News from Schwing Bioset

Replacing Failing Filter Press Yields Huge Improvements

 

Schwing Bioset Application Report 22, Seneca Water

Written by Larry Trojak, Trojak Communications

Version also published in WE&T Magazine, October 2016 Issue

 

When the Seneca (S.C.) Water Treatment Plant embarked on a recent expansion project, its overall goals were fairly straightforward: eliminate the use of chlorine in purification, relocate its new chemical treatment process, and upgrade the alum sludge dewatering operation. On that last point, plant officials opted to replace an outdated and difficult to maintain batch filter press with a different technology altogether — a fully-automated screw press — to handle its dewatering needs. In doing so, they not only eliminated an ongoing maintenance headache, they also dramatically improved the efficiency of their dewatering operations as well as their overall residuals management operation.

 

Water for Sale

Built on a hill overlooking Lake Keowee, the Seneca Water Treatment Plant is a 20 million gallon per day (MGD) facility located in Seneca, South Carolina, that serves more than 39,000 residents in and around Oconee County in the far northwestern part of the state. According to Steve Fletcher, the lake is owned by Duke Power Company, which allows the City to draw raw water for municipal purposes.

“As part of the agreement with Duke Power, we take in and treat the lake water, then, once purified, wholesale it to area communities,” he said. “That 20 MGD number is our peak permitted flow — our actual volumes vary, but are generally in the seven to 10 MGD range.”

Storage facilities for the treated and purified water currently consist of three ground storage clear wells and eight elevated tanks with a total capacity of 6.5 million gallons.

Seneca Water Screw Press

 

Risk Management

Until this latest expansion, water disinfection was done using chlorination which, while effective, was seen as a serious potential hazard, said Fletcher.

“When this plant was first built in 1968, there was literally one house in the immediate area,” he said. “However, the lake’s popularity has attracted large-scale development — both residential and commercial — and today the area immediately around the water plant is dense with some very nice homes. Should one of our three one-ton cylinders of chlorine gas have ruptured, it could have seriously affected people for a mile around the plant. We didn’t want to risk that any longer and decided that generating our own sodium hypochlorite was a much safer alternative.”

In addition to the change in chemical process, the expansion also resulted in a brand new operations building which houses not only the offices and administrative staff for the plant, but also includes a new laboratory facility and a common area that will be made available to city residents for meetings and other functions.

“This project really grew as we went along, as did the price tag which went from $3 million to $10 million.” Said Fletcher. “But we knew that, as long as we were making changes, we might as well make all the improvements we’ve talked about wanting for a long time.  Right now this is one of the most functional — and beautiful — water treatment plants around.”

 

Residuals Shortcomings             

Treatment of alum sludge at Seneca Water, the by-product of using aluminum sulfate as a coagulant, has a storied history. When the plant was originally built in 1968 there was no treatment effort at all; sludge was simply returned to the lake. The advent of clean water regulations changed all that and Seneca Water was soon recovering and disposing of its sludge in an area landfill. To dewater the material, Fletcher said the plant officials in about 1990 opted for use of a plate and frame filter press.

“Once installed, that press remained in place up to the recent upgrade and eventually became one of the main motivations behind a re-tooling of the sludge process,” he said. “I’m sure that, in its day, it was a solid performer. In recent years, however, it had become such a headache to maintain that it was a full-time job just keeping it operational. In addition, it ran as a batch process which meant it had to stop after every batch of dewatered sludge it created. We knew there were better solutions available out there and we started looking at them.”

It’s worth noting that the overall configuration of the alum sludge plant was sorely lacking as well. At the time, sludge was collected in the backwash holding basin, sent to a vertical turbine transfer pump, then routed up to a thickener.

“Unfortunately, that thickener was on the top of a hill on the other side of the plant,” said Fletcher. “Hardly the most efficient layout. Once thickened, sludge came back down the hill into a diaphragm pump and into the filter press. The transfer pumps were not only costly to run and almost always in need of rebuilding, they weren’t really designed to pump sludge so they were continually stopping up. All those things collectively got us thinking about ways to improve the overall biosolids process — starting with the press.”

 

Trials and Errors

After a fairly lengthy process of demos and trials, Seneca Water, working through their consulting engineer, chose a screw press from Schwing Bioset, Inc. Fletcher said the unit best met established criteria which were focused on cost versus performance.

