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

Abstract

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.

Characterization of persistent organic pollutants and culturable and non-culturable bacterial communities in pulp and paper sludge after secondary treatment

“…Soft and hard wood and non-wood fibres are used in pulp-paper mills as raw materials. Hence, natural wood extractives (such as tannins, resin acids and lignin) and xenobiotics compounds generated during pulping process of paper production (such as chlorinated lignin, phenols, dioxins and furans) are readily detected in pulp-paper wastewaters (Vidal et al, 2021). Therefore, pulp-paper mills are one of the most environmentally destructive sectors, discharging a wide range of toxic pollutants into the environment.…”

Electrode material impact on microbial fuel cell and electro‐Fenton systems for enhanced slaughterhouse wastewater treatment: A comparative study of graphite and titanium

“…The high turbidity values signified a substantial presence of suspended solids, indicating poor water clarity and potential interference with light penetration in aquatic environments (Jafar‐Sidik et al, 2017). Similarly, elevated color intensity suggested the existence of organic matter and pollutants that contributed to the wastewater's visual discoloration (Vidal et al, 2021). The increased chloride concentrations and high COD levels indicated the likelihood of contamination by industrial and organic sources (Wahyuni et al, 2022).…”

Effects of Black Liquor Shocks on the Stability of Activated Sludge Treatment of Kraft Pulp Mill Effluent: Morphological Alteration in Daphnia magna and Mutagenicity and Genotoxicity Response in Salmonella typhimurium

“…The treatment of kraft pulp mill effluent is essential for reducing pollutant load and complying with environmental legislation and standards. Conventional treatment technologies such as activated sludge (AS) and moving-bed biofilm reactors (MBBR) are currently installed in kraft pulp mills to remove organic compounds and acute toxicity from the kraft mill effluents [1,2]. The AS aerobic degradation of organic compounds ranges between 50 and 65% of the chemical oxygen demand (COD) [1,3].…”

“…Despite the primary and secondary effluent treatment systems implemented by most mills, a series of studies pointed to wood-derived intermediate products that could be formed and released during normal mill operations, including chlorocimenes, resin acids, chloroethens, flavonoids, and phytoestrogens. Some of these compounds were classified as endocrine-disrupting compounds (EDCs) and were suspected to accumulate in sediment, potentially becoming bioavailable to fish, for example [1,11]. Direct and indirect toxicity assessments, making use of ecotoxicological tests, can play an important role in supporting decision making [12].…”

“…Several types of mutagenic compounds have been identified in the pulp kraft mill effluent [20]. High-molecular-weight compounds generate organic matter that is difficult to biodegrade in biological systems; therefore, color is present in the final effluent [1,21,22]. However, the low-molecular-weight compounds, below 1000 g/mol, pose the greatest toxicological, mutagenic, and carcinogenic risk, as they easily penetrate the cell membrane [23][24][25].…”