Waste Water Treatment Technology for Small Scale Pulp and Paper Mills in Thailand. (Part 1). Analysis of the Present Situation of Machine and Hand Made Paper Mills from Paper Mulberry.

Despite the declining tendency of small-scale mills producing hand and machine made washi, corresponding mills in northern Thailand which mainly use paper mulberry are gradually increasing in number. In spite of all the attention currently given to environmental conservation, the waste water treatment situation has not yet been so far clarified. The authors therefore surveyed and analyzed waste water from one pulp mill (Sawankalok), three hand-made paper mills (Sawankalok and Samutsakhon), two pulp and hand-and machine-made paper mills (Sawankalok and Chiangmai), and two hand-made paper mills (Bangkok).Analysis showed that effluent volumes of waste water from pulping and paper-making processes from paper mulberry (Broussonetia papyrifera) were as follows.Soaking process before cooking 8.011.2 times volume/paper mulberry white bark kg (air dry) Cooking process 6.0 8. 5 timesCleaning process for pulp 16.0 22.4 timesBleaching and screening process 10.5 11. 2 timesWashing process 21. 0 22.5 timesProcess of paper making by machine around 50 timesThese several different sources of waste water were mixed and the whole was discharged into waste ponds consisting of three to seven ponds connected in series and exposed to strong tropical sun light for over to one month, sometimes with aeration and stirring but mostly without aeration. Cooking waste liquor had a high COD concentration of 16, 000-22, 400 mg/L and was dark in the color but was diluted with waste water from other processes.Waste water in the final ponds had the following properties, pH 89, electric conductivity 0.73.1 mS/cm, dissolved oxygen 0.04-5.2 mg/L, COD 70-210 mg/L, and BOD 1520 mg/L.