An overview of treatment processes being employed in Indian Pulp & Paper Industry with a status overview of Indian Pulp & Paper Industry

1. Water Pollution Control in Pulp & Paper Industry: Status & Overview By: VaibhavNautiyal M.E. – Environmental Engineering (2009-2011 Batch) Roll No. – ME/ENV/04 Guided By: Prof. (Dr.)S.K. Singh (Professor & Dean) Deptt. Of Civil & Environmental Engineering Dr. Bharat Jhamnani(Assistant Professor) Deptt. Of Civil & Environmental Engineering

3. Highly capital, energy and water intensive industry

4. Highly polluting process and requires substantial investments in pollution control equipment

6. This large gap is attributed to the use of obsolete technology/equipments and poor water management practices.

8. Segregation of Indian Mills (Basis: Raw material Use)

11. Raw Materials Hardwood Bamboo Various types of reeds and grasses Agricultural Residues like wheat straw and bagasse Note: Of these, bamboo accounts for nearly 60 to 70% of the total tonnage

13. Characteristics of Kraft-mill wastes

14. Process Flow Diagram Acid sulphite Liquor Alkaline Sulphate Liquor (Kraft) Neutral Sulphite Pulp Log White water Or Reuse Water Debarked Log Fine Pulp Wood Preparation Washing Screening Pulping Wood Chips Purified Pulp Evaporation (Heat generation As by-product) Thickening Unbleached Pulp Kraft and neutral sulphite recovery Bleaching Fillers Dye Size Alum Starch Finishing and converting Paper Machine Stock Preparation

16. Refiner Mechanical Pulping

17. Semi-Chemical Pulping

18. Chemical Pulps

19. Alkaline Chemical Pulping

20. Sulphite Chemical Pulping

22. Log Flume Blowdown, Barker bearing cooling water (Wood Preparation Stage)

23. Sulphite Spent Liquor, Blow-pit Collected Spills (Pulping)

24. Condensate, Dreg Washing, Mud Washing, Acid Plant Wastes (Evaporation Stage)

25. Weak Liquor (Screening)

26. Bleach Wastes

28. Contd…. Solid Wastes Bark Refuse, Wood particles and slivers sawdust Knots fibres (Screening Stage) Fiber losses during Washing and Thickening Stages Fibers, Fillers and Brokes from Paper Machine Broke and coatings during finishing and coating stage

30. In the production of dissolving pulps, it is also regarded as part of the refining process.

31. In less highly refined pulps, it is regarded as removing wood extractives and bark specks and conferring superior strength characteristics.

33. Pulp Bleach Sequences

35. Recycle & Reuse Practices Adopted Process Changes and Modifications Intra-section recycle & reuse Inter-section recycle & reuse Oxygen De-lignification Recovery Chemical Recovery (Black Liquor) Pollution Prevention Programs

37. Sedimentation and Floatation

38. Physico-Chemical Methods

39. Chemical Flocculation

40. Activated Carbon Adsorption

41. Ultra Filtration

42. Reverse Osmosis

43. Chemical Oxidation

46. Floating particles such as logs, are removed by bar screens with 15 mm spacing from centre to centre.

47. SS removal of over 70% (settleable solids – 85%) and a BOD removal of about 10 – 30% can be achieved through primary clarification.

50. The Process comprises of following steps:

51. Addition of metal salt

52. Adjustment of pH at an optimum value

53. Flocculation during slow stirring

54. Increasing the Floc Size using Polyelectrolyte

57. Use in Tertiary sequence following primary and biological processes, and

58. Use in a physical and chemical treatment in which the raw wastewater is treated in primary clarifier with or without chemical coagulants.

59. Two Size Classification:

60. Powdered Activated Carbon (PAC) – Diameter <0.074 mm (200 Sieve)

61. Granular Activated Carbon (GAC) – Diameter >0.1 mm (~140 Sieve)

62. Can achieve high removals of dissolved and colloidal pollutants in wastewater.

64. Reverse Osmosis Process Applied Pressure Pure Water Semi-permeable Membrane Direction of Flow

66. Oxidation with air under extreme temperature and pressure, and under ambient condition, in the presence of excessive amount of strong oxidants or Catalysts.

