Paper Mill Biosolids Research Articles

Recycling of Paper Mill Biosolids: A Review on Current Practices and Emerging Biorefinery Initiatives

In a rapidly urbanizing global society, the issue of solid waste management has become even more challenging in recent times. Manufacturing of paper, an integral part of human civilization, generates a substantial amount of effluent sludge, which invariably needs extra monetary resources to dispose‐off in millions of tons annually around the world. Currently, most of the widely practiced disposal options, landfilling and incineration, invariably pose serious environmental risks to immediate neighborhoods as well as to society at large. Recent stricter environmental legislations and general public awareness have been forcing paper producers to follow a sustainable approach in dealing with residual biomass generated at their facilities. At the same time, reducing waste at source and recycling have become an integral part of waste management of some responsible companies and governments of the industrialized world have also taken a number of initiatives in this regard. This review presents a holistic overview on current practices in dealing with paper sludge and their environmental and economic implications. Also presented is a comprehensive discussion on emerging biorefinery trends leading to value‐added utilization of primary, secondary and mixed biosolids originating from effluent treatments plants, especially from paper mill operations.

Effect of green manure and supplemental fertility amendments on selected soil quality parameters in an organic potato rotation in Eastern Canada

The effects of green manure, crop sequence and off-farm composts on selected soil quality parameters were assessed in a three-year organic potato (Solanum tuberosum L.) rotation in Eastern Canada. Three crop sequences varying in preceding green manure [red clover (RCl) + RCl, and beans/buckwheat or carrots + oats/peas/vetch mixture (OPV)] as main plots and four fertility treatments applied in the potato phase only [control; inorganic fertilizer; municipal solid waste compost (MSW); composted paper mill biosolid (PMB)] as subplots were compared. In 2008 and 2010, changes in selected soil quality parameters (0–15 cm) were assessed prior to planting of potatoes and at potato tuber initiation stage. Potentially mineralizable nitrogen (N) and the acid phosphatase enzyme activity average values across years were greater following RCl (1.51 abs and 622 kg ha−1) compared with OPV (1.32 abs and 414 kg ha−1) at potato planting. Soil NO3–N average value was greater following RCl compared with OPV (63 vs. 52 kg ha−1) at tuber initiation. For the other measured parameters, OPV and RCl were similar. The soil organic carbon (C) and particulate organic matter-C were greater under PMB and MSW (31.1 and 7.57 kg ha−1) compared with fertilizer treatment (27.9 and 6.05 kg ha−1). The microbial biomass C and microbial biomass quotient were greater under MSW (216 kg ha−1 and 0.73 %) than PMB and fertilizer (147 kg ha−1 and 0.50 %) across crop rotations. Annual legume green manures and off-farm composts can be used to satisfy potato N requirement and maintains soil quality in organic potato rotations.

Repeated Annual Paper Mill and Alkaline Residuals Application Affects Soil Metal Fractions

The application of industrial residuals in agriculture may raise concerns about soil and crop metal accumulation. A complete study using a fractionation scheme would reveal build-up in metal pools occurring after material addition and predict the transformation of metals in soil between the different forms and potential metal release into the environment. An experimental study was conducted from 2000 to 2008 on a loamy soil at Yamachiche, Quebec, Canada, to evaluate the effects of repeated annual addition of combined paper mill biosolids when applied alone or with several liming by-products on soil Cu, Zn, and Cd fractions. Wet paper mill biosolids at 0, 30, 60, or 90 Mg ha and calcitic lime, lime mud, or wood ash, each at 3 Mg ha with 30 Mg paper mill biosolids ha, were surface applied after seeding. The soils were sampled after 6 (soybean [ (L.) Merr.]) and 9 [corn ( L.)] crop years and analyzed using the Tessier fractionation procedure. Results indicated that biosolids addition increased exchangeable Zn and Cd, carbonate-bound Cd, Fe-Mn oxide-bound Zn and Cd, organically bound Cu and Zn, and total Zn and Cd fractions but decreased Fe-Mn oxide-bound Cu in the uppermost 30-cm layer. With liming by-products, there was a shift from exchangeable to carbonate-bound forms. Even with very small metals addition, paper mill and liming materials increased the mobility of soil Zn and Cd after 9 yr of application, and this metal redistribution resulted into higher crop grain concentrations.

