At the Wastewater Treatment Plant (WWTP) in Snohomish, Washington, just north of Seattle, nothing has really visibly changed with the Lakeside Screw Pumps that were installed in 1995—apart from the color.

Two 72-inch screw pumps and one 42-inch screw pump from Lakeside Equipment Corporation are now red (from their original blue), simply to match the plant’s color scheme, and more than three decades are on, with the help of new lower sealed bearings, are still happily working away. The paint job came about after seventeen years of service in 2012 when the highly robust screw pumps were treated to a sandblast and clean up. The thirty-years-plus of service is testament not only to Lakeside as the manufacturer, but to the diligent team of three at the City of Snohomish Wastewater Treatment Plant for their maintenance regime, especially in light of increasingly changing and challenging weather conditions.

Serving a population of 10,000, the plant has, in recent years, had to endure more and more instances of flooding that effectively leave the facility on an ‘island’. Heavy rain that melts the winter snow on the nearby Cascade mountain range sends excessive volumes of water rushing into the river that the facility discharges to. The Snohomish River can also be adversely affected by tides from the Salish Sea as well.

PROBLEMS WITH THAWING SNOW

Duane Leach, senior wastewater treatment plant operator for the city of Snohomish, says, “We get plenty of rain here anyway, but warmer winters and a spring that seems to be arriving earlier and earlier, causes the problems we face with the thawing snow.

“We’re gradually separating the flows in our pipe network, of which about half still contains a mix of sewage and stormwater. With 50 percent of that stormwater now going directly to our old lagoon, we’re under slightly less pressure, but during many eventful challenges that the plant has faced, the Lakeside screw pumps have always been a constant, working away, especially the 42-inch unit, which is in use 24/7. Depending on flows, our SCADA system and our PLCs (programmable logic controllers) will make one or both of the 72-inch screw pumps kick in, but the 42-inch runs all the time.”

Leach, who has been at Snohomish WWTP since 2013 and working in sewer department prior for the city since 2007, adds, “Once per month we grease the upper bearings. Once a year we grease everything. We clean the headworks and the screw pumps once per week to make sure that there’s no buildup of odors. We use a fire hose to spray down all the built up of FOG (fats, oils, grease) along with the dreaded flushable, oh wait, not to be flushed wipes, while any gravel or rocks are carefully removed. During that weekly clean, we simultaneously run all three screw pumps to again check that everything is running smoothly.

“We changed out a motor quite some time ago, along with the upper gear box has been refurbished, and when we took them out for sandblasting in 2012, we switched to sealed bearings. So long as we routinely maintain the screw pumps, they work great. We love them—and their reliability is perfect with only three of us on site.”

Every day without fail, Leach and one his colleagues dutifully walk around the entire plant, with eyes, ears and noses wide open.

“It’d be much easier to go round in the truck,” says Leach, “but on foot we can see and hear everything.”

Leach is usually joined on the daily inspection round by Frank Schorsch (maintenance worker/operator), who has worked at the plant since 2007, or sometimes by Karen Allen (lab technician/operator), who joined in 2004. The team’s long-standing service continuity allows a vast amount of experience and knowledge to be called upon.

POPULAR FOR RECREATION AND SALMON FISHING

Despite being open (uncovered) screw pumps, the city of Snohomish WWTP lives in harmony with its neighbors, free from noise and odor complaints. In fact, there is a popular walking trail for residents and visitors around the plant, which prior to its construction, was basically a 25-acre settling pond.

“Our Snohomish River is very popular for recreation and salmon fishing, so we are very proud of our work to protect it,” added Leach.

In 1996, stringent new total maximum daily loads (TMDL) immediately challenged the plant to handle its ammonia levels, but the installation of a submerged fixed film solved the problem. Since then, the WWTP has won multiple ecology awards for its good practices, including its most recent accolade: The Lakeside Equipment Corporation Plant of the Year.

“This was totally unexpected,” continues Leach. “A real honor. You have to be spot-on with your site maintenance to be considered.”

Lakeside’s long-standing wastewater equipment representative for the region, Goble Sampson, also sang the praises of the city of Snohomish WWTP. Based at numerous locations across the Western United States, Goble Sampson’s Joshua West, who works in the company’s Washington office, comments, “We’re always here to provide back up to the city, whose treatment plant team set a fantastic example that the whole industry should be very proud of. Duane, Frank, Karen, and the city of Snohomish thoroughly deserve the award for their dedication in maintaining such a well-run wastewater treatment plant.”

Lakeside Equipment Corporation (established 1928) is blessed with a large number of plants, that decades on, are still in incredible working order. It is only right that hard working treatment plant operators, who are largely unsung heroes, get the recognition that they deserve.

