Search

In the present study, adsorption of colour and other pollutants from agro-based paper mill effluent onto fabricated coal fly ash nanoparticles (CFA-N) have been investigated. Response surface methodology was applied to evaluate the operational conditions for maximum ouster of colour from effluent by nano structured CFA-N. Maximum reduction in colour (92.45%) and other pollutants were obtained at optimum conditions: 60 min interaction time, 60 g/L adsorbent dosage and 80 rpm agitation rate. The regression coefficient values (adjusted R2 = 0.7169; predicted R2 = 0.7539) established harmony between predicted and the experimental data. The adsorption equilibrium results matched perfectly with both Langmuir and Freundlich isotherms with maximum adsorption capacity of 250 platinum–cobalt/g. Additionally, the efficacy of CFA-N was also assessed in a continuous column mode. Furthermore, the feasibility of treated effluent for irrigation purpose was checked by growing the plant Solanum lycopersicum. Overall, the findings demonstrated the outstanding role of inexpensive and abundantly available CFA-N in treatment of paper mill effluent to the required compliance levels. HIGHLIGHTS Nano fly ash was successfully utilized for removal of colour and other pollutants from agro-based paper mill effluent.; RSM using BBD was used to optimize the operational conditions.; Quadratic models have been established for the response variables.; Fixed-bed column adsorption studies illustrated the feasibility of nano fly ash for pilot-scale applications.; The reusability of treated effluent for irrigation was examined.

Anaerobic digestion (AD) is an essential technology for wastewater management, resource recovery and biogas production, and it is considered as an efficient and reliable treatment method for many wastewaters. Operating parameters have been shown to directly affect the stability and treatment performance of AD, especially temperature. For 180 days, the AD of recycled paper mill wastewater (RPMW) was carried out in a modified anaerobic inclining-baffled (MAIB) reactor under various temperature conditions, i.e. 29 °C (low mesophilic), 37 °C (mesophilic) and 55 °C (thermophilic). It was found that total COD removal of 94, 96 and 76%, and methane yields of 0.125, 0.196 and 0.256 L CH4/g CODremoved were attained at temperatures of 29, 37 and 55 °C, respectively. Throughout the three transition periods, the pH level in the MAIB reactor fluctuated slightly within the range of 5.8–6.5 without affecting the system stability. The results concluded that thermophilic condition strongly influenced the MAIB reactor performance, leading to lower COD removal, higher methane yield and gradually recovered pH level. Highlights Novel modified anaerobic inclining-baffled (MAIB) reactor, which combines the development of attached and settled microorganisms, was operated for the treatment of recycled paper mill wastewater (RPMW).; The operational temperature intensive analysis of MAIB was investigated at thermophilic and mesophilic conditions.; The system compartmental characteristics were also analyzed and discussed.

In recent years, the use of microalgae as feedstock for many marketable products, such as animal/aqua feeds, bioplastics and fertilizers, has gained renewed interest due to their fast growth potential coupled with relatively high lipid, carbohydrate and nutrient content. An algal biorefinery at an industrial site has the potential to sustainably and profitably convert carbon dioxide emissions into microalgal biomass and concomitantly reduce nitrogen and phosphorus from wastewaters. Industrial wastewaters are a potential alternative to traditional media used for large-scale microalgal cultivation. Pulp and paper mills are major consumers of water resources and discharge a huge amount of water to nearby lakes or rivers. This study investigated whether pulp and paper mill waste water is suitable for microalgal cultivation with the aim of achieving significant biomass production. Six different process waters from one Canadian pulp and paper mill were tested with two freshwater green microalgae. All of these waters were unable to support growth of microalgae due to inadequate nutrient concentrations, colour, turbidity and possible toxicity issues. HIGHLIGHTS Two freshwater microalgae strains were screened for potential growth on pulp and paper effluents.; Pulp and paper wastewater effluents were unable to support growth of the microalgae.; Chemical residues from the pulping process, such as peroxide and tannin, may inhibit algal growth.

This study examined the responses of a population of brook stickleback (Culaea inconstans) exposed to pulp mill effluent at Jackfish Bay, Lake Superior, Canada, in May 2007 and May 2011. Brook stickleback were extirpated from the effluent-receiving site, presumably due to anoxia after this period. Females at the effluent-receiving site had significantly larger gonad sizes in 2007 and 2011. In 2011, effluent-exposed female gonadal development was significantly advanced when compared with reference sites; they were the second most mature when compared among three different reference sites. Analysis of 7-ethoxyresorufin-O-deethylase activity revealed that effluent-receiving site females had greater CYP1A induction in 2007 and significantly greater CYP1A induction in 2011. Effluent-receiving site males showed significantly reduced CYP1A induction in 2007 and significantly greater induction in 2011. Chemical evaluation of sediment from the receiving environment showed elevated levels of resin acids and the polycyclic aromatic hydrocarbon, retene. Higher condition factors and more mature gonads were consistent with higher winter and spring temperatures modified by effluent or by lake vs. stream environments. Overall, effects on effluent-exposed brook stickleback were not consistent with reported effects in white sucker exposed to the same effluent in previous studies. This article has been made Open Access thanks to the kind support of CAWQ/ACQE (https://www.cawq.ca).

The activated sludge process within the pulp and paper industry is generally run to minimize the production of waste activated sludge (WAS), leading to high electricity costs from aeration and relatively large basin volumes. In this study, a pilot-scale activated sludge process was run to evaluate the concept of treating the wastewater at high rate with a low sludge age. Two 150 L containers were used, one for aeration and one for sedimentation and sludge return. The hydraulic retention time was decreased from 24 hours to 7 hours, and the sludge age was lowered from 12 days to 2–4 days. The methane potential of the WAS was evaluated using batch tests, as well as continuous anaerobic digestion (AD) in 4 L reactors in mesophilic and thermophilic conditions. Wastewater treatment capacity was increased almost four-fold at maintained degradation efficiency. The lower sludge age greatly improved the methane potential of the WAS in batch tests, reaching 170 NmL CH4/g VS at a sludge age of 2 days. In addition, the continuous AD showed a higher methane production at thermophilic conditions. Thus, the combination of high-rate wastewater treatment and AD of WAS is a promising option for the pulp and paper industry. Funding agencies: Swedish Energy Agency [32802-2]; Scan-dinavian Biogas Fuels AB; Poyry AB; BillerudKorsnas AB; SCA; Fiskeby Board AB; Purac AB

This study deals with chemical oxygen demand (COD), phenol and Ca +2 removal from paper mill industry wastewater by electrocoagulation (EC) and electro-Fenton (EF) processes. A response surface methodology (RSM) approach was employed to evaluate the effects and interactions of the process variables and to optimize the performance of both processes. Significant quadratic polynomial models were obtained (R 2 = 0.959, R 2 = 0.993 and R 2 = 0.969 for COD, phenol and Ca +2 removal, respectively, for EC and R 2 = 0.936, R 2 = 0.934 and R 2 = 0.890 for COD, phenol and Ca +2 removal, respectively). Numerical optimization based on desirability function was employed; in a 27.55 min trial, 34.7% of COD removal was achieved at pH 9 and current density 96 mA/cm 2 for EC, whereas in a 30 min trial, 74.31% of COD removal was achieved at pH 2 and current density 96 mA/cm 2 and H 2 O 2 /COD molar ratio 2.0 for EF. The operating costs were calculated to be 6.44 €/m 3 for EC and 7.02 €/m 3 for EF depending on energy and electrode consumption at optimum conditions. The results indicate that the RSM is suitable for the design and optimization of both of the processes. However, EF process was a more effective technology for paper mill industry wastewater treatment as compared with EC.

