Forest Industry Wastewater Research Articles

Long term experience with the nutrient limited BAS process for treatment of forest industry wastewaters

The nutrient limited biofilm-activated sludge (BAS) process was developed with the aim to ensure maximum biological treatment efficiency in combination with good process stability, low sludge production and minimum effluent concentration of nutrients. The first full scale nutrient limited BAS (NLBAS) processes were implemented at Södra Cell Värö and Stora Enso Hylte in 2002. Since then another three full scale installations have been built. The aim of this study was to investigate and summarise the long-term treatment results, process stability, sludge production and sludge characteristics for the five full scale NLBAS processes. It was of particular interest to compare the nutrient limited operating mode with regard to the different types of production and wastewater that the mills represent (kraft, TMP and newsprint, bleached CTMP). The study showed that after the initial start-up period, which varied from a couple of weeks to three to four months, all plants meet their respective discharge limits. The sludge production for the different plants varies between 0.07 and 0.15 kg TSS/kg COD and the sludge characteristics are with few exceptions excellent. In conclusion, the nutrient limited BAS process is suitable for both upgrades and new installations of biological treatment for different types of forest industry wastewaters.

Application of Ozonation and Biotreatment for Forest Industry Wastewater

This research is focused on the integrated process for the treatment of bleached Kraft pulp mill effluents. Pre-ozonation of softwood and hardwood combined bleaching effluents at alkaline pH resulted in 50 and 44% COD abatement, respectively. Segregation of highly polluted streams of bleaching process can be recommended to reduce the cost of treatment since the COD removal yield of CEH effluents was higher than combined bleaching effluents. Moreover, biodegradability of CEH effluents in terms of BOD5/COD ratio was increased from 0.16 to 0.32. Noticeable color removal was achieved by pre-ozonation of the CEH stage and combined bleaching effluents. Pre-ozonation enhanced the performance of subsequent algal treatment in the sequential batch reactor (SBR) and activated sludge treatment. Algae have a higher ability to degrade AOX producing compounds together with a high COD removal rate. Although pre-ozonation increased the abatement rate of COD of SBR, the AOX removal rate remained constant as 87%.

The fate of metals in forest industry wastewater treatment systems

The capture/removal of a range of metals was estimated for a number of pulp and paper wastewater treatment systems. Both long-term wastewater data and accumulated sludge data were examined. Only copper and lead were effectively captured (greater than 50%) by all sites and estimate methods. Zinc capture exceeded 50% in all but one case. Qualitatively, iron, aluminium, cadmium, and cobalt were usually captured to a significant extent. The sludge inventory-based approach and the wastewater system inlet-outlet approach gave reasonably similar capture estimates.

Effects of Composted Pulp and Paper Industry Wastewater Treatment Residuals on Soil Properties And Cereal Yield

The aim of this study was to investigate effects of pulp and paper industry wastewater treatment sludge composts on soil and cereal crops. Five forest industry wastewater sludge composts were tested in a field study which was conducted in a silty clay soil in southern Finland with barley in 1998, with oats in 1999 and with barley in 2000. Two composts contained only pulp mill biosludge and bark in a ratio of 1:4 and 1:2, respectively. Two other composts were mixtures of biosludge and primary sludge with the addition of bark in a ratio of 1:2 and 3:4, respectively. These two wastewater sludges originated from a pulp mill and from a recycled paper mill. The fifth compost consisted of biosludge and primary sludge from a board mill. Two application rates of each compost were studied: the low rate was based on an annual P fertilization rate recommended for barley, 50-200 m3/ha; and the high rate was a double or triple the low rate depending on the mineral N concentration of the compost, 150-600 m3/ha. Based on the Finnish fertilizer recommendations, nutrient demands of the test plants were annually fulfilled by mineral fertilizers depending on the treatment. Total contents of N, P, K and Ca in composts were 8.8-17.5, 0.7-3.9, 1.5-6.5, and 4-25 g/kg dry matter, respectively. Especially at high doses, composts had beneficial effects on soil bulk density, porosity, C and N contents and C:N ratio. Despite the high total N rates applied with the composts, the mineralization following crop harvest did not significantly increase soil nitrate late autumn or following spring as compared to the soils that received mineral fertilization. There was no significant difference in the grain yields between plots that received mineral fertilization and compost treatments supplemented with mineral fertilizers. However, there was a decreased fertilization effect of some composts on straw yields during the first experimental year, indicating immobilization of mineral N. Heavy metals added in soil with the composts did not significantly increase their concentrations in the grain crops. All the composts had relatively low nutrient contents and low fertilizing value, but beneficial effects on soil properties and were regarded as soil conditioners. Soil improving and fertilizing effects of the composts varied annually depending on the weather conditions during the growing season. Heavy metal concentrations of the composts studied were far below the limit values set for the soil conditioners in the Finnish government regulations.

