Saturday, February 5, 2011

Pervious Concrete

Pervious Concrete

Pervious Concrete has a greater void content in contrast to regular concrete which is achieved by manipulating the water and cementitious material ratio to essentially produce a void around aggregate particles. The product is a result of little or no sand that enhances the void content upto 25% consequently allowing water to drain through it at a rate of 5 gal/ft²/ min or 200 L/m²/min. Previous Concrete reduces chances of flash floods and is inline with rain water harvesting methodologies as it strives to capture storm water and allow it percolate into the ground thereby boosting groundwater recharge simultaneously easing the demand on storm water runoff control structures

Pervious Concrete areas have proven to be so successful that EPA has recommended use of Pervious Concrete as a Best Management Practice (BMP) for storm water runoffs. Use of Pervious Concrete also minimizes land use for otherwise storm water runoff control structures such as detention or retention basins.

Certain governing bodies mandate first flush (1-inch/25mm) pre-treatment before its subsequent release to the environment. Studies show a considerable pollution reduction (TSS, TP, TN and metals) achieved by natural degradation. To encourage this relatively new find, U.S. Green Building Council’s Leadership in Energy & Environmental Design (LEED) Green Building Rating System (Sustainable Sites Credit 6.1) considers allotting a credit point due to its potential of controlling stormwater runoff and pollution prevention. The lighter color of this concrete has an added advantage of absorbing less heat and storing even smaller portion of it owing to its porous structure.

Although initial costs of installing Pervious Concrete pavements is higher, it proves economical and is widely recognized as the lowest life-cycle cost option available for paving because:

  • · Superior durability and strength
  • · Fewer repairs
  • · Minimizes need of runoff retainers leading to lower property costs
  • · Little overproduction as its made on-site
  • · Can be recycled at the end of its life-cycle.

Sunday, December 12, 2010


Rainwater harvesting is done to:

· Ease the demand on the city’s water supply;

· To relieve the seriously depleting groundwater reserves and allow for their levels to rise; and

· Because it’s the purest form of water available requiring practically little or no treatment.

Some of the simplest design include a open basin with some kind of filtration unit. Over the years, rainwater harvesting has steadily gained importance and its designs have gained wide scale publicity. It’s main components include:

1. Catchment: Surface that receives water supply. A variety of plains may serve as catchment areas ranging from rooftops to paved and unpaved open spaces.

2. Coarse Mesh: A large spacing wire mesh is positioned at the entrance of the opening to filter out debris.

3. Guters: Semi-cylindrical conduits that channel water from sloping rooftops to appropriate piping or storage tanks. A 10-15% factor of safety is recommended with reinforcing to support the weight of water.

4. Pipes/Conduits: To transport collected water from one system to another.

5. First Flush Valve: To divert the first flush of water to drains to prevent contamination from settled dust and particulates.

6. Filteration System: A filter unit is required to remove all floatables and suspended particles. Sand filters are easy and economical to use that consist of a layer of coarse media followed by gravel and then sand. Such filters have an added advantage of disinfection as they target microorganisms.

7. Storage Tanks: Various options are available in the market.

International Trends:

Japan: A simple rainwater harvesting system is in place that collects water from rooftops, utilizes a sedimentation tank to settle heavier particles and then transfers the supernatant solution to a sump; from which water is withdrawn with a handpump.

Thailand: Thai harvest rainwater and store it in large jars. They prefer this to other sources of water particularly due to its superior taste.

Saturday, December 11, 2010

New Human Right!

Right to Clean Water and Sanitation for All

UN declared basic right to clean water and sanitation to all. Here is an excerpt from their homepage.

By a vote of 122 in favour to none against, with 41 abstentions, the General Assembly today adopted, as orally revised, a resolution calling on States and international organizations to provide financial resources, build capacity and transfer technology, particularly to developing countries, in scaling up efforts to provide safe, clean, accessible and affordable drinking water and sanitation for all.

Friday, October 16, 2009

Green Terrace!

They say a Picture is worth a thousand words... here... 3 pictures to inspire everyone to plant more trees!