The activated sludge process is an old technology, but still the most commonly used one for treatment of wastewater. Despite the wide spread usage the technology still suffers from instability (Tandoi et al. 2006) and high operating cost. Activated sludge processes often carry a large solids inventory. Managing the total inventory without interference is the key component of the optimization process described in this paper. Use of nutrients is common in pulp and paper effluent treatment. Feeding enough nutrients to support the biomass growth is a delicate balance. Overfeeding or underfeeding of nutrients can result in higher costs. Detrimental substances and toxic components in effluents entering a biological treatment system can cause severe, long lasting disturbances (Hynninen & Ingman 1998; Bergeron & Pelletier 2004). A LumiKem test kit is used to measure biological activity with adenosine triphosphate (ATP) in a pulp and paper mill. ATP data are integrated with other standardized mill parameters. Measurements of active volatile suspended solids based on ATP can be used to quantify the living biomass in the activated sludge process and to ensure that sufficient biomass is present in order to degrade the wastewater constituents entering the process. Information about active biomass will assist in optimizing sludge inventories and feeding of nutrients allowing the living biomass to re-populate to create optimal efficiency. ATP measurements can also be used to alert operators if any components toxic to bacteria are present in wastewater. The bio stress index represents the stress level experienced by the microbiological population. This parameter is very useful in monitoring toxicity in and around bioreactors. Results from the wastewater process optimization and ATP measurements showed that treatment cost could be reduced by approximately 20–30% with fewer disturbances and sustained biological activity compared to the reference period. This was mainly achieved by the removal of detrimental substances and optimized nutrient dosage.

This essay outlines the use of an anaerobic baffled reactor (ABR) treating pulp and paper wastewater during its start-up period. For this purpose, a pilot with four chambers and overall volume of 45 liters was fed continuously through the equalization tank of Mazandaran wood and paper wastewater treatment plant, in the north of Iran. The influent was classified as low strength slowly biodegradable wastewater. The average soluble chemical oxygen demand (SCOD) and biochemical oxygen demand (BOD) of the influent were about 1,130 and 320 mg/L, respectively. Results show that the start-up was accomplished in 90 days in which the ABR reached its maximum SCOD removal of 60%. This was achieved at the controlled mesophilic temperature (37 °C) and optimum hydraulic retention time (HRT) of 24 hours. In spite of the influent characteristics, the performance of ABR has not been inhibited and mostly influenced by HRT. The gradual hydrolysis and acidogenesis were observed within the ABR. The majority of chemical oxygen demand (COD) removal takes place in the first chamber. In addition, the concentrations of readily biodegradable organics (BOD to COD ratio) have been increased and doubled through the reactor. Moreover, the total values of pH, volatile fatty acids and alkalinity remained constant. Consequently, this system can be approved for application as a pretreatment unit for paper mill industrial wastewater treatment plants.

The reuse of wastewater by the pulp and paper industry reduces environmental impacts by contributing to raw water conservation, thereby making a greater volume of fresh water available for nobler purposes, and reducing wastewater treatment. This study evaluated a proposed system of water reuse at a Kraft pulp and paper plant in Brazil, based on a survey of water quality required by its consumption points, supplied by its water treatment plant. Results after ultrafiltration included: turbidity of 0,3 NTU and pH 7,5, average values of BOD 66,4 mg/L, COD 9,6 mg/L and the colour of 280,5 ppm Pt were measured after ultrafiltration. The ultrafiltered wastewater was considered available for reuse, and its quality was compared with that of the water supplied by the water treatment plant, which provided for the classification of potential reuse points. Water colour was identified as the limiting factor for reuse; thus the reuse points were two Kraft paper machines, and the water flow to the liquid ring formations that generate the vacuums inside nineteen pumps for these two machines. The advantages of this proposal for water reuse include: ultrafiltered water quality sufficient for the vacuum pumps, the small distance between the point of reused water generation and the paper machines section, and the reused water has no contact with the final product. The calculated cost and return time for the water reuse system was US$ 607.020,00 in 15 years.

This paper presents the design and operational performance data of an anaerobic/aerobic hybrid side-stream Membrane Bioreactor (MBR) process for treating paper mill effluent operated over a 6 month period. The paper mill effluent stream was characterized by a chemical oxygen demand (COD) range of between 1,600 and 4,400 mg/L and an average BOD of 2,400 mg/L. Despite large fluctuations in COD feed concentration, stable process performance was achieved. The anaerobic Expanded Granular Sludge Bed (EGSB) pre-treatment step effectively lowered the organic loading by 65 to 85%, thus lowering the MBR COD feed concentration to consistently below 750 mg/L. The overall MBR COD removal was consistent at an average of 96%, regardless of the effluent COD or changes in the hydraulic retention time (HRT) and organic loading rate (OLR). Combining a high-rate anaerobic pre-treatment EGSB with a Modified Ludzack–Ettinger (MLE) MBR process configuration produced a high quality permeate. Preliminary NF and RO results indicated an overall COD removal of around 97 and 98%, respectively.

Aerobic biological treatment with activated sludge is the predominant process all over the world for treatment of pulp and paper industry wastewater. 50–70% of the biodegradable organic material is oxidized to CO2 and the rest is converted to bacterial biomass, typically termed as excess sludge or waste activated sludge (WAS). Handling and disposal of WAS in general and in particular from the pulp and paper industry face different processing difficulties, regulatory stringency due to organochlorine contamination and reluctance of people for reuse. With an objective of reducing the net disposable biomass, ozonation of WAS from a pulp and paper mill and from a laboratory scale batch activated sludge process operated with the wastewater and bacterial seed of the same pulp and paper mill have been carried out. With the mill sludge having predominant filamentous organisms 18% MLSS was reduced at an ozone dosage of 55 mg O3/g dry MLSS solid (DS) resulting in 2.5 times COD increase. With the laboratory sludge which is well structured and flocculating, only 6% MLSS was reduced at an ozone dosage of 55 mg O3/g DS. Ozonation mineralizes 26% and 20% AOX compounds embedded in the secondary sludge in the mill and laboratory sludge respectively at an ozone dosage of 55 mg O3/g DS. During ozonation, absorbed/adsorbed lignin on biomass was released which resulted in increased colour concentration. Ozonation can be a potential oxidative pretreatment process for reducing the WAS and paving the way for cost effective overall treatment of WAS.

