The treatment of pulp and paper mill effluent: a review

The manufacture of paper generates significant quantities of wastewater; as high as 60 m3/tonne of paper produced. The raw wastewaters from paper and board mills can be potentially very polluting. Indeed, a recent survey within the UK industry has found that their chemical oxygen demands can be as high as 11000 mg/l. This paper reviews the processes involved in paper making and examines the effects which they could have on the environment. It also evaluates the treatment processes which are used to minimise these effects. In line with the majority of UK practice, it focuses mainly on aerobic biological treatment and, in particular, on the activated sludge process. This means that there is an in-depth discussion about the problems associated with filamentous bacteria and sludge "bulking". The paper also discusses the way in which anaerobic digestion can be applied to the treatment of liquid wastes from the manufacture of paper.     

Coliform bacteria and nitrogen fixation in pulp and paper mill effluent treatment systems

The majority of pulp and paper mills now biotreat their combined effluents using activated sludge. On the assumption that their wood-based effluents have negligible fixed N, and that activated-sludge microorganisms will not fix significant N, these mills routinely spend large amounts adding ammonia or urea to their aeration tanks (bioreactors) to permit normal biomass growth. N(2) fixation in seven Eastern Canadian pulp and paper mill effluent treatment systems was analyzed using acetylene reduction assays, quantitative nitrogenase (nifH) gene probing, and bacterial isolations. In situ N(2) fixation was undetectable in all seven bioreactors but was present in six associated primary clarifiers. One primary clarifier was studied in greater detail. Approximately 50% of all culturable cells in the clarifier contained nifH, of which >90% were Klebsiella strains. All primary-clarifier coliform bacteria growing on MacConkey agar were identified as klebsiellas, and all those probed contained nifH. In contrast, analysis of 48 random coliform isolates from other mill water system locations showed that only 24 (50%) possessed the nifH gene, and only 13 (27%) showed inducible N(2)-fixing activity. Thus, all the pulp and paper mill primary clarifiers tested appeared to be sites of active N(2) fixation (0.87 to 4.90 mg of N liter(-1) day(-1)) and a microbial community strongly biased toward this activity. This may also explain why coliform bacteria, especially klebsiellas, are indigenous in pulp and paper mill water systems.     

Microwave, ultrasonic and chemo-mechanical pretreatments for enhancing methane potential of pulp mill wastewater treatment sludge

Microwave (2450 MHz, 1250 W), ultrasonic (20 kHz, 400 W) and chemo-mechanical (MicroSludge® with 900 mg/L NaOH followed by 83,000 kPa) pretreatments were applied to pulp mill waste sludge to enhance methane production and reduce digester sludge retention time. The effects of four variables (microwave temperature in a range of 50-175 °C) and sonication time (15-90 min), sludge type (primary or secondary) and digester temperature (mesophilic and thermophilic) were investigated. Microwave pretreatment proved to be the most effective, increasing specific methane yields of WAS samples by 90% compared to controls after 21 days of mesophilic digestion. Sonication solubilized the sludge samples better, but resulted in soluble non-biodegradable compounds. Based on the laboratory scale data, MicroSludge® was found the least energy intensive pretreatment followed by sonication for 15 min alternative with net energy profits of 1366 and 386 kWh/tonne of total solids (TS), respectively. Pretreatment benefits were smaller for thermophilic digesters.     

Effect of nitrogen source on methanol oxidation and genetic diversity of methylotrophic mixed cultures enriched from pulp and paper mill biofilms

Methanol-oxidizing bacteria may play an important role in the development and use of biological treatment systems for the removal of methanol from industrial effluents. Optimization of methanol degradation potential in such systems is contingent on availability of nutrients, such as nitrogen, in the most favorable form and concentration. To that end, this study examined the variation in growth, methanol degradation, and bacterial diversity of two mixed methylotrophic cultures that were provided nitrogen either as ammonium or nitrate and in three different concentrations. Methanol-degrading cultures were enriched from biofilms sampled at a pulp and paper mill and grown in liquid batch culture with methanol as the only carbon source and either ammonium or nitrate as the only added nitrogen source. Results indicate that growth and methanol removal of the mixed cultures increase directly with increased nitrogen, added in either form. However, methanol removal and bacterial diversity, as observed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR–DGGE) methods, were higher when using nitrate as the nitrogen source for enrichment and growth, rather than ammonium. Based on results described here, nitrate may potentially be a better nitrogen source when enriching or working with mixed methylotrophic cultures, and possibly more effective when used as a nutrient addition to biofilters.     

