New method for identification of natural and anthropogenic organic matter in receiving waters of pulp and paper mill discharge

Abstract

Pulp and paper mills (PPMs) are one of the most water-intensive industries in the world. Where sulphite pulping is used to produce pulp for paper and other products, lignosulfonates (LSF) dominate the organic component of PPM wastewaters. Currently, there is no information about the quantitative composition of organic matter (OM) and contribution of LSF to the OM pool in lakes and rivers located within the zone of PPMs’ influence. Addressing this gap in our understanding, a method was developed for the characterization of allochthonous (humic substances, HS) and anthropogenic (LSF) components of OM, and labile organic substances. The method is based on the extraction of HS from a water sample with DEAE-cellulose, introducing an experimentally determined adjustment coefficient for partial LSF sorption. The method was applied to the second largest freshwater lake in Europe, Lake Onego (also known as Onega), and its Kondopoga Bay, receiving wastewaters of Kondopoga PPM. The method’s effectiveness was demonstrated through spatial segregation of the river and wastewaters in the bay in different seasons, first as a source of HS, and the second as a source of LSF. The vertical distribution of the river and wastewaters was indicated using conductivity, temperature, and TP. The proposed method demonstrated that HS in Kondopoga Bay make up on average 63% of the total OM pool and 17% of labile OM. However, LSF accounts for an average of 20% and up to 39% of the total OM pool, which confirms the high degree of anthropogenic impact on water quality of the bay.