Crop yield and soil fertility as affected by papermill biosolids and liming by-products

Ziadi, N., Gagnon, B. and Nyiraneza, J. 2013. Crop yield and soil fertility as affected by papermill biosolids and liming by-products. Can. J. Soil Sci. 93: 319–328. Papermill biosolids (PB) in combination with alkaline industrial residuals could benefit agricultural soils while diverting these biosolids from landfill. A greenhouse study was conducted to evaluate the effect of three types of PB at rates of 0, 30, and 60 wet Mg ha−1, as well as five liming by-products at 3 wet Mg ha−1 along with 30 Mg PB ha−1 on crop yield, nutrient accumulation, and soil properties. De-inking paper biosolids (DB, C/N of 65) were applied to soybean [Glycine max (L.) Merr.], and two combined PB (PB1, C/N of 31; and PB2, C/N of 14) were applied to dry bean (Phaseolus vulgaris L.) and barley (Hordeum vulgare L.), respectively. The liming by-products included lime mud (LM), wood ash (WA) from paper mills, commercial calcitic lime (CL), Mg dissolution by-product (MgD), and Mg smelting and electrolysis work (MgSE). Compared with the control, PB2 increased barley yield and total Mg and Na accumulation, and both PB increased plant N, P, and Ca accumulation in barley and dry bean. The impact of DB on soybean was limited. The addition of liming by-products to PB or DB did not affect crop attributes except the combination with MgSE, which severely reduced the growth of dry bean and, to a lesser extent, soybean. Soil NO3-N was immobilized following DB application, whereas there was a net release with both PB. Combining PB and liming by-products produced the greatest changes in soil properties at harvest. Generally, LM and CL raised pH and Mehlich-3 Ca, and MgSE caused a strong increase in Mehlich-3 Mg and Na and water-soluble Cl. When used with appropriate crops, biosolids from paper mills and alkaline residuals other than MgSE can efficiently enhance soil fertility by providing organic C and macronutrients for balanced crop fertilization.

Crop yield and soil fertility as affected by papermill biosolids and liming by-products

Ziadi, N., Gagnon, B. and Nyiraneza, J. 2013. Crop yield and soil fertility as affected by papermill biosolids and liming by-products. Can. J. Soil Sci. 93: 319-328. Papermill biosolids (PB) in combination with alkaline industrial residuals could benefit agricultural soils while diverting these biosolids from landfill. A greenhouse study was conducted to evaluate the effect of three types of PB at rates of 0, 30, and 60 wet Mg ha-1, as well as five liming by-products at 3 wet Mg ha-1 along with 30 Mg PB ha-1 on crop yield, nutrient accumulation, and soil properties. De-inking paper biosolids (DB, C/N of 65) were applied to soybean [Glycine max (L.) Merr.], and two combined PB (PB1, C/N of 31; and PB2, C/N of 14) were applied to dry bean (Phaseolus vulgaris L.) and barley (Hordeum vulgare L.), respectively. The liming by-products included lime mud (LM), wood ash (WA) from paper mills, commercial calcitic lime (CL), Mg dissolution by-product (MgD), and Mg smelting and electrolysis work (MgSE). Compared with...

