Articles & Case Studies

New Screen and Grit System solves tricky balancing act for Baldwin

Posted: Monday 20th September 2021

One would think that with a population of just 1,200 people, wastewater treatment in Baldwin, Michigan, would be pretty straightforward…

But for this village, it’s been a yo-yo of a journey for the past two decades, with treatment required for 75,000 gallons of sewage per day, right up to 200,000 gallons per day – and back down again – and at various levels in between. For any treatment plant operator, this has presented quite a challenge – and even now, it looks like flow could go back all the way down again to 75,000 gallons.

Rural Baldwin attracts plenty of visitors for its world-class trout fishing and canoeing (with the Pere Marquette River protected by The Wild and Scenic Rivers Act) - but the big differentials in population have been because of the North Lake Correctional Facility, which at capacity, has had 1600 inmates and up to 400 staff. Under the new Biden administration, it is expected to close – again – but time will tell.

In the late 1990’s the village of Baldwin brought in Grand Rapids-based Fishbeck (long-established engineers, architects, scientists and constructors) to design the original 75,000 gallons per day Sequencing Batch Reactor (SBR) plant, but as Jim Truxton, President of the Village of Baldwin, explains, construction was well underway when everything had to change with the building of North Lake Correctional Facility.

“At the time”, he said, “it was a unique opportunity for the state of Michigan to house the facility, and we couldn’t be blind to the fact that there would be significant Federal Government grants towards upscaling our wastewater treatment plant as a solid investment for the future of Baldwin”.

‘Took in waste from septage trucks’

He added: “Over the years, I doubt anyone could have foreseen the on/off, open/closed saga, but then, opinions and policies can change when new administrations are elected. During a long period of closure for North Lake – for around seven and half years - our treatment plant was running at only 30% capacity, so to generate some much-needed income, we took in waste from septage trucks. In this part of Michigan, there are a very large number of septage tanks, so we knew there was a strong demand”.

Waste from these septage vehicles went into a primary pump station – and was pumped via a nearly three-mile-long force main, which travels underneath both an abandoned railroad and wetlands area, prior to discharging at the wastewater treatment plant.

In early 2018, Fishbeck completed the design and bidding for an $8M expansion of the Wastewater Treatment Plant (including the upgrading of the primary pump station) – proceeding with building as construction managers.

“Prior to this”, continued Jim Truxton, “there just wasn’t enough flow to move the grit, so it accumulated in the force main”.

For the new headworks, Fishbeck and the Village of Baldwin chose a Raptor Micro Strainer Screen (with a ¼-inch diameter perforated plate screenings basket) and a SpiraGrit Vortex Grit System – both made by Lakeside Equipment Corporation of Bartlett, Illinois.

Dave Conklin, Senior Engineer at Fishbeck, said: “We help Baldwin with water supply, wastewater treatment, including regulatory requirements, planning and grant applications. We have previously specified Lakeside’s headworks equipment, based on its competitive pricing and performance. We have also had excellent experience with the manufacturer’s representative, Dubois Cooper of Plymouth, who are very knowledgeable and responsive. Both businesses were highly involved in the start-up of equipment – and any troubleshooting that was needed. They also organized good quality training, kept us up to date and provided meaningful warranties”.

The real fun began at Baldwin in March 2019 when as part of the upgrade, new, larger pumps were installed to help move the legacy of grit, which was estimated to be occupying around two thirds of the force main.

For Infrastructure Alternatives of Rockford, who professionally manage 130 wastewater treatment plants, Division Director, John Barthels, said: “Getting all this accumulated grit out of the line resulted in a huge amount of material for the Lakeside equipment to deal with – probably around six to ten times the normal amount. We knew from other treatment plants that Lakeside performs very well, but this was a big test. It certainly demonstrated its robustness”.

He added: “Historically, infrastructure in the US has been underfunded, so as operators we have to squeeze as much out of it as we can. With Lakeside though, which is high-end quality – and by working with equally trustworthy companies such as Dubois Cooper – and Fishbeck, we know that this is very long-lasting equipment”.

Over a wide range of daily flow rates, Lakeside’s SpiraGrit Vortex Grit System captures grit particles in the flat-floor circular upper grit chamber. Rotating paddles maintain the flow velocity inside the grit chamber, with grit removed from the storage hopper by a self-priming pump to a Raptor Dry Grit Washer. Organics are separated from the grit particles via the introduction of upwardly directed wash water and a grit stirrer assembly. The removed organics are automatically recycled back to the process. After removal of the organic material, the clean grit is removed via a grit dewatering screw and discharged into a dumpster.

In the headworks channel, Lakeside’s Raptor Micro Strainer Screen captures debris such as plastics, hygienic articles and fibers. A brush on the central screw cleans the screenings basket and conveys solids up to the compaction zone/dewatering chamber. After passing through the compaction zone, the dewatered solids enter a discharge chute which directs the solids into a dumpster at a lower level.

The screen and grit equipment were constructed from Type 316 stainless steel for superior corrosion resistance.

‘An amazing amount of grit’

Jim Truxton, President, Village of Baldwin, added: “There was an amazing amount of grit. For the first six months of the installation, a 10 cubic yard dumpster was filled to the brim - every week. Now that the process has settled down after that initial wave of grit, the whole thing works just fine. All that is required is some periodic cleaning and basic preventative maintenance”.

Lakeside’s Raptor Micro Strainer Screen and SpiraGrit Vortex Grit System are no strangers to large volumes of grit from septic tanks. At Indian River County’s Residuals Dewatering (Biosolids) Facility in Florida, the equipment successfully deals with wastes from commercial, industrial and municipal sources, as well as a huge volume of residential septic tank cleanings.

“One way or another, it’s been quite a journey”, said Jim Truxton. “With or without North Lake Correctional Facility, we now have a very professionally managed wastewater treatment plant with equipment that delivers excellent performance for the long-term. Plus, we have a team of highly skilled and conscientious professionals behind us all the way. With our groundwater discharge and close proximity to such a precious waterway as the Pere Marquette, we rightly have to be very careful with our treatment processes. If somebody pees in the river, the EPA are there before they’ve zipped their fly back up”.

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August 2021

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