The semi-permeable membrane used in reverse osmosis contains tiny pores through which water can flow. The small pores of this membrane are restrictive to such organic compounds as salt and other natural minerals, which generally have a larger molecular composition than water.

These pores are also restrictive to bacteria and disease-causing pathogens. Thus, reverse osmosis is incredibly effective at desalinating water and providing mineral-free water for use in photo or print shops. It is also effective at providing pathogen-free water. In areas not receiving municipally treated water or at particular risk of waterborne diseases, reverse osmosis is an ideal process of contaminant removal. Read more

The process of filtration involves the flow of water through a granular bed, of sand or another suitable media, at a low speed. The media retains most solid matter while permitting the water to pass. The process of filtration is usually repeated to ensure adequate removal of unwanted particles in the water (Ramstorp, 2003). This type of slow filtration over a granular bed is generally known as slow sand filtration. It is the oldest method of filtration but still widely used in municipal water treatment plants today.

More modern filtration systems use carbon as the main constituent material of the filter. This carbon is compressed into a solid block form, as opposed to the more loosely structured, granular, sand filters. Such filters often include other media substances, in addition to the compressed, solid carbon. This type of water filter is known as a multimedia filter. These filters clean water through both physical and chemical processes. Read more

Reverse osmosis refers to a process of water purification that has been used primarily for the desalination of seawater. To understand reverse osmosis, it is first necessary to understand osmosis.

Osmosis is the term for the phenomenon whereby if a semi-permeable membrane separates two salt solutions of different concentration, water will migrate from the weaker solution through the membrane to the stronger solution, until the solutions are of the same salt concentration. Reverse osmosis subverts this process. Read more

The current major concerns in regard to water quality are lead and disinfection byproducts (Binnie et al, 2002). Lead is a key operational and treatment concern for municipal water treatment plants. It cannot be considered independently of other water quality and treatment issues.

In fact, it seems that water disinfection and protection from lead infiltration are at odds with each other. The pH level required for disinfection must be below 8.0, but the pH level required to minimize lead solvency in plumbing systems is often 8.0 or higher.

Water treatment plants provide clean, disinfected water to home plumbing systems, but this water is immediately contaminated from lead as it passes through the plumbing system. The solution to this problem may be the removal of lead from plumbing systems, a factor that would completely revolutionize the plumbing industry. Read more

In honor of World Water Day, the Columbia Water Center is releasing a video and two infographics about its work.

In “Deeper than Water”, director Gabe Askew evokes the preciousness of water through a the stunning images of jewels in an unfolding box, suggesting that if we are to truly care for our most valuable resource, we must go beyond digging to find the right crops and planting methods, design more intelligent infrastructure, prioritize ecology and invest in climate science.

India

No place in the world more clearly embodies the most challenging and diverse aspects of the global water crisis than India, the world second most populous nation. The story of water in India is on the one hand a distressing parable about good intentions and unintended consequences of a nation that averted famine by mining its groundwater–and on the other a story of hope, in which cooperation and bold thinking offers real hope for balance resource use and improving livelihoods.

“The Story of Water in India” outlines the food/water/energy crisis in India, and presents different solutions the Columbia Water Center is pursuing in the country. For more information about the Columbia Water Center’s work in India, check out our India project pages. Read more