SOME FAQS ABOUT CITY WATER SUPPLY THAT MUST BE KNOWN

Q. Will our cities become short of water with expansion?

As cities expand a greater pressure is being put on water resources required to meet the needs of urban populations in cities around the world. There is a need to maintain adequate water supply as well as the quality of the water supplied so that the health of urban dwellers does not deteriorate. It must be remembered that water for the most part is not destroyed by use. With proper recycling and management urban dwellers need not suffer water shortage. This point needs to be highlighted before we proceed,

WITH PROPER MANAGEMENT AND RECYCLING OF WATER, URBAN AREAS DO NOT NEED TO SUFFER WATER SHORTAGE OR POOR WATER QUALITY


Q. What is the proper and inexpensive way to recycle water?

There is a proper way to recycle water and an improper way. The proper way mimics the natural processes through which water has been recycled on land for millions of year, which is collecting it in ponds where an initial purification takes place by aerobic and anaerobic bacterial processes. The water then seeps into the ground whereby it gets filtered. The water can then be pumped out and supplied with minimal treatment. Similarly rainwater too can be fed into lakes in and around the city for recharging ground water.

Q. How about just taking water from the ground without building lakes and ponds

The water will then run out sooner or later. The ground water table will go down if it is not recharged. A few lucky areas, especially those close to mountains may have swift underground streams and it may be possible to extract ground water without the water table going down. In that case it is not necessary to build rain fed lakes. However, it is still a good idea to make wastewater lakes and ponds to prevent dirty water from reaching rivers and polluting them.

Q. How about taking the water from rivers or natural lakes for urban supply?

If a city is lucky enough to be near a river it can take water from it but it must not be so much that down stream life is adversely affected. It must be remembered that water from lakes and rivers needs to be treated before supply and the process can be more expensive than just taking pure ground water. In addition many methods of chemical purification of water that are not very expensive have adverse side effects on the environment. For example chemical purification with chlorine can lead to production of very harmful dioxins in the environment.

As regards lakes near cities the water may be much too polluted to supply even after the usual treatment. An example is Nainital town situated at 2000 meters height around a lake in the Himalayas. Even here it is necessary to pump out ground water for urban supply.

There are many cities around the world that do not have a river nearby for water supply. Often water is pumped in from dams and rivers far way. It can be more expensive than simply taking the local ground water, provided of course that the water table could be maintained.

How about Rain Water Harvesting?

UNFORTUNATELY THE TYPE OF RAIN WATER HARVESTING THAT IS OFTEN PROPOSED BY WELL MEANING BUT INADEQUATELY INFORMED ENVIROMNMENTALIST IS VERY HARMFUL. They propose directing rainwater close to the ground water through shafts. This directs surface pollution to the ground water without the benefit of natural filtration through the ground. This is a fast route to polluting ground water and spoiling the underground source for long periods of time.

Should rainwater be wasted then?

NO, as said earlier, it should be directed to lakes and ponds near the city from where it will return into the ground water after natural purification.

Can all the water used by a city be recycled? Doesn’t some get lost?

Yes some is lost through evaporation but it is not a full loss because some returns to the ground as rain. The real loss is when water flows into a river that flows into the sea or very far away from the city. Some water is also converted to biomass such as trees but this is not a loss because trees improve the environment of a city greatly. The benefit outweighs the loss by far.

Can ground water level fall in an area and rise in another?

Yes that happens often. Monitoring stations and pump houses are required around the city to draw water from areas where the ground water level is rising not falling.


Isn’t ground water bad some times?

Yes, in some areas ground water has harmful contents such as too much salt or even very harmful components such as arsenic, fluorides and nitrates.

What can be done in areas where ground water is bad?

When ground water is unfit or harmful for humans in any city or village then it is necessary to have two types of water supply. One purified by expensive methods such as reverse osmosis for drinking and cooking and the rest for washing etc. Nitrates and pesticides in the water can be prevented by an advisory for organic farming in a buffer zone around the city.