Effectiveness of algae in the treatment of a wood-based pulp and paper industry wastewater

In this study, the ability of algae to treat a wood-based pulp and paper industry wastewater was investigated. Tests were performed in batch reactors seeded with a mixed culture of algae. Under different lighting and initial wastewater strength conditions, changes in COD, AOX and color contents of reactors were followed with time. Algae were found to remove up to 58% of COD, 84% of color and 80% of AOX from pulp and paper industry wastewaters. No remarkable differences were observed in COD and color when light intensity and wastewater strength were changed, while AOX removals were strongly affected. Algal species identification studies revealed that some green algae (Chlorella) and diatom species were dominant in the treatment. The study also showed that algae grew mixotrophically, while the main mechanism of color and organics removal from pulping effluents was partly metabolism and partly metabolic conversion of colored and chlorinated molecules to non-colored and non-chlorinated molecules. Adsorption onto algal biomass was not so effective.     

Identification of bacteria contaminating pulp and a paper machine in a Canadian paper mill

Over 100 bacteria from pulp and slime samples in a Canadian paper mill were identified by partial sequencing of their 16S rDNAs. Seventy-one percent of the isolates could be assigned to a bacterial genus with a high level of confidence. Another 12% exhibited at least 95% similarity within their 16S rDNA sequence with unidentified organisms that originate from warm or wet environments. Pseudomonas, Bacillus, and Pseudoxanthomonas isolates were represented at a relatively high proportion in both pulp and slime samples. This is the first time that Pseudoxanthomonas strains have been isolated from pulp and slime samples on a paper machine. Electronic Publication     

Effects of a pulp and paper mill on the ecology of the La Trobe River,Victoria, Australia

Four riverine animal communities were measured to assess the impact of extensively treated wastewater from a pulp and paper mill on the lower La Trobe River in Victoria, Australia. Benthic macroinvertebrates in channel and bankside habitats were sampled using a new air-lift corer. Population density was expressed in relation to substrate volume. Other communities measured at five sites upstream and downstream of the mill's wastewater outfall were the zooplankton, and the animals associated with submerged littoral vegetation. Ten environmental variables were also measured during the two sampling periods.A total of 50 benthic macro-invertebrate taxa were dominated by Oligochaeta, Chironomidae and Bivalvia. Benthic communities upstream and downstream of the outfall were very similar. Benthic samples showed large unexplained variation between stations and seasons, despite the similarity of stations and the stratified sampling design, but within-sample variation was small. There was some evidence that benthic faunal patchiness was associated with patterns of stream-bed scouring and deposition in periods of high flow. Littoral samples collected 28 taxa, dominated by Decapoda and Hemiptera. The benthic and littoral communities were quite distinct, with only three species common to both.Only two of the biological and environmental variables responded to wastewater from the mill: total dissolved solids rose by 20–25% over upstream levels; and zooplankton density increased by 2–3 orders of magnitude. It was concluded that wastewater treatment had successfully avoided the major environmental problems often associated with pulp and paper mills.     

Energy decision making in a pulp and paper mill: selection of LCA system boundary

Background, aim, and scope  

North American pulp and paper mills are facing tremendous challenges, which may necessitate major mill modernizations. An example is process modification to reduce dependency on purchased power, which is an expensive resource. Such modifications may have environmental implications at the mills’ sites, on their product life cycle, and on other interconnected systems, and therefore, systematic tools such as life cycle assessment (LCA) need to be applied. Different LCA system boundary approaches can be used for such process design applications, and these approaches need to be compared to determine their respective benefits and limitations in this context. This study compares setting the system boundary according to a cradle-to-gate approach [attributional LCA (ALCA)] and a system expansion [consequential LCA (CLCA)] approach using a case study, which deals with implementing cogeneration and increased de-inked pulp production at an integrated newsprint mill.     

Production of polyhydroxyalkanoates by activated sludge treating a paper mill wastewater

Production of polyhydroxyalkanoates (PHAs) in activated sludge treating wastewater represents an economical and environmental promising alternative to pure culture fermentations. A process for production of PHA from a paper mill wastewater was examined at laboratory scale. The three stage process examined consisted of acidogenic fermentation to convert wastewater organic matter to volatile fatty acids (VFAs), an activated sludge system operating under feast/famine conditions to enrich for PHA producing organisms and accumulation of PHA in batch experiments. After fermentation of the wastewater, 74% of the soluble COD was present as VFA (acetate, propionate, butyrate and valerate) and the resulting PHA after batch accumulation consisted of 31-47 mol% hydroxybutyrate and 53-69 mol% hydroxyvalerate. The maximum PHA content achieved was 48% of the sludge dry weight and the three stage process exhibited a potential to produce 0.11 kg of PHA per kg of influent COD treated.     

