70% to 80% of the gross volume of rainfall. In the above example, the actual usable amount of rainwater would be about 49 m3 to 56m3 in a year.

Disadvantages

The disadvantages of the rainwater harvesting and utilisation systems are:• The catchment area and storage capacity of a system are relatively small. Thereis a great variation in weather. During a prolonged drought, the storage tankmay dry up.• Maintenance of rainwater harvesting systems, and the quality of collected water,can be difficult for users.• Extensive development of rainwater harvesting systems may reduce the incomeof public water systems.• Rainwater harvesting systems are often not part of the building code and lackclear guidelines for users/developers to follow.• Rainwater utilisation has not been recognized as an alternative of water supply

system by the public sector. Governments typically do not include rainwaterutilisation in their water management policies, and citizens do not demandrainwater utilisation in their communities.• Rainwater storage tanks may be a hazard to children who play around it.• Rainwater storage tanks may take up valuable space.• Some development costs of larger rainwater catchment system may be too highif the costs are not shared with other systems as part of a multi‐purpose network

case studyThe Dhule town Dhulia (Dhule) latitude 21o10' and longitude 75o20' is the chief town of the district as the headquarter, lying 57 km. north of Chalisgaon on the Bombay-Nagpur route of the central railway, with which it is connected by a broad gauge line. It is well connected by road network and is located at the crossings of NH-3, NH-6 and NH-211. It is situated on the southern bank of the Panzara River on the outer side of the bend of the river near the extremity of the easterly course just before it turns northwards to join the river Tapi. The town and its suburbs, covering an area of nearly 26.68 km2 are well shaded by avenues of fine trees. The town area is developing in all directions. Many villages around

the town have developed and constitute the peri-urban characteristics and are deprived of basic amenities such as water supply and drainage.BermudaThe island of Bermuda is located 917 km east of the North American coast. The island is 30 km long, with a width ranging from 1.5 to 3 km. The total area is 53.1 km2. The elevation of most of the land mass is less than 30 m above sea level, rising to a maximum of less than 100 m. The average annual rainfall is 1,470 mm .A unique feature of Bermuda roofs is the wedge-shaped limestone “glides” which have been laid to form sloping gutters, diverting rainwater into vertical leaders and then into storage tanks. Most systems use rainwater storage tanks under buildings with electric pumps to supply piped indoor water. Storage tanks havereinforced concrete floors and roofs, and the walls are constructed of mortar-filled concrete blocks with an interior mortar application approximately 1.5 cm thick. Rainwater utilisation systems in Bermuda a reregulated by a Public Health Act which requires that catchments be whitewashed by white latex paint; the paint must be free from metals that might leach into water supplies. Owners must also keep catchment tanks, gutters, pipes, vents, and screens in good repair. Roofs are commonly repainted every two to three years and storage tanks must be cleaned at least once every six years.

Island of Hawaii, USA

At the U.S. National Volcano Park, on the Island of Hawaii ,rainwater utilisation systems have been built to supply water for1,000 workers and residents of the park and 10,000 visitors per day. The Park’s rainwater utilisation system includes the rooftopof a building with an area of 0.4 hectares, a ground catchment area of more than two hectares, storage tanks with two reinforced concrete water tanks with 3,800 m3 capacity each, and 18redwood water tanks with 95 m3 capacity each. Several smaller buildings have their own rainwater utilisation systems as well. A water treatment and pumping plant was built to provide users with good quality water.

Acid RainIntroduction : Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals and infrastructure. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which react with thewater molecules in the atmosphere to produce acids. Some Governments have made efforts since the 1970s to reduce the release of sulfur dioxide and nitrogen oxide into the

