Scalable wastewater treatment for pulp and paper industry

Paper, Board Machine and Pulp Dryer Effluent

The wastewater generated from paper,board machines or pulp dryers presents several challenges due to its unique composition. It is typically rich in zero-fibers, small suspended solids, and phosphorus. Zero-fibers and small suspended solids can cause operational issues such as clogging, reduced efficiency in downstream treatment systems, and the risk of product contamination if the water is reused.

Additionally, elevated phosphorus levels contribute to nutrient pollution, which can lead to eutrophication in receiving water bodies if not properly treated.

Unlike chemical coagulation, our AxoPur electrocoagulation system does not introduce chloride ions, which allows the purified water to be safely recirculated back into the production process, reducing water usage and effectively removing suspended solids and phosphorus.

Bark Press Water

In the woodyard, the debarking of wood logs is followed by the pressing of the bark into pellets. This process generates a bark press effluent rich in transition metal ions, various extractives, and oxygen-consuming organics. The bark press water often exhibits high ecotoxicity and is poorly purified using traditional biological processes, such as aerated lagoons or activated sludge systems. Our solutions can efficiently remove transition metal ions as well as troublesome extractives, while requiring minimal space.

Bleach Plant Effluent

In the bleach plant, two distinct wastewater streams are generated: an acidic flow and an alkaline flow. To optimize treatment, these flows are typically mixed to neutralize each other, resulting in a combined wastewater stream. This mixed effluent presents several challenges due to its complex composition, which includes suspended solids, phosphorus, various transition metal ions and oxygen-consuming organics, resulting in high COD and BOD levels. These organic pollutants can require advanced biological or chemical treatment, to reduce the pollutant load before discharge into the environment.

Coating Kitchen Effluent

The coating kitchen is the place where the coating mixture for paper is prepared using pigments and binders to achieve a smoother and finer printing surface. The wastewater from the coating kitchen has many similarities with paint and is made up of pigments and binders.

The challenges of purifying the effluent concern the cracking of an emulsion and removing suspended solids—tasks for which our solutions are highly effective. However, the effluent often requires dilution before treatment, which in steady-state operation can be obtained using the purified water.

De-inking Effluent

In stock preparation from recycled paper, the paper is disintegrated in a pulper, releasing contaminants such as ink and microbes that have grown in the paper.

These contaminants result in highly polluted effluent, which necessitates the removal of microbes, suspended solids, and often oils/fats and oxygen-consuming organics, making the treatment process challenging and requiring specialized methods for effective purification.

Leachate/Stormwater

Many pulp and paper mills contain historic landfills, and leachate from these landfills, along with stormwater from large hardened surfaces, is becoming an increasing concern for environmental authorities. Transition metal ions, emulsified oil, and possibly PFAS are likely to be present in these waters. It is crucial for mills to investigate the composition of such waters proactively, allowing them to prepare an action plan for purification when needed. For highly efficient purification of PFAS-containing water,  we offer a range of systems and solutions. Among our options, our AxoPur segment provides highly efficient primary purification, while our Water Maid FlexKarb system serves as an excellent choice for fine filtration. For complete PFAS removal, an ion exchange filter can be used as a final step.

Boiler Fly Ash

Boiler fly ash is formed in the top of the recovery boiler where the spent liquors from kraft pulping following evaporation are incinerated. The process is part of the recovery of the cooking chemicals and at the same time recovers energy.

The boiler fly ash primarily consists of sodium sulfate and potassium chloride, but it also contains trace amounts of toxic transition metal ions, including cadmium, mercury, lead, arsenic, and zinc.

By using the selective cleaning abilities of AxoPur, the non-toxic sodium and potassium ions and their counterions in the form of sulfate and chloride could pass right through the process whereas the toxic transition metal ions are selectively captured and brought to a secured final handling. This selective treatment approach ensures both the safety of the environment and the continued efficiency of the recovery process.

Whitewater

The water circulating in the short and long circulations around the paper machine or pulp dryer is essential for maintaining the paper production process. However, this water can encounter several issues, particularly with nozzles and sprays, due to the accumulation of contaminants. Suspended solids, oil/fats, and especially microbes tend to grow rapidly in warm, nutrient-rich water. Our systems can handle these challenges efficiently without the addition of chloride ions.

Fiber Deposits in Recipients

Fiber deposits in recipients represent a historic environmental debt formed during a time when external effluent treatment was not yet implemented. At that time, mercury-containing anti-slime agents were frequently used. These fiber deposits are often vast in size, and anaerobic digestion occurs within them, likely leading to the formation of methylated mercury, which evaporates into the air.

The proper handling of these fiber deposits from an environmental perspective has long been a topic of debate. Recently, a policy shift has been observed, moving away from leaving the deposits as they are and toward advocating for their safe removal. This aims to restore both the chemical and ecological status of the recipients in alignment with the EU Water Framework Directive.

Pilot projects now planned include the suction removal of fiber deposits for further processing on land, where the sludge will be dewatered, and the water will be returned to the recipient. In particular, the water pressed from the fibrous sludge is expected to have high concentrations of mercury, in addition to suspended solids and oxygen-consuming organics, which directly contribute to the COD and BOD of the water. Our systems are highly effective at purifying wastewater containing mercury to ultra-low levels, while also capturing and removing suspended solids.

Mellfiq offers a wide range of systems and solutions for processes in the pulp and paper industry to tackle contaminants, odor, and air emissions.

Enhance efficieny and savings with wastewater treatment

The paper industry faces several challenges related to wastewater management, environmental impact, and resource optimization. Wastewater from paper and board machines, pulp dryers, and bleach plants often contains contaminants such as suspended solids, phosphorus, and organic materials, which can be difficult to treat with traditional methods. Our advanced technologies effectively targets and removes contaminants without the need for harsh chemicals, offering a more sustainable solution while maintaining a minimal physical footprint.

Recirculating water purification

Our Axolot systems ensures comprehensive purification, delivering a high yield of purified water that can be efficiently recirculated into the process. This enables significant energy savings, as the water’s temperature remains stable throughout purification. Furthermore, the floc containing separated contaminants, with its high dry solids content, is ideal for energy recovery, enhancing operational efficiency

Optimal odor control with ozonation

In the pulp and paper industry, processes such as pulping, sludge handling and wastewater treatment are particularly prone to strong odors. These processes often release sulfur compounds, hydrogen sulfide and volatile organic compounds, and chlorine-based gases, leading to unpleasant odors.

Mellifiq has a long history of developing innovative advanced air treatment solutions for odor emissions. Our ozonation technology effectively neutralizes these odors, ensuring cleaner air and a more sustainable production environment.

Our solution includes the Ozonetech RENA Pro ozone solution which effectively controls odors by using ozone to break down harmful compounds. The system also helps eliminate air contaminants, creating a cleaner and healthier atmosphere in surrounding areas.

Read more on Odor Control.