Semiconductor Manufacturing Research And Application Of Arsenic Wastewater Treatment Technology

This paper is about treatment of arsenic wastewater from Gallium Arsenide (GaAs) semiconductor production and processing. The status and development of arsenic wastewater treatment techniques were firstly reviewed in this paper. An arsenic removal technique based on coagulation and sedimentation by ferric chloride (FeCl3) was proposed, which was adapted for the arsenic wastewater in this study. According to treatment requirements and field conditions, a suitable process route that was wastewater regulation+two-stage FeCl3coagulation and sedimentation+sand filtering was developed, followed by construction drawing design, engineering construction, process debugging and cost-benefit analysis. A good removal of arsenic was obtained during trial operation of the project, and the average arsenic concentration of effluent could be effectively controlled below0.02mg/L.FeCl3coagulation and sedimentation was selected as a principal method to treat the arsenic wastewater by comparing arsenic removal efficiencies of CaCl2, FeCl3and polyaluminium chloride (PAC). The feasibilities of convenient operation and effluent quality to meet discharge standard were analyzed and compared between one-stage and two-stage coagulation and sedimentation. The results of the experiment study showed that the actual operation would be not convenient for one-stage treatment on condition that effluent meet the standard due to too large amounts of sludge and too long settling time. Because the amounts of FeCl3and produced sludge were reduced significantly in two-stage treatment, of which the aim of the first stage was to obtain good settling performance and the aim of the second stage to get good effluent quality, convenience of operation was improved obviously.Sequencing batch operation mode was selected to improve the flexibility and reliability of process operation. Technique design calculation, engineering materials and equipment selection, and process construction drawing design were done in this work. The author of this paper had understood the design requirements and content of construction drawings including process, electrical system and instrument&control system in this project. The author assisted the person in charge of the project in organization, preparations and construction to guarantee engineering’s quality and quantity. The author also participated program debugging, single machine debugging, online debugging, process debugging and test running. Some debugging methods were learned, and a lot of experience and lessons were accumulated through this work.In conclusion, successful completion and operation of the arsenic wastewater treatment engineering indicates that the process route based on two-stage FeCl3coagulation and sedimentation is suitable for treatment of arsenic wastewater from GaAs semiconductor production and processing, and has a good demonstration effect on other arsenic wastewater from related industries.