atmosphere with positive results. Nitrogen oxides can also be produced naturally by lightning strikes, and sulfur dioxide is produced by volcanic eruptions. The chemicals in acid rain can cause paint to peel, corrosion of steel structures such as bridges, and weathering of stone buildings and statues.The Effects of Acid Rain on Ecosystems : Effects of Acid Rain on Fish and WildlifeThe ecological effects of acid rain are most clearly seen in aquatic environments, such as streams, lakes, and marshes where it can be harmful to fish and other wildlife. As it flows through the soil, acidic rain water can leach aluminum from soil clay particles and then flow into streams and lakes. The more acid that is introduced to the ecosystem, the more aluminum is released.Some types of plants and animals are able to tolerate acidic waters and moderate amounts of aluminum. Others, however, are acid-sensitive and will be lost as the pH declines. Generally, the young of most species are more sensitive to environmental conditions than adults. At pH 5, most fish eggs cannot hatch. At lower pH levels, some adult fish die. Some acidic lakes have no fish. Even if a species of fish or animal can tolerate moderately acidic water, the animals or plants it eats might not. For example, frogs have a critical pH around 4, but the mayflies they eat are more sensitive and may not survive pH below 5.5.

Effects of Acid Rain on Plants and TreesDead or dying trees are a common sight in areas effected by acid rain. Acid rain leaches aluminum from the soil.  That aluminum may be harmful to plants as well as animals. Acid rain also removes minerals and nutrients from the soil that trees need to grow. At high elevations, acidic fog and clouds might strip nutrients from trees’ foliage, leaving them with brown or dead leaves and needles. The trees are then less able to absorb sunlight, which makes them weak and less able to withstand freezing temperatures.VisibilityThe sulphuric acid produced from the emissions of SO2 reacts with alkaline compounds in the air to form fine particles of ammonium sulphate and calcium sulphate, among others. These particles produce haze, especially at high levels of humidity. This effect is particularly evident in the relatively clean air areas of the western states. In many of the National Park areas the sulphate creates 50 to 60percent of the degradation in visibility. In the East it is closer to 70 percent, and the total haze is much greater. It is difficult to quantify the effect overshot periods because of the many factors including humidity and carbonaceous and soil particles that contribute to the phenomenon. Nevertheless, historical studies on a regional basis suggest that decreased visibility is related to increased sulphate particle

concentration in both the western and eastern United States.Future Change in EffectsIf acidic deposition were to increase, all effects would, of course, be increased. Experimental data and calibrated models allow us to estimate the degree of enhancement where the effects at ambient levels of acid deposition have been quantified, such as with lakes. Since the public and the political leadership are committed to reducing air pollution, acid rain will not be allowed to increase. In fact, the proposed legislation would require a substantial decrease in SO2 emissions. The only issues beingdebated are the rate and extent of the reduction. Therefore, it is not useful to analyze the effects of increased emissions. In the short term over the next several decades a worst-case scenario might assume that present levels of emission and acidic deposition wouldcontinue unchanged. If so, the situation described above with regard to human health, the rate of building materials' damage, the decline of high elevation red spruce trees, crops, visibility, and the percent of lake area made inhospitable to fish would not change. In the very long term, sustained acid rain at present levels might cause the leaching of sensitive soils to the extent that tree nutrition could be affected and some additional lakes and streams would become too acid to sustain healthy fish populations.

Effects on other receptors would remain unchanged. If the emissions of SO2 were abruptly cut in half, as proposed by some legislation, acidic deposition would be decreased by only about 30 percent since the relationship is not linear. Such a decrease would presumably be beneficial to all receptors, but in the cases where no significant negative effects have been demonstrated crops, forests, building materials, and human health we cannot quantify any improvement. Visibility would improve over thelong term, but since only a fraction of the interference is due to sulphate aerosols, the improvement would be proportionally less than the 30 percent reduction in acid formation. In the glaciated and other areas where the lake and stream chemistry is essentially in equilibrium with the acidity of the rain, a new equilibrium would be reached in less than a decade. Some of the most affected surface waters would recover to fishable status, but less than 30 percent of the lake areas would do so.

Prevention of Acid Rain : One side of prevention is government

environmental regulations, to limit the quantity of emissions released into the atmosphere. To follow these regulations, industries can add “scrubbers” to their smoke stacks to reduce the amount of sulphur released. Another option is washing the coal before it is burned, which reduces the amount of sulphur in the coal. To reduce the amount of car exhaust pollution,

catalytic converters can be used in vehicles to make the exhaust less harmless.