Metal Availability following Paper Mill and Alkaline Residuals Application to Field Crops

Land application of residuals from the forest industry can help to restore soil fertility, but few studies have assessed the effects of metal accumulation in plants. An experimental study was initiated in 2000 on a loamy soil at Yamachiche, QC, Canada, to evaluate the effects of repeated annual applications of combined paper mill biosolids, when applied alone or with several liming by-products. This study assessed the accumulation of Cu, Zn, Mo, and Cd in plants and soil after 6 (soybean [ (L.) Merr.]) and 9 [corn ( L.)] crop yr. Wet paper mill biosolids at 0, 30, 60, or 90 Mg ha were surface applied after seeding. Calcitic lime, lime mud, and wood ash were applied wet each at 3 Mg ha with 30 Mg wet paper mill biosolids ha. Repeated applications of paper mill biosolids increased plant and soil metal concentrations after 6 and 9 yr in the order of Cd > Mo (soybean) > Zn > Cu. Liming increased soil pH and Mo availability and decreased Zn and Cd availability. Metals in crop stover responded more positively to applications than those in grains, but the concentrations in plant tissues were generally well below critical values. The Cu/Mo ratio of soybean plants at pH > 6.8 fell below 2:1, however, and may pose a risk for inducing Cu metabolism disorder in ruminants. Results of this study indicate that paper mill biosolids and alkaline residuals, when applied with respect to regulations and soil pH, have a limited effect on metal accumulation in plants and soil.

Papermill biosolids and alkaline residuals affect crop yield and soil properties over nine years of continuous application

Gagnon, B. and Ziadi, N. 2012. Papermill biosolids and alkaline residuals affect crop yield and soil properties over nine years of continuous application. Can. J. Soil Sci. 92: 917-930. Residues from paper and wood mills are a valuable source of nutrients for field crops, but little is known about the effectiveness of repeated applications over many years. A study was initiated at Yamachiche, QC, to assess the effect of continuous applications over 9 yr of combined papermill biosolids (PB), applied alone or with several liming by-products, on grain yield, plant nutrient accumulation, and soil fertility in a loamy soil cropped to grain corn, dry bean, and soybean. The PB treatments (0, 30, and 60 Mg wet ha−1) and liming by-products [calcitic lime (CL), lime mud (LM), wood ash (WA)], and two magnesium residuals, each at 3 Mg wet ha−1 along with 30 Mg PB ha−1) were surface applied annually at post-seeding. In the last 6 yr, the two treatments receiving magnesium residuals were replaced with 90 Mg wet PB ha−1 and mineral N fertilizer (MIN), respectively. Repeated annual applications of LM followed by CL increased soil pH the most (up to 1.4 unit). Crop yields were not significantly affected by treatments in the first 3 yr but subsequent applications of PB at 90 Mg ha−1 increased yields in grain corn (+1.9 Mg ha−1) and dry bean (+0.77 Mg ha−1) relative to the control, while PB with WA increased yield in soybean (+0.85 Mg ha−1). The PB at 30 Mg wet ha−1 with supplemental N (average of 45 kg N ha−1), or at 60 Mg wet ha−1 applied alone, achieved yields comparable with MIN treatment under corn. The PB applications increased soil organic matter and all major soil nutrients except K and Mg. The results of this study indicate that PB and alkaline residuals can be effectively applied to agricultural soils over many years although PB exceeding 60 Mg wet ha−1 yr−1 induce significant nitrate leaching.

Papermill biosolids and alkaline residuals affect crop yield and soil properties over nine years of continuous application

Gagnon, B. and Ziadi, N. 2012. Papermill biosolids and alkaline residuals affect crop yield and soil properties over nine years of continuous application. Can. J. Soil Sci. 92: 917-930. Residues from paper and wood mills are a valuable source of nutrients for field crops, but little is known about the effectiveness of repeated applications over many years. A study was initiated at Yamachiche, QC, to assess the effect of continuous applications over 9 yr of combined papermill biosolids (PB), applied alone or with several liming by-products, on grain yield, plant nutrient accumulation, and soil fertility in a loamy soil cropped to grain corn, dry bean, and soybean. The PB treatments (0, 30, and 60 Mg wet ha-1) and liming by-products [calcitic lime (CL), lime mud (LM), wood ash (WA)], and two magnesium residuals, each at 3 Mg wet ha-1 along with 30 Mg PB ha-1) were surface applied annually at post-seeding. In the last 6 yr, the two treatments receiving magnesium residuals were replaced with 90 Mg wet PB ha-1...

