Thermomechanical Pulp Mill Research Articles

Biomechanical pulping: a mill-scale evaluation

Mechanical pulping process is electrical energy intensive and results in low paper strength. Biomechanical pulping, defined as the fungal treatment of lignocellulosic materials prior to mechanical pulping, has shown at least 30% savings in electrical energy consumption, and significant improvements in paper strength properties compared to the control at a laboratory scale. In an effort to scale-up biomechanical pulping to an industrial level, 50 tons of spruce wood chips were inoculated with the best biopulping fungus in a continuous operation and stored in the form of an outdoor chip pile for 2 weeks. The pile was ventilated with conditioned air to maintain the optimum growth temperature and moisture throughout the pile. The control and fungus-treated chips were refined through a thermomechanical pulp mill (TMP) producing lightweight coated paper. The fungal pretreatment saved 33% electrical energy and improved paper strength properties significantly compared to the control. Since biofibers were stronger than the conventional TMP fibers, we were able to reduce the amount of bleached softwood kraft pulp by at least 5% in the final product. Fungal pretreatment reduced brightness, but brightness was restored to the level of bleached control with 60% more hydrogen peroxide. The economics of biomechanical pulping look attractive.

Monitoring aquatic environments receiving industrial effluents using small fish species 2: Comparison between responses of trout‐perch (Percopsis omiscomaycus) and white sucker (Catostomus commersoni) downstream of a pulp mill

AbstractTo further evaluate the suitability of small fish species for sentinel monitoring, a comparison was made between the responses of trout‐perch (Percopsis omiscomaycus) and the larger white sucker (Catostomus commersoni) under similar conditions of pulp mill effluent exposure and mobility. Fish were collected upstream and downstream of a thermomechanical pulp mill on the Kapuskasing River, Ontario, Canada, where the presence of a hydro dam restricts the movement of fish between reference and exposure areas. Trout‐perch collected downstream of the mill were shorter, lighter, and younger than upstream fish, whereas exposed white sucker were longer, heavier, and, for male sucker, older than reference fish. Only male trout‐perch showed induced hepatic mixed function oxygenase activity (7‐ethoxyresorufin‐O‐deethylase). Both forskolin‐stimulated in vitro production of 17 β‐estradiol in trout‐perch and plasma concentrations of 17 β‐estradiol in sucker were significantly depressed in exposed fish. The inconsistency in responses between species made it difficult to determine how the opposing responses were related and which species was most sensitive to instream conditions. Despite the discrepancies, use of an interpretation framework indicated that both species identified similar potential problems (e.g., size‐selective mortality and recruitment problems), suggesting that either species could be used as a sentinel species at this site.

Source and identity of compounds in a thermomechanical pulp mill effluent inducing hepatic mixed-function oxygenase activity in fish

The source and identity of two mixed-function oxygenase (MFO)-inducing substances present in the primary-treated effluent of a thermomechanical pulp (TMP) mill producing newsprint was determined. The source was pinpointed by exposing rainbow trout (Oncorhynchus mykiss) to various process effluents sampled throughout the mill. Exposure concentrations were based on the flow of these process streams in relation to the final effluent flow. Contaminated TMP steam condensates were identified as the major process source of MFO-inducing substances. Using conventional extraction and fractionation procedures, an MFO-inducing fraction was isolated. The major gas chromatographic peaks in this fraction were identified by gas chromatography/mass spectrometry as juvabione, dehydrojuvabione, and manool, all naturally occurring extractives in balsam fix (Abies balsamea). These substances were extracted and isolated from balsam fir and TMP condensates. Trout exposed to juvabione and dehydrojuvabione responded by exhibiting significant hepatic MFO inductions. No MFO induction was observed for manool. Secondary treatment in an activated sludge system effectively eliminated the MFO-inducing potential of the combined mill effluent consistent with a corresponding 90% reduction of both juvabione and dehydrojuvabione.

Practical experiences with aerobic biofilters in TMP (thermomechanical pulping), sulfite and fine paper mills in Canada

An industrial aerobic biofilter technology has been piloted extensively in Canada on several types of pulp and paper mill effluents, resulting in one full scale operational facility at one Canadian fine paper mill. In addition two industrial scale pilot plant tests were performed with the same technology, one in an integrated sulfite pulp and paper mill and one in a TMP mill. In the case of the fine paper mill, the full scale plant has two cells (8 m × 8 m × 6 m height of the media) and treats an unclarified but screened effluent with a loading of 3500 kg BOD/d. The system produces low quantities of biosludge (0.28 kg TSS/kg BOD removed), has a rapid rate of recovery after shock loadings and is very energy efficient (150 kW installed power for aeration). Pilot plant treatability studies were performed at one integrated Canadian sulfite mill using a combination of a biofilter-aerated lagoon system. The biofilter treated the most concentrated stream (sulfite pulp mill effluent) and this stream was then combined with the remaining wastewaters of the mill and polished in an aerated stabilization basin (ASB). The high quality ASB effluent (50 mg BOD/L/30 mg TSS/L) was non toxic to rainbow trout, Daphnia magna and photoluminescent bacteria. Integrated TMP mill effluents were treated in a 5 m3 aerobic biofilter filled with two types of media (10 to 20 mm and 20 to 30 mm). Under average loading conditions of 3.5 kg BOD/d.m3 media, the system produced effluents meeting regulation limits for BOD, TSS as well as for toxicity.

