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This study forms part of a suite of three technology studies from Pira focusing on chemical, water and energy recovery in pulp and paper making. The availability of fresh, uncontaminated water globally is decreasing at a rapid rate. In industrialised countries, the recovery and reuse of treated effluent is becoming increasingly essential. Stronger demands from environmental authorities and companies wanting to be seen as environmentally friendly have stimulated the development of new processes and technical improvements that have led to a decrease in fresh water consumption within the industry. This study takes an in-depth look at the various measures being adopted by the pulp and paper industry to reduce water consumption and treatment techniques and equipment to recover and reuse waste water. Essential reading for your company.
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- Measures to reduce water consumption
- Current techniques for the recovery and reuse of water
- Emerging and future techniques of waste water treatment
Contents
Introduction
- Paper demand and growth
- Pulp and paper making processes
- Water requirement for pulp and paper making
- Key drivers for water recovery and recycling
Water Consumption in Pulp and Paper Mills
- Water consumption pattern in different countries
- Water consumption norms/standards
- Latest trends in water consumption
Measures to Reduce Water Consumption
- Separation of process and non-process waters
- Process modification including recycle/reuse
- Water conservation in pulp mill
- Increased delignification before bleaching
- Process redesign including improvement in quality and management of machine backwater
- Total system closure with zero liquid effluent
- Rationalisation and mill-wide integration of the hot, warm, cold and cooling water systems/applying pinch technology
- Case studies
In-Process Treatment of Water for Recycling
- Separation of suspended solids
- Separation of colloidal and dissolved substances
- Internal kidney treatment
Waste Water treatment for Recovery of Water
- Major contaminants of wastewater from pulp and paper making
- Contamination arising from increased use of recovered fibres - adhesives, micro-organisms, food residues, etc.
- Microflotation and membrane filtering for recovery of raw materials and reducing fresh water use
- Removal of dissolved and colloidal materials via ultrafiltration or nanofiltration techniques
Purification of Process Water in Closed Cycle Mills
- Closed cycle in mechanical pulp mills
- Closed cycle in kraft pulp mill
- Closed cycle in sulphite pulp mill
- Closed cycle in paper mills utilising recycled fibres
Effect of Increased Closure and Closed Loop Systems
- Water usage
- Benefits
- Problems
Emerging Techniques of Waste Water Treatment
- Advanced oxidation treatment technologies
- Fungal/Enzymatic treatment
- Sequential anaerobic/aerobic bio-processes
- Membrane processes
- Other techniques
Future Prospects of Water Recovery in Pulp and Paper Making