My own modest attempts... its a start! :)

Tuesday, October 13, 2009

Oxymoron: Killing the “Dead Sea”!

Dead Sea located between Israel & Jordan is 1300 feet below sea level. Its salinity is 10 times that of the Mediterranean Sea making life in the Dead Sea impossible. Only certain bacteria and algae capable of surviving its extreme climate have managed to sustain. Dead Sea’s salinity is caused by the absence of any rivers originating from it. Most rivers only drain to the Dead Sea (feeding it with salt from the surroundings) and the only respite for the collected water is evaporation which concentrates the salt content considerably. However, rising temperatures (accelerating evaporation) aren’t solely responsible for Dead Sea’s declining levels. Water use in the surrounding areas has increased steadily and the outgoing water volume is not compensated enough by the incoming rivers that seem to be narrowing by contamination.

Water from the Dead Sea is useless for human use or industrial purposes directly due to its high salinity. However desalination plants have made Dead Sea waters usable. It is a good source of hydroelectricity. (The falling levels have raised pumping costs! )

Thus the Dead Sea which allowed humans to float on; is shrinking, leaving some treacherous sink hole amidst its receded areas. A controversial solution to this problem is building a canal that linked the red and dead sea. Red Sea is considerably less saline and the water added to the Dead Sea will require treatment to make it more saline! They intend to use the wastes from desalination plants to fill the Dead Sea. Some environmentalists are concerned of the effects of this artificial watering of the Dead Sea and understandably raised their voicea when the neighboring countries wanted to abandon pilot testing of this experiment and proceeding to large scale refilling!

Sunday, July 26, 2009

Cloud Seeding


TOI once again introduced this new technology to me. Seeding was a term that was familiar only when used in context of agriculture and farming. To manipulate the constituents of clouds to enable more precipitation sounded bizarre! Research on this topic revealed that cloud seeding is an old technique that is currently being exacted. Cloud Seeding efforts were initiated by Dr. Vincent J. Schaefer at NY in 1946; when he was attempting to create clouds in a lab experiment. The experiment was carried out in a chilled chamber that was further cooled by dry ice. Dry ice was the accidental catalyst as the ice crystals ultimately provided a nucleus around which droplets of water coalesced that would produce rain.



Static Method/Cold Rain Process:

Presence of clouds is indispensable for producing rainfall. Cloud seeding merely increases the potential of causing greater precipitation. Ice crystals required for ‘Natural Rain’ (ensuing from unseeded cloud), are formed when cold water comes in contact with dust particles in the atmosphere. These ice crystals act as a nucleus that attracts formation of water droplets around it. Water droplets coalescence around these ice crystals and increase in size until they are large enough to detach causing rain!

Cloud seeding is expected to provide substitutes of such ice crystals which ultimately exploits greater proportion of water vapor in the cloud. The seeding effort done using silver iodide (it is similar to ice crystals in structure)is expected to achieve maximum coalescence of water vapor engendering more rainfall.

Warm Rain Process: For cloud formation in tropical climate that do not reach freezing point

In tropical climates, water droplets form around a “hygroscopic particle” such as dust which acts a nucleus around which droplets coalescence until they are large enough to detach and cause rain. Calcium chloride is used as a substitute to attract more water droplets achieve greater precipitation.



1. Seeding is a controversial method because it is a relatively new technology which is still evolving and is therefore not popular among some scientists. Others insist of its credibility and quote that “Absence of evidence is not evidence of absence; sometimes it can just take a long time for clear evidence to accumulate.”


2. Cloud seeding is used in Russia to clear the skies to prevent rainfall on special occasions. The Russians apparently crave for clear weather and hence attempt to “empty” their skies by inducing premature rainfall. They use a mixture of silver iodide, cement and liquid nitrogen to seed their clouds. However, last year, cement dislodged for seeding purposes failed to fragment and fell through the atmosphere to the ground in a solid form destroying private property!


For additional information please refer the SOAR (Seeding Operations & Atmospheric Research ) website that specializes in weather modification services and details atmospheric research technologies.