“We looked at a number of manufacturers and a number of different technologies and knew that the Schwing Bioset unit would best meet our needs,” he said. “Our old press was taking in sludge with 4% to 5% solids and dewatering it to about 24% solids, so we were hoping for at least that. However, many of the presses we tested were giving us product in the 16% to 17% range — we definitely didn’t need a step backward. The team from Schwing Bioset brought their demo unit online and almost immediately we were getting dewatered sludge in the 28% to 32% range. Equally important, however, was the fact that the screw press was fully-automated rather than a batch-process design. That meant we no longer needed to have a man assigned to the press six hours a day, every day, as we’d done in the past.”

With Seneca Water committed to the Schwing Bioset screw press, additional changes were made to the alum sludge processing line, including the addition of a Model 300 large bubble mixer from Pulsed Hydraulics, Inc. (Oroville, Wash.).

“In the past, we’d had problems with the sludge settling and stagnating in some of the lower parts of the holding basin,” said Tommy Clayton, a Class A operator at the Seneca plant. “This PHi bubble mixer keeps the sludge moving and further increases production through the Schwing Bioset screw press. It has very low energy demands, has no other moving parts and runs off a compressor which we need for the press as well. The two are a perfect fit.”

Seneca Dewawtering Screw Press

 

Pressing Issues

The increase in production with the screw press in place was immediate and substantial. Because of the batch nature of the former plate and frame press, Seneca Water was forced to process sludge continuously all year long. According to Fletcher, that has changed with the addition of the Schwing Bioset unit.

“Now, with the continuous dewatering process we can have material being collected in the basins and, when ready, can get caught up in just two to three weeks. There really is no comparison between the two presses, but it’s safe to say that we can probably do close to two tons of alum sludge a day with the Bioset press while the old press took two days to do just a ton.”

Those old production figures were affected by both the cleaning process and by maintenance-related downtime. The plate and frame press, said Fletcher, had to be washed down after every batch — a process that could take as long as three hours. By comparison, the Bioset screw press has a self-cleaning function in which the screen gets sprayed — while the unit is in operation — cleaning it off.

“That means continuous production and no lost time, which is huge” said Fletcher. “We are saving no less than six hours a day in manpower alone just by nature of not having to have a man on the filter press handling the batch process, cleaning it and so on. However, without a doubt, we are benefiting most by finally having a press that is reliable — we are no longer having to constantly work to keep that unit operational. We simply start up the Schwing Bioset unit and it runs all day long.”

 

Working Together 

Once dewatered, Seneca’s sludge is collected and sent to an area wastewater treatment plant where it is mixed with that facility’s dewatered biosolids and trucked to a landfill in a collaborative city/county effort.

“There are so many facets of our operation that have been improved with this latest expansion,” said Fletcher. “We are much more efficient now, our process is better and far more reliable, and the risk of danger from chemical exposure has been eliminated. That’s a very nice turnaround for us and a benefit to the Seneca community as a whole. We couldn’t be happier with the way things turned out.”

 

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Tags: Water Plants, Screw Press, Dewatering, Water Treatment

Pressing Issues (for Water Treatment Plant)

 

Published in WaterWorld Magazine, February 2016. Written by Larry Trojak.

When a new plant that Davidson Water Inc. (Lexington, N.C.) had recently inaugurated started producing levels of solids almost double what it had anticipated, the company worried that all its advance planning was for naught and the dewatering facet of the process was doomed. However, one of the key components in that effort, a new screw press, met the challenge, giving plant operators the results - and the peace of mind - they needed.

To view this story in its entirety on WaterWorld Magazine's website, click here.

 

To learn more about Schwing Bioset and our screw presses, click here. 

 

Tags: Water Treatment, Screw Press, Dewatering, Ferric Sludge

We Dewater Water Plants Too - Part Two Alum Sludge

 

Written by Tom Welch, October 26, 2015

Seneca Light & Water, serving the region of Oconee County in South Carolina, operates a 20 million gallons per day (MGD) Water Treatment facility that uses the 18,500-acre Lake Keowee as its source.  The original plant started in March of 1969 as a 4 MGD facility and has advanced to the current rating with several upgrades.

