The pulp and paper (P&P) industry is one of the heaviest users of water.

With water used in nearly every step of the manufacturing processes, P&P mills produce large volumes of wastewater and residual sludge waste, presenting a number of issues in relation to wastewater treatment, discharge, and sludge disposal. However, increasingly advanced treatment technologies, including innovative strategies geared towards water reuse and resource recovery, present viable solutions for P&P manufacturers in terms of wastewater and solid waste management.

Contaminants inherent to P&P waste streams include effluent solids, sediments, absorbable organic halides (AOX), chlorinated organic compounds, and chemical oxygen demand (COD) and biological oxygen demand (BOD) contaminants.

According to industry experts, approximately 85% of the water used in the P&P industry is used as process water, resulting in relatively large quantities of contaminated water and necessitating the use of onsite wastewater treatment solutions. Treatment options include primary treatment such as clarification to remove solids and particulate matter, and secondary biological treatment processes for removing biodegradable organic matter and decreasing the effluent toxicity.

Membrane filtration is today an industrial process in the pulp and paper industry. The rising demand for environmental protection, energy savings and recovery of valuable products has accelerated the application of membrane filtration. The most important application in the pulp and paper industry are: Purification of effluents from kraft bleach effluent.

As different pulp bleaching methods have developed over recent years, membrane filtration have proved to be a viable technology for treating both total chlorine free and elemental chlorine free bleaching streams. For total chlorine free bleaching, membranes also provide an effective method of closing the chelating stages and allow the filtrates to be used as bleach plant wash liquors.