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The CityForest Corp. tissue mill in Ladysmith, Wis., is located on a wide bend of the Flambeau River. The name symbolizes the company’s method of operation and the philosophy of the owners. The facility produces parent rolls of tissue paper for converting plants using post-consumer and post-industrial reclaimed fiber. In addition to using reclaimed fiber—in itself an environmentally-benign process—the mill takes great pains to be a good neighbor and to minimize the facility’s impact on its natural surroundings.
An example of this commitment was clearly illustrated by recent work to the effluent treatment system and other process flows in the mill as part of a major expansion. Despite a doubling of tissue paper output, and the addition of a deinking operation, the mill is using less raw water than before, and its effluent is little changed. Several other facets of mill operation are also designed to minimize impact on the environment, including land application of the mill’s wastes (sludge). Efforts to work with the local community to handle storm water runoff using mill assets are a further indication of this commitment, and a great pride to the company and its employees, notes David Bailey, environmental manager at the mill.
TISSUE EXPANSION. The majority of recent work on the effluent treatment system of the mill occurred last year in conjunction with an expansion in primary Papermaking capacity. In 1999, a new 36,000 tpy state-of-the art paper machine was added that raised tissue capacity to 48,000 tpy. At the same time, a new 100-tpd deinking plant was added to meet the expanded fiber requirements of the mill as well as handle lower grade feed stock.
Before installation of the deinking plant, the mill used high-grade wastepaper stock. The increased organic load generated by the additional Papermaking capacity, in conjunction with the deinking operation, would have exceeded treatment plant capacity. Thus, a number of changes were made in this area as part of the overall expansion project.
SECONDARY TREATMENT EXPANSION. Before addition of the new machine and fiber plant, the treatment plant had capacity to handle effluent with 3,000 to 4,000 lb/day of biological oxygen demand (BOD). The expansion increased the load of organic materials to the effluent system, and subsequently BOD levels rose to 6,000 to 7,000 lb/day. Therefore, the secondary treatment system was upgraded as part of the expansion.
The project consisted of two major components: adding aerator capacity and increasing retention time in the secondary treatment aeration basin. The addition of three new 40-hp Aqua Aerobics aerators increased aeration capacity from 200 hp to more than 300 hp. In conjunction, it was necessary to increase the capacity of the system in order to increase retention time. Aerator basin capacity increased from 750,000 gallons to 1 million gallons via reconfiguration of the existing system.
Before the expansion the aeration basin was gravity fed, operating so that liquid sought its own level depending on the flow. Thus, at a certain flow, it sought one level, and if flow increased, the level in the basin simply rose. This method of operation was modified by adding an overflow weir box with an adjustable gate to the interior of the basin.
The operational target is now set at 1 million gallons. As part of this, flow through the basin changed —it was actually reversed—to most efficiently utilize existing infrastructure. As noted, the basin was originally gravity fed. A pumping station was added to the primary effluent feed line to accommodate the higher water elevation in the aeration basin. In addition, the plug flow design of the basin was upgraded to operate in a step feed mode by adding two new inlets to distribute flow across three points.
The combination of increased aerator horsepower coupled with increased retention time means the system can now handle up to 7,800 lb/day of BOD. With the modified system, the mill can operate well below permit levels despite the increase in production. The secondary treatment system is capable of operating at 98% BOD removal efficiency. Final effluent typically has total suspended solids (TSS) of less than 10 mg/l and a BOD of less than 10 mg/l.
Minor changes were also made in the primary clarifier area. Before this project there was no separation in the mill between water and solids rejects. Now there are three dissolved air flotation (DAF) units, within the mill. The DAF solids can now be sent directly to the dewatering process, bypassing the primary clarifier. This has increased the efficiency of the primary clarifier by reducing the hydraulic and solids load. The settled material from the primary clarifier is combined with the other solids flows and mixed in the blend tank.
The increased wastewater flow, and associated increase in BOD load, also led to an increase in fiberclay generation. Thus, a new 2.0-m-wide Andritz gravity belt thickener was installed as part of the expansion. The previous system had to handle 20 to 25 tpd at a process flow of up to 200 gpm. The new unit is designed to handle 500 to 600 gpm, and process up to 65 dry tpd. A variable speed drive allows it to match flow requirements. The feed to the press is at 2% solids and exits at about 40% solids.
INNOVATIVE LAND APPLICATION. The mill’s disposal process is also designed to minimize impact on the environment. A portion of the sludge, termed fiber-clay, is used for soil conditioning by local farmers. It is particularly useful in light, sandy soils, where it functions as a conditioner to hold water in the soil.
