Screen & Clean
MacIntosh Services is one of the largest commercial linen rental supply companies in the scenic Lehigh Valley area of northeastern Pennsylvania. From its headquarters there, the company supplies table linens, cloth napkins, uniforms, chef’s apparel, aprons and towels to restaurants, hotels and other facilities throughout Pennsylvania and New Jersey.
In order to process this large volume of laundry, the company uses more than 90,000 gal of clean water per day. In fact, it is the largest single user of municipal water in the Bethlehem, Pa., metropolitan area.
Recycling Reduces Water Consumption
In the course of its operations, MacIntosh Services generates up to 75,000 gal of wastewater per day. “We try to recycle and reuse at least 40% of the wastewater we generate,” said Gary Shaffer, chief engineer.
In 1996, the company installed a 48-in.-diameter Vibroscreen circular vibratory screener from Kason Corp. with an 80-mesh screen to remove most of the larger solid waste particles before treating the wastewater using standard aeration and flocculation procedures.
“The residue from the screener contains all sorts of solid waste, including not only lint, but also food particles, corks and even gloves,” Shaffer said.
The circular vibratory screener separates bulk solid materials from solids and slurries using multiplane, inertial vibration that causes particles to pass through apertures in the screen while oversized particles travel across the screen surface in controlled pathways to the screen periphery, where they are discharged. The in-line model installed here features one imbalanced-weight, continually operating gyratory motor mounted directly beneath the screening chamber.
Internal Hollow Rings Prevent Screen Blinding
A Kleen-Screen rings anti-blinding device prevents fibrous, stringy and sticky materials from blinding the screen. The multiplane inertial vibration of the screener causes the rings to move continuously across a perforated stainless steel plate, shearing fibers and scraping away gummy materials. Because they are hollow, the rings promote product flow over the entire screen surface, maximizing screening efficiency.
Untreated wastewater enters the first compartment of a two-compartment wastewater pit and is metered into the Kason screener. The screened water discharges into a 1,250-gal storage tank from which the water is pumped through a four-pass heat reclaimer to preheat incoming city water. The wastewater is pumped to the second compartment of the wastewater pit, to a 5,000-gal storage tank and then to the wastewater pretreatment system.
Recycle Screening Deck Increases Capacity
As the business continued to grow, the volume of wastewater generated began to exceed the capacity of the 48-in.-diameter screener.
“We really needed to go to a 60-in. unit, but the space we had available simply did not permit it,” Shaffer said. “The solution was to add a Kason recycle screening deck on top of the existing screener, increasing its capacity from 100 to 150 gal up to 225 to 250 gal per minute without increasing its diameter.”
Positioned directly above the screening deck, the recycle deck has a screen of identical mesh. The upper screen deck is fed with more material than it can efficiently screen. Material passing through the upper screen deck is directed to the unit’s discharge outlet. The overflow and all oversized solid particles are directed from the upper screen onto the lower screen of the same mesh, where it is screened in normal fashion.
Effluent is treated in an onsite aeration and flocculation facility to remove solid waste, then returned to the city of Bethlehem to be further treated and added to the municipal water supply or reused at MacIntosh Services. Solid waste is removed in the form of sludge, which is dewatered and pressed into cakes.
“We remove 300 to 450 tons of sludge a year,” Shaffer said. “In fact, the water that we treat and return is sometimes even cleaner than the city water we use originally.”
New Technology Streamlines Operations
“Rapid changes in technology continue to affect every aspect of our business,” said Jim Rodgers, Jr., president of Macintosh Services. “We continue to invest our resources in new technologies that will help us streamline our operations, increase our efficiency and improve customer service.”