On a more personal level, there are many things you can do to help prevent acid rain. Try to use your car as little as possible: walk, use public transportation, and carpool. Turn the heat down in your house, and don’t use air conditioning (these things require more gas burning). Conserve water by running a washing machine or dishwasher only with a full load. And remember to turn off lights, and use energy efficient lightbulbs! By following these tips, you will reduce the emissions of fossil fuels by using less energy. If we all pitch in and do our part, we can improve our quality of life and the beautiful earth on which we live.

Chemical Equations Related to Acid Rain:Pure water is neutral and has a pH of 7.Natural rain water is slightly acidic mainly because of dissolved CO2 which produces carbonic acid or H2CO3

H2O(l) + CO2(g) <==> H2CO3(aq)The pH of unpolluted rainwater ranges from pH 5 to 6.Acid rain is rain water with a pH of less than 5. In some parts of the Northern Hemisphere the pH of the rain water has been as low as 2!Acid rain is caused by industrial pollutants.The main

industrial gases responsible are SO2 and NOx (a mixture of NO and NO2).Major sources   of industrial sulfur dioxide. SO2(g) comes from mining smelters and the burning of coal.i) The roasting of minerals releases SO2(g) fromMetal sulfide + oxygen ----> Metal oxide + SO2(g)ii) Electrical power stations that burn coal produce sulfur dioxide from the sulfur impurities in the coal.S(s) + O2(g) ----> SO2(g)The SO2(g) combines with water to produce sulfurous acid.H2O(l) + SO2(g) ----> H2SO3(g)Note: Sulfur dioxide is not readily oxidized to sulfur trioxide in dry clean air. Water droplets and dust particles however, catalyze the reaction between O2 and SO2 in the air producing sulfur trioxide, SO3.This dissolves in water and produces sulfuric acid which is a much stronger acid. This can cause considerable damage to buildings, vegetation and fish populations by destroying fish eggs.SO2(g) + ½O2(g)  ---> SO3(g)H2O(l) + SO3(g) ---> H2SO4(aq)Source of nitrogen oxidesSources of NOx are more widespread. Nitrogen is a diatomic molecule and is fairly inert because its

triple bond. However, at temperatures over 1300°C, nitrogen combines with oxygen to form nitrogen monoxide.   N2(g) + O2(g)  --> 2NO(g) These high temperatures can be achieved byi) the internal combustion engine (human activity)ii) lightning in the atmosphere (natural source) The nitrogen monoxide slowly combines with oxygen to form soluble nitrogen dioxide gas.  2NO(g) + O2(g) --> 2NO2(g)Nitrogen dioxide readily dissolves in water producing a mixture of nitric and nitrous acids. 2NO2(g) + H2O(l) --> HNO3(aq) + HNO2(g) Acidic rain is mainly caused by atmospheric pollutants of sulfur dioxide and nitrogen oxides.The chemical formula of acidic rain is dependent upon the type of acids present. Acidic rain is a complex mixture of nitrous, nitric, sulfurous and sulfuric acids which all combine to lower the pH.Case Studies : 1.Acid rain in china 2003, acid rain fell on more than 250 cities nationwide and caused direct annual economic losses of 110 billion yuan ($13.3 billion), equal to nearly three per cent of the country’s gross domestic product. The regional acid-rain pollution is still out of control in some southern cities,

especially in the southwestern areas. With the exception of Chongqing, the average pH value of the central districts was lower than 5.0 and the acid rain frequency was 70 per cent. The acid rain in southern China was mainly distributed in the Pearl River delta and central and eastern areas of Guangxi.In Beijing, the government is pouring money into moving polluting industries out of the capital in an effort to clean up the city before the Olympics in 2008.

Causes : Major causes of acid rain are the rapidly growing number of cars on the roads, and the increasing consumption of cheap, abundant coal, as the country struggles to cope with energy shortages and meet power demand. China is the world’s largest source of soot and sulphur dioxide (SO2) emissions from coal, which fires three-quarters of the country’s power plants. More than 21 tonnes of SO2 were discharged in China in 2003, a rise of twelve per cent on the previous year. It is estimated that the country will consume more than 1.8 billion tons of coal in 2005, emitting an additional six million tons of SO2. The growth of nitrates, due to a swift rise of automobile and coal consumption, plus overuse of fertilizers, is playing an increasing role in the country’s acid-rain pollution. In short, China’s explosive economic growth is outpacing environmental protection efforts.

