Equipment & Systems
HEALTH & SAFETY: CANADIAN MILL FIRST IN WORLD TO GAIN ENVIRO CERTIFICATION
WINDSOR, QC -- Domtar Inc.'s Windsor Business Centre has been awarded the Responsible Care certification by the Canadian Chemical Producers' Association -- thereby becoming the first paper mill in the...
January 1, 2000 By Pulp & Paper Canada
WINDSOR, QC — Domtar Inc.’s Windsor Business Centre has been awarded the Responsible Care certification by the Canadian Chemical Producers’ Association — thereby becoming the first paper mill in the world to achieve such a recognition. Domtar started its march to certification in May 1996, when the company announced its intention to strengthen its relationship with the community, to better focus its efforts on the protection of the environment and to ensure a better working environment for all its employees. “Achieving the Responsible Care certification is a significant event,” the company said in a press release. “However, this recognition is only a beginning for us and not an ending.” Earlier in 1999, the Quebec government’s ministry of environment gave Domtar the Phenix — an award recognizing its environmental efforts.s view of logging as the worst perpetrator of deforestation, the truth is that logging is actually part of reforestation programs that most forest products companies conduct. The key to reducing deforestation is not to stop logging, but rather to better manage the human population, intensify agricultural production and make urban areas denser. Population management allows us to give over less forest areas to agriculture land. If we then reuse the land intensively, we also reduce the need for more agricultural land. Urban densification allows for more people on less land and, therefore, less deforestation.
Forestry has also been accused of being the demise of many animal and plant species. Moore can find no scientific proof to support that notion and proffers instead that forestry has not disturbed the natural habitat of species any more than any naturally-occurring phenomenon.
“To the best of our knowledge, no species have become extinct because of forestry. The spotted owl, for example, has actually increased…. There is no old growth forest, but (the spotted owl) is doing fine in second growth redwood forest.”
To support his position on the resilience of the forest, and the positive influence of human intervention, Moore points to the 1980 eruption of Mount St. Helen. Part of the land is owned by the US government and part by Weyerhaeuser. After the eruption, the government did not use any extraordinary means to rejuvenate the land, whereas Weyerhaeuser disturbed the site by plowing the field, and introduced two-year-old seedlings to the site. In 2026 there will be a harvest of the Weyerhaeuser land. The government land still looks barren.
“A couple of interventions by human beings can make a huge difference,” Moore said. “I am not saying it’s right or wrong.”
Moore also showed a slide of land that had been clear cut in the 1930s, and how it is now home to various species of animals, birds, insects, etc. He suggested that people think of a clear cut as a temporary meadow, an area where the sun can actually reach the soil. Clear cuts are actually healthier than meadows, which are actually small deserts, as there is not enough moisture in the soil for anything to grow.
Moore’s recipe for the path to sustainability: grow more trees, increase area of forests, reverse deforestation by getting rid of pastures, grow more fuel wood, and use more wood as a substitute for non-renewable fuels.
The US Environmental Protection Agency requires that bleached kraft, soda and sulphite mills implement best management practices (BMP) for the management, spill prevention, and control of spent pulping liquor, soap and turpentine. A panel of mill, corporate and consultant personnel discussed the challenges faced and checkpoints needed in developing a plan.
Two papers were presented about Weyerhaeuser’s BMP plan. The first, by Tom Smith, described the highlights of a system that was implemented at the Longview, WA, mill. The bleached kraft mill had several non-pulp and paper sources of water that fed into the effluent system.
The corporate steering team decided to establish a test-site and template for other Weyerhaeuser mills contemplating BMP plans. An independent consultant did the engineering analysis. The mill had been modernized and the BMP became a good opportunity to review the alterations.
The mill regulated physical modifications:
– turpentine storage containment,
– turpentine processing equipment isolation;
– back up power supply to sump pumps;
– alert mechanism for potential sump overflows needed to develop means to alert operators.
Improvements, including additional implementation, were made for automated monitoring of conductivity, pH and temperature.
Teri Ard presented a corporate perspective on the Weyerhaeuser BMP implementation. She described the lead mill approach, its definition and standard practices.
BMP regulations requires:
– that you look for cost-effective and consistent ways to implement BMP,
– that you provide a boundary for engineering and BMP plans.
Companies planning to implement a BMP, said Ard, should carefully define the terms for application.
BMPs: Prevention, collection, or caught in the middle? This was the title of the presentation of Donald Spivey, CH2M Hill. He described the merits of a BMP for spill recovery and spill prevention and described the primary and secondary objective of the BMP order. The flexibility provided in the 1998 BMP requirements empowers individual mills to develop BMP programs based on spill prevention, spill control and recovery, or some combination of these.
