Anaerobic treatment of pulp and paper mill effluents – status quo and new developments

Abstract

Since the early 1980s, anaerobic treatment of industrial effluents has found widespread application in the pulp and paper industry. Over 200 installations are treating a large variety of different pulp and paper mill effluents. Amongst various anaerobic systems the UASB and IC are the most applied anaerobic reactor systems. Anaerobic treatment is well feasible for effluents originated from recycle paper mills, mechanical pulping (peroxide bleached), semi-chemical pulping and sulphite and kraft evaporator condensates. The advantages of anaerobic pre-treatment are (1) net production of renewable energy (biogas), (2) minimized bio-solids production, (3) minimal footprint and (4) reduced emission of greenhouse gases. Via in-line application of anaerobic treatment in closed circuits (paper kidney technology) further savings on cost of fresh water intake and effluent discharge levies are generated.

Anaerobic Digestion of Wastewaters from Pulp and Paper Mills : A Substantial Source for Biomethane Production in Sweden

“…These can maintain a high solids retention time combined with a low HRT (often in the range of hours), thus preventing wash-out of the microorganisms. These high-rate AD processes also facilitate a higher organic loading rate (OLR) compared to a CSTR, at high process efficiency provided that the wastewaters are rich in dissolved organic material (Habets and Driessen, 2007 systems. In this thesis UASB is considered as an overarching concept for high-rate AD processes with a fluidised granular bed with or without internal recirculation of reactor liquid or gas for increased upflow velocity.…”

“…It should also be noted that, by 2005, about two thirds of all full-scale plants were installed at recycled paper mills that generate wastewater mostly rich in starch and with low concentrations of inhibitory compounds. The remaining AD applications were operated at pulp mills, mostly treating methanol-rich condensates from chemical pulping (especially sulphite pulping) or effluents from mechanical pulping (Habets and Driessen, 2007). More than 80% of these full-scale implementations were high-rate anaerobic sludge bed systems.…”

“…Among these wastewaters the highest biomethane potentials were found for methanol-rich condensates (Paper I), which often are treated in full-scale AD when applied at a kraft mill (Habets and Driessen, 2007) and their digestion in high-rate AD processes have been investigated extensively (e.g. Dufresne et al, 2001;Xie et al 2010;Badshah et al, 2012).…”

“…The generated wastewaters contain high concentrations of organic material and are commonly treated in wastewater treatment plants, integrated with the mill, mostly relying on aerated biological processes that consume large amounts of electricity (Meyer and Edwards, 2014). By implementing AD as a step in the present wastewater treatment system, biogas can be produced and the energy consumption for aeration as well as sludge production can be reduced considerably leading to a decrease in environmental impact for a specific mill (Habets and Driessen, 2007). This solution also opens up for an increase of the production at the mill as the wastewater treatment often limits their production capacity (pers.…”

“…wood extractives and lignin), AD has been implemented to a limited extent and mainly at recycled paper mills (Habets and Driessen, 2007). The number of AD processes in the pulp and paper industry worldwide has doubled during the last decade to a total of around 380, which corresponds to less than 10% of all mills (Meyer and Edwards, 2014).…”