Biosolids from Treated Swine Manure and Papermill Residues Affect Corn Fertilizer Value

Biosolids derived from treatment of animal manure or industrial effluents can be used on farms, but their fertilizer value must be assessed. A 3‐yr field study was conducted on a clay soil in Quebec, Canada, to evaluate the effect of several biosolids on silage corn dry matter (DM) yield; N‐use efficiency; and soil N, P, Cu, and Zn availability. Raw liquid swine (Sus scrofa) manure (LSM), biosolids from four swine manure treatments (aerobic digestion [AER], anaerobic digestion [DIG], filtration [FIL], anaerobic digestion followed by chemical flocculation [DIG+FLO]), combined papermill biosolids (CPB), de‐inking paper biosolids (DPB), and mineral N fertilizer (MIN) were applied before corn planting at a targeted rate of 150 kg total N ha−1. The DIG and DIG+FLO biosolids resulted in silage corn DM yield, N accumulation, and early season soil N availability comparable to LSM with an N‐use efficiency about 70% of that for MIN. The AER biosolid resulted in low DM yield with an N‐use efficiency only 10% of that for MIN; FIL and CPB had an N‐use efficiency almost 40% of that for MIN, whereas DPB caused a decline in DM yield compared to a no‐N control. The LSM‐derived biosolids increased availability of soil P (0.34 kg kg−1 excess P) and, to some extent, Cu and Zn. The CPB and DPB biosolids had little impact on soil P, but DPB markedly increased Zn availability. Manure‐derived biosolids and CPB were satisfactory N sources for silage corn while manure‐derived biosolids caused soil P enrichment when applied based on crop N requirement.

GROUND BEETLES (CARABIDAE) ARE AFFECTED BY MULCH IN ORGANIC HIGHBUSH BLUEBERRIES

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Organic Horticulture: Productivity and Sustainability GROUND BEETLES (CARABIDAE) ARE AFFECTED BY MULCH IN ORGANIC HIGHBUSH BLUEBERRIES

Potential utilisation of pulp and paper mill biosolids in composting and plant production: a case study at St. Marys Papers Ltd. (Canada)

The use of St Marys Paper biosolids as a soil additive or growth cover was investigated. Biosolids were mixed with a commercial potting media in five vol/vol ratios and employed in a greenhouse study. The biosolids were found to improve Pinus banksiana seedling growth, a 50% biosolids:50% ProMix mixture yielding the tallest plants and highest dry mass. To further biologically stabilise the biosolids, in-vessel composting studies were undertaken. Results indicated that a 3 parts biosolids:1 part wood chips:1 part sawdust mixture and initial C : N ratio of 30 sustained thermophilic conditions for 12 days reaching a maximum temperature of 52°C and final C : N ratio of 21.

Soil phosphorus fractions following annual paper mill biosolids and liming materials application

Industrial by-products such as paper mill biosolids (PB) and different liming materials have been used as fertilizers and amendments in agricultural soils for many decades. However, little is known about the effects of their repeated application on soil nutrient availability, particularly phosphorus (P). A 6-yr field study (2000-2005) was conducted in the province of Quebec to investigate the effect of repeated annual applications of different PB and industrial by-products on selected soil chemical properties, especially soil P fractions. Different PB rates (0 to 90 Mg wet ha-1) and several liming products (lime mud, wood ash, calcitic lime, and Mg by-products) were annually applied to field crops after seeding. Soils were sampled before seeding in May 2003 and at harvest in October 2005. Results showed that HCl-P was the largest P pool, accounting for about 64% of the total P fraction, and that the repeated applications of liming products significantly increased this pool and decreased the organic P pools. The NaOH-Po and residual-P were significantly lower in 2005 than in 2003, indicating that PB application without supplemental P fertilizer inputs enhanced the mobility and/or mineralization of NaOH-Po and the transformation of recalcitrant P to more labile forms with time. Lime mud (LM) was found to be the best liming material owing to its high neutralization capacity and positive effect on soil P availability over time. Key words: Paper mill biosolids, alkaline residuals, lime, wood ash, soil P fractions