Spill prevention BMPs require less capital equipment than spill collection and recovery BMPs, reported Spivey. The former places more emphasis on the implementation of monitoring systems such as sewer conductivity monitors and alarms and tank high level alarms. These monitoring systems, he informed, when coupled with a management system that focuses on reducing mill soda losses, are an effective BMP measure that can reduce or eliminate the need for collection and recovery facilities in many BMP process areas.
In a later discussion, the speakers offered up what each thought was the most important issue regarding implementing a BMP. Moderator Kirsten Vice, H.A. Simons (now with CPPA) said that everything should come back to the engineering cost analysis. Tom Smith thought the flow systems should be monitored carefully. Teri Ard said that it is imperative that maintenance and operators support the goals. Ultimately, the group agreed, if you are happy with the BMP plan, you will have no problem defending it if something goes wrong.
The first paper in the activated sludge session also focused on prevention. Amy Lo, Domtar Innovation, spoke about a knowledge-based control system to prevent operational upsets in biological wastewater treatment. The ideal diagnostic program will provide an ongoing preventive health assessment of microbial populations to system operators and mill management. Such assessments are comprehensive with little requirement for expert knowledge in secondary treatment.
A model with a numerical index function to reflect the health status and performance of microbial populations in a biological treatment process was successfully developed. Robert Martin, Grays Harbor Paper L.P., spoke about downsizing a paper treatment plant cost-effectively to meet a 40-fold reduction in waste load. He described how the mill modified the treatment plant to accommodate the lower load.
In Phase I the aeration system was modified in order to reduce energy costs, maintain treatment efficiency, and restore the integrity of the aeration system.
Of four possibilities, the company chose the off-zone aeration because there was no downtime to install it, the energy savings, and the mill could fabricate many components itself.
In Phase 2, for odor control of the primary classifier, return activated sludge (RAS) flow from the second clarifier was directed to the inlet of the primary clarifier.
In summary, the system was cost-effectively downsized. Aeration now has good integrity; energy savings were realized; odors are being controlled and National Pollutant Discharge Elimination System (NPDES) effluent limits are easily me
Suppliers highlighted new technology in the quick and informative presentations (QuIPs). Christopher Davis, Hercules Pulp and Paper Division, said that technology had been developed that controls biofilm formation unlike any product currently on the market.
The biofilm control technology is said to provide superior deposit control on paper machines. The FDA-approved technology can remove biocides going to the treatment plant.
In response to a question about the half-life of the product, Davis said that it is biodegradable, and consumed by bacteria. The product was not tested on a continuous, but on a semi-continuous basis. Biocides and biodispersants were fed on an intermittent basis.
Rosanna DiLabio, Praxair Canada, spoke about upgrading Fraser Papers Inc. Edmundston, NB, wastewater treatment plant using pure oxygen. The ASB was working a little above capacity. Two in-situ oxygenators were used to introduce oxygen into the cell.
The result of the trial indicated that oxygen was very beneficial for this wastewater treatment system. The researchers have seen increased biological activity in oxygen cells; decreased BOD in final effluent; increased TSS in effluent; increased nutrient requirements, and reduced bioaugmentation products.
Lance Mason, Severn Trent Environmental Services, described experiences with autocalibrating dissolved oxygen systems in pulp and paper wastewater treatment facilities.
Alberta Newsprint, Slave Lake and Millar Western were studied. Without temperatures around 20C it is impractical to carry out any reliable check using these instruments.
All of the instruments installed in these three facilities have been linked to the control room by conventional analog signals, as well as modems connected to extension phones within the facility. This latter functionality has allowed both the mill and the supplier to access the instruments and the information contained within them over the international telephone networks. It is these three facilities that led to the refinement of the equipment to make it work in this type of physical environment.
Mike Williams, ViroGroup, talked about environmental data management using linked databases. Linked databases talk to each other. The information is stored in table and can be used by other databases. For example, continuous environmental monitoring data for boilers can be queried in a process database. Therefore, excess emissions reports can be automated.
With linked databases, data never need be entered more than once. To start simply determine which environmental data are needed. Environmental tasks will be streamlined with a linked database. Staff will have more time for other environmental tasks.
Ari Tamminen, Kvaerner Chemetics, said that techniques for reduction of NOx emissions have now been evaluated in two full-scale installations. These installations include both staged air low-NOxincineration and catalytic reduction of flue gas. These kraft pulp mills have striven to reduce their total NOx emission by minimizing emissions from the new incinerators. One mill has chosen technology based on staged combustion and the other mill has equipped the new incinerator with catalytic cleaning on NOx (SCR).
The conclusions show that staged incineration of SOG and NCG reduce the emission of NOx by about 10%.
