Guest Post: Fresh Water Through Hydraulic Jump

This guest post from Jim Duer covers something we all need to aware of – clean water. He discusses a very important, low-cost method for cleaning water, the hydraulic jump. In case you haven’t heard of the hydraulic jump, here’s the Wikipedia description:

“A hydraulic jump is a phenomenon in the science of hydraulics which is frequently observed in open channel flow such as rivers and spillways. When liquid at high velocity discharges into a zone of lower velocity, a rather abrupt rise occurs in the liquid surface. The rapidly flowing liquid is abruptly slowed and increases in height, converting some of the flow’s initial kinetic energy into an increase in potential energy, with some energy irreversibly lost through turbulence to heat. In an open channel flow, this manifests as the fast flow rapidly slowing and piling up on top of itself similar to how a shockwave forms.”

Thanks for posting this story, Jim. May it encourage more people to continue the quest for clean water.

Fresh water is a natural resource that is becoming less and less abundant. Only three percent of all the water in the world is clean enough to drink. The cycle of nature’s water replenishment system has been interrupted by urban development. The ground is now covered by impervious streets and buildings, which do not allow rainwater to leech into the aquifer below.  In some parts of the country the natural aquifers have been irreparably damaged due to over use without replenishment.  The use of water is becoming more and more restricted every day.  The recycling of water as part of the green movement is gaining popularity in the United States.

What is happening with most rainwater is not good.  It is either being sent out to sea or combined with sanitary sewers. The most troubling is the latter.  There are nearly 800 communities serving 40 million people with combined sanitary and storm water systems. Clean rainwater is being diverted to sewage treatment plants in this case. It is then mixed with sewer sludge and becomes the treatment plant’s problem.  More energy and chemical use is the result of the two mixing, which costs the plant or the taxpayer money.  If the capacity is reached then the overflow is pumped directly into the nearest waterway.  Our rivers are accepting millions of gallons of raw sewage every time a significant rain happens.

Now is the time for people as well as communities to find ways to reduce water use, reuse grey water, and recycle water wherever possible.  It will take a massive effort to counter the changes in our topography as well as our mistaken sewer systems. Engineers and inventors are continuously finding ways to conserve, reuse, and reclaim water. There is no time like the present to start looking at what can be done as individuals and communities. Google, the most widely used search engine in the world, tells me there are 165,000 inquiries every month on just the keyword Harvesting Rainwater.  There is a demand for change and this generation must be the change.

Harvesting rainwater is the best solution to the issues we face regarding fresh water. In order to get the most from the water harvested it needs to be filtered as it is collected. Nature teaches us the principle of naturally filtering by what is commonly known as a hydraulic jump. Nearly any creek provides evidence of how a jump filter operates. Water flows over rocks that are rounded by the streaming current. As water flows into a depression a flow vortex occurs that is commonly referred to as a hydraulic jump.  Sediment is caught in the vortex and then is drawn away downstream as the clean water falls into the depression. The rain collection systems that use hydraulic jump filters are 98 percent efficient.

The Hydraulic jump filter is mounted in the top of the cistern.  There are two outlets and one inlet on the filter. If the rain event is not significant enough to create the hydraulic jump, a filter must do the cleaning.  When a major rain event occurs, the filter is cleaned by the vortex rotating over the surface. The clean water falls and fills the cistern as the dirty overflow water carries the sediment and debris away.  Hydraulic Jump filters feature very low maintenance and are easy to install.  The use of a hydraulic jump filter makes harvesting rainwater a more viable solution to the world’s fresh water depletion.

Jim Duer is a homebuilder in West Michigan who has a wife and four amazing children.  He is licensed to build and licensed to pastor in the Wesleyan church, and says his passion is leading young people to good stewardship, faith, and a quality life.

Photo: jball359



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