Nitrogen transformations revealed by isotope dilution in an organically fertilized hybrid poplar plantation

Measuring nitrogen (N) transformations from organic fertilizers can help in selecting applications rates that provide sufficient soluble N to promote tree growth in short-rotation plantations. The objective of this study was to determine how organic fertilizers (papermill biosolids, liquid pig slurry) affected microbially-mediated N transformations in soils. Soil samples were collected from a hybrid poplar plantation before fertilization, 1 month after fertilizer application and at the end of the growing season. Net N mineralization and nitrification were evaluated during a 28 d laboratory incubation, while gross N transformations were assessed using a 15N isotope dilution technique. Pig slurry application increased soil ammonium (NH4-N) and nitrate (NO3-N) concentrations within 1 month, while papermill biosolids increased soil NH4-N and NO3-N concentrations at the end of the growing season. Gross N consumption rates were greater than gross N production rates. The NH4-N and NO3-N consumption rates were positively correlated with labile carbon and microbial biomass. The gross nitrification rate was 18 to 67% of the gross mineralization rate but 30% or less of the gross NH4-N consumption rate, indicating that NH4 consumption was overestimated by the isotope dilution technique. We conclude that N cycling in this hybrid poplar plantation was characterized by rapid consumption of plant-available N following N mineralization and nitrification.

Environmental impact of repeated applications of combined paper mill biosolids in silage corn production

Paper mill biosolids (PB) may provide benefits for crop yields and soil nutrients. However, few data are available on metal accumulation and pathogenic populations resulting from applications in silage corn production. A study was initiated to determine the effect of annual spring application of combined PB during 3 consecutive years, with or without calcitic lime, on yield and on the environmental risk posed by N, P, heavy metals (Cu, Zn, Cd, Mo) and Escherichia coli to a silage corn cropped in a loamy sand in eastern Ontario, Canada. Treatments consisted of complete mineral NPK fertilization (PB0), 30 Mg wet weight ha-1 with supplemental N and K, and 60 and 120 Mg wet ha-1 supplemented with K, either with or without 2.5 Mg ha-1 calcitic lime. The PB at 30 Mg wet ha-1 with reduced mineral N and PB at 60 Mg wet ha-1 provided comparable yields to the mineral N fertilization in all years, whereas application of PB at 120 Mg wet ha-1 increased corn yield by 6.0 Mg ha-1 in the third year. After 3 yr, contents of soil NO3-N and the P saturation index (P/Al) were increased, indicating a possible risk of nitrate and P leaching. Lime increased soil pH by 0.8 unit, which in turn caused a large increase in the tissue Mo concentration and Mo uptake by silage corn. The PB, particularly at 120 Mg wet ha-1, produced significant accumulations of Cd and Zn in soil, plant tissue and uptake. The PB showed small counts of E. coli, and consequently very little contamination was observed in the soil and on the harvested crop. Based on these results, the PB used are a good source of nutrients that benefits silage corn yields and represent as well a low risk for human and animal health and for the environment when the application does not exceed 60 Mg wet ha-1 yr-1.Key words: Zea mays L., paper mill biosolids, lime, heavy metals, cadmium, molybdenum, Escherichia coli

Crop performance on soils receiving annual papermill biosolid amendments with and without supplementary nitrogen