The effluent of the Tasman pulp and paper mill (Kawerau, New Zealand) has been intensively studied for its effects on the health of fishes between 1998 and present. This review summarizes peer-reviewed scientific literature on the reproductive effects of the Tasman Mill effluent on fishes. In the 1990s there was an emerging body of literature from around the world showing that exposure to pulp and paper effluent could cause subtle reproductive alterations in exposed fishes. Locally, the Tarawera River had proved to be a difficult environment to conduct field studies. To overcome some of the difficulties with studying fish populations in the Tarawera River, initial studies on the reproductive health of fishes were focused on mesocosm and laboratory bioassays. During the later part of this period of study, wild fish population sampling was conducted inriver to assess the cumulative impact of multiple discharges. The initial mesocosm studies were conducted with rainbow trout exposures over an entire reproductive development cycle. The Tasman Mill effluent was initially observed to cause reductions in gonad size in females corresponding with lower circulating sex steroid hormones and reduced egg and larval sizes. This result was not observed again in the two subsequent long-term exposures conducted after 2001. Laboratory studies initially found the effluent to have a masculinizing effect on female mosquitofish (Gambusia affinis). This mosquitofish masculinization response disappeared after 2001 and was also not seen in effluent-exposed wild populations. Upstream and downstream populations of the native common bully (Gobiomorphus cotidianus) showed different reproductive timing, and investigation revealed that genetic differences were a potential reason for these differences. Subsequent investigation compared the Tarawera River bully to genetically similar Rangitiki River bully and found no evidence of reproductive alterations. The entire body of published data was assessed with regards to changes at the mill and chemical profiles of the effluent. It was evident that continuing effort on the part of the mill has resulted in gradual improvement in effluent quality over the duration of the studies. However, the disappearance of reproductive effects as assessed by multiple bioassays corresponds to one major change: screen room closure in the pulp mill. This change would have resulted in wood extractives being shunted from the treatment system to the recovery boiler, resulting in a net reduction in compounds derived from wood.

The use of constructed wetlands (CW) to treat domestic as well as industrial wastewater is rapidly emerging as a viable alternative in India. Constructed wetland systems offer several potential advantages as a wastewater treatment process. These advantages include simple operation and maintenance and lower construction and operating costs. The study evaluated the effectiveness of the subsurface flow constructed wetland for pulp and paper mill wastewater treatment and also the effectiveness of plant species. A pilot scale study was conducted to examine the feasibility of a CW system for treatment of pulp and paper mill wastewater during summers as well as winters at different hydraulic retention time (HRT) such as 1.5 days, 3.5 days and 6.5 days. Wetland beds were prepared with easily available plants such as Typha angustifolia and Canna indica. Specific performance objectives were to decrease biochemical oxygen demand (BOD), chemical oxygen demand (COD), total solids (TS) and color. Comparison of mean inlet and outlet concentrations showed that the CW system could effectively reduce the output of TS (87.6 ± 1.1%), COD (86.6 ± 2.0%), BOD5 (80.01 ± 0.1%), color (89.4 ± 0.6%) during summer and TS (72.15 ± 0.71%), COD (70.94 ± 2.3%), BOD5 (72.07 ± 2.2%) and color (74.90 ± 0.47%) during winter at 3.5 days HRT.

Pulp and paper mill effluents (PPMEs) may contain high levels of otherwise naturally occurring organic pollutants such as plant sterols, which are suspected endocrine disrupting chemicals. Exposure to such chemicals may cause various physiological and morphological abnormalities that have been reported in the fish and other aquatic life inhabiting PPME receiving waters. Plant sterols, or phytosterols, form a constituent of wood extractives that may be released into the effluents during the pulping and paper making processes. Isolation and analysis of sterols from the complex mixture of PPMEs is challenging and standard analytical protocols do not exist. The need for having a reliable method for analyzing a particular environmental contaminant such as plant sterols cannot be overemphasized. In the present study a technique was modified for reliable analysis of PPME sterols. The technique involves liquid-liquid extractions using methyl-t-butyl ether and trimethyl-silylation derivatizations of the extracted sterols. Identification and quantification of the PPME sterols were accomplished by gas chromatography and mass spectrometry. Analytical problems were resolved by conducting multiple extractions, drying the sterol extracts, and redissolving and silylating the extracts at an increased derivatization temperature of 70°C. This shortened the suggested incubation period from 12 to 4 h. The modified technique offered improved method sensitivity and reproducibility, and successfully quantified campesterol, β-sitosterol, β-sitostanol, stigmasterol, stigmastanol, cholesterol, and ergosterol in PPMEs. Primary and secondary treated PPMEs analyses suggested 800 ± 190 µg/L total sterols in primary effluents, and 211 ± 90 µg/L in biologically treated final effluents. β-Sitosterol, β-sitostanol, and campesterol alone accounted for about 80% of the total sterols. A general comparison of the sterols in primary and secondary effluents suggested about 73% removal across the secondary treatment systems sampled.

Pulp and paper mill effluents have been reported to cause changes in reproductive indicators of fish in laboratory and field studies. These changes include reduced egg production and gonad size, and altered hormone levels and expression of secondary sex characteristics. We examined the performance of biotreatment plants for their potential in abating effects of pulp and paper mill effluents on fish reproduction under laboratory conditions. A bleached kraft mill effluent (BKME) treated in an aerated lagoon and a thermomechanical pulp mill effluent (TMPE) treated by aerobic sludge in a sequential batch reactor were selected for study. Mature fathead minnows (Pimephales promelas) were exposed to effluents before and after biotreatment under continuous renewal conditions for 21 days. Egg production was monitored daily, while morphometric parameters (length, weight, gonad size), secondary sexual characteristics, and steroid hormone and vitellogenin levels were measured at the end of the effluent exposure. The effluent from both mills before biotreatment impaired the reproductive capacity of minnows (egg production) at concentrations of 10 and 20% vol/vol, but not at 2% vol/vol. Exposure to biotreated effluents from both mills at concentrations of 2, 10, 20, and 40% vol/vol caused no significant differences in overall reproductive capacity of minnows as compared with controls. These results indicate that biotreatment can significantly improve the quality of a BKME and an effluent from a TMP mill with respect to the reproductive capacity of fish as determined in laboratory tests.

Specific power consumption and reduction of BOD, COD, TS, pH, and chemical elements were used to determine the treatment efficiency of Fe, graphite and Al electrodes with alum and wood ash as supporting electrolytes on the effluent from a Kraft pulp and paper mill in Kenya. Five sampling points were selected along mill's effluent treatment system: primary settling tank (SP1), first aerated lagoon (SP2), second aerated lagoon (SP3), stabilization pond (SP4), and at discharge point (SP5). Operating costs were also compared between treatments. Graphite electrodes combined with alum showed the lowest power consumption (0.5 to 3.9 mWh/m3), followed by Al and Fe. All the electrodes reduced color from a maximum of 3,200°H to the minimum local standard of 15°H. However Al electrode with alum was the most effective method for BOD and COD reduction by over 60% and 58.8% respectively and generated less sludge at all sampling points. The cost of treatment was lowest with graphite electrode (US$0.006 to 0.0008 per m3 of effluent), but highest with Al electrodes combined with wood ash (US$31.74 to 8.34 per m3). Further study is required for the effectiveness of increasing the concentration of wood ash leachate at higher concentration and current density.