Composting and utilization of forest industry wastewater sludges

Two different forest industry wastewater sludges were composted in piles. The piles were founded with leachate collection systems. The aim was to study the progress of the composting process, the amount and quality of leachates as well as the toxicity of the sludges and leachates. The sludges consisted of mixtures of primary and biosludge. The piles were monitored for eight months by physical measurements, chemical analyses and toxicity tests. The leachates were collected for six months. The lignin concentrations and the amount of mycelium were measured from the sludges and from the soil. Test plots and control plots were established to a field with different amounts of composted sludge in order to study the applicability of the sludges in agriculture. The results showed that both sludges were amenable to composting. The original sludges were toxic but the toxicity decreased during composting and all the sludges were proved to be non-toxic at the end of composting. The leachates were determined non-toxic and the heavy metal concentrations were low in both sludges and leachates. The sludges proved to be suitable for use as soil improver in agricultural plant production.

Controlling the Settling of Activated Sludge in Pulp and Paper Wastewater Treatment Plants

Forest industry wastewaters are difficult to clean: hydraulic and organic load variations, filamentous bulking or pin-point flocs negatively impact depollution processes. The addition of a fine, mineral, talc-based powder, Aquatal, into the aeration tanks of wastewater treatment plants connected to pulp and paper factories has been successfully tested since end of '97. The first case-study presents full results obtained over a period of 18 months in a 20,000 p.e. plant connected to a paper factory. The mineral powder was regularly added to control sludge volume index, thereby ensuring low suspended solids concentration in the outfluent. Plant operators could easily adapt biomass concentration to match organic load variation, thereby maintaining pollution micro-organisms ratio constant. In a second case study, a trouble-shooting strategy was implemented to counteract filamentous bulking. A one-off, large dosage enabled the plant operator to deal effectively with poor settleability sludge and rapidly control sludge blanket expansion. In both cases, the main common characteristics observed were an increase in floc aggregation and the production of heavier and well-structured flocs. The sludge settling velocity increased and an efficient solid/liquid separation was obtained. After a few days, the mineral particles of Aquatal were progressively integrated into the sludge floc structure. When the mineral powder was added to the activated sludge in the aeration basin, chemical interactions frequently encountered with other wastewater treatment additives did not pose a problem. Moreover, with this mineral additive, the biological excess sludge displayed good thickening properties and dewatering was improved. Despite the addition of the insoluble mineral particles, the amount of wet sludge expelled did not increase. Aquatal offers a rapid solution to floc settleability problems which so frequently arise when physical or biological disorders appear in forest industry wastewater treatment plants.

Accuracy of Water Quality Predictions with Loading Scenarios of Forest Industry Waste Waters

The environmental effects of the Finnish industrial loadings are in practice decided by water courts as they give permits. In decision-making they use an inspection procedure. Since 1970s in Finland within this procedure one method of environmental evaluation has been the application of numerical water quality models. At the Kokemäenjoki watercourse water quality effects of the paper and pulp mills in Mänttä, Lielahti and Valkeakoski were studied with two or three dimensional water quality models. On the basis of these results the costs and benefits of different loading options were considered. Now, after more than a decade, the response of the lake waters to the nutrient and BOD loading can be seen in the water quality monitoring results. We used these observations and studied the accuracy and limitations of these early water quality models.

Composting of Forest Industry Wastewater Sludges for Agricultural Use

The feasibility of composting of pulp and paper industry sludges was studied. The aim was to study the progress of the composting process and the toxicity and applicability of the sludges in agriculture. Five different sludges were used: two biosludges and three biosludge and primary sludge mixtures. The sludges were composted in seven piles, two smaller of them founded with leachates collection systems. The piles were monitored throughout the composting period by physical measurements, chemical analyses and toxicity tests. Also the lignin concentrations were measured from the sludges and from the soil as well as the amount of mycelium. The results showed that all sludges were easily composted and they will be suitable for the use as soil improvement in agricultural plant production. Toxicity of the sludges decreased during composting and all the sludges were proved to be non-toxic at the end of the composting. Heavy metal concentrations were low in all sludges and leachates. The leachates were also non-toxic and the concentrations of nutrients were low.