Decolorization of pulp and paper mill effluent by growth ofAspergillus niger

Pulp and paper mill effluent was decolorized by growth ofAspergillus niger. Adding glucose (2.0 g/l) and NH₄H₂PO₄ (1.0 g/l) improved decolorization by the fungus (leaving 19% of original colour) and reduced the BOD₅ (43%) and the COD (41%) of the effluent after 48 h of incubation.

---

Résumé L'effluent d'un atelier de pâte à papier a été décoloré par la croissance d'Aspergillus niger. L'ajout de glucose (2.0 g/l) et de NH₄H₂PO₄ (1.0 g/l) a amélioré la décoloration de l'effluent par la molsissure, lalssant 19% de la couleur originale, réduisant la DBO₅ de 43% et la DCO de 41%, après 48 h d'incubation.

---

---

This work was carried out at the Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore-641 003, India.     

Quantifying functional gene populations: comparing gene abundance and corresponding enzymatic activity using denitrification and nitrogen fixation in pulp and paper mill effluent treatment systems.

The relationship between the abundance of three functional genes and their corresponding biochemical reaction rates was investigated in several activated sludge and mill effluent microbial communities. Gene probes were prepared for two key denitrification genes (nirS and nirK) and for one nitrogen-fixation gene (nifH) and were validated using a variety of strains of known nir and nif genotype. ATP-based measures of viable cell numbers were used to provide total population sizes. In certain microbial communities (activated sludge enrichment cultures and multiple samples taken from the same mill primary clarifier), a strong correlation was observed between gene abundance and biochemical activity rates. However, when comparing several different nonenriched activated sludge bioreactors and separate primary clarifier microbial communities, the ratio of specific gene abundance to biochemical activity rates varied widely. These results suggest that in cases where a microbial community is not fully induced for a given biochemical activity or when very different communities are compared, quantitative gene probing can give a better measure of a community's potential to carry out the encoded function than can the relevant biochemical assay. However, the gene quantitation method employed here probably underestimated the true number of probed genes present in the microbial communities due to nirS and nifH genes in the communities having reduced DNA sequence similarity with the probes used.     

Effects of pulp and paper mill effluents on estuarine and marine ecosystems in Canada: a review

This review examines the impact of pulp and paper mill effluents by comparing effects from Canada's east and west coasts at a time when revisions to the federal Fisheries Act (Pulp and Paper Effluent Regulations) are being finalized. Pulp and paper mill effluents from Canadian coastal mills were usually acutely toxic at source, and in many cases had marked deleterious effects on receiving waters due to toxicity, high biochemical oxygen demand (BOD), and total suspended solids (TSS) loadings. Extreme reductions in ambient dissolved oxygen, impacts on benthic and intertidal organisms, changes in water colour and primary productivity, have been demonstrated over the years and continue to cause environmental damage. Contamination of biota by a wide range of chlorinated organic compounds has been more recently the focus of investigations.While sublethal effects of lowered dissolved oxygen levels and suspended solids on the water column and bottom communities are well known, the potential effects of major organochlorine contamination of water (measured as Adsorbable Organic Halogens=AOX), sediments, and biota are not fully understood, especially under natural and perturbated conditions. The findings of recent North American and Scandinavian studies which describe liver enzyme activation, histological damage, reproductive and population level changes in fish, are a major concern as they are a sign of ecosystem stress and pathology.The environmental effects described herein are long-term impacts which will not respond quickly to changes in pollutant loading. Integrated site-specific assessments need to be undertaken to document ecosystem response to process and treatment improvements at mill sites. Current biomonitoring techniques including measures of population structure and ecosystem function are needed in addition to sensitive biochemical indicators of contaminant exposure.     

Viscosity dynamics and the production of extracellular polymeric substances and soluble microbial products during anaerobic digestion of pulp and paper mill wastewater sludges

Bioprocess and Biosystems Engineering - The production processes of the pulp and paper industry often run in campaigns, leading to large variations in the composition of wastewaters and waste...     