The two recently retired authors have a combined career experience of over 65 years in carrying out research directed at assessing effluent effects on marine and freshwater receiving waters. As such, their work directed at the environmental information needs of the forest products industry has represented a continually evolving research program. This paper reflects a history of issues and progress on pulp and paper mill effluent research before their careers began, the progression of issues and research during their careers, how questions have changed and evolved, and also looks forward to the remaining questions that need to be addressed concerning effluent effects.

Mosquitofish (Gambusia) are sexually dimorphic; adult males have an elongation of the anal fin to form a copulatory structure known as a gonopodium. Several studies since the early 1980s have reported elongated anal fins in female mosquitofish exposed to pulp and paper mill discharge, a phenomenon known as masculinization. Although adverse impacts have been suggested in these previous reports, the influence of masculinization on reproductive success has not been assessed for pulp mill effluent-exposed eastern mosquitofish (Gambusia holbrooki or affinis). The current study compared fecundity (number of fry per female at parturition) to an index of masculinization (ratio of anal fin rays 4 to 6). Pregnant females were collected from two effluent-receiving streams in Florida: Rice Creek and the Fenholloway River, over two reproductive seasons (2003 and 2004). Masculinization was consistent between years, with clear effects at the Fenholloway River site, while the response was minimal or nondetectable at the Rice Creek site. Masculinization was not correlated with the production of fry/fecundity at either site. Data suggest differing reproductive seasonal strategies between basins and populations but do not demonstrate any effects of pulp and paper exposure on reproductive success in mosquitofish.

Reproductive impairment in fishes exposed to pulp and paper effluent has been observed in the wild for three decades. Despite intense research, identification of causative agents, if indeed the changes are strictly chemically mediated, has yet to be achieved. This review examines the body of research developed over the last six years that was directed at understanding the mechanisms of reproductive dysfunction in fishes associated with pulp mill effluent exposures. Research has continued to show diminishing effects of effluent exposure on fish reproductive physiology. Observations of exposure to androgens and estrogens continue to be observed and new evidence suggests that antiestrogens may be present. The presence of androgenic steroids remains a consistent observation, and those androgens appear to be native to wood. Recent studies have also suggested a number of alternate mechanisms beyond androgens or estrogens. One such possibility is that neuroactive substances are interfering with endocrine balance critical to reproduction. A second possibility is that some reproductive effects in the field may be due to nutritional factors, and thus reproductive impacts are caused by indirect effects of pulp mill effluent exposure. Ongoing mechanistic studies, particularly with paired field-lab components, are required to make further progress.

The regulatory Environmental Effects Monitoring (EEM) program in Canada has found that pulp and paper mill effluents reduce the gonad size of wild fish. In such cases, there is a need for Investigation of Cause (IOC) and Investigation of Solution (IOS) studies to find the cause(s) for these responses as well as cost-effective mitigation strategies. IOC and IOS work requires the availability of practical (in terms of time and effluent volume needs) and biologically meaningful tests for assessing fish reproduction in the laboratory. One available fish reproduction test uses adult fathead minnow (Pimephales promelas) and involves a two- to three-week pre-exposure period and a three-week exposure to a test substance. Work was undertaken to determine if both the pre-exposure and effluent-exposure phases could be reduced, leading to a shorter test with a lower effluent volume requirement. For this purpose, effluent samples were taken from two thermomechanical (newsprint) pulp mills and used in tests with ≤7 days of pre-exposure and 5 to 6 days of effluent exposure. Egg production was monitored in each test, and in tests with effluents from one mill, other endpoints - such as gonad somatic indices and whole-body sex steroid levels, as well as vitellogenin activity in males - were measured. The shortened fish reproduction test in this study provided results similar to tests of longer duration, specifically in terms of egg production, and was able to distinguish between pulp and paper mill effluents of different potencies. The test was also found to be directly applicable for toxicity identification evaluation work as it was clearly able to distinguish between the solids and soluble fractions of a biotreated newsprint mill effluent. As such, the test is a promising tool for EEM-related IOC and IOS work.

In the pulp and paper industry, the water use minimization is a constant target. One way to reduce water use is to recycle the effluent in a closed-cycle concept. In paper mills, the main source of liquid effluent is the so-called whitewater, which is the excess water, originated from pulp stock dewatering and other fibre contaminated water. This research studied the reuse of paper mill whitewater after membrane ultrafiltration (UF) in the paper machine and in the pulp bleach plant of an integrated mill. Contaminant removal and flux behaviour of the UF system were evaluated. The treatment by ultrafiltration was technically feasible and the treated whitewater had good potential to be reused in some processes in the paper machine. The reuse of ultrafiltered whitewater in the bleaching plant was not recommended because of the high level of soluble calcium present in this stream. Therefore, a combined treatment of the whitewater using the principle of precipitation and ultrafiltration was proposed showing good results and enabling the use of the treated whitewater in the bleach plant.

The study was based on a full scale activated sludge plant (AS) compared to a parallel operated pilot membrane bioreactor (MBR) with flat sheets membranes. Both systems received their influent from an anaerobic bioreactor treating paper mill wastewater. MBR produced an effluent of much better quality than AS in terms of suspended solids, containing 1 mg/L or less in 80% of the monitoring time, while the AS effluent contained 12 mg/L. This could save the necessity of further treatment by filtration in the case of MBR. Other effluent quality parameters, such as organic matter (COD and BOD), phosphorus and ammonia nitrogen, did not indicate substantial differences between AS and MBR. Calcium carbonate scaling and formation of a bacterial layer on the membrane caused severe flux reduction. The membrane blockage because of scaling and biofouling proved to be very serious, therefore, it required proper and more complicated maintenance than the AS system. This study leads to the conclusion that in the case of paper mill wastewater, after anaerobic biotreatment, if there is no need for excellent effluent quality in terms of suspended solids, the replacement of the AS by the MBR would not be strongly justified, mainly because of maintenance cost.

Since the early 1980s, anaerobic treatment of industrial effluents has found widespread application in the pulp and paper industry. Over 200 installations are treating a large variety of different pulp and paper mill effluents. Amongst various anaerobic systems the UASB and IC are the most applied anaerobic reactor systems. Anaerobic treatment is well feasible for effluents originated from recycle paper mills, mechanical pulping (peroxide bleached), semi-chemical pulping and sulphite and kraft evaporator condensates. The advantages of anaerobic pre-treatment are (1) net production of renewable energy (biogas), (2) minimized bio-solids production, (3) minimal footprint and (4) reduced emission of greenhouse gases. Via in-line application of anaerobic treatment in closed circuits (paper kidney technology) further savings on cost of fresh water intake and effluent discharge levies are generated.