Controlling the settling of activated sludge in pulp and paper wastewater treatment plants

Forest industry wastewaters are difficult to clean: hydraulic and organic load variations, filamentous bulking or pin-point flocs negatively impact depollution processes. The addition of a fine, mineral, talc-based powder, Aquatal, into the aeration tanks of wastewater treatment plants connected to pulp and paper factories has been successfully tested since end of 997. The first case-study presents full results obtained over a period of 18 months in a 20,000 p.e. plant connected to a paper factory. The mineral powder was regularly added to control sludge volume index, thereby ensuring low suspended solids concentration in the outfluent. Plant operators could easily adapt biomass concentration to match organic load variation, thereby maintaining pollution micro-organisms ratio constant. In a second case study, a trouble-shooting strategy was implemented to counteract filamentous bulking. A one-off, large dosage enabled the plant operator to deal effectively with poor settleability sludge and rapidly control sludge blanket expansion. In both cases, the main common characteristics observed were an increase in floc aggregation and the production of heavier and well-structured flocs. The sludge settling velocity increased and an efficient solid/liquid separation was obtained. After a few days, the mineral particles of Aquatal were progressively integrated into the sludge floc structure. When the mineral powder was added to the activated sludge in the aeration basin, chemical interactions frequently encountered with other wastewater treatment additives did not pose a problem. Moreover, with this mineral additive, the biological excess sludge displayed good thickening properties and dewatering was improved. Despite the addition of the insoluble mineral particles, the amount of wet sludge expelled did not increase. Aquatal offers a rapid solution to floc settleability problems which so frequently arise when physical or biological disorders appear in forest industry wastewater treatment plants.

Accuracy of water quality predictions with loading scenarios of forest industry waste waters

The environmental effects of the Finnish industrial loadings are in practice decided by water courts as they give permits. In decision-making they use an inspection procedure. Since 1970s in Finland within this procedure one method of environmental evaluation has been the application of numerical water quality models. At the Kokemaenjoki watercourse water quality effects of the paper and pulp mills in Mantta, Lielahti and Valkeakoski were studied with two or three dimensional water quality models. On the basis of these results the costs and benefits of different loading options were considered. Now, after more than a decade, the response of the lake waters to the nutrient and BOD loading can be seen in the water quality monitoring results. We used these observations and studied the accuracy and limitations of these early water quality models.

Composting of forest industry wastewater sludges for agricultural use

Abstract The feasibility of composting of pulp and paper industry sludges was studied. The aim was to study the progress of the composting process and the toxicity and applicability of the sludges in agriculture. Five different sludges were used: two biosludges and three biosludge and primary sludge mixtures. The sludges were composted in seven piles, two smaller of them founded with leachates collection systems. The piles were monitored throughout the composting period by physical measurements, chemical analyses and toxicity tests. Also the lignin concentrations were measured from the sludges and from the soil as well as the amount of mycelium. The results showed that all sludges were easily composted and they will be suitable for the use as soil improvement in agricultural plant production. Toxicity of the sludges decreased during composting and all the sludges were proved to be non-toxic at the end of the composting. Heavy metal concentrations were low in all sludges and leachates. The leachates were also non-toxic and the concentrations of nutrients were low.

Thermophilic anaerobic treatment of sulphur rich forest industry wastewater.

Thermophilic anaerobic treatment of sulphur-rich paper mill wastewater (0.8-3.1 gCOD/1, 340-850 mgSO4/l; COD:SO4 3.4-5.3) was studied in three laboratory-scale, upflow anaerobic sludge blanket (UASB) reactors and in bioassays. The reactors were inoculated with non-adapted thermophilic granular sludge. In the bioassays, no inhibition of the inoculum was detected and about 62% COD removal (sulphide stripped) was obtained. About 70 to 80% of the removed COD was methanised. In the reactors, up to 60-74% COD removal (effluent sulphide stripped) was obtained at loading rates up to 10-30 kgCOD/m3d and hydraulic retention times down to 6 to 2 hours. The effluent total sulphide was up to 150-250 mg/l. Sulphide inhibition could not be confirmed from the reactor performances. The results from bioassays suggested that both the inoculum and sludge from the UASB reactor used acetate mainly for methane production, while sulphide was produced from hydrogen or its precursors.