68. Two processes are generally followed i.e. HOWARD Process and STRELLENERT Process.

69. The Howard Process is a precipitation with lime as a coagulant, in 3 stages to a final pH of 11.

72. A full scale anaerobic lagoon treating about 18,000 cu m/day of pulp mill wastewater gives 50 to 60% reduction in BOD in 20 days.

73. Normal Design Figures adopted:

74. Depth, m - 2.5 – 5.0

75. Retention Time, d - 5.0 – 50.0

78. Typical oxygen transfer devices utilize between 3 and 5 HP per 1000 cu m of wastewater and detention time ranging from 4 to 6 days, with nearly 80% BOD removal.

79. Dissolved oxygen content of 0.2 to 0.5 mg/l is necessary to sustain aerobic condition.

81. Activated Sludge Process Most successful methods for treating pulp and paper mill wastewaters and these operate at high oxygen levels. The normal drawbacks in the system are foaming in aeration tank, cost of nutrients and colour intensification. If properly designed and operated, an activated sludge process will give very good treatment result.

84. Rising sludge, occurring when sludge that normally settles rises back to the surface after having settled.

85. Bulking sludge, which settles too slowly and is not compactable, caused by the predominance of filamentous organisms.

86. Insufficient reduction of organic load, probably caused by a low solids retention time; insufficient amount of nutrients such as P or N (rare in fisheries wastewaters); short-circuiting in the settling tank, poor mixing in the reactor and insufficient aeration or presence of toxic substances.

88. Trickling filters that use plastic packing have been built in round, square, and other shapes with depths varying from 4 to 12 m (14 to 40 ft).

89. The plastic packings have a high surface area per unit volume (100 m2/m3), a high void ratio (95%) and are designed to provide uniform distribution of the wastewater.

90. BOD reduction of 50-80% is achieved.

92. Rotating Biological Contactor Media Discs or Panels Media Discs or Panels One Media Pack Media Support Motor Shaft 35-40% Submerged Optional air distributor Pipe Front View Side View

94. Steam for Reuse in Pulp and paper Mills Sale to Road Industry Sale to Food Industry Sale to Regional Market Sulphate Furnace Road Binder Plant Vanillan Plant Sale to Regional Market and Internal Use Dry Sludge Sulphite Liquor Reused Incinerated Sulphite Reused Sulphite WasteLiquor Fines Fines Paperboard Plant Low Grade Wrapping Paper Excess Fines Ca(HSO3)2 Pulp Product NaHSO3 Wood Pulp Mill Bark Logs Pressed Hardboard Groundwood Pulp Plant Steam Plant Sale to Regional Market Sale to World Market Fine PaperMill Concentrate Sulphate Binder Reuse

95. Assuming that the total production of fine paper is 1000 tonnes per day. The remaining quantities are calculated based on this production as below: Computation of trees at the complex Production of fine paper = 1000 tonnes/day (907.2 kg/day X 103) Fiber loss from papermill = 1.68% of production. Therefore, suspended solids going into waste streams from papermill = 1.68/100 X 1000 = 16.8 tonnes/day (15.24 kg/day X 103) Total wood pulp produced per day = 1000 + 16.8 = 1016.8 tonnes (922.44 kg X 103) Quantity of sulphite liquor generated in wood pulp mill = 300 gallon/ton (1.24 X 10-3/kg) of pulp produced White concentration of dissolved solids in sulphite liquor = 11% Thus, dissolved solids going in sulphite liquor = 110,000 X 8.34 X 300 X 10-6 = 275.22 lb/ton (1.376 X 10-1 kg/kg) of pulp Total sulphite wastewater dissolved solids produced per day = 275.22 lb/tonnes X 1016.8 tonnes/day X tonnes/2000 lb = 139.9 tonnes/day (1.269 X 10-5 kg/day) On an assumption that the amount of bark produced is generally 15% (by weight) of the pulp production. Therefore, bark production = 15/100 X 1016.8 = 152.5 tonnes/day (1.38 X 105 kg/day) Total tonnage of trees used in the complex = 1016.8 + 139.9 + 152.5 = 1309.2 tonnes/day (1.187 X 106 kg/day)

