Activated Sludge Treatment of Paper Mill Effluents

Introduction The pulp and paper industry is the second largest industrial water consumer in Europe with a usage of 35 m3/ton paper and a production of 85.2 M tons/year. Its effluents cause considerable damage to the receiving waters if discharged untreated since they have a high biochemical oxygen demand (BOD), chemical oxygen demand (COD) and contain chlorinated compounds, suspended solids (mainly fibres), fatty acids, lignin, and sulphur compounds. Environmental legislation has affected the pulp and paper industry. A number of UK mills are authorised under Integrated Pollution Control (IPC), so they have to demonstrate that they are using best available techniques not entailing excessive cost (BATNEEC) to control emissions to the environment. The use of primary treatment followed by secondary biological treatment, which is the approach adopted by UK mills, is considered to be BATNEEC for the industry.