Ozonation as a Treatment for Mechanical And Chemical Pulp Mill Effluents

Abstract Eighteen effluent types from seven thermomechanical (TMP), chemithermomechanical (CTMP), bleached chemimechanical (BCMP), and kraft pulp mills were treated in the laboratory with ozone alone or ozone in conjunction with aerobic biological treatment. Except for one mechanical pulp mill effluent, all effluents ozonized showed rapid and selective destruction of their acute toxicity, juvabiones (JB), and resin and fatty acids (RFAs) over biological and chemical oxygen demand (BOD and COD) by ozone. For acute toxicity and RFA/JB removal, aerobic biotreatment of mechanical mill effluent streams produced additive but not synergistic effects when combined with ozone treatment. Ozonation of biotreated kraft effluents yielded substantial decreases in the biologically recalcitrant residual adsorbable organic halogens (AOX), converted COD to BOD, and usually produced large decreases in color.

Effects of a secondary‐treated Thermomechanical Pulp Mill effluent on aquatic organisms as assessed by short‐ and long‐term laboratory tests

The chronic effects of secondary-treated effluent from a thermomechanical pulp (TMP) mill were assessed by means of long-term and short-term laboratory toxicity tests. The effluent used for the tests was sampled at a western Canadian mill using mostly softwoods and < 10% recycled fiber as furnish. In the long-term test, the effects of the effluent on the life cycle of fathead minnows (Pimephales promelas) were studied. In this experiment, which began with the egg stage and continued through to sexual maturity and reproduction, the fish were exposed in the laboratory to well water (control) and five concentrations (1.25%, 2.5%, 5%, 10%, or 20%) of effluent for 202 d. None of the effluent concentrations significantly affected the hatching of the eggs, the mortality, weight, length, gonad size, gender balance, and reproduction of the hatched fish, the prevalence of gross morphological and histopathological changes, and the hatchability of the first generation eggs. Two short-term tests, each lasting 7 d, were also performed. In these tests, 100% effluent caused no change in the survival/growth of minnow larvae or in the survival/reproduction of Ceriodaphnia.

A survey of pulp and paper mill effluents for their potential to induce mixed function oxidase enzyme activity in fish

The potential of 31 secondary-treated pulp and paper mill effluents from eight different mills to induce mixed function oxidase (MFO) activity, in the liver of rainbow trout ( Oncorhynchus mykiss), was investigated by short-term (4-day) laboratory exposures to 10% effluent concentration. Two of six thermomechanical pulp (TMP) mill effluents investigated caused increased EROD activity while there was no increase caused by the two chemi-thermomechanical pulp (CTMP) mill effluents tested. In contrast, with one exception, EROD activity was significantly induced as a result of exposure to bleached as well as unbleached kraft mill effluents. The replacement of chlorine in the bleaching of kraft pulp by chlorine dioxide or non-chlorine containing compounds (such as peroxide) did not eliminate the final mill effluent's ability to induce EROD activity. Rather, the kraft cooking process used to convert wood into pulp may itself be a source of MFO-inducing substances.

Terpenes Emitted to Air from TMP and Sulphite Pulp Mills

Terpenes were studied at two Swedish pulp mills processing wood from Norway spruce (Picea abies). Field samples were adsorbed from air on Tenax cartridges and analyzed in the laboratory by thermal desorption and gas chromatography. The emissions from a large thermomechanical pulp (TMP) plant consisted mainly of chemically unchanged hydrocarbon monoterpenes from the wood. The major monoterpenes were alpha-pinene (>50 %) and beta-pinene (20-30 %).The proportions of ten additional components were determined in the process emissions, which may be recovered to turpentine.The process emissions from a sulphite pulp mill consisted predominantly of the alkylbenzene para-cymene, formed from monoterpenes by acid reactions in the digestors. The contribution of the emissions to photo-oxidant formation in the surrounding region may be significant for both types of mills.

Fluidized Bed Technology in the Anaerobic Treatment of Forest Industry Wastewaters

The reasons for studying anaerobic fluidised bed technology for the treatment of forest industry wastewaters are twofold: the very large volume enforcing hydraulic loading beyond the limits tolerated by conventional anaerobic techniques and the low nutrient need compared with aerobic methods. In this paper we describe the results obtained for four different pulp mill waste streams: sulfite bleaching and evaporator condensate wastewaters , wastewater from displacement bleaching of kraft pulp and from thermomechanical pulping. We found that all four could be purified anaerobically within a hydraulic detention time of ≤12h and with a treatment efficiency of 3 to 4 kg of CODCr removed m−3 d−1. 80 to 90% of the CODCr of the thermomechanical pulp mill wastewater and evaporator condensate could be removed during anaerobic treatment, yielding ≥0.5m3 of biogas kg−1 CODCr removed. The bleaching wastewaters needed aerobic post-treatment and yielded little or no biogas.