Characterisation of organic fractions of pulp and paper mill wastewater with a manometric respirometric biochemical oxygen demand method and automatic chemical oxygen demand analyses

Abstract

The manometric respirometric method was applied to a characterisation of organic material in pulp and paper mill wastewater, which is usually high in organic content and inhibitory substances. Preliminary tests, including experiments with an extra microbial seed as well as dilution series, were carried out before the characterisation analyses in order to optimise the method. Three different physical-chemical methods were then used to characterise organic fractions. Influent organic fractions were specified with two methods in which the determination of the soluble biodegradable and the soluble inert fraction differed. In the third method, the influent fractions as well as the new metabolic products generated during the biodegradation process and an estimate of the mineralised part of the influent biodegradable fraction were determined without any hypothetical conversion factors. The results showed that a remarkable part of the detected oxygen demand was consumed for the biotransformation of biodegradable fractions into new inert organic products, not only for mineralisation. The amount of these new metabolic products, measured after biochemical oxygen demand analyses, was significant. It was also noticed that volatile organic compounds can have an influence on the chemical oxygen demand value of effluents.     

Nitrogen and phosphorus removal by high latitude mat-forming cyanobacteria for potential use in tertiary wastewater treatment

As part of a program to develop biological wastewatertreatment systems for cold climate areas four strainsof filamentous, mat-forming cyanobacteria isolatedfrom Arctic and Antarctic environments were evaluatedfor their nutrient stripping and growth capabilities. A tropical strain, Phormidium bohneri, known forits excellent performance in wastewater treatment, wasused as a comparison. Experiments were done inartificial media under controlled batch cultureconditions to avoid interactions with indigenousmicroorganisms such as bacteria and protozoa. Theculture medium simulated real effluents containinghigh concentrations of nitrate and phosphate.Temperatures (5, 15 and 25^°C) and irradiances(80, 210, 350, 640 and 1470 µmol photon m^-2s^-1) wereselected according to situations encountered in avariety of field conditions. For all irradiancelevels, growth was satisfactory at 15 and 25 ^°C,but limited at 5 ^°C. At 25 ^°C a satisfactory nitrogen removal rate (3.5and 4.0 mg N L^-1d^-1) was obtained forone polar strain (Phormidium tenue) and thecontrol P. bohneri. At 15 ^°C, the bestnitrogen removal rate (3.5 mg N L^-1d^-1)was measured with P. bohneri while the best ratefor the polar strains was around 2.3 mg NL^-1d^-1. At 15 ^°C, a phosphorusremoval rate of 0.6 mg P L^-1d^-1 wasobtained with P. bohneri and polar strains P. tenue and Oscillatoria O-210. Nitrogen(NO₃ ^-) and phosphorus (PO₄ ^3-)uptake rates increased as a function of irradianceover the range 80 to 350 molphoton m^-2s^-1. Our results indicate thattertiary biological wastewater treatment at lowtemperatures (5 ^°C) cannot be anticipated withthe polar strains tested, because they arepsychrotrophic rather than psychrophilic and thus growtoo slowly under conditions of extreme cold. However, it appears that these cyanobacteria would beuseful for wastewater treatment at moderately cooltemperatures (c. 15 ^°C), which are commonduring spring and fall in northern climates.     

Bacterial metabolism of chlorinated dehydroabietic acids occurring in pulp and paper mill effluents

Chlorinated dehydroabietic acids are formed during the chlorine bleaching of wood pulp and are very toxic to fish. Thus, destruction of these compounds is an important function of biological treatment systems for pulp and paper mill effluents. In this study, 12 strains of diverse, aerobic resin acid-degrading bacteria were screened for the ability to grow on chlorinated dehydroabietic acids as sole organic substrates. All seven strains of the class Proteobacteria able to use dehydroabietic acid were also able to use a mixture of 12- and 14-chlorodehydroabietic acid (Cl-DhA). None of the strains used 12,14-dichlorodehydroabietic acid. Sphingomonas sp. strain DhA-33 grew best on Cl-DhA and simultaneously removed both Cl-DhA isomers. Ralstonia sp. strain BKME-6 was typical of most of the strains tested, growing more slowly on Cl-DhA and leaving higher residual concentrations of Cl-DhA than DhA-33 did. Strains DhA-33 and BKME-6 mineralized (converted to CO(inf2) plus biomass) 32 and 43%, respectively, of carbon in Cl-DhA consumed. Strain DhA-33 produced a metabolite from Cl-DhA, tentatively identified as 3-oxo-14-chlorodehydroabietin, and both strains produced dissolved organic carbon which may include unidentified metabolites. Cl-DhA removal was inducible in both DhA-33 and BKME-6, and induced DhA-33 cells also removed 12,14-dichlorodehydroabietic acid. Based on activities of strains DhA-33 and BKME-6, chlorinated DhAs, and potentially toxic metabolite(s) of these compounds, are relatively persistent in biological treatment systems and in the environment.     

