Overcoming Onsite Reuse Woes

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Courtesy of Orival, Inc.

The buzz words “water reuse” are very pervasive in today’s culture.  Everyday we receive newspapers, e-newsletters and conference announcements that speak of drought, water shortages, global warming, discharge prohibitions and conservation.  The wastewater treatment plant at one Midwest municipality has proactively demonstrated its determination to do its conservation duty by reusing up to 2000 gpm of effluent for various on-site applications.  That is 2.88 million gallons of water per day not being taken from drinking water resources.

Located along the banks of one of the largest tributaries to the Mississippi River, this 100 MGD (million gallons per day) wastewater treatment plant has a large demand for service water with low suspended solids.  This water is needed for automatic cleaning devices on the primary bar screens located at the point raw wastewater enters the treatment process (head-works).  (What marvelous devices these automatic cleaning mechanisms are.  This author has manually cleaned his share of bar screens with a garden rake and a bucket.  It doesn’t get much nastier.)  Someone is flushing, showering, washing clothes, doing dishes or gargling twenty-four hours a day.  Therefore, the bar screen cleaning mechanism never rests.  At the other end of the treatment plant are belt presses used to dewater sludge. 

These presses need a steady supply of spray water to keep the belts clean and porous.  Pumps of various horsepower, configuration and brand are scattered over the entire facility.  Many of these have seals that must be drenched in water throughout their duty cycle.  This water must be absent of any particulates that could cause scaring or erosion of shafts and seals.  Service water at hose bibs and equipment wash stations need not utilize valuable potable water.  And last and somewhat unique to this facility is the need for water to cool three large V-12 internal combustion engines that run off of methane gas generated in the anaerobic sludge digesters.  These engines in-turn drive large generators to produce much of the electrical power needed to run the wastewater treatment facility.

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