Minimization of Environmental Impact of Kraft Pulp Mill Effluents: Current Practices and Future Perspectives towards Sustainability

Kraft mill effluents are characterized by their content of suspended solids, organic matter and color due to the presence of lignin, lignin derivatives and tannins. Additionally, Kraft mill effluents contain adsorbable organic halogens and wood extractive compounds (resin acids, fatty acids, phytosterol) and show high conductivity due to the chemical compounds used in the digestion process of pulp. Currently, Kraft mills are operating under the concept of a linear economy and, therefore, their effluents are generating serious toxicity effects, detected in daphnia, fish and biosensors. These effluents are treated by activated sludge and moving bed biofilm systems that are unable to remove recalcitrant organic matter, color and biological activity (toxicity) from effluents. Moreover, under climate change, these environmental effects are being exacerbated and some mills have had to stop their operation when the flows of aquatic ecosystems are lower. The aim of this review is to discuss the treatment of Kraft pulp mill effluents and their impact regarding the current practices and future perspectives towards sustainability under climate change. Kraft pulp mill sustainability involves the closure of water circuits in order to recirculate water and reduce the environmental impact, as well as the implementation of advanced technology for these purposes.

Endocrine Disruptor Impacts on Fish From Chile: The Influence of Wastewaters

Industrial wastewaters and urban discharges contain complex mixtures of chemicals capable of impacting reproductive performance in freshwater fish, called endocrine-disrupting compounds (EDCs). In Chile, the issue was highlighted by our group beginning over 15 years ago, by analyzing the impacts of pulp and paper mill effluents (PPME) in the Biobio, Itata, and Cruces River basins. All of the rivers studied are important freshwater ecosystems located in the Mediterranean region of Central Chile, each with a unique fish biodiversity. Sequentially, we developed a strategy based on laboratory assays, semicontrolled-field experiments (e.g., caging) and wild fish population assessments to explore the issue of reproductive impacts on both introduced and native fish in Chile. The integration of watershed, field, and laboratory studies was effective at understanding the endocrine responses in Chilean freshwater systems. The studies demonstrated that regardless of the type of treatment, pulp mill effluents can contain compounds capable of impacting endocrine systems. Urban wastewater treatment plant effluents (WWTP) were also investigated using the same integrated strategy. Although not directly compared, PPME and WWTP effluent seem to cause similar estrogenic effects in fish after waterborne exposure, with differing intensities. This body of work underscores the urgent need for further studies on the basic biology of Chilean native fish species, and an improved understanding on reproductive development and variability across Chilean ecosystems. The lack of knowledge of the ontogeny of Chilean fish, especially maturation and sexual development, with an emphasis on associated habitats and landscapes, are impediment factors for their conservation and protection against the threat of EDCs. The assessment of effects on native species in the receiving environment is critical for supporting and designing protective regulations and remediation strategies, and for conserving the unique Chilean fish biodiversity.

A solid-phase extraction method that eliminates matrix effects of complex pulp mill effluents for the analysis of lipophilic wood extractives

The extraction of lipophilic wood extractives from pulp and paper process waters proves to be a challenging task, due to harsh and alternating process and sample conditions. This study has determined the potential use of polymeric sorbents for solid-phase extraction (SPE) and compared to classical silica-based reversed-phase packed columns, with polymeric hydrophilic-lipophilic balanced (HLB) cartridges being the sorbent with the most potential. Recovery functions were obtained with an internal standard mixture representative for the main lipophilic wood extractive groups, which are fatty acids and alcohols, sterols, sterol esters and triglycerides. The impact of pH, sample volume and sample matrix, expressed as TOC and cations, on the retention behavior of lipophilic extractives during SPE of industrial samples were determined with polymeric HLB sorbent. High variations in the composition of pulp mill matrices led to different optimal extraction conditions. Thus, a new SPE protocol was developed, which bypasses matrix interferences and omits the loss of analytes due to sample preparation. The method is applicable to different pulp mill effluents with large discrepancies in pH and sample matrices, resulting in recoveries >90 % with RSD <5 % for all lipophilic wood extractives.

Immobilization of Powdered Coal Fly Ashes (CFAs) into CFA Beads and Column Studies on Color Removal from Pulp Mill Effluents Using These CFA Beads

In this study, immobilization process of the three (3) powder CFAs was studied. The major results on immobilization process were briefly presented. A total number of fifteen (15) column studies from the combination of the five (5) types of CFAs beads and the three (3) PMEs samples were performed. In each column study, a set of aggregate parameters of flow rate, empty bed contract time, operational time, and throughput volume was studied, and the data was fitted to existing modeling of breakthrough curves. The overall operational time was 12–24-hour, color removal efficiencies were 40–90%, and throughput volume of treated PMEs was 10–14 bed volume. For the column study, the correlation coefficient R2 value for each combination indicated that the Thomas model had a better fit with the observed data than the Adams-Bohart model, and the color adsorption capacities of CFA beads varied in a wide range of 0.31–28.23 mg/g.

Characterization of thermophilic aerobic granular sludge for the treatment of bleached kraft pulp mill effluent

The objective of this work was to evaluate the physical characteristics of the thermophilic granular aerobic sludge used in the treatment of bleached kraft pulp mill effluents. Four sequential batch reactors (SBRs) were operated with cycles of 12 hours. Reactor (R1-FSR) with flocculent sludge was used as control. The other three reactors (R2-GSR, R3-GSR+100, and R4-GSR+200) were operated with granular aerobic sludge. Concentrations 100 and 200 mg. L-1 of calcium were applied in the R3-GSR+100 and R4-GSR+200, respectively. The pH was maintained in the neutral range in all reactors. The experimental plan was carried out for 490-day period, in 5 phases at different temperatures of 35 °C to 55 ºC. All SBRs showed COD removal efficiency above 60% in all temperature ranges. The granule average diameter in the R2-GSR, R3-GSR+100, and R4-GSR+200 ranged from 5 to 8 mm. The reactor R3-GS+100 showed better stability due to the addition of 100 mg. L-1 of calcium. The granular sludge sedimentation velocity was 40 m.h-¹, which was eight times higher than the flocculent sludge. Thermophilic treatment (55 °C) using aerobic granular sludge proved to be a promising way for treating bleached kraft pulp mill effluent without a prior cooling process.