Is it possible to ration water such as a supply for limited hours in a city?

Many cities do that, but this is very harmful practice. DURING THE HOURS WHEN THE SUPPLY IS SHUT DOWN, POLLUTED URBAN SEEPAGE ENTERS THE PIPE JOINTS AND MIXES IN GOOD WATER LEADING TO A POOR HEALTH OF THE URBAN DWELLERS. A round the clock twenty four-hour supply prevents that. Occasional shutdowns for maintenance can be managed easily by warning the city dwellers not to use the water for cooking and drinking for a few hours after supply is restored.

How else to manage if water is in short supply?

The easy and natural way to limit water consumption and wastage is to have a differential rate of water use i.e. beyond a certain usage a penal rate of use that is twice or four times can be applied. However, as said at the outset, with proper management water need not be short because water is not destroyed by use. The small loss that takes place through evaporation, chemical conversion etc. is easily made up by rain or water supply from a distant river.

Can Ground water level rise too fast if it is too well managed?

Yes that has happened in some cities. In some cities the water table went up so much that it began to seep into basements. If that happens the best solution is to direct it away from the cities through canals to distant rivers.

DANGERS OF RAIN WATER HARVESTING

Over the last century, human population has grown and along with it there has been a tremendous growth in cities. A direct consequence of this growth is that urban populations in many cities across the world are facing water shortages. Along with sunshine and fresh air, water is a primary requirement for life and any shortage in its supply spells a diminished quality of life.

There are primarily three sources of water available to human populations – rain, surface water such as lakes and rivers and lastly ground water. The source of all three is rain that rises from the abundant oceans on the planet. However with increasing use and population growth, both surface and ground water is not only getting depleted but also getting polluted.

Whenever water shortages occur there is often a cry to conserve water. One basic point is forgotten in this cry – WATER CANNOT BE DETROYED – by most natural processes. It requires chemical and other possesses such as electrolysis to destroy. In most cases water is recycled over and over, therefore cities facing water shortages need to reexamine the recycling processes that are taking place in the city.

A solution that has been proposed in some cities is called Rain Water Harvesting. It is suggested that rainwater should be collected and directed to deep bores inside the ground so that it reaches underground sources. A primary shortcoming of this process has been overlooked. When surface water percolates naturally to underground sources it undergoes purification through natural filtration. If it is directly sent into the ground to the water table or close to it then surface pollution reaches the ground water without the benefit of this purification. The result is that ground water is then polluted and looses its potable quality.

The alternative of directing rain water to shallow covered pits ( of no more than ten feet depth ) is an alternative since then an adequate ground depth may still be available for purification. However such pits , although good for daily domestic waste water are usually not enough to store rain water.

Incase a city desires to increase its ground water supply the alternative of storing rain water in several artificial lakes in and around a city or town is a viable option. In this case the water purifies as it percolates into the ground. It can then be pumped out to augment city supplies with minimal treatment. Further the city waste and sewage water too can be treated in a similar manner by directing it into lagoons designed to purify the water through both aerobic and anaerobic processes. Eventually some of this water percolates into the ground to improve ground water supplies. Such systems exist in several towns around the world. These lakes need to be stocked with fish in order to minimize the menace of mosquitoes. Usually, such lakes need to be aerated otherwise the depletion of oxygen in water causes the fish to die from time to time. Wind Mill driven or solar cell aeration systems are a better option than electricity driven pumps. Solar and wind devices produce intermittent electricity or intermittent mechanical power and that is what is precisely required by lakes for aeration.

Surface storage of water is therefore the proper way to store rainwater whereas the so-called Rainwater Harvesting is the improper way. One need not worry about the loss of surface water through evaporation since that tends to augment precipitation and return to ground again as highly pure water in the form of rain.

