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Papermills- Some benchmarks and typical problems found in this industry
The pulp and paper industry uses 84% of the energy consumed by the forest
products industry. Some average benchmarks include: Solid Waste generation-
.01-.26 tons per ton of product (TPT), Landfill cost-$10-20 million, Knots-
reuse them or waste, wood yard waste - .02-.06 TPT, Sludge from a de-inking Water consumption is huge at a papermill. Currently, paper mills are consuming water in the range of ~150-300 m3/ton for pulp manufacturing and ~50-95 m3/ton for paper manufacturing against water consumption of ~40-70 m3/ton and ~10-40 m3/ton for pulp and paper respectively, at modern paper mill in developed countries. The major portion of fresh water consumption is due to various washing stages of unbleached and bleached pulp which, may not need fresh water. This is why many mills are converting into a closed mill type of process. Unfortunately, if the wastewater is not clean enough, problems can cycle up.
This reuse of materials creates value-added products while helping meet two environmental objectives: reusing and recycling. If you remove the ash and lime and possibly sell this to local brick, construction companies or road fill, many times you will have cleaner biosolids. These biosolids then can be used in the bark boiler if you have one onsite and lower your energy costs. The biosolids sometimes can be used for compost. There are some companies that are using paper solids for retention aids in mining applications also. Did you know that a 1% capture of fiber that is returned back to the front of the plant can equate to up over a million dollars a year? Here is an example of a papermill that looked at beneficial reuse- they produced 43.3 tons per day of solids off their paper machines. 62.85 tons per day were loading their primary clarifier. With a little digging we found that they produced 7 tons of lime that was easy to isolate. We looked at taking this and selling it off. We then looked at the ash content. Their was ~ 10 tons per day fly ash from their fluid bed boiler. We looked for homes for this also. When you took away the lime and ash content, most of the solids loading on the primary were cleaner and could then be returned back to the bark boiler. This would reduce energy costs, take loading off the aeration lagoon, (not to mention the wear and tear on the clarifier rakes) and solids disposal loading off the sludge ponds and landfills. Overall, huge amounts of savings in all areas. Papermills generate large amounts of sludge. These can be used in many different ways, depending upon collection and processing. Paper Mill Sludge that is uncontaminated and dewatered can be used as a fuel or energy source in bark boilers, as a bulking agent or carbon source for composting, used in animal bedding, or can be used as a raw material in the manufacture of absorbents. Papermill sludge can also be used as alternative cover at a sanitary landfill when mixed with soil in a 50/50 volume. EPA Office of Compliance Sector Notebook Project, Profile of the Pulp and
Paper Industry. More information can be obtained on the EPA website
http://es.epa.gov/oeca/sector or by
Boiler and Cooling Tower Blowdown Cooling Tower Microscopic analyses Paper mills are notorious for holding solids too long in the clarifier. Why does it matter how long I hold the solids? Holding papermill influent or effluent and associated solids too long generally causes not only septic conditions, which can generates odors, but also generates low D.O. conditions. Low D.O. conditions cause the bacteria to generate specific compounds with sulfides and/or organic acids. Holding times of influent should always be kept to a minimum. Generation of septic conditions can also contribute to ashing in the clarifier, since the solids are turning anaerobic in the bottom of the clarifier and generate gases that cause clumps of solids to float to the top. This increases solids carryover. These conditions usually lead to the growth of excessive levels of filaments later on in the aerobic biological portion of the system. Sometimes, anaerobic sludge is sent to the primary clarifier via the belt press supernatant. This can also lead to an increase in septic conditions in a primary clarifier, since you are seeding the system with bacteria that like to grow in anaerobic or facultative conditions. Filamentous bacteria can be a problem is solids are held too long in a clarifier also. Total System Optimization- Case History Solids handling and other papermill
troubleshooting Bioaugmentation in once through lagoons can significantly impact not only BOD and TSS in the final effluent, but a properly designed program can help lower solids generation in lagoons that lead to costly dredging. Troubleshooting Lagoon Systems Wastewater in the Fall- Problems and Solutions Hurricane or Severe Weather Upset recovery program Wild Weather Extremes that can impact your plant More on Papermills: Take a tour of a papermill Solids Holding in a papermill Lagoons-Winter BOD issues and bioaugmentation Learn how Environmental Leverage can help your plant Bioaugmentation in Papermills- impact on BOD and TSS
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Ash
generation rates are approximately 0.04 TPT from Georgia pulp mills. Bark boiler
ash and other solid by-products, when mixed with manufactured composted topsoil,
make prime soil conditioners. 
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