As part of this innovative land spreading operation, the mill stores fiber-clay on site in a 12,000 yd3 facility for use in the spring and fall. A local contractor handles loading, hauling, and spreading of the material. The mill aids land-spreading use by supplying a spreader to disperse the material. The remainder of the fiber-clay by-product, about 75% of the total generated by the mill, is used by the local municipal landfill as a daily cover.
Five and one half days per week the fiber-clay mix generated by the mill is used as daily cover at the local landfill. One and one-half days per week it goes into storage at the mill for land application. This equates to about 150 yd3/week (or 25%) going to storage for land application.
A soil conditioner acts as a sponge to hold water and other additives such as nutrients close to the plants. An aspect of fiber-clay when used as a soil conditioner is that it has a nitrogen demand, since it has a lot of carbon, and thus competes for nitrogen in the soil. However, the mill makes provisions for fertilizer at the time of application and since the mill adds nutrients at the wastewater treatment plant, which becomes part of the fiber-clay, nitrogen demand is kept in check. The soil condition program is regulated and managed under the mill’s national WPDES permit, implemented and approved through the state Department of Natural Resources.
As part of its commitment to keeping the environment clean, fresh water use has been reduced from 1.5 million gpd to an average of 1.3 million to 1.4 million gpd despite the mills expanded operation. This equates to a decrease in fresh water use from 18,000 gal/ton of paper produced to 12,000 gal/ton.
The company is also proud of its active involvement with the P3 Pollution Prevention Partnership, an effort of the Wisconsin Paper Council. It illustrates the company’s commitment to minimize the effect of its operations, notes Bailey. The program is a voluntary effort to reduce environmental impact.
Another sign of being a good neighbor and of the company’s commitment to the environment according to Bailey is its work with the local community to handle storm water runoff. During a big storm, or during snowmelts, city storm sewers handle a large and sudden increase in load. To minimize the impact of this water discharge on the Flambeau River, the mill is currently working towards an agreement with the city on a project to use company land as a holding pond. When the project is completed, storm water would flow into this pond and then gradually dissipate by filtering through the sandy pond naturally.
CityForest takes great strides to be an employee friendly workplace. Some of the staff were formerly employed at the mill prior to its purchase in 1993. Its 85 employees work on a team concept. Staff, from the mill manager on down, strive to have a good work environment, with benefits and pay designed to have all em-ployees act like owners. A four-person staff provides en-vironmental related support to the mill including the operation of the effluent plant and environmental lab.
The staff’s commitment to quality has been a key to the mill’s success, according to mill manager Cliff Bienert. The quality of the mill’s products was enhanced by the addition of the new machine as well as work on the No. 1 machine, where a new winder and headbox were added in 1997. The addition of the deinking plant allows the mill to use a variety of furnishes, and has improved the cost structure of the mill by allowing use of lower grade stocks, Bienert notes.
One interesting facet is that the mill has been chosen as one of five recycled fiber facilities to participate in the Environmental Protection Agency’s (EPA) secondary fiber mill study. This is designed as a data gathering effort to determine whether or not there is a need for any regulatory changes for recycled fiber mills.
| A look at CityForest Corp. |
| CityForest Corp. acquired the former Pope & Talbot (P&T) mill in 1993 and re-opened it in September of that year. The name is a reference to its use of recovered fiber from surrounding towns and cities as its fiber source. Before its acquisition, the mill – located on the site since 1902 – had been idle since 1992 when P&T consolidated its Midwest tissue operations into its Eau Claire, Wis., facility.
CityForest, a private company based in Ladysmith, Wis., was formed by its current CEO Wayne Gullstad. The company acquired the mill with the initial goal of building a deinking facility to sell pulp. However, the strategy changed owing to poor market conditions for deinked market pulp.
In 1999, a new No. 4 paper machine was added. The 104-in.-wide Voith Sulzer Crescent former has a 15-ft. Yankee dryer and a design speed of 6,000 fpm. A new 100-tpd deinked pulp line was added as part of the expansion. The mill primarily uses sorted office waste, including coated book grades. Coinciding with the startup of the new machine, the No. 2 and No. 3 paper machines were shutdown in 1999. One of the original machines, the 148-in.-trim No. 1 paper machine continues to operate.
The mill produces 8.5- to 24-lb dry crepe tissue parent rolls, with the large majority consisting of 100% recycled fiber. A minor amount of product is made using either market pulp or high grade feed stocks. Parent rolls are shipped mainly to U.S. converters, but the mill also has customers in Canada, Mexico, and Panama. The finished products are mainly for away-from-home markets and include bath tissue, household towels, napkins and center-pull towels such as those used in restrooms.
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