tailieunhanh - Waste Treatment in the Process Industries - Chapter 10

Nhà máy giấy và bột giấy là một nguồn chính của ô nhiễm công nghiệp trên toàn thế giới. Các bước thành bột và tẩy trắng tạo ra hầu hết các chất thải lỏng, rắn, và khí (Bảng 1) [1]. Bột là một quá trình mà trong đó các nguyên liệu được xử lý cơ học hoặc hóa học để loại bỏ lignin để tạo điều kiện thuận lợi cho cellulose và tách sợi hemixenluloza và cải thiện các tính chất làm giấy sợi. . | 10 Treatment of Pulp and Paper Mill Wastes Suresh Sumathi Indian Institute of Technology Bombay India Yung-Tse Hung Cleveland State University Cleveland Ohio . POLLUTION PROBLEMS OF PULP AND PAPER INDUSTRIES Pulp and paper mills are a major source of industrial pollution worldwide. The pulping and bleaching steps generate most of the liquid solid and gaseous wastes Table 1 1 . Pulping is a process in which the raw material is treated mechanically or chemically to remove lignin in order to facilitate cellulose and hemicellulose fiber separation and to improve the papermaking properties of fibers. Bleaching is a multistage process to whiten and brighten the pulp through removal of residual lignin. Pulping and bleaching operations are energy intensive and typically consume huge volumes of fresh water and large quantities of chemicals such as sodium hydroxide sodium carbonate sodium sulfide bisulfites elemental chlorine or chlorine dioxide calcium oxide hydrochloric acid and so on. A partial list of the various types of compounds found in spent liquors generated from pulping and bleaching steps is shown in Table 2 2-4 . The effluents generated by the mills are associated with the following major problems Dark brown coloration of the receiving water bodies result in reduced penetration of light thereby affecting benthic growth and habitat. The color responsible for causing aesthetic problems is attributable to lignin and its degradation products. High content of organic matter which contributes to the biological oxygen demand BOD and depletion of dissolved oxygen in the receiving ecosystems. Presence of persistent bio-accumulative and toxic pollutants. Contribution to adsorbable organic halide AOX load in the receiving ecosystems. Measurable long-distance transport 100 km of organic halides such as chloroguaiacols thereby contaminating remote parts of seas and lakes 5 . Cross-media pollutant transfer through volatilization of compounds and absorption of .