The Seneca water plant uses aluminum sulfate as a coagulant to lower the turbidity of the water.  After a series of processes, the waste aluminum sulfate is dewatered so that as little water as possible is hauled away with the solids.  Historically, a plate and frame press had been used.  Although that equipment provided a reasonably dry product, about 24% solids, the equipment was only able to run in batch processes, was labor intensive, and was not a clean process to work with.

In 2012, Seneca began a search to identify new dewatering techniques that could replace the aging plate and frame presses.  Several pilot studies were completed, and Schwing Bioset was invited to run their screw press pilot in May of 2013.  The pilot proved successful with a result of 27% solids, which was better than the performance of the existing plate and frame press, as well as the other screw press that had been tested.  The Schwing Bioset equipment was chosen as the best value and the new FSP 0403 screw press was designed into the new dewatering building that was commissioned in September of 2015.

The dewatered alum sludge is hauled to the nearby wastewater treatment plant and mixed with the dewatered Biosolids and then hauled jointly to the landfill.  Now in normal production, the FSP 0403 screw press is producing 30% solids on average with a high of 34%, which is even better than the pilot results.  This is all being done with a polymer dose of 5 pounds of active polymer per ton, which has proven to be very cost effective thus far.

Seneca Light & Water has met their goal of replacing their aged plate and frame technology with a very energy efficient screw press that allows continuous processing. 

The new facility in Seneca, South Carolina, is Schwing Bioset’s second successful water plant startup in the Carolinas this year.

To read Part 1 of this blog, which discusses the screw press installation at a water plant using ferric, go here.

To learn more about our dewatering capabilities or this project specifically, contact this blog’s author, Tom Welch, and/or visit our website here: SBI Screw Presses. For other inquiries, call 715.247.3433, visit our website, or follow us on social media.

 

Schwing Bioset FSP 503 Screw Press Dewatered Alum Sludge

 

Tags: Water Treatment, Screw Press, Dewatering, Water Plants

We Dewater Water Plants Too – Part One Ferric Sludge

 

Written by Tom Welch, July 7, 2015

Although primarily thought of as a technology for dewatering in wastewater plants, Schwing Bioset’s screw press has also been successfully applied in water plants.  We recently completed an installation of a screw press at the Davidson Water (ferric sludge) water treatment plant. 

Take a look at part one of a two part article on the successful application of Schwing Bioset’s screw press technology on ferric and alum sludge generated by water treatment plants.

Davidson Water, Inc. is located in Lexington, North Carolina, and is a large membership cooperative with a plant capacity of 35 million gallons per day.  Upon successful pilot trials, Davidson Water selected the Schwing Bioset FSP 602 machine for dewatering its full scale operations.  They are now running at about 85% throughput and obtaining 27-30% solids, with greater than 95% capture rate and less than 20 pounds of active polymer per ton.  Recent operating conditions have achieved dry solids contents as high as 38%!

Davidson Water’s current operations are surpassing the performance demonstrated during on-site pilot trials that were completed almost two years ago and are exceeding their expectations.  Take a look at the photos below of the Davidson Water installation, which show the simple set-up and exceptional performance. 

Stay tuned for Part Two of 'We Dewater Water Plants Too' on dewatering the alum sludge for a water treatment plant in South Carolina.

To see video of the Screw Press in action or learn more about it, contact a Schwing Bioset Regional Sales Manager, call 715.247.3433, email marketing@schwingbioset.com, and/or visit our website here: SBI Screw Presses.

 

Davidson_Water_1 Davidson_Water_2 Davidson_Water_3

Tags: Water Treatment, Screw Press, Dewatering, Ferric Sludge, Water Plants

Pedaling for Water

This year at WEFTEC®, the Water Environment Federation’s Annual Technical Exhibition and Conference, Schwing Bioset’s Josh and Adam DiValentino pedaled amongst the crowd in the 5th Annual Bicycle Ride to support Water For People.

The 2012 WEFTEC charity bike ride raises awareness and funds to support Water For People, a charity that helps people in developing countries improve quality of life by supporting the development of locally sustainable drinking water resource, sanitation facilities and hygiene education programs.

Adam announced, “It was a good time for a great cause. I’m proud to say we kept up for 23miles, which is impressive on the bikes we rode.”

peddling for clean water

Tags: WEFTEC, Water Treatment