Two papers were presented in a session on tertiary treatment. Both dealt with treatment of effluent water prior to reuse in the mill.
Allan Elliott, Paprican, compared the quality of biologically treated water and river water in his presentation. He also discussed the improvements that can be made with tertiary treatment.
The study looked at three different tertiary treatments: sand filtrations (SF), granulated activated carbon (GAC) and alum coagulation (AC). Clarified water was sent to tertiary treatment. Twenty different parameters were considered, such as BOD, COD, TSS, TDS, etc. When compared to mill river water the biologically treated effluents produced in pilot and full scale plants were less turbid and had lower concentrations of aluminum, iron and silica. However, these effluents contained target amounts of dissolved solids, including COD, color, sulphate, calcium and magnesium.
The researchers found that mill processing increases the levels of 19 of the 22 parameters that they studied. With the full-scale biologically treated effluent, color and COD were best removed by GAC adsorption and alum coagulation.
In the second presentation, Tiina Riippa, Enso Publications Papers, evaluated the possibilities of reusing treated process water in a printing paper mill water system. There were two limiting parameters: the microbiological nature of the remaining suspended solids, and the color of the water. Filtration and ozonation studies showed promising results as a method to eliminate microbes in the waters. Microfiltration with a pore size of 0.5 m removed all the suspended solids, but it had no effect on water color.
Ozone had biocidal effects and potential for reducing the color of the water. To be able to reduce fresh water consumption the treated water should be reusable for machine showers, chemical dilution or cooling and sealing purposes. These tests indicated that the quality of the treated water is not high enough for the substitution of fresh water. The treatment of TMP filtrate will not have detrimental effects on pulp quality. The organic load of TMP and PM water system would be lowered and the quality of the water should be good enough for chemical dilution and equipment cleaning and flushing.
Discussion continued on the treatment of wastewater in the final session on biological nutrients. Rob Hunter, Tasman Mills, (formerly Tasman Pulp and Paper Co.) described the operation of an ASB wastewater treatment system treating kraft and newsprint wastewater without the addition of nutrients.
“We haven’t used nutrients in about four years,” said Hunter. No nitrogen can be found anywhere in the system. Dissolved oxygen (DO) is controlled in pond 2 though no control is usually required.
The mill has an on-site mill-wide sewer monitoring system with conductivity probes in all of the sewers. Alarms are set up in the areas of concern, including the clarifier. The first signs of an upset usually arise in the DO and a rise in the pH. The first action is to cut the aerators from 18 to as few as five. The operation of the aerators is juggled in order to maintain the target DO at the Pond 2-3 cutting of 1 mg/L. As the pH drops, the aerators go back on. By the end of the spill pH works its way back to seven.
The system needs better control strategy, which Hunter described as ‘a bit seat of the pants’. Better training for the operators on-site and a greater understanding of the data provided from the sewer monitoring system would alleviate operational problems.
Dr. Michael Richard looked at causes and needs of phosphorous in pulp and paper activated sludge. Phosphorous supplementation is generally required for wastewater treatment as this type of wastewater is almost always lacking in sufficient phosphorous for good biological treatment. Severe phosphorous deficiency results in incomplete BOD removal and a high effluent soluble BOD.
Pulp and paper activated sludges have a phosphorous content ranging from 0.5 to 1.5% by weight. The phosphorous content of these sludges decreases with increases in non-volatile content, due to clay and inorganic material dilution of the biomass. The variable content of phosphorous in the sludges makes it difficult to judge the sufficiency or deficiency in content.
Treatment temperature, sludge age, wastewater organic composition, treatment system configuration and wastewater inorganic chemistry are all identified as factors that affect phosphorous needs.
A second session on BMPs looked at applicatons being done to conform to the regulation, rather than development or implementation of a program. Pierre Brub, UBC, looked at the costs and operating temperature of treating evaporator condensate using a high-temperature membrane bioreactor (MBR). Kinetic informat
ion and the characteristics of the evaporator condensate at a local kraft pulp mill were the basis for a preliminary design for an MBR system. Two scenarios were considered : 1) Treatment of the fouler fraction of the evaporator condensate only, and; 2) treatment of the fouler fraction and approximately 50% of the cleaner fraction of the evaporator condensates.
Temperature significantly affected the rate of membrane removal. The lab studies proved to be feasible.
In scenario 1 costs for polymeric membranes were favorable compared with ceramic membranes. Cost estimates for bioreactors are lower than for steam stripping. Biological treatment is cheaper than steam stripping.
In scenario 2 the costs were similar.
Based on design, the combined capital and operating costs for a high temperature MBR are significantly less than for a steam stripping system for both scenarios investigated, particularly if polymeric membranes can be used.
