Back grinding (BG) wastewater consists mainly of high-purity water and high concentrations of inorganic particles. If the BG wastewater could be treated and recycled efficiently, it should be sort of economic benefit. In this study, appropriate pre-treatment technologies are evaluated to obtain the feasible recycle system. From the chemical coagulation experiment, the addition of PAC or FeCl3, both of them can obviously reduce the turbidity and suspended solid concentrations (SS). In addition, polymer can advance the sedimentation process. Considering the cost of practical operation, the turbidity of BG waste water could be removed up to 97% by using polyaluminum chloride as the coagulant (2.2 mg/L) and polymer as the coagulant aid (0.5 mg/L) in the pH=7 condition . In sand filtration experiment, the turbidity and SS can¡¦t be effectively removed if the coagulation isn¡¦t used on BG wastewater. It demonstrates that BG wastewater contains high concentration of nano-scale particles. The rate of removable turbidity can reach 99% under applying coagulation, sedimentation, and sand filtration. In ultra-filtration experiment, both of spiral-wound (SW) and hollow-fiber (HF) can remove more than 99.9% of turbidity. For the flux of behavior, the performance of pre-treatment water is better than non-treatment water. Thus, it reveals that appropriate pre-treatment can lower the load of membrane filtration system. For the obtained recycle water, the grade of standard can achieve the grade of the cooling tower required.
However, due to its high particle-containing characteristics, the commonly used reverse-osmoses (RO) membrane filtration technology can not be directly applied for purification process because the fouling/clogging problem would cause the frequent membrane replacement. In this lab-scale feasibility study, pre-treatment technologies (e.g., sand filtration, chemical coagulation, ultra-filtration) were applied to reduce the turbidity and particle concentrations of the BG wastewater (collected from a semiconductor manufacturing plant) before RO filtration unit. The BG wastewater contained turbidity and suspended solid concentrations of 3,200 NTU and 96 mg/L, respectively. The measured pH and conductivity of the BG wastewater were in the ranges of 6.8 to 7.2 and 14 to 18 £gS/cm, respectively. Moreover, the particle sizes of the solids varied from 300 to 700 nm. Thus, applying conventional sand filtration along could not effectively remove the nano-scale particles. Results from the chemical coagulation experiment reveal that the turbidity and particles of the BG wastewater could be significantly removed (up to 95% of turbidity and particle removal) by the coagulation/sedimentation process using polyaluminum chloride as the coagulant (2.2 mg/L) and polymer as the coagulant aid (0.5 mg/L). Results also indicate that up to 99% of turbidity and particle removal could be obtained with the application of ultra-filtration unit after the coagulation/sedimentation process. Results from this study indicate that applying appropriate pre-treatment technologies (coagulation and ultra-filtration) would lower the fouling rate and extend the life of RO membrane used for BG wastewater purification.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0128110-161738 |
| Date | 28 January 2010 |
| Creators | Chen, Ya-hsin |
| Contributors | Wen-Liang Lai, Jimmy C. M. Kao, Yi-Chu Huang, Sheng-Jie You, Chia-Yuan Chang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0128110-161738 |
| Rights | not_available, Copyright information available at source archive |
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