Goble Sampson made very strong recommendations about the city of Snohomish, and after very careful consideration, when comparing other sites with strong track records, we felt that this exemplary WWTP was a worthy winner. Knowing that our screw pumps are still going strong after more than thirty years fills us with enormous pride.

The future looks bright in Snohomish. It is the only plant in the whole of Washington state to use peracetic acid (PAA) instead of chlorine; a move that has helped keep it in firm compliance.

And with the planned conversion of the rest of the city’s pipe network to full separate sewage and stormwater, an increase in the plant’s capacity can help bring about opportunities for population growth and investment.

Dan Widdel is president of Lakeside Equipment Corporation. Lakeside Equipment Corporation is an engineering and manufacturing company concentrating on helping to improve the quality of our water resources. Lakeside started in the spring of 1928 to engineer, develop, and provide water purification systems to municipalities and companies throughout North America. For more information, visit www.lakeside-equipment.com.

Precise monitoring of viscosity during the melting process is crucial for quality assurance in quartz glass production. In this project, a Sensor Technology TorqSense torque transducer (SGR541) was used to enable real-time conclusions to be drawn about material homogeneity, purity and the progress of material bonding.

In modern glass technology, precise control of melting conditions is of fundamental importance: the viscosity of a melt in particular has a decisive influence on its further processing, quality, and homogeneity. In the laboratory, viscosities are often determined using rotational viscometers: a spindle is rotated at a constant speed in the sample, the required torque is measured and the viscous resistance—that is, the viscosity—is determined.

THE ROLE OF VISCOSITY

In our customer’s project, this concerns the melting of quartz glass. Viscosity is not only a measure of fluidity but also allows conclusions to be drawn about the internal state of the melt—for example, cavities (air bubbles) or incomplete material bonding.

Focusing on precision glass components to improve the manufacturing process for quartz glass in terms of quality and process reliability. The challenge was that the glass is first melted at high temperatures and then has to reach a defined viscosity zone for further processing. Only in this range can it be guaranteed that the melt is homogeneous (no air bubbles), the connection or fusion of different material batches has taken place completely, the transition to the shaping or quenching/pre-forming process starts reliably.

The objective was to reliably monitor the viscosity of the quartz glass melt in order to detect deviations in the melting process at an early stage and to establish process-reliable feedback for control and quality assurance.

The viscosity of molten glass plays a key role in processing, as it determines the flowability and thus the moulding behavior, bubble removal, degassing, and homogenization. In the case of quartz glass, the conditions are particularly demanding with: high temperatures and viscosities having a strong influence on the viscosity curve. 

TORQSENSE PROVIDES ACCURACY

The TorqSense SGR541 was chosen because of its great robustness against extreme process conditions (temperatures, thermal shocks, possible vibrations) in the melting range of quartz glass with separate sensor unit and electronics. Calibration was performed using reference samples or model melts in order to map the torque/viscosity relationship in detail in the specific process setup.

The sensor was integrated into the process—typically between the motor/agitator (or melt mixing system) and the impeller (or melt stirrer)—and connected to the process control system in real time. Since torque transducers can be sensitive to lateral forces, double bearings should be used to avoid transverse forces.

The relevant target values for viscosity were defined together with the customer: e.g., a range from X to Y at temperature T, at which the melt is considered homogeneous and no bubbles are mobile.

Reference curves were created using laboratory or pilot melts with known compositions and viscosity values. This allowed the sensor output to be mapped to absolute or relative viscosity.

The sensor continuously provided torque data from which the viscosity was derived. Trend analysis enabled early detection of deviations—for example, if the viscosity did not fall within the target range, which could indicate trapped bubbles or incomplete mixing of the material batches.

As soon as the measured viscosity deviated from the target curve, measures were taken immediately: adjustment of the temperature, extension of the stirring time, addition of degassing (refining), or even return of the batch for reprocessing.

POSITIVE RESULTS

The introduction of monitoring using SGR541 had the following positive effects:

• The melt could be continuously monitored for homogeneity and freedom from bubbles. Deviations were detected early and corrected.
• The data obtained (torque/viscosity curves) provided valuable insights into the behavior of the quartz glass melt, enabling future process optimizations.

This method is also used successfully in other applications—e.g., plaster mixtures, coal slurries, and liquids containing magnetic particles—where conventional viscometers fail and viscosity monitoring is required. In industries such as cosmetics and pharmaceuticals—e.g., in the manufacture of shampoos or medical solutions—it is also important to monitor viscosity during mixing. This allows you to determine when the process is complete and the desired consistency has been achieved.

Sensor Technology Ltd. has been manufacturing quality torque measurement solutions and wireless load sensors for over forty years, with the growth of TorqSense sales and the launch of LoadSense and HeliNav encouraging rapid expansion and investment. For more information, visit www.sensors.co.uk.