Bioremediation of pulp and paper mill effluent by a novel fungal consortium isolated from polluted soil

Two basidiomycetous fungi (Merulius aureus syn. Phlebia sp. and an unidentified genus) and a deuteromycetous fungus (Fusarium sambucinum Fuckel MTCC 3788) were isolated from soils affected with effluents of a pulp and paper mill over several years. These isolates were immobilized on nylon mesh and the consortium was used for bioremediation of pulp and paper mill effluent in a continuously aerated bench-top bioreactor. The treatment resulted in the reduction of color, lignin and COD of the effluent in the order of 78.6%, 79.0% and 89.4% in 4 days. A major part of reductions in these parameters occurred within first 24h of the treatment, which was also characterized by a steep decline in the pH of the effluent. During this period, total dissolved solids, electrical conductivity and salinity of the effluent also registered marked decline. It is pertinent to note that this is the first report of bioremediation of pulp and paper mill effluent by an immobilized fungal consortium.     

Euglena sp. as a suitable source of lipids for potential use as biofuel and sustainable wastewater treatment

Prolific algal growth in sewage ponds with high organic loads in the tropical regions can provide cost-effective and efficient wastewater treatment and biofuel production. This work examines the ability of Euglena sp. growing in wastewater ponds for biofuel production and treatment of wastewater. The algae were isolated from the sewage treatment plants and were tested for their nutrient removal capability. Compared to other algae, Euglena sp. showed faster growth rates with high biomass density at elevated concentrations of ammonium nitrogen (NH₄-N) and organic carbon (C). Profuse growth of these species was observed in untreated wastewaters with a mean specific growth rate (μ) of 0.28 day^?1 and biomass productivities of 132 mg ?L^?1? day^?1. The algae cultured within a short period of 8 days resulted in the 98 % removal of NH₄-N, 93 % of total nitrogen 85 % of ortho-phosphate, 66 % of total phosphate and 92 % total organic carbon. Euglenoids achieved a maximum lipid content of 24.6 % (w/w) with a biomass density of 1.24 g ?L^?1 (dry wt.). Fourier transform infrared spectra showed clear transitions in biochemical compositions with increased lipid/protein ratio at the end of the culture. Gas chromatography and mass spectrometry indicated the presence of high contents of palmitic, linolenic and linoleic acids (46, 23 and 22 %, respectively), adding to the biodiesel quality. Good lipid content (comprised quality fatty acids), efficient nutrient uptake and profuse biomass productivity make the Euglena sp. as a viable source for biofuel production in wastewaters.     

Heterogeneity and spatial distribution of bacterial background contamination in pulp and process water of a paper mill

Identifying the source and the distribution of bacterial contaminant communities in water circuits of industrial applications is critical even when the process may not show signs of acute biofouling. The endemic contamination of facilities can cause adverse effects on process runability but may be masked by the observed daily variability. The distribution of background communities of bacterial contaminants may therefore be critical in the development of new site-specific antifouling strategies. In a paper mill as one example for a full-scale production process, bacterial contaminants in process water and pulp suspensions were mapped using molecular fingerprints at representative locations throughout the plant. These ecological data were analyzed in the process–engineering context of pulp and water flow in the facilities. Dispersal limits within the plant environment led to the presence of distinct groups of contaminant communities in the primary units of the plant, despite high flows of water and paper pulp between units. In the paper machine circuit, community profiles were more homogeneous than in the other primary units. The variability between sampled communities in each primary unit was used to identify a possible point source of microbial contamination, in this case a storage silo for reused pulp. Part of the contamination problem in the paper mill is likely related to indirect effects of microbial activity under the local conditions in the silo rather than to the direct presence of accumulated microbial biomass.     

The potential of legumes as a nitrogen source for the reclamation of derelicht land

Summary White clover (Trifolium repens) growing in association with grasses on colliery spoil amended with lime and complete fertilizer proved to be an effective nitrogen source for the developing ecosystem. Nitrogen transfer from the clover to an associated grass became aparent within 22 months of sowing.