Colour removal from pulp and paper mill effluent using lignite as an adsorbent

Treatments that are usually employed by pulp and paper industries comprise sedimentation, aeration, activated sludge processing and anaerobic treatment. These methods have proven to be effective for removing suspended solids and for significantly decreasing COD and BOD. However, the resultant water still has colour, which is generally unacceptable to the community. This leads to the need for colour removal as a secondary stage in wastewater treatment. Some treatments that have been reported to deal with colour removal are photocatalysis, oxidation, electrocoagulation, biological treatments and adsorption. Among these methods, adsorption is still considered to be one of the simplest and economical methods. Activated carbon is probably the most prominent adsorbent used in wastewater treatment. Unfortunately, the high costs associated with its activation, regeneration and maintenance have been significant drawbacks to its use. Lignite, a low rank coal, is a cheap and readily available material that has well known adsorption properties. Here we report on the use of lignite as an adsorbent for colour removal from treated pulp and paper mill effluent. Two types of experiments were carried out. In batch experiments, various amounts of lignite were added to the wastewater. In filter bed experiments, the wastewater was passed through a fixed bed of lignite. After treatment the water was isolated and examined. The results demonstrated the ability of raw lignite to remove some colour, Total Organic Carbon (TOC) and total phosphorus from the effluent. It was found that the adjustment of the pH of the wastewater was crucial due to some colour leaching from lignite. These preliminary results suggest the potential of lignite, as a cheap and readily available adsorbent, to be utilized in wastewater treatment.