Energy from Sewage – Renewable energy to be tapped to make environment green:

Energy from Sewage – Renewable energy to be tapped to make environment green:

Sewage treatment, that is, the physical, chemical and biological processes used to clean industrial and domestic wastewater, has improved significantly over the past 20 years. However, the energy requirement to treat sewage to the highest standard has been quite large. Further tightening of water quality standards, especially in developed nations; suggest energy costs will increase substantially in future. We will discuss here about possibility of renewable energy generation from sewage, to offset the extra energy requirement for sewage treatment and also to use surplus energy for domestic purpose. In fact, the actual energy used will depend on the quality of sewage and intensity of treatment required.

A. Typically, there are three stages of treatment:

(a) Primary - Solids are physically settled out.

(b) Secondary - Bacteria convert organic matter to a carbon-rich sludge.

(c) Tertiary - Further treatment may be used to remove more organic matter and/or disinfect the water.

The effluent is generally discharged to fresh, ground or coastal water. Sludge is applied to agricultural land, incinerated, used for land reclamation or used for other purposes, such as composting or landfill etc.

B. In order to increase energy efficiency of water treatment and reuse of treated water few points have been discussed. By implementing these measures energy savings and efficiency of about 40% may be achieved:

(a) Choosing low-energy treatment options, if possible. However, local constraints may limit choice.

(b) Replacing machine parts, such as pumps and motors, with more efficient versions.

(c) Optimizing processes using sensor technology. For example, pumping can be adjusted according to flow.

(d) Reusing water. “Greywater” from bathing, laundry and washing dishes can be reused to flush WCs. This may provide savings of around a third of daily household water demand.

C. Energy generation - There are mature, widely-practiced technologies for generating fuels from sewage treatment. Moreover, research has identified future methods for exploiting sewage as an energy resource as well.

1. Current Technologies for Energy Production -

(a) Sludge Incineration - Most of the sewage sludge produced at sewage treatment plant is applied to agricultural land as a soil conditioner, reducing the need for fertilizer. Sludge may also be incinerated, with the option of energy recovery. However, to incinerate sludge, it must be dry enough to burn with no extra energy input other than that needed to fire up the incinerator. It therefore needs dewatering, using energy intensive processes such as centrifugation or thermal dehydration. Centrifugation requires less energy but surplus heat from incineration that can be used for thermal dehydration. There has been strong opposition from some sections of the public over incineration of wastes due to fears about impacts on human health. At present, reuse of sludge via application to land is generally considered a more acceptable option.

(b) Biogas - Biogas production from sewage sludge treatment, via a process called anaerobic digestion, is already a well established means of generating energy in many developed countries. Bacteria used to organic matter in sludge to produce a mixture of methane (CH4 of 60 – 65%), carbon dioxide (CO2 of 35 – 40%) and trace gases. Impurities, such as hydrogen sulfide and water, are removed and the resulting biogas is then commonly used in boilers or combined heat and power systems. Biogas may also be used for other applications, such as vehicle fuel, if CO2 is also removed. Anaerobic digestion also reduces the solids content of sludge by up to 30%, reducing the energy costs involved in its transport.

2. Future Technologies for Energy Production - There are several novel technologies that produce energy or fuel as a by-product of sewage treatment, although further work is needed to improve performance, reliability and cost-effectiveness.

(a) Conversion of sludge to oil and gas - Under carefully controlled conditions and extreme temperatures (450 – 1000 degree Celsius), sludge may undergo chemical reactions to produce fuels that may be used for energy production. Processes include gasification, which produces syngas (similar to natural gas), and pyrolysis, which produces bio-oil (similar to diesel oil). There is interest in these as potential alternatives to incineration of sludge. However, operational costs are high, particularly those of maintaining high temperatures, and conditions must be carefully controlled to prevent formation of harmful by-products, such as hydrogen cyanide.

(b) Biomass Crops - In some of the European countries, sewage sludge is applied as fertilizer to willow plantations. The trees are periodically coppiced and the wood used for fuel. Research into applying partially-treated, liquid sewage to biomass crops is also underway. Passage of the sewage through the soil acts as a final polishing step for treatment, degrading organic matter, reducing nitrogen and phosphorus and producing a cleaner effluent. Little energy is required and capital and operational costs are low. However, it is not yet known how efficient this system will be at removing pollution and there must be appropriate land available.

(c) Hydrogen from Sewage - There is much interest in hydrogen as a fuel, because it can be produced from a wide range of materials and provides power with minimal air pollution. Bacteria use organic matter to produce hydrogen by fermentation. However, applications for hydrogen, such as fuel cells, are not yet in widespread use.

(d) Microbial Fuel Cells - These devices offer the possibility of simultaneous sewage treatment and energy production, with water, CO2 and inorganic residue as by-products. Bacteria use organic matter to produce electricity. To date, only lab-scale microbial fuel cells have been developed in some of the developed countries that are able to power small devices.

D. Discussion on energy conservation and renewable energy in relation to sewage treatment system –

(a) Energy conservation is possible through the twin practices of efficient water use by consumers and efficient energy use by the water industry.

(b) There are well-established renewable energy options, such as biogas, and novel technologies, such as gasification, for sewage treatment. Many need further investment and research.

(c) Economic and water quality considerations are key drivers for the water industry. Integration of energy related objectives into the existing regulatory framework will be necessary.