As opposed to effluents from chemical pulp production, very little is known about the endocrine potential of papermaking effluents. To evaluate the endocrine potential of biologically treated effluents from the main grades produced in Germany (fine, graphic and packaging papers), 16 samples were studied by means of the Recombinant Yeast Estrogen Assay (R-YEA). 10 samples were tested positive; seven of them were effluents from recovered paper processing mills. Possible sources of endocrine disruptors in addition to wood components include papermaking chemicals, paper converting chemicals, if recovered paper is used, and/or detrimental substances introduced by impurities in these chemicals. Six of the above samples were subjected to individual substance analyses to detect endocrinologically active or potentially endocrinologically active substances. Even though phthalate compounds were detected in concentrations between 0.46 and 2.36 μg/L, only two of the six samples were tested positive in the R-YEA, because the test fails to adequately detect this compound's class. Despite this drawback, the R-YEA will be used for further studies because of the great variety of potential endocrine substances present in paper mill effluents. In particular, mechanical and recycled fibre pulps as well as the constituents of chemical additives must be investigated in more detail.

Phytoplankton and macroinvertebrate assemblages were used to assess the impact of a kraft pulp and paper mill effluent in Kenya, on River Nzoia downstream of the discharge point in relation to changes in water quality during May to June and November 2008 (rainy and dry seasons, respectively). Total phosphorus concentration increased from 0.027 mg.L-1 upstream to 0.04 mg.L-1 downstream. Ammonia nitrogen (NH3-N) concentration was 0.51 mg.L-1 upstream and 0.86 mg.L- 1 downstream. Nitrate concentration stood at 1.18 mg.L-1 upstream compared with the 2.23 mg.L-1 downstream. The pH changed from 4.5 to 5.0 upstream to 5.5 to 6.0 downstream, while DO increased from 6.57 to 7.03 mg.L-1 downstream. The BOD5 (biochemical oxygen demand after five days) values remained almost unchanged from 4.63 mg.L-1 upstream to 4.67 mg.L-1 downstream. Taxon composition of phytoplankton and macroinvertebrates correlated with adverse environmental gradients resulting from the mill's effluent discharge. Overall, there was a shift in composition and abundance of both phytoplankton and macroinvertebrates, with the downstream site recording high numbers of tolerant taxa (i.e., Microcystis sp. and Chironomus sp.). It was recommended that water quality monitoring with effluents of this nature be done using a combination of chemical analysis and biological indicators such as phytoplankton and macroinvertebrates.

Pulp and paper companies all over the world certify their environmental management systems assuming public commitments for the continuous improvement of their relationship with the environment. Once certified, they consider themselves having done their part. But is this enough? This work has been carried out with the clear intention of provoking the professionals who can give the much needed answers for the construction of environmental sustainability in the pulp and paper sector.

Colour discharges are gaining renewed focus in the pulp and paper industry as increasingly strict regulatory limits are placed on wastewater quality and aesthetics. In-mill process improvements, such as ECF bleaching and oxygen delignification, have decreased wastewater colour loadings. However, a survey of 12 pulp and paper mill systems found that effluent treatment using aerated stabilisation basins (ASB) leads to average increases in colour of 20-40%. In some instances, this phenomenon may even double the influent colour levels. Activated sludge systems did not produce a colour increase. The measured increases that follow ASB secondary treatment may be sufficient for a mill to fail prescribed discharge standards. A detailed field survey focusing on sections of an integrated bleached kraft mill ASB treatment system was undertaken. The average increase in colour at the final point of discharge was 45%. The major changes in colour concentration occurred in the inlet to the main treatment pond, and in polishing ponds that followed the main treatment pond. Both of these areas receive little or no aeration. No significant change was observed in the highly aerated main pond. These results, along with literature reports, suggested that redox conditions play a major role in influencing colour behaviour. To test this, two series of paired continuously stirred reactors were used to treat whole mill effluent from two ECF bleached kraft mills in parallel. The first series initially treated under anaerobic conditions, followed by an aerobic reactor, while the second series reversed this order. With the initial anaerobic stage, effluent colour increased by 18% and 19% for the first and second series respectively. Subsequent treatment by aerobic bacteria further increased colour by 14% and 6%, for a total increase of 32% and 25%. Initial aerobic treatment, however, did not lead to any significant change in colour for either effluent. Further anaerobic treatment following aerobic conditions produced only small increases in colour. These results are consistent with the ASB and activated sludge system survey, suggesting that anaerobic conditions at the head of treatment systems initiate the observed increases in effluent colour in ASB treatment systems.

The effect on fish reproduction of final treated effluent from a thermomechanical pulp mill in Saint John, New Brunswick, Canada, was studied using mummichog (Fundulus heteroclitus), an endemic fish species of the Atlantic coast of North America. A 1997 artificial stream study at the same mill showed a reduction in gonad sizes in mummichog after a 28-day exposure to 3% final treated effluent. In 2005, we reevaluated final treated effluent, and conducted a toxicity source evaluation to identity waste stream sources within the mill that may cause reproductive effects. Relative to reference, no significant differences in gonad size, plasma levels of gonadal sex steroids, egg production, or stage of egg development were observed in fish exposed to 1, 3, 10, 30, and 100% final treated effluent or in-mill waste streams. Unlike the previous study in 1997, these data indicate a low potential for an effect of final effluent on fish reproduction. Since the 1997 study there were no major process changes that could explain the differences in the results. However, there was high variability in gonad size, egg production, and endocrine endpoints measured in the more recent test, which resulted in low power to detect differences. This has prompted research to refine the current reproductive test by optimizing study design.

A study was undertaken to remove colour from a kraft mill's treated effluent in Kenya and determine the suitability of phosphate rock to replace wood ash during the electrochemical process. The electrochemical method alone, electrochemical combined with alum (ELCAL), wood ash leachate (ELCAS) and phosphate rock (ELPHOS) solutions at a rate of 165 to 1,000 g/m3 were tested. Effluent characteristics were determined after complete removal of colour. Same reduction rates of TS (85%) and TSS (89%) were recorded by ELCAS and ELPHOS. However, ELPHOS removed more COD (86 to 91%) and more BOD (85 to 92%) than ELCAS. Furthermore, the pH of ELPHOS treated solution was 9.3, within the Kenya Local Government's allowable limit. Power reduction with ELCAS and ELPHOS varied between 53 to 73% and 49 to 69% respectively but the difference was not statistically significant. Overnight aeration further improved the quality of ELCAS and ELPHOS treated effluent, reducing BOD and COD values to 0 mg/l. ELPHOS cost ($0.29/m3) was nevertheless three times higher than that of ELCAS ($0.10/m3), mainly because of free wood ash. ELPHOS did not also increase effluent phosphorus. It was therefore recommended that various ways be explored in making ELPHOS more economical to replace ELCAS.