Solid, slightly soluble phosphorus compounds as nutrient source in activated sludge treatment of forest industry wastewaters

The aim of the study was to determine if solid, slightly soluble compounds can be used as nutrient source in activated sludge treatment plants instead of liquid phosphoric acid. Four different solid materials were tested in lab-scale solubility tests to find compounds which are least soluble. Two materials were chosen for further studies: apatite and raw phosphate. The use of apatite and raw phosphate as nutrient source was studied in lab-scale activated sludge reactors along with a control reactor where phosphorus was added in liquid form. The phosphorus dosage, measured as elementary phosphorus, was the same for all three reactors. The reactors were fed with pre-clarified chemi-thermomechanical pulp mill (CTMP) wastewater. There were no significant differences in the reductions of organic matter between the three reactors. The mean effluent concentration of total phosphorus was 3 mg P/l in the control reactor and less than 1 mg P/1 in the other two reactors. The soluble phosphorus concentration was more than 2 mg P/l in the control reactor and less than 0.5 mg P/l in the other two. Apatite was an even better nutrient source than raw phosphate. Further lab-scale tests were conducted using two different grain sizes of apatite. No significant differences were found between the studied grain sizes (<0.074 mm and 0.074 mm-0.125 mm). Apatite was then used in full-scale at a CTMP-mill two different times. The experiments showed that the mean concentrations of phosphorus can be reduced radically by using apatite as a nutrient source instead of liquid phosphorus. Solid phosphorus compounds are a viable alternative to reduce the phosphorus load from forest industry wastewater treatment plants.

Solid, slightly soluble phosphorus compounds as nutrient source in activated sludge treatment of forest industry wastewaters

The aim of the study was to determine if solid, slightly soluble compounds can be used as nutrient source in activated sludge treatment plants instead of liquid phosphoric acid. Four different solid materials were tested in lab-scale solubility tests to find compounds which are least soluble. Two materials were chosen for further studies: apatite and raw phosphate. The use of apatite and raw phosphate as nutrient source was studied in lab-scale activated sludge reactors along with a control reactor where phosphorus was added in liquid form. The phosphorus dosage, measured as elementary phosphorus, was the same for all three reactors. The reactors were fed with pre-clarified chemi-thermomechanical pulp mill (CTMP) wastewater.There were no significant differences in the reductions of organic matter between the three reactors. The mean effluent concentration of total phosphorus was 3 mg P/1 in the control reactor and less than 1 mg P/1 in the other two reactors. The soluble phosphorus concentration was more than 2 mg P/I in the control reactor and less than 0.5 mg P/1 in the other two. Apatite was an even better nutrient source than raw phosphate. Further lab-scale tests were conducted using two different grain sizes of apatite. No significant differences were found between the studied grain sizes (< 0.074 mm and 0.074 mm -0.125 mm).Apatite was then used in full-scale at a CTMP-mill two different times. The experiments showed that the mean concentrations of phosphorus can be reduced radically by using apatite as a nutrient source instead of liquid phosphorus. Solid phosphorus compounds are a viable alternative to reduce the phosphorus load from forest industry wastewater treatment plants.

Optimal growth conditions for Acinetobacter isolates from activated sludge treating forest-industry wastewaters

Three Acinetobacter isolates (identified by API 20 NE as A. baumannii, A. junii, A. lwoffii) from activated sludge treating forest-industry wastewaters were used as model organisms for polyphosphate-accumulating bacteria to optimize growth conditions for acinetobacters. The optimal concentrations of carbon, nitrogen, phosphorus, magnesium and potassium for the growth of these isolates were determined by using four sets of factorially designed experiments. Maximum growth was obtained with an average C:N:P ratio of 100:14:1.5 (on a weight basis) in the medium. The average N:P ratio of about 10 is twice the ratio that is usually considered optimal for bacterial growth in activated sludge. Magnesium and potassium are crucial for polyphosphate metabolism. A. baumannii did not respond to either magnesium or potassium additions, and A. junii had a linear response to potassium. Comparison of the optimal molar Mg:P (0.93–1.8) and K:P (0.56) ratios obtained for A. lwoffii and A. junii in the experiments to the corresponding ratios in the influent wastewaters indicates that magnesium and potassium would not limit growth and concomitant polyphosphate formation in acinetobacters. The results based on the optimal concentrations of elements in the medium may provide a better basis for optimizing the growth conditions than data on the chemical composition of bacterial cells.