Nitrogen availability is often a limiting factor for optimum crop growth on agricultural soils amended with papermill biosolids (PB). The objective of our study was to evaluate the effect on corn (Zea mays L.) and soybean (Glycine max L.) production of adding supplementary nitrogen fertilizer to soils amended with increasing rates of PB. Papermill biosolids were applied annually on four agricultural soils in southern Ontario, Canada. Treatments included three rates of PB (50, 100, and 150 Mg ha-1), combined with four levels of nitrogen fertilizer [crop recommended [CR], [CR] + 0.5 kg N Mg-1 PB, [CR] + 1.0 kg N Mg-1 PB, and [CR] + 1.5 kg N Mg-1 PB]. In addition, non-amended plots were also established receiving either (a) zero PB and zero nitrogen fertilizer or (b) zero PB and [CR] nitrogen fertilizer only. All the plots received the same treatment combinations, i.e., PB × N, each year for the duration of the study. In corn, [CR] nitrogen fertilizer was insufficient to satisfy plant growth and PB decomposition requirements. Supplementary nitrogen fertilizer at a rate of 1.0 kg N Mg-1 PB was generally required to maintain or increase corn grain production relative to the control plots receiving the [CR] nitrogen fertilizer only. Corn grain yield increases ranged from 1000 to 6000 kg ha-1 relative to the control at some of the research sites. The optimum rate of supplementary nitrogen fertilizer varied by soil texture (location) and year. In contrast, production of soybean did not require high supplementary nitrogen fertilizer, or in some cases any, in order to maintain or increase yields at most locations. Our study shows that nitrogen fertility management had a greater impact on yields in production systems planted to corn than soybeans while receiving annual PB amendments. No residual effects on corn yield or corn grain protein content were observed after PB amendments were stopped.Key words: Papermill biosolids, carbon:nitrogen ratio, corn, soybean, nitrogen fertilizer

Response to annual applications of de-inked papermill biosolids by field earthworms on three agricultural soils

Papermill biosolids (PB) have been used as soil conditioners on agricultural soils, to reclaim mining soils, and to rehabilitate old landfill sites. Earthworm population responses to a de-inked PB were measured on three agricultural soils in southern Ontario, Canada. Four rates of PB, 0, 50, 100, and 150 Mg ha −1, were applied annually for 3 years. In addition, plots receiving the PB treatments were planted to corn ( Zea mays L.) and soybean ( Glycine max L.). Earthworm populations prior to PB applications ranged from 9 to 22 individuals m −2 on the sandy loam and loam soils. Linear increases in earthworm populations were observed ranging from approximately 153 to 280 individuals m −2 after 3 years of PB amendments. On the clay loam soil, initial fall earthworm populations were about 124 individuals m −2 which increased to 482 individuals m −2 after 2 years of PB applications. Earthworm population increases to PB amendments were evident after 2–3 years at the sites measured.

Papermill Biosolids Effect on Soil Physical and Chemical Properties

Papermill biosolids (PB) can provide multiple benefits to the soil system. The purpose of this study was to quantify the effects of a high C/N ratio (C/N = 100) de-inked PB on soil physical and chemical properties, including soil bulk density, infiltration rates, wet aggregate stability, total soil carbon, and heavy metal concentrations. Four rates of PB (0, 50, 100, and 150 Mg ha(-1)) were applied annually, for up to 3 yr, on four agricultural soils in Ontario, Canada. Decreases in soil bulk density between 0.27 and 0.35 g cm(-3), relative to the nonamended treatment, were observed in soils receiving PB treatments over 3 yr. Total soil carbon increased within 1 yr on PB-amended soils planted to soybeans but not on soils planted to corn. Hydraulic conductivities (K fs) were greater in all soils receiving PB amendments relative to the nonamended treatment throughout the study. Other properties measured, such as pH and electrical conductivity, were relatively unchanged after 2 yr of PB applications. While some increases in heavy metal accumulation occurred, there were no clear trends observed at any of the sites related to PB rates. The results of this study provide support to the idea that annual applications of PB can add significantly to the stability of soil structure.