There is an increasing trend towards the closure of white water recirculation loops in papermaking, often leading to need for system modification. A pilot-scale study was conducted using pulsed electrocoagulation technology to treat the wastewater of an old corrugated containerboard (OCC)-based paper mill, to evaluate its treatment performance. The operating variables were: a current density of 0 to 240 A/m2, a hydraulic retention time of 8 to 16 min and a coagulant (anionic polyacrylamide) dosage of 0 to 30 mg/L. The water quality indicators investigated were electrical conductivity, suspended solids (SS) and chemical oxygen demand (COD). The results obtained during the pilot-scale studies were favourable. Under the operating conditions without coagulant addition, the highest removals for conductivity, SS and COD were 47.7%, 99.3% and 75%, respectively. The use of coagulant remarkably enhanced the removal of both conductivity and COD. Using a coagulant dosage of 30 mg/L, the highest removal rates achieved for the three water quality indicators were 54.5%, 99.6% and 92.7%, respectively. These water quality levels are adequate to allow for the reuse of at least a part of the treated wastewater as makeup process water in papermaking.

Thermophilic aerobic treatment of settled pulp and paper mill effluent was studied under mill premises with two comparative pilot processes; suspended carrier biofilm process (SCBP) and activated sludge process (ASP). Full-scale mesophilic activated sludge process was a reference treatment. During the runs (61 days) hydraulic retention times (HRTs) were kept 13 ± 5 h and 16 ± 6 h for SCBP and ASP, respectively. Corresponding volumetric loadings rates (VLR) were 2.7 ± 0.9 and 2.2 ± 1.0 kg CODfilt m-3d-1. Temperatures varied between 46 to 60°C in both processes. Mesophilic ASP was operated with HRT of 36 h, corresponding VLR of 0.7 kg CODfilt m-3d-1. Both SCBP and ASP achieved CODfilt (GF/A filtered) removals up to 85%, while the mesophilic ASP removal was 89 ± 2%. NTU values were markedly higher (100-300) in thermophilic effluents than in mesophilic effluent (30). Effluent turbidity was highly dependent on temperature; in batch experiment mesophilic effluent sample had NTU values of 30 and 60 at 35°C and 55°C, respectively. As a conclusion, both thermophilic treatments gave high CODfilt removals, which were close to mesophilic process removal and were achieved with less than half of HRT.

Photocatalytic oxidation (PCO) is a promising technology for purification of biological pretreated wastewater or destruction of non-biodegradable compounds. For this reason PCO has been investigated as a last step of purification of biologically pre-treated paper-mill effluents. The influence of the parameters pH, TiO2-modification, TiO2-concentration, catalyst re-use, concentration of substances to be oxidised (wastewater quality) has been determined. The TOC of the biologically pretreated wasterwater was up to 55 mg L-1. This wastewater was treated with a previously presented aerated cascade photoreactor which was modified for batch experiments. A high specific oxidation rate of up to 0.76 g TOC m-2 h-1 as well as a complete TOC mineralization has been achieved after the optimisation of the process parameters. The complete destruction of recalcitrant compounds will offer the opportunity to reuse the wastewater in the production process. The increase of the BOD5/TOC ratio after a short irradiation period indicates the transformation of recalcitrant organic compounds to better biodegradable intermediates. The use of PCO as a pre-treatment step for the enhancement of the biodegradability of wastewater, containing recalcitrant or inhibitory compounds is an alternative to a long and energy-intensive total pollutant mineralization.

A submersible UV/VIS spectrometer was used to monitor a paper mill wastewater treatment plant. It utilises the UV/VIS range (200-750 nm) for simultaneous measurement of COD, filtered COD, TSS and nitrate with just a single instrument. The instrument measures in-situ, directly in the process. Paper mill wastewater shows typical and reproducible spectra at various process measuring points. There is a relative maximum at 280 mm due to the absorbance by dissolved organic substances, mainly ligninic acids. Comparison of absorbance spectra distinctly shows the decrease of this peak, indicating biological degradation throughout the treatment process. Summarising, one can say that paper mill wastewater cannot be monitored by a simple UV probe measuring only the absorbance at a single wavelength. The required information can only be gained from the whole spectra. Regarding plant control it is suggested that only the overall spectral information is used. Calibrations to conventional parameters are now merely carried out for purposes of reference-checking.

The European paper industry produces 70 million tons of paper annually, being one of the most water consuming industrial processes. The reduction in water use leads to partially recirculated water into industrial processes. This results in quality deterioration and a drop in productivity. Because of this, the socalled zero effluent operation has only been applied in a few papermills around Europe. Existing technologies usually operate within the mesophilic range. However, most of the mills work at a 50-70°C water circuit temperature range due to the positive effects on productivity and energy consumption. In this paper, a thermophilic aerobic treatment (55°C) combined with ultrafiltration is tested, this combination reaches mesophilic COD removal rates. Moreover, problems with water settleability under high temperatures are now avoided and the suspended solids free effluent gives water more possibilities of being reused.

Fathead minnow (Pimephales promelas) lifecycle tests have been used to assess the effects of many North American pulp mill effluents. Fish are exposed under controlled laboratory conditions to final effluent, from the egg stage through hatching, juvenile stage and mature adult stage. Outlined here are methods for the lifecycle test (which takes from 4 to 5 months to complete) with sampling of juvenile fish at 1, 2 and 3 months of age, and sampling of mature adults after breeding. The results of most fathead minnow lifecycle studies have shown that pulp mill effluents cause metabolic and reproductive disruption (enlarged livers, reduced egg production, smaller gonads, decreased sex hormones and reduced secondary sex characteristics). Thus, the fathead minnow lifecycle assay is able to mimic the most commonly observed changes seen in wild fish exposed to pulp mill effluents. Sensitive indicators of reproductive effects in fathead minnows exposed for a lifecycle to pulp mill effluents include secondary sex characteristics, time to first reproduction and number of eggs laid. Egg production is often the most sensitive response to pulp mill effluents. Because of the length and cost of full lifecycle tests, a shortened assay using adult fish was developed as a screen for endocrine-disrupting compounds. This assay, the terminal reproduction test, has been used with success on a few pulp mill effluents. The assay exposes fathead minnow breeding pairs for three weeks to effluent, and compares egg production, sex characteristics and bioindicators of reproductive performance in pre-exposure versus post-exposure fish. For assessment of pulp mill effluents, it appears that the sensitivity of the shortened terminal reproductive fathead minnow assay may be improved by assessing bioindicators of reproductive performance (such as circulating levels of sex hormones, and circulating or hepatic vitellogenin) along with changes in secondary sex characteristics and egg production.