Thomas Welander, ANOX AB, described a study that looked at biological removal of methanol from kraft mill condensate. Welander said that though there is no corollary in Sweden, the MACT part of the EPA Cluster Rules has created an interest in biological treatment of kraft mill condensate as a possibility to remove methanol. His study compared aerobic and anaerobic biological treatment of kraft mill condensate in laboratory, pilot plant and full-scale trials.
Laboratory trials were done with anaerobic alone and anaerobic/aerobic treatment. The general advantage of anaerobic treatment is lower cost but it proved to be more sensitive to disturbances. The sequential anaerobic/aerobic treatment of condensates benefited from COD removal in the anaerobic stage at a favorable cost and from the additional removal of organic matter in the aerobic stage, ensuring a maximal COD removal over the whole process.
In pilot plant trials, COD removal was around 90% with an HRT of 15 days and with aerobic post treatment. The aerobic post treatment also worked well at the elevated temperature resulting in a COD removal around 90% over the total process.
The results obtained in the full-scale trial confirmed the expected 90% removal of soluble COD and complete elimination of methanol over the combined anaerobic/aerobic treatment.
The next paper in the session looked at the success of in-plant effluent control and environmental performance at a South American mill. Bahia Sul Pulp and Paper mill produces eucalyptus bleached kraft pulp and printing and writing papers. The mill, said Ricardo de Aguiar Quadros, has a sophisticated system for controlling spills. Conductivity sensors in the channels and level sensors in the pumping pit control the system. In the case of spill these sensors trigger automatic gates, controlled by the increase of conductivity, which closes the effluent channel, directing the leakage to the pumping pit. As the level in the pit rises, the pumps start to transfer the effluent to spill tanks that feed the process line back.
The mill’s effluent treatment system has two main streams of effluents: one general, or alkaline, stream that comes from the administrative buildings and several points of the industrial process, except the bleaching plant acid stage. The other stream, an acid stream is formed exclusively by the acid stages of the bleaching plant. The effluent treatment plant monitoring program checks the quality of the final effluent before it is discharged to the Mucuri River.
Results of the study showed that in-plant control resulted in the decrease of AOX in the inlet of the effluent treatment plant, and as a consequence, in the reduction of the AOX level in the final effluent.
The final effluent presents a BOD level of about 0.25 kg/admt, and TSS level of 0.4 kg/admt. De Aguiar Quadros said that though the Brazilian mill has no obligation to comply with American regulations, its final effluent parameters accord with the USEPA Cluster Rules.
Douglas Barton, NCASI, turned his attention to another set of regulations. He presented a Demonstration of Compliance monitoring for the MACT I “hard-piping” option.
Three kraft mills participated in the study. Total hazardous air pollutants (HAP) destruction in excess of 92% was calculated for all inlet/outlet data sets collected at the participating mills.
The study found no correlation between the fraction of total HAPs biodegraded and effluent soluble BOD5 or aeration basin MLVSS. The range of on-line aerator horsepower, according to the study, did not vary over the course of the study, thus no attempt was made to relate aerator horsepower to the fraction of HAPs biodegraded.
Jamie Curley, University of Manchester Institute of Science and Technology, discussed the challenges of choosing or developing appropriate technology for reducing effluent, especially for a high quality specialty tissue mill. The mill studied was disposing 1000 dry tonnes per year (dt/y) of papermaking sludge. The eliminated sludge consists of good quality papermaking fibres and PCC filler. The mill wanted a program to eliminate or minimize these losses.
A major point of drain loss was the overflow from the backwater storage tanks. These were converted to a Stowford Separator system, which also acts as a solids separation device. The separator contains and concentrates solids in the bottom of the tank where they will be discharged to the pulpers when water is required. It is then returned to the process, while the displaced water at the top of the separator will be low in solids and thus allows clearer water to be sent to any downstream purification unit. Clearer water reaching the purification plant, according to Curley, will also reduce the energy and chemical use at the plant.
Computational fluid dynamics help to improve the speed of the design process.
A computer model of the entire system helps to plan strategies on mill operation and costs.
A similar interest in catching fillers and reducing water use came from a study done by Universit du Qubec. Mohini Sain described experiments using sodium alumino silicate as a porous filler in the wet end and the effect or residual sodium alumino silicate in white water as a replacement for microparticle system in its clarification by dissolved air flotation (DAF).
In summary the research report says that white water consistency during recycling of wet end filtrate can be reduced by replacing a relatively less porous magnesium silicate with highly porous sodiumaluminosilicate. Porous filler not only improved retention but also reduced suspended solid content white water. This laboratory simulation test developed by circulating white water is expected to provide preliminary information on the effect of porous fillers in wet end retention and white water circulation.
Print this page