Mixtures of papermill biosolids and pig slurry improve soil quality and growth of hybrid poplar

AbstractHybrid poplar plantations in Quebec, Canada, are generally established on marginal agricultural lands characterized by low pH and low inherent soil fertility. Here, we tested the hypothesis that two potential organic fertilizer (OF) sources, papermill biosolids (PBs) and liquid pig slurry (LPS), would improve soil quality and the growth performance of hybrid poplars (Populus trichocarpa × Populus deltoides), especially if applied in mixtures rather than separately. The fertilizer treatments included an unfertilized control, inorganic fertilizer (IF) (calcium ammonium nitrate and triple superphosphate) and OFs (PBs alone, LPS alone and two combinations of PBs and LPS) applied at two rates. Fertilizers were broadcast within 1 m of tree trunks and unincorporated, to prevent damage to tree roots. Hybrid poplar growth was the greatest in plots fertilized with a combination of PBs and LPS, suggesting that the two OFs complemented themselves and/or interacted to improve soil nutritional quality. PBs were the most efficient at raising soil pH, providing plant‐available Ca and increasing nitrification rates over the long term, whereas LPS provided more readily available NO3‐N, P and K. Applied together, PBs and LPS interacted to provide more extractable P and mineralizable NH4‐N than when applied separately. OFs increased soil biological activity, notably basal respiration, microbial biomass, metabolic quotient and mineral N production rates. Community‐level catabolic profiles of the extractable soil microflora in plots with OFs differed significantly from the control and IF treatments. This implies that surface‐applied OFs may induce fundamental changes to the diversity and composition of microbial communities in the underlying rooting zone. Although this study has shown beneficial effects of OF mixtures on soil quality and hybrid poplar growth, further research should focus on their possible environmental impacts.

Investigation of Pathogenic Escherichia coli and Microbial Pathogens in Pulp and Paper Mill Biosolids

Biosolids produced from pulp and paper mill wastewater treatment have excellent properties as soil conditioners, but often contain high levels of Escherichia coli. E. coli are commonly used as indicators of fecal contamination and health hazard; therefore, their presence in biosolids causes concern and has lead to restrictions in land-spreading. The objectives of this study were to determine the following: (1) if E. coli from the biosolids of a wastewater-free pulp and paper mill were enteric pathogens, and (2) if other waterborne microbial pathogens were present. E. coli were screened for heat-labile and heat-stable enterotoxin and verocytotoxin virulence genes using a polymerase chain reaction. Ten isolates were also screened for invasion-associated locus and invasion plasmid antigen H genes. None of the 120 isolates carried these genes. Tests for seven other microbial pathogens were negative. Effluents and biosolids from this mill do not contain common microbial pathogens and are unlikely to pose a health hazard.

Assessing the impact of land-applied biosolids from a thermomechanical (TMP) pulp mill to a suite of terrestrial and aquatic bioassay organisms under laboratory conditions

The potential impact on a variety of bioassay organisms when pulp-mill biosolids from a thermomechanical pulp mill (western Canada) were applied to a reference soil has been investigated in a laboratory setup. The current research assessed acute, chronic, and reproductive impacts using a battery of terrestrial and aquatic organisms. Terrestrial organisms were exposed to soil amended with different concentrations of biosolids, while aquatic organisms were used to assess the impact of biosolids’ runoff into receiving waters. The former bioassays showed that an application rate of 20 tonnes hectare −1 (t ha −1) “bone-dry” biosolids applied to reference soil produced no observable adverse impact on the terrestrial organisms. In the latter assays, undiluted (100%) and 50% diluted biosolids’ runoff into receiving water had a detrimental impact on the aquatic organisms. However, concentrations not exceeding 25% (environmentally relevant concentrations) had neither an acute nor chronic impact compared to reference populations. The organisms’ abilities to reproduce were also unaltered. While this study only examined the biosolids from one mill, there is the potential that land-application of characteristically well-defined pulp mill biosolids may constitute an acceptable way of disposing of pulp and paper mill biosolid residues. However, the biosolids coming from different mills, with differing processes, must be dealt with on a case-by-case situation. Each series of biosolids must be rigorously tested for toxicological impact in the laboratory under tightly controlled conditions. Subsequently, field experimentation must be conducted before definitive conclusions can be made.