The aim of this research was to study the effects of chemical spills on activated sludge metabolic activity and settleability. On-site, laboratory-scale tests were carried out at three pulp and paper mill activated sludge plants. Oxygen uptake rate (OUR) and dissolved organic carbon (DOC) removal were used for monitoring of metabolic inhibition. The effects of chemicals on 30-min settled sludge volume were studied. Accidental release reports from five pulp and paper mills were analysed. Thirty-four chemicals were selected to the laboratory tests. Of the tested chemicals 2 biocides, monochloro acetic acid, soft soap and turpentine inhibited the OUR of the sludge and thus, had an acute toxic effect on the activated sludge. The biocides and disperging agent reduced DOC removal. Aluminium sulphate and optical brightener had a negative effect on sludge settleability and thus, they may cause losses of activated sludge from treatment plant. In conclusion, maximum possible spill of the five chemicals may reduce the performance of the activated sludge.

A survey of the concentrations of nonylphenol ethoxylates (NPnEO) and their metabolites in the primary and secondary treated effluent and sludge samples collected from pulp and paper mills was conducted. Through the coordination of the Pulp and Paper Research Institute of Canada (PAPRICAN), 19 Canadian and one U.S. mill of various process types and waste treatment methods supplied samples in this study. Previously developed solid-phase extraction, supercritical fluid extraction, high performance liquid chromatography and gas chro-matography/mass spectrometry methods were used for the determination of NPnEO and their metabolites, nonylphenol (NP) and the carboxylates (NPEC), in effluent and sludge samples. The levels of NPnEO ranged from

In Canada, effluents from pulp and paper mills are regulated for toxicity. The regulation requires ≥50% survival of rainbow trout (Oncorhynchus mykiss) exposed to full-strength (i.e., 100%) effluent for 96 h in tests that must be conducted monthly. The regulation also calls for ≥50% survival of Daphnia magna exposed to 100% effluent for 48 h in weekly monitoring tests. Every year, about 10 to 25% of the mills exceed the regulatory limit at least once in tests with either rainbow trout or Daphnia magna. Between 1996 and 2003, we investigated 84 such cases from 32 mills. Of the 84 investigations, 49 involved only trout, 29 involved only Daphnia, and six involved both species. We identified the actual cause of toxicity in 70% of the cases and partially or tentatively identified the toxicant(s) in 17% more. In the cases involving only trout, the most frequent causes of toxicity were related to biotreatment performance (e.g., ammonia). In the cases involving only Daphnia, the most frequent cause of toxicity seemed to be related to polymeric formulations. For those cases involving both trout and Daphnia, the cause of toxicity was traced to more than one compound or to excess concentrations of a specific compound resulting from a spill or biotreatment-related problems.

A TAML® catalyst (0.5 μM, 0.23 mg/L of effluent) combined with hydrogen peroxide (6.5 mM, 0.19 g/L of effluent) were capable of permanently removing 46% of the colour from bleach plant effluent (Eop, pine-derived) in one hour at 5,000 L effluent per day. Increasing concentrations to 2 μM catalyst (0.9 mg/L of effluent) and 22 mM peroxide (0.75 g/L of effluent), resulted in removal of 78% of the colour. In addition, 29% of the chlorinated organic material (AOX) was also removed. A laboratory investigation indicated that the oxidative process predominantly removed phenolic structures. The low aromatic content of the effluent meant that the majority of the organic material was not substantially altered during treatment. Thus chemical oxygen demand was essentially unchanged. This technology was able to remediate colour from effluents derived from both softwood (pine) and hardwood (eucalypt). Laboratory studies on catalyst life-time during effluent treatment, demonstrated that activity was maintained for a sufficient period to eliminate all the chromophore available to the active species, but that the catalyst did not survive long enough to be discharged into the receiving environment. Microtox tests showed that catalyst degradation products were not toxic to the receiving environment.

Wet oxidation (WO) is a well established process for purification of concentrated municipal and industrial wastewaters. Many attempts have been made to modify the WO process or to create a suitable combination of processes. This work was undertaken to investigate wet oxidation integrated with coagulation, i.e. to treat the sludge remaining after coagulation with a WO process. The possibility of regeneration of the used coagulant was also considered. Two waters from paper mills were used: TMP (thermomechanical pulp) circulation water and membrane concentrate. About 50% of the COD in the original water can be removed by coagulation using Fe2(SO4)3. The results from the wet oxidation experiments show the positive effect of iron in the chemical sludge as a catalyst. The efficiency of the WO process was enhanced almost by 100%. The remaining dissolved organic matter can be easily removed biologically.

In this paper we briefly describe pinch technology as a practical tool for effective energy management in the pulp and paper industry. Results indicate good steam savings. Recently pinch technology has been extended to water management. We have developed a customized methodology for the pulp and paper industry, to eliminate or reduce fresh water intake. Although the methodology is not fully developed it is a “proof of concept” that pinch principles can be applied to water related problems. The eventual combination of both thermal and water pinch will thus provide a structured and comprehensive approach for plant wide efficiency increase.

Blue mussels (Mytilus edulis) were caged at three sites situated at increasing distance from the point of discharge of a pulp and paper mill effluent from July to October 1998. Two additional cages were deployed: one inside and one at the mouth of the adjacent industrialized Pictou Harbour. After 90 d exposure, we measured growth, survival, haemocyte counts (HC), phagocytic activity (PA), lysosome retention (LR) and bacterial clearance (BC). There was a small but significant difference in growth between cages. Mussels closest to the mill effluent grew the most while those at the mouth of the harbour grew the least. Mussels from three cages showed similar difficulty in clearing bacteria; the cage inside the harbour, the cage nearest to the pulp mill effluent and the cage furthest from the pulp mill, receiving a mixture of both pulp mill and harbour effluents. The mussels from those cages also showed the highest heavy metal burdens and conversely, the cage showing the most rapid clearance, outside both effluents, also showed the lowest heavy metal burden. Mussels caged in the pulp mill effluent showed lower PA and LR and higher mortality during the bacterial clearance test than other mussels. These results suggest that immunological biomarkers might be a useful and more sensitive adjunct to endpoints presently being measured from caged bivalves in environmental effects monitoring (EEM) programs, and assessments of aquatic environmental quality.

A question raised again and again over many decades by pulp and paper mill personnel and local authorities in many countries is, "Does the finding of large numbers of coliform enteric bacteria in the mill water or biotreatment system indicate a real health hazard for the mill workers or the downstream public?" Some of the difficulties in answering this question arise from the widespread misunderstanding of what coliform indicator (enumeration) tests can tell us. Increasing scientific understanding over the last 30 years has greatly altered the coliform indicator tests, the types of bacteria enumerated, and our ability to distinguish harmless from pathogenic (disease-producing) bacteria. This brief review discusses our current understanding of where and when it is appropriate to use coliform indicator assays and the meaning of the results.