Small Community Gas Turbine Power Plants

Small and simple gas turbine power plants to produce electricity for communities isolated from a grid or a community wishing to remain so can be a reliable means of power supply at reasonable rates. Such power plants need to be simple in order to reduce maintenance needs. Research engineers love to play with thermodynamics and will go to any lengths to increase thermal efficiency even if it means that the final constructed plant is complex, expensive and results in frequent maintenance shut downs. For a gas turbine plant this implies using multistage turbines with intermediate heating and several heat exchangers. While the additional complexity may be justified for large gas turbine plants where thermal efficiency has an important bearing on running costs, it is not advisable for small independently managed gas turbine power plants that range from a few kilowatts to a Megawatt capacity.

A gas turbine plant involves a compressor stage coupled to a turbine for expansion. Heating of the working fluid is carried out after compression. The fluid that leaves the turbine after expansion carries a considerable amount of heat and thermodynamic principles suggest its utilization to partially heat the incoming working fluid before compression in a heat exchanger. It is suggested here that atmospheric air be the working fluid for simple gas turbine plants and it be heated in a furnace after compression without the use of any heat exchangers. The surplus heat carried in the exhaust air can be utilized by using it as the air required for combustion in the furnace. A single stage turbine may be utilized to further eliminate the need of reheat and additional heat exchanger and stages.

The heat of combustion can then be generated by burning various materials such as wood, waste, coal if available etc. Biogas if available in the community is best reserved for cooking and heating needs. The power so generated may be augmented by partial use of wind and solar energy. The plant furnace can be enclosed in a hot chamber that can be utilized for various purposes such as a bread oven or brick making plant.

New Ice Age?

The recent cold weather in Northern Europe has made me wonder if a new ice age is around the corner. If it really did come about, I wonder what that would do to the current debate on global warming. Would the world then start pushing for a more rapid increase of Green House Gases?

Personally I worry less about the release of green house gases as compared to the rapidly depleting forest and tree cover on our planet as mentioned in my other posts. I believe that unless mankind begins to work seriously to undo that damage it will be difficult to achieve stable climatic conditions.

Supercritical Steam Power Plants in Iceland

Recently I chanced upon a Scientific American Article that quoted my book on supercritical steam in the article “One Hot Island: Iceland's Renewable Geothermal Power” by Christopher Mims at:
http://www.scientificamerican.com/article.cfm?id=iceland-geothermal-power&page=3
Although I was not quoted accurately, the inference of the author was correct in its conclusion that use of supercritical steam remains one of the available methods of increasing thermal efficiency of steam power plants. Increasing such efficiencies also reduces the amount of green house gases produced per unit of power generated. Although the emission of greenhouse gases is not an issue when using geothermal energy, the use of supercritical steam will nevertheless allow the maximum utilisation of geothermal energy.I am delighted that Christopher Mims has found this book useful towards making use of Iceland’s geothermal reserves in an efficient manner.

Time for New Posts

I realise that I have been neglecting this blog while I concentrated on another blog of mine. I hope to return to it soon with new energy related posts. In the meantime some visitors have found that this blog has useful references to many thermal and renewable energy resources. Therefore I shall continue to retain them in future too.

Carbon dioxide is not the cause of global warming

It seems that the burning of fossil fuels that produce carbon dioxide is often incorrectly blamed in the media for global warming. Carbon dioxide accounts for just 0.0383% of the atmosphere. The amount is too minuscule to have any significant effect on global warming. In fact water vapor is a stronger greenhouse component of the atmosphere. In fact the percentage of carbon dioxide in the atmosphere has fallen to suffocatingly dangerous levels for plants. They need it for photosynthesis and are a source of food for animals and humans. Greenhouse owners who raise carbon dioxide content about three times find that plants grow fifty percent faster.

Scientists have concluded that human activity over the last century has probably contributed to global warming. If so, then the probable cause is deforestation and not the production of carbon dioxide through burning of fossil fuels.