Paques - Water Treatment for the Pulp and Paper Industry

Paques has developed biological treatment systems especially for the paper industry. At the moment, innovative processes make it possible to produce paper without discharging effluent. A significant reduction in both energy and water consumption is achieved. Paques has one hundred full scale references in the pulp and paper industry treating process water of various pulp and paper mills, of which already 6 paper mills are operating without waste water discharge.

WASTE PAPER RECOVERY REQUIRES COD REMOVAL TO PREVENT UNPLEASANT ODOURS

The use of waste paper as a raw material for paper production has numerous advantages, including the reduced need to cut down trees and an enormous reduction in the quantity of waste. However, producers encounter certain disadvantages when using recycled paper. Organic materials, salts and fillers are released during the pulping process along with valuable paper fibres. When water usage is reduced, these materials accumulate and cause problems such as the generation of unpleasant odours, deposits on the machinery and a slowing down of the paper machine.

WATER RE-CIRCULATION AND PURIFICATION SYSTEMS

The water re-circulation and purification process developed by Paques prevents the problems that arise as a result of reduced water usage. High quality recycled paper can be manufactured without producing wastewater. The system can be used over a wide temperature range (20°C to 60°C, 68°F to 140°F), eliminating the need to cool the process water, which in turn leads to a reduction in energy usage.

ANAEROBIC AND AEROBIC BIOLOGICAL TREATMENT REDUCES SCALING POTENTIAL AND WASTE SOLIDS DISCHARGE

The process has been developed in such a way that space requirements are kept to a minimum. A BIOPAQ® IC reactor is used as the initial step in the treatment process. The name of this anaerobic reactor is derived from the "gas-lift" driven internal circulation that is generated within a tall, cylindrical vessel. These reactors have been operational in the paper industry since 1996. The second step in the purification process is a mechanically mixed and aerated tank. The aerating injectors can be cleaned in a simple way without the need to empty the aeration tank. Potential scaling materials are combined into removable fine particles. At the same time, the materials that may cause an odour nuisance are oxidized into odourless components. The process can be completed by a third and a fourth step. The third step focuses on suspended solids recovery and removal. The fourth step is an additional water-softening step with lamella separation (Astraseparator®) and continuous sand filters (Astrasand®) in order to produce fresh water substitute. The benefits are:

• Advantages of this green solutions approach
• Reduction in fresh water costs
• Savings in energy costs
• No effluent surcharges
• No water discharge permit needed
• Minimized space requirement
• Few chemicals needed
• Very few waste products
• Biogas production makes positive energy balance
• Emissions of volatile organics drastically reduced

ADDITIONAL BENEFITS OF ANAEROBIC/AEROBIC CONCEPT FOR PROCESS WATER QUALITY

Low COD and BOD levels in the paper making process water and better drainage in the wet end of the paper machine create:

• Prevention of the CaCO3 from coating layers becoming soluble
• Removal of water hardness and "sticky" substances
• Removal of conductivity and of sulphate from the process water
• Absence of the typical acid odour that is common with closed water systems