Going Green in the Land of 10,000 Lakes

Effluent Treatment Plant at Liberty Paper

2015-03-17 - Voith Meri Environmental Solutions, Inc. is helping to set higher standards for wastewater treatment with the addition of the Effluent Treatment Plant at Lib-erty Paper Incorporated in Becker, Minnesota. After more than two years in operation, the effluent treatment plant has proven to be robust and efficient since the start-up and processes an average of 9,700 kg COD per day.

Liberty Paper’s (LPI) need for this facility was sparked by their steady growth and desire to maximize production. When Meri and LPI began negotiations for an effluent treatment plant (ETP), the local water treatment facility had reached its capacity and LPI had out-grown the wastewater infrastructure, which was provided by the municipality. Either the city had to upgrade their operations to treat the increased CBOD load or the burden had to be taken off the city. LPI’s original intent was to execute a turn-key project. Engineering, procurement and construction would be from one supplier. As they got further into the project development they discovered the potential costsaving through a unique partnership with Meri. LPI started to consider playing the role of general contractor but they needed a partner that would be more than just a vendor. A partner to take a leadership role, therefore removing some of the risk from LPI. They had never approached a Project quite like they approached this one.
Chuck Legatt, LPI Mill Manager
Larry Newell, LPI Vice-President Manufacturing, explains, “I think it was more of a custom-approach to this project, it was more of a risk for us, more of a risk for Meri as well, and the outcome was very good. The outcome was one that I would replicate again. I think it was a very good way to approach a project." Tom Murphy, ETP Manager at LPI, agrees, “We like things managed as a one-stop-shop. We don’t want five companies with their hands in it – we want to be able to go directly to one company – Meri. No matter what the problem was, Meri was always willing to deal with it.” Chuck Legatt, LPI Mill Manager, preferred the low-risk approach, “We’re a single mill operation. We needed to build up a pretty high level of confidence in the Meri team that they could deliver to the expectations of the Mill. We’re a unique compa-ny, somewhat risk adverse. We would have been the first effluent treatment plant of its kind installed in the United States by the Meri Group.”
Meri’s Advanced Anaerobic Effluent Treatment Technology at a Glance An-aerobic processes are used for the treatment of highly loaded effluents. Anaerobic bacteria in the form of biopellets are used for the conversion of dissolved COD in to methane (biogas). In the paper industry anaerobic technology is mainly used in board and packaging mills.
Advantages of Anaerobic Effluent Treatment Technology Anaerobic treatment of waste water has found a perfect application in industrial waste water treatment, especially in applications with high COD concentrations. Compared with aerobic treatment, the main advantages of anaerobic treatment could be summarized as: reduced footprint, lower energy consumption and minimum sludge production.
Reduced Footprint Among the different anaerobic reactor technologies available, the R2S Reactor achieves volumetric loads as high as 25 kg COD/m3/day. One other important consideration is the fact that the R2S is up to 30 m in height, which significantly reduces the footprint required for effluent treatment plants.
Lower Energy Consumption Aerobic treatment requires oxygen to oxidize the organic compounds. This oxygen is introduced into the system by means of blowers and other devices that have a high-energy consumption. A system designed to treat 10,000 kg COD/day, for example, would require 15 MWh per day. On the other hand, each kilogram of COD treated in an anaerobic system yields 2.4 kWh – a difference of 39 MWh per day!
Minimum Sludge Production Aerobic treatment yields a large amount of biological sludge that needs to be removed from the system and dewatered or stabilized in order to optimize sludge disposal costs. Depending on the system, up to 60% of the converted COD will be converted to new sludge. This number contrasts with the average sludge growth observed in anaerobic systems of 2% to 5%.
The Current Situation in the United States Paper mills in general, including OCC mills like LPI, require large amounts of water and therefore require a large waste water facility to cope with the high COD and calcium levels typically found in this application. The state-of-the-art R2S Reactor design allows for continuous and effi-cient removal of calcified biomass. The COD discharge of LPI is 9,700 kg per day. The ETP system that Meri designed utilizes a cooling stage followed by a pre-acidification tank and the R2S Anaerobic Reactor. The process continues with a CO2 stripping reactor, which facilitates hydrogen sulfide conversion for odor reduc-tion and calcium carbonate precipitation. The last step is a LIME TRAP® for calcium carbonate and solids removal as well as a centrifuge decanter for sludge thickening.//