The paper industry’s objective is to provide treatment to meet permits and / or to allow for in-mill recycling in a reliable and cost effective manner. External effluent treatment is critical and substantially reduces the level of suspended solids that are be discharged locally.
A common primary treatment method is the process of clarication to reduce and remove TSS and other particulate matter generated in the paper-making process. The amount of BOD is also lowered in the wastewater.
Secondary biological treatment is then used to remove residual BOD, COD and TSS. Other AOX and bacteria are also removed. Microbes and nutrients such as nitrogen and phosphorus are commonly used to further treat organic materials. Anaerobic digestion may also be used to generate less sludge for the amount of BOD removed. As solids materials are broken down, biogas may be produced and can be used to harness energy onsite.
Tertiary and other advanced treatment technologies are also being incorporated at pulp and paper mills to generate clean water for reuse or local disposal.