Possible solutionsThe Chinese government has made significant efforts and progress in energy saving and consumption reduction. Energy consumption has gone down year by year over the past two decades. However, China’s environment has been ravaged by two decades of breakneck growth, and by the pressure of feeding and housing a population of 1.3 billion. In industry, the rate of smoke and dust removal from industrial waste gas has been reduced, and the government has taken measures such as the introduction of levying charges for pollution emissions, and issuing licences for discharging air pollutants. It has also promoted the adoption of clean coal, energy conservation and desulphurization technologies to help with the prevention of acid rain. The Chinese government hopes that by 2010 the total amount of discharged pollutants in industrial wastewater and the total amount of industrial waste discharged will be lower than in 1995. This will be achieved by setting quotas for SO2 emissions from thermal power plants and urging them to install desulphurisation facilities. China has already banned the use of coal in the areas most severely affected by SO2 emissions, but sulphur is not the only enemy in the fight against acid rain.2. Acid rain in India Urban air pollution is probably the most well-known problem created by rapid industrialization. Air pollution around major factories, thermal

power plants, open mines and quarries has attracted a lot of attention. Rain over India is much less acidic than most of the other countries in Asia, Europe and North America. However, it has become more and more acidic over the last few decades. The pH of rain in India ranges from 5.9 to 8.4, and the average is about 6.7. India seems to be much better off than the USA (4.15–6.19), Canada (4.23–5.96), Germany (4.05–4.25), Norway (4.10–4.40), and most other countries. However, there are places in India where things are not so good. Parts of south Bihar and West Bengal are likely to be the worst affected, along with the southernmost tip of the Indian peninsula. Occasional rains with a pH of 4.8 have been reported from Chembur in Mumbai and a pH of 4.5 from Delhi. The more worrying trend is the gradual acidification of the rain in India over the last couple of decades – the pH has decreased from 7.0 to 6.1 in Delhi, and from 9.1 to 6.3 in Agra.Causes and impactsThermal power plants in India, which generally use coal with relatively high sulphur content (0.5 per cent to three per cent), are the major source of oxides of sulphur – they release about 2,500 tons per year. Oxides of nitrogen are produced during high-temperature combustion. The greatest source of nitrogen oxides is road vehicles.India has been rather lucky to have predominantly alkaline-rich soils. For example, in the Thar Desert in the northwest of India, the aerosols from coastal areas help reduce the

acidity to a considerable extent. Higher temperatures prevalent in India also contribute towards transforming the oxides of sulphur to sulphates and oxides of nitrogen to nitrates. India also does not have natural sources of sulphur emission like volcanoes. These factors have kept the acid rain in check so far. However, the emissions from the increasing number of power plants, industries, fossil-fuel burning and vehicles have gradually begun to overcome the natural checks. In 1990, none of the ecosystems in India was threatened by acid rain. However, if steps are not taken to control emissions, by the year 2020 about 85 per cent of the ecosystems will be threatened by acid rain.possible solutionIndia’s solutions are similar to that of many other countries: the use of cleaner fuels, a gradual switching to renewable energy and the use of catalytic converters. In addition, a 66–130 million-hectare wasteland should provide enough ground for growing biomass and using renewable sources of energy in a sustainable manner.

ConclusionThe causes and effects of acid rain are now rather well understood. Fortunately, the effects have been limited, and there is no evidence to suggest that they will worsen in the next few decades with present emissions. Coincidentally, during the 1980s technologies for controlling the emissions of the precursors of acid rain have advanced rapidly. When fully implemented, these

will reduce the emissions from coalfired boilers to such low levels that the effect on the environment will be undetectable. The crash effort to reduce emissions in the current bills before Congress is estimated to cost on the order of $100 billion over the next 20 years and will not permanently solve the problem. An alternative policy (RNSPS + 40), which consists of tightening the New Source Performance Standards (to 0.1 pounds of SO2 per million BTU) to take full advantageof the new advanced technologies and setting a reasonable age limit (40 years) beyond which old pre-NSPS boilers must be shut down or controlled, could eliminate the acid rain problem at a net cost that is close to zero. All that is required for this more optimal solution is a moderate amount of wisdom and patience.

A Picture to describe Acid Rain’s Potential :