Recalcitrant organic compounds (chemical oxygen demand sources) in biologically treated pulp and paper mill effluents: their fate and environmental impact in receiving waters

Abstract

Most North American pulp and paper mills now biologically treat (biotreat) their liquid effluent. However, treated water still contains effluent‐derived recalcitrant organic material (EROM), measured as chemical oxygen demand (COD), for which emission limits exist in Europe and are being considered in the U.S. Production of microbially resistant, dissolved natural organic material (NOM) typically found in Canadian stream and lake waters occurs slowly under gentle conditions, while mill EROM is generated from lignocellulosics by faster and harsher processes. Similarity of the environmental effects of NOM and pulp and paper mill EROM are examined. Changes occurring over 4 months in biologically treated effluent from two modern Canadian mills and lake NOM when sealed in gas‐ and light‐permeable bags and placed in a pristine Quebec lake are reported. Addition of microbial co‐metabolites significantly improved the dark mineralization of organochlorines surviving mill biological treatment. Mill EROM was light sensitive, nonacutely toxic in the Microtox assay, and similar to NOM in the surrounding lake in most bulk properties. There was no evidence to suggest that placing specific limits on mill EROM (COD) emissions would be environmentally beneficial.

Excessive greenhouse gas emissions from wastewater treatment plants by using the chemical oxygen demand standard

“…It has been reported that a significant contributor to COD is recalcitrant dissolved organic matter (RDOM) (Jiao et al, 2021), which accounts for the majority of all dissolved organic matter and can act as an important carbon sink (Hansell, 2013;Jiao et al, 2010). RDOM exists in large quantities in influent wastewater, the wastewater treatment processes, and effluent wastewater (Archibald et al, 1998;Bockhorn et al, 2005;Jin et al, 2011;Lu et al, 2018). The relative contribution of refractory organic matter to the total organic matter has been reported to be as high as 91% in typical WWTPs in Switzerland (Kappeler and Gujer, 1992).…”

Potential for Enhancement of Aerobic Biological Removal of Recalcitrant Organic Matter in Bleached Pulp Mill Effluents

“…Increasingly stringent effluent quality requirements are being incorporated into mill operating licenses, especially with regard to COD and color discharges [2,7,8]. For example, World Bank guidelines for financing new kraft pulp mills include limits of 300 mg COD l -1 and 15 kg COD per ton of pulp [9].…”

“…These stricter regulations stem from the fact that model ecosystem studies have indicated a correlation between effluent COD and adverse effects, such as toxicity, observed in receiving waters, which suggests that a decrease in the amount of dissolved organic matter liberated to the environment determines the adverse environmental effects of effluents [8,10]. However, results presented elsewhere [7] showed little or no correlation exists between COD and effluent chronic toxicity. Despite this controversy on the true environmental significance of COD remaining in biologically treated effluents, Brazilian kraft pulp mill operating licenses include effluent COD limits, usually expressed as concentrations (mg l -1 ) and not production loads (kg ton -1 ).…”

Electrochemical Treatment of Chemical Industry Wastewater Using Steel and Tiruo2 Electrodes

“…The concern regarding conservation of the environment has lead to great interest for environmental technology in using the water and energy resource. This interest seeks the materials recycling, reduction of water consumption and the reduction of conventional treatment costs (ARCHIBALD et al, 1998).…”