Optimal growth conditions for Acinetobacter isolates from activated sludge treating forest-industry wastewaters

Optimal growth conditions for Acinetobacter isolates from activated sludge treating forest-industry wastewaters

Dissolved air flotation in the treatment of industrial wastewaters with a special emphasis on forest and foodstuff industries

The suspended solids separation is an essential element in almost any wastewater treatment system. If sedimentation, dissolved air flotation and filtration are compared, flotation has both the largest operational ranges concerning influent suspended solids concentration and particle size, and load bearing capacities. When considering the suitability of flotation as a wastewater treatment process, important factors are the effluent and sludge qualities, operation and costs. To get a comprehensive conception of flotation, those factors are presented and discussed. Flotation is widely used in forest industry wastewater treatment, as well as in process water recirculation. It is also proven technology in foodstuff industry wastewater treatment. Several cases from both industries are presented.

Dissolved air flotation in the treatment of industrial wastewaters with a special emphasis on forest and foodstuff industries

The suspended solids separation is an essential element in almost any wastewater treatment system. If sedimentation, dissolved air flotation and filtration are compared, flotation has both the largest operational ranges concerning influent suspended solids concentration and particle size, and load bearing capacities. When considering the suitability of flotation as a wastewater treatment process, important factors are the effluent and sludge qualities, operation and costs. To get a comprehensive conception of flotation, those factors are presented and discussed. Flotation is widely used in forest industry wastewater treatment, as well as in process water recirculation. It is also proven technology in foodstuff industry wastewater treatment. Several cases from both industries are presented.

Overview of the Anaerobic Toxicity Caused by Organic Forest Industry Wastewater Pollutants

Numerous types of organic environmental pollutants are encountered in forest industry effluents which potentially could inhibit consortia of anaerobic bacteria. The purpose of this study was to collect anaerobic bioassay data from the literature to better estimate the impact of these pollutants on anaerobic wastewater treatment systems. The most important methanogenic inhibitors in forest industry wastewaters are wood resin, chlorophenols and tannins. These compounds account for toxicity in alkaline pulping liquors, bleaching effluents and debarking wastewaters, respectively. Adaptation to chlorophenol toxicity can be expected since they are eventually degraded in anaerobic systems. Wood resin compounds, on the other hand, are not biodegraded anaerobically and therefore their toxicity is persistent. Toxicity in forest industry wastewaters does not necessarily preclude anaerobic treatment. A variety of techniques can be employed to diminish inhibition, such as dilution and detoxification treatments.

Presumptive fecal streptococci in environmental samples characterized by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

The use of fecal streptococci as fecal indicators requires better knowledge of the ecology of these bacteria. We isolated 371 presumptive fecal streptococci from environmental samples--domestic wastewater, forest industry wastewater, contaminated surface and seawater, well water, cow dung, bird droppings, and pristine waters--and clustered them according to their protein profiles in one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Some clusters could be tentatively identified with the help of reference strains. Samples from each environment had a typical composition of streptococcus types. Enterococcus faecalis was present, but not as a dominating enterococcal species, in samples in which fecal contamination was probable. Enterococcus faecium, Enterococcus durans, Enterococcus hirae, and Enterococcus mundtii had protein profiles that were difficult to distinguish from each other. These bacteria were found in a variety of samples. Enterococcus casseliflavus and Enterococcus gallinarum had identical protein profiles. On the basis of the maximum temperatures for growth and pigment production, isolates of this protein profile group common in forest industry wastewaters were identified as E. casseliflavus. Lactococcus lactis subsp. lactis was also found in this environment. Nearly all strains from pristine waters belonged to protein profile groups which could not be identified with the aid of known Aerococcus, Enterococcus, Lactococcus, or Streptococcus strains. The maximum temperatures for growth and the results of fatty acid analysis were in general agreement within each protein profile group.