What is the Work of ETP in Paper and Pulp Industry?
The pulp and paper (P&P) industry has made significant progress in treating both process water and wastewater, thereby limiting pollutant discharge to receiving waters. This covers a wide range of wastewater treatment methods that offer P&P companies cost-effective ways to limit the release of biological or chemical oxygen demand, toxicity, solids, color, and other pollutant load indicators.
The pulp and paper industry is an energy-intensive manufacturing process, with energy costs accounting for nearly 13% of total production costs. This industry consumes a large amount of fresh water (between 60 and 230 m3 per tonne of paper produced), resulting in large amounts of wastewater. It is the sixth-largest polluter (after the oil, cement, leather, textile, and steel industries), emitting a wide range of wastes into the environment.
The pulp and paper industry's major environmental concerns are the high consumption of fresh water and the generation of a large volume of toxic wastewater.
The working of ETP in pulp and paper industry
Traditional wastewater treatment systems, which frequently include primary clarification followed by activated sludge processes, have been widely used in the P&P industry. Supplemental treatments, such as anaerobic biological stages, advanced oxidation processes, bioreactors, and membrane filtration technologies, can achieve higher levels of pollutant removal.
Process modelling as internal process water treatment are being used extensively in the pulp and paper industry to save water and close water circuits, as well as to significantly reduce environmental impact.
Solids and dissolved matter are present in pulp and paper mill effluents.
Screening, settling/clarification, and flotation are the primary methods used to remove solids from pulp and paper mill effluents. The method chosen is determined by the characteristics of the solid matter to be removed as well as the purity requirements for the treated water.
Screens, grid chambers, and settling tanks are used to separate the solids from the effluents. Screens are units that work in the sieving/filtration process. The screens' purpose is to remove coarse, bulky, and fibrous components from the effluents.
The paper industry employs a wide range of effluent treatment systems. The best process combination for each individual case is determined by the grade-specific quality of the effluent to be treated.
Following is a Flow Chart of the Effluent Treatment Plant (ETP) Process
Technology of Sedimentation
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Biological Treatment
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Technology for Anaerobic Digestion
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Aerobic Digestion
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Secondary Clarification
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Advanced and Tertiary Treatment
1: Technology of sedimentation
Sedimentation technology is the most basic and cost-effective method of separating solids from liquids. Following effluent treatment processes, it achieves high efficiency when the solid substances suspended in the effluents settle as completely as possible in a sedimentation tank and settled sludge is removed from the sedimentation tank. In the paper industry, sedimentation equipment with sets of lamella-shaped passages is used, particularly for effluents with high fiber concentrations.
2: Biological treatment
The action of microorganisms in biological wastewater treatment is intended to degrade pollutants dissolved in effluents. These substances are used by microorganisms to survive and reproduce.
Pollutants are used as fertilizer. However, such degradation activity requires that the pollutants be soluble in water and non-toxic.
3: Technology for anaerobic digestion
Anaerobic treatment of industrial effluents has been widely used in the pulp and paper industry since early 1980s. Several hundreds of installations treat a wide range of pulp and paper mill effluents.
Anaerobic treatment is most commonly used for effluents from recycle paper mills, particularly during containerboard production. Wastewater from mechanical pulping (peroxide bleached), semi-chemical pulping, and sulphite condensates can also be treated.
4: Aerobic technology
Aerobic microorganisms require oxygen to function metabolically. Special aeration equipment provides oxygen to the effluent in the form of air during effluent treatment. Paper mill effluents can be completely biologically degraded using aerobic treatment. Aerobically operated plants are more stable and less sensitive to changes in effluent and plant parameters.
5: Tertiary and advanced wastewater treatment
Tertiary and advanced wastewater treatment are used to remove specific wastewater constituents that secondary treatment cannot remove. To remove nitrogen, phosphorus, additional suspended solids, refractory organics, or dissolved solids, various treatment processes are required.
Sometimes it is referred to as tertiary treatment because advanced treatment usually follows high-rate secondary treatment. However, advanced treatment processes are sometimes combined with primary or secondary treatment {e.g., chemical addition to primary clarifiers or aeration basins to remove phosphorus) are used in place of secondary treatment (e.g. overland flow treatment of primary effluent)}.
Parameters of treated effluent water
Typical nutrient concentrations in treated wastewater effluent from conventional treatment processes are as follows:
Phosphorus (P) - 10 mg/l
Nitrogen (N) - 50 mg/l
Potassium (K) - 30 mg/l,
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