96. Groundwood pulp production Recovery of suspended solids from paper mill = 16.8 tonnes/day (1.52 X 104 kg/day). Assume that 100 tonnes (907.2 X 102 kg) of ground pulp is required for production every day. Fiber loss in the groundwood pulp plant = 0.6 tonnes/100 tonnes of the groundwood pulp = 0.6/100 X 100 = 0.6 tonnes/day (544.3 kg/day) Total groundwood pulp produced and lost per day = 100 + 0.6 = 100.6 tonnes/day (912.6 X 102 kg/day) Therefore, used newspaper required =100.6 – 16.8 = 83.6 tonnes/day (758.4 X 102 kg/day) Assuming 50% of the groundwood pulp is recycled and the remaining is used in the production of paperboard.

97. Paperboard production Loss of fines from groundwood pulp production is about 0.5% of the production. Let us say that paperboard production = X tonnes/day X + 5/100 X = 50 tonnes pulp/day (543.59 X 102 kg/day) 1.005 X = 50 X = 49.75 tonnes paperboard/day (451.32 X 102 kg/day) Fines recovered from paperboard waste = 50 – 49.75 = 0.25 tonnes/day (226.79 kg/day) 0.25 tonnes/day of fines can be used to produce low grade wrapping paper and pressed hardboard. With no loss of fines and with a 50-50 product production split, 113.64 kg of each product can be manufactured.

98. Sulphite Recovery The solids concentration of spent sulphite liquor drawn from the digestors may vary from 6 to 16% with an average value of 11%. These solids may contain as much as 68% lignosulphonic acid, 20% reducing sugars, and 6.7% calcium. Complete evaporation of the sulphite waste liquor produces both a fuel which can be burned without an additional outside fuel supply and a salable by-product such as synthetic vanillan and road binder.

100. Waste heat from one section of the complex can be used as a process heat for another section, the concept being minimization of waste heat. It is accepted that thermal discharges may result in anomalous stratification in the receiving basin, lowering of capacity to hold oxygen, increased reaction rates and metabolism. These effects vary significantly with the chemical and meteorological conditions associated with the water body.

101. The lethal effects of thermal pollution are sometimes obvious, whereas the sub-lethal effects on food chains and waste assimilative capacities are not easy to foresee without careful study.

102. The present industrial complex outlined can reduce waste heat discharged to the hydrosphere and atmosphere. The two significant areas of concern are:

103. Utilization of solid wastes from the plant to achieve energy efficiency.

105. Status of R&D & Quality Control One of the major reasons for the slow modernization of Indian pulp and paper industry till recent past has been a low level of investments on Research and Development (R&D) for the development of indigenous new technologies, process modifications, environmental management etc. On an average, the R&D investment in pulp and paper sector of the country is less than 0.1% of the total turnover compared to more than 5% in developed countries. Nearly 50% of the R&D investment comes from government agencies. Most of the laboratories are equipped with instruments/testing facilities required for quality control of paper products. Only a few mills have full fledged testing facilities for other areas of paper making like raw material evaluation, black liquor analysis and environmental monitoring

106. Cleaner Production Programme Most of the mills are implementing cleaner production techniques and programme for improving their product quality as well as environmental status Areas like raw material development and use, efficient water utilisation, adoption of energy efficient and green technologies, generation of green energy and careful control and management of environmental problems are being accorded top priority by most of the mills. Mills are also working towards resource recovery/ optimisation by employing process automation and upgrading paper machines. There has been increasing efforts by the mill for recycling/ reuse of process back water to reduce the effluent discharge and water consumption. The application of biotechnology particularly enzymatic pre-treatment of pulp before bleaching is now gaining importance. The use of enzymatic pre-treatment of pulp has been demonstrated successfully in saving of bleaching chemicals (chlorine 12-15%) & AOX reduction by 20-25%.

107. THANK YOU!