Sewage system overflows present a messy situation for everyone involved. There's E.coli levels to monitor, equipment to repair, and finally, heavy EPA fines to pay. A municipality may be charged $27,000 for every day untreated wastewater seeps into public waters.
Events, like the fire that shut down the North Harlem Wastewater Treatment Plant and caused millions of gallons of raw sewage to flow into the Hudson and Harlem Rivers, can't be prevented. However, having the right rig of pumps and sensors coupled with diligent maintenance can prevent mechanical failures, polluted waters, and penalties.
Accidents, increased water flow into sewer lines, and equipment breakdowns can cause sewage system overflows, or SSO's. When water is flushed down toilets or spilled down drains of residential and business properties, the liquid travels downhill through underground pipes to a treatment plant strategically placed at the bottom of the slope. The plant's location allows gravity to do most of the work. Once dirty water reaches the plant, it's filtered and chemically treated with decontaminants like chlorine and ultraviolet light to kill harmful organisms before it's released into a body of water or reused.
When topography is level, lift stations pump water to a higher elevation to generate enough potential energy to bring it to a treatment plant. At its most basic level, a lift station consists of a sensor, a switch, a reservoir and a pump. Sensors monitor changing water levels and decide when to trigger a switch that turns the pump on or off.
"One pump failing can be catastrophic," APG representative Doug Moore said. "When lift stations have multiple pumps, there's a back up in case one fails."
APG, Automated Products Group, sells sensors utilized by lift stations in wastewater treatment plants. There are many sensor solutions on the market, ranging from simple float switches to sophisticated ultrasonic sensors. Each level sensor is suited for a particular environment and setup. For example, if a lift station only has one pump, a float switch is a reliable, cost-effective option that's durable and keeps employees away from hazardous material. A float switch is a weighted sensor dangling from a cable in a tank like a baited fishing line in a pool. As water level rises, the sensor begins to float and the angle between the sensor and cable changes. When a critical angle is reached, the pump is turned off.
However, servicing a large metropolitan area with a one-pump lift station is not sustainable and so additional pumps and water level sensors are needed. Employing multiple float switches in a more powerful lift station means more cables swimming in moving water that could lead to entanglement, sensor failure, and SSO's. One way to avoid the mess while keeping the extra horsepower is to use a float switch such as APG's TK that measures at multiple water levels, discounting the need for extra switches.
Investing in continuous level sensors may also insulate a municipality from EPA censoring. While they're more expensive that a float switch, sensors such as an ultrasonic sensors or submersible pressure sensors allow for continuous level measurement and a variable speed drive, prolonging a pump's life. On the contrary, float switches can signal a pump to turn on or off once a specific water level is reached which means a pump is either 100% off or 100% on. Variable speed drives allow a pump's energy output to match the work that needs to be done.
Taking the time to research the correct setup for a wastewater treatment can prevent system failures such as the one experience by the city of Dubuque, IA. The city agreed to pay a $205,000 civil penalty fine, spend $3 million on improvements to its wastewater treatment plant over the next three years, and $260,000 on an extra credit environmental project when it was found to be in violation of the Clean Air and Water Act. Over 165 miles of sewer pipes, three major pump stations, and eight lift stations comprises the city's water treatment system that services 92,000 residents along the Mississippi River. Approximately 39 SSO's and 687 violations regarding solids and chemicals discharged into protected waters occurred during 2002 and 2007.
Maintenance and improvement costs are minimal compared to staggering fines owed to state and federal governments when treatment plants are found to be noncompliant or fail completely. An advanced float switch like that from APG costs $100 and can last five to ten years. But it's not really about the money. By 2050, the United Nations estimates that two billion people living in 48 countries will lack sufficient water. In the year 2050, the same two billion will make up 21% of the earth's projected human population.
Resalin Rago Water Level Sensors - APG is a top dealer of water level sensors, selling high quality products and related technology, which includes ultrasonic sensors and cable suspended float sensors.
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