The installation of in-mill biological treatment for reducing the concentration of dissolved organic matter and microbial growth in the whitewater system h as been shown to be an interesting alternative for facilitating further closure of paper mill water circuits. In the present study the possibility of operating biological treatment of whitewater from different types of paper production under the environmental conditions prevailing in respective whitewater system, i.e. temperatures between 37 and 52°C and pH-values from 3 to 8. It was shown that high removals of soluble COD, 70-90%, could be achieved even at high temperatures and non-optimal pH-levels. Laboratory scale whitewater systems operated with and without a bioprocess were used for studies of the effect of a bioprocess on key parameters such as slime growth, spore formers and odorous compounds. The introduction of a bioprocess in the whitewater circuit effectively lowered the amount of soluble organic matter and eliminated odorous VFA. However, the operation strategy and control of the bioprocess showed to be crucial, especially the dosing of nutrients, in order to avoid increased rather than decreased biofilm growth in the whitewater system.

The feasibility of aerobic vessel composting and anaerobic digestion for the treatment of pulp and paper mill sludges were studied. The composting studies made use of primary and secondary sludge from a de-inking and paper mill. In six parallely aerated 500 1 vessels with various carbon : nitrogen (C:N) -ratios, the most optimal performance was obtained with C:N -ratios of c. 22–35, while higher and lower ratios delayed the temperature increase. With the optimal ratios, the thermophilic stage was reached within 36 h, and the stage lasted for about seven days. In the scale-up study (18 m3 compost vessel), the thermophilic stage was reached within 24 h. An effective dehydratation of the mass was obtained as the total solids (TS) content of the compost increased from 31.3– to 63.8– within 21 days. The anaerobic digestion of pulp and paper mill sludges was studied using two mesophilic 5 1 digesters, their feed sludges consisting of a mixture of municipal sewage sludge and primary and secondary sludge from a pulp and paper mill. With this feed mixture and with a loading rate of about 1.0 kg volatile solids (VS)/m3d a removal of about 27 to 40– VS and methane production of about 180 1/kgVSadded feed sludge were achieved during the 80 d study period. The study showed that pulp and paper mill sludges are amenable to both aerobic composting and anaerobic digestion.

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.

As part of an extensive audit of the Alkaline-Peroxide Mechanical Pulping (APMPTM) plant at the Malette Quebec Inc. mill in St. Raymond, Que., effluents were sampled from various stages of the process for comprehensive chemical characterizations, aquatic toxicity testing and anaerobic biotreatability assessments. In addition, untreated and secondary treated combined effluent from the integrated paper mill were sampled to determine the effectiveness of a conventional activated sludge process at the mill site. During the one-day sampling period, the APMP plant processed a mixed wood furnish consisting of 50% spruce/balsam fir and 50% aspen, with a chemical charge of 3.5% sodium hydroxide and 3.8% hydrogen peroxide on oven-dry fibre, while the Machine Finish Coated (MFC) paper production rate was 100 odt/d (oven dry metric tonnes per day). Measured production-specific contaminant discharge loadings from the novel APMP process were 56 kg BOD5/odt and 155 kg COD/odt in a combined effluent flow of 28 m3/odt. Sources of process effluent were chip washing, three stages of wood chip pretreatment and chemical impregnation (i.e., Impressafiner stages), interstate washing and pulp cleaning. The three Impressafiner pressates were found to be the most concentrated (i.e., 12-26 g COD/L) and toxic streams. Microtox testing of the pressates revealed EC50 concentrations of 0.07-0.34% v/v. The warm and concentrated effluents generated by the non-sulphur APMP process were found to be highly amenable to anaerobic degradation as determined by batch bioassay testing. Filterable BOD5 and COD(f) of the process effluents were reduced by 87-95% and 70-77%, respectively, with corresponding theoretical methane yields being attained. Acid-soluble dissolved lignin compounds exhibited biorecalcitrance, as revealed by limited removals of 34-55%, and were the main constituents contributing to residual COD(f), while resin and fatty acids (RFA) were reduced by 80-94%. The conservatively operated full scale activated sludge treatment process achieved a similar high 74% COD(f) removal from the whole mill effluent, while BOD5 and RFA reductions were virtually complete and the treated effluent was non-toxic, as measured by Microtox.

Closing the water circuit in waste paper processing mills results in high concentrations of COD in the recirculating white water. Part of the COD is easily degradable and causes problems with microbiological growth in the water system. The load of dissolved COD to a paper mill producing moulded paper was determined: partly the incoming dissolved COD with the waste paper and partly the production of dissolved COD in the stock preparation and paper machine. Pilot-plant experiments with biofiltration document that it is possible to remove efficiently easily degradable COD from the recycling white water. Very high loads have been applied to the filter owing to the high temperature and easy degradable carbon. Controlling the dosage of nutrients is essential to avoid growth problems in the white water system. It is shown that nutrients can be dosed to the filter with concentrations close to zero in the effluent, and still achieve significant removal capacity of the filter.

Rainbow trout exposed to effluent from a UNOX (oxygen activated sludge) treatment plant were found to exhibit signs of distress during the first hours of exposure. While the final effluent was not acutely lethal at full strength, it was still important to determine the cause of the distress to ensure that the mill's effluents remain in regulatory compliance. The use of a series of effluent manipulations involving pH adjustment and aeration as well as observations of symptoms exhibited by the fish were successful in identifying carbon dioxide as the cause of fish distress for the UNOX-treated effluent. For rainbow trout, the symptoms of exposure to elevated levels of carbon dioxide of 100 mg/L or greater included loss of equilibrium, erratic swimming, gasping at the surface, sinking to the bottom of the test container and paralysis. The fish were found to eventually recover as the carbon dioxide was stripped from the effluent due to aeration during the test. A carbon dioxide concentration of 250 mg/L, however, was found to be lethal to trout A survey of mills using oxygen activated sludge treatment systems indicated that the carbon dioxide levels in effluents from such operations can range from 48 to 251 mg/L. Solutions for eliminating the fish distress and possible mortality associated with such effluents would be to lower the carbon dioxide level to below 100 mg/L by aeration or pH adjustment.

In this paper, elimination of color from the effluents of the secondary stage biological treatment plant of an integrated pulp and paper mill located at a tourism resort was investigated by using a marine outfall system. The investigated mill has a full-scale aerated lagoon system treating effluents from a chemical pre-treatment plant. The colored effluents from the treatment plant have been discharged to a river ending in the Mediterranean and this has resulted in deterioration of the natural appearance of the coastal waters used for recreational purposes. In this study, a marine outfall system with a diameter of 1200 mm and a multiport diffuser of 290 m were planned to eliminate the color problem from the lagoon effluents. The required initial dilution to reduce the color to unnoticeable levels in the marine environment was determined 70 by laboratory-scale dilution experiments. In addition to these investigations, long-term full scale treatment results of the related industry are presented. Oceanographic studies and water quality measurements were performed to evaluate the effects of effluents from the industry on the marine environment. Bioassay tests were also conducted to assess the toxic impacts of the secondary treatment effluents on the macro fauna using Lapistes retucularis as a test species. Considering these findings, a marine outfall system was designed. The designed marine outfall system is currently under construction.