World Environment Day:

World Environment Day:

United Nations General Assembly in1972 established the World Environment Day (WED). On the same day United Nations Environment Programme (UNEP) was created too. Today World Environment Day is celebrated world over in many ways. World Environment Day (WED) is not just another day but a special day about you and me. Green concerts, essay and poster competitions, rallies, tree planting, recycling efforts, clean-up campaigns etc. are some of the ways people, organisations and the governments express their concern towards the environment. WED is also used to enhance political attention and action. Pledges are made and actions are taken, which lead to the establishment of permanent governmental structures dealing with environmental management and economic planning. WED is hosted every year by a different city and commemorated with an international exposition through the week of June 5.

The United Nations Environment Programme (UNEP) has announced the 2008 World Environment Day events will be held in New Zealand. New Zealand is one of the first countries to pledge a carbon-neutral future, demonstrating their readiness to find solutions to Climate Change impacts.

The focus of the global 2008 celebrations will be on the solutions and the opportunities for countries, companies and communities to de-carbonize their economies and changing habits of present life-styles towards low carbon economy for achieving cleaner environment.

We should not think that, investment in environment-friendly technologies is a burden. On the other hand, it is our moral, social, and legal obligation we must fulfill. Moreover, it makes good business sense in the medium and long term. Wherever possible - and it is possible in many cases - we should also implement low cost green technologies that are appropriate to our needs and conditions.

MOST IMPORTANT MESSAGES IN THIS YEAR’S WED ARE -

* WE MUST REDUCE OUR CONSUMPTION OF NON-RENEWABLE RESOURCES.

* WE MUST REDUCE THE GREENHOUSE GASES WE RELEASE.

* WASTE REDUCTION, REUSE, AND RECYCLING ALLOW US TO USE FEWER RAW MATERIALS, CONSERVE NATURAL RESOURCES, PRESERVING LANDFILL SPACE AND MINIMIZING ENERGY USE.

* GROW GREEN, GROW MORE TREES

May our Surround Always Remain … Healthy and Euphoric … May All the Trees … Bloom and flourish … Sending good wishes… For World Environment day – 5th June 2008 From: Partha Das Sharma http://www.environmentengineering.blogspot.com

Reduce Reuse Recycle – Effective way to go green economically – Conservation of Energy:

Reduce Reuse Recycle – Effective way to go green economically – Conservation of Energy:

Ways to reduce, reuse, and recycle, whatever possible, is to save money and reduce waste dumped in landfill and other form of pollution.The key to reducing the amount of waste which is dumped and to reduce pollution is to:
REDUCE - make less waste in the first place.
REUSE - reuse items where possible, or find alternative uses for them.
RECYCLE - recycle as much as possible so the materials can be used to make something new. Recycle also helps in reducing or saving our precious natural resources.

The concept of Reduce Reuse Recycle is applicable to any sphere of life – whether it is in home front or in industries such as energy and power. Energy efficiency, as a concept, became a part of the public discussion now and it is increasingly related with green and eco-friendly environment. The phenomenal ‘oil price hike’ made the industrial world look for alternative fuels and supply sources and ways to conserve them. The concept of Reduce Reuse Recycle again has become very important for power and energy industry.

Simultaneously more efficient use and more productivity became an in thing even in countries where petrol guzzlers had a right of way on the motor- way, in a manner of speaking. Energy conservation has since become a global concern. This has as much to do with sustainable development as with the availability of newer technologies. Hence the call for learning the three new R’s - Reduce, Reuse, Recycle.

There are as yet few takers for the concept of energy saving in most of the urban centers. Some thing as basic as switching off a light or a fan, not to speak of an air conditioner, when no body is around, is a simple drill most offices and establishments refuse to put into practice. What is necessary is a willingness to conserve energy and to go green. Thing needed most is awareness that neither a law nor a government regulation offer anything more than a road map.

In fact, energy conservation is an important element of energy policy. Energy conservation reduces the energy consumption and energy demand per capita, and thus offsets the growth in energy supply needed to keep up with population growth. This reduces the rise in energy costs, and can reduce the need for new power plants, and energy imports. The reduced energy demand can provide more flexibility in choosing the most preferred methods of energy production.

Energy conservation is important because of the limited amount of nonrenewable energy sources on Earth, it is important to conserve our current supply or to use renewable sources so that our natural resources will be available for future generations. Energy conservation is also important because consumption of nonrenewable sources impacts the environment. Specifically, our use of fossil fuels contributes to air and water pollution. For example, carbon dioxide is produced when oil, coal, and gas combust in power stations, heating systems, and car engines. Carbon dioxide in the atmosphere acts as a transparent blanket that contributes to the global warming of the earth, or "greenhouse effect." It is possible that this warming trend could significantly alter our weather. Possible impacts include a threat to human health, environmental impacts such as rising sea levels that can damage coastal areas, and major changes in vegetation growth patterns that could cause some plant and animal species to become extinct.

As discussed, by conserving energy we lower the amount of pollutants we release into the air and thereby help to keep the air clean. By reducing emissions, energy conservation is an important part of lessening climate change, thus helping us to go towards greener environment. The interaction between the natural resources and the population has to be maintained at a balance in order to ensure the continuity of the human race. Energy is essential to life and its conservation has become an absolute necessity.

Energy conservation has been recognized as a priority for a very long time in almost every nation, but concrete steps have not been taken seriously and the few that have been taken lack in perspective and determination. The growth and demand for energy is increasing at a very fast rate, specially in the industrial sector, the transport sector and the house hold sector, thereby putting a great deal of pressure on the available resources. The need of the hour has now become conservation and preservation. At the same time awareness among people has also to be created to fulfill the above goal.