No abstract

Toxicity of tetra-methyl ammonium hydroxide (TMAH) was investigated in an upflow anaerobic sludge bed (UASB) by anaerobic toxicity assay test. System performance was determined by monitoring total organic carbon (TOC) and ion chromatograph (IC) analysis. The result indicates that TMAH concentration less than 10 000 mg/L is nontoxic to the anaerobic archaea. TMAH containing in the wastewater was completely degraded under anaerobic condition and was transferred to biogas (CH 4 and CO 2 ) and NH 3 . The maximum volumetric loading of UASB is 6.95 kg TMAH/m 3 -day (4.0 kg TOC/m 3 -day) and 7.30 kg TMAH/m 3 -day (4.1 kg TOC/m 3 -day) for synthetic wastewater and wastewater from a full-scale thin-film transistor liquid crystal display manufacturing industry during the 240-day experiment, respectively. The removal efficiencies of THAM containing wastewater were both higher than 95% treated by UASB.Index Terms-Anaerobic, anaerobic toxicity assay (ATA) test, methanogen, tetra-methyl ammonium hydroxide (TMAH), thin-film transistor liquid crystal display (TFT-LCD), upflow anaerobic sludge bed (UASB).

The applications of membrane processes in anaerobic biological wastewater treatment still have some limitations due to severe membrane scaling and fouling, although they have been proven to achieve superior COD removal and biomass retention. An innovative anaerobic membrane process for wastewater treatment was conducted to control the membrane scaling problems. The process comprises an anaerobic reactor, an aerobic reactor, and a membrane separation tank. Anaerobic sludge from a full-scale UASB reactor treating food wastewater was inoculated to anaerobic and aerobic reactor to purify synthetic wastewater consisting of glucose and sodium acetate. The anaerobic reactor was operated in a sludge bed type without three-phase separator. The aerobic reactor can eliminate residual organics from the anaerobic reactor effluent using facultative microorganisms. To provide solid-liquid separation, hollow fiber ultrafiltration module was submerged in the separation tank. The results clearly show that the anaerobic membrane process combined methanogenic and aerobic COD reduction is a stable system. No fatal scaling was found after two months of operation even without chemical cleaning for the membrane. It was also found that inorganic precipitates formed in the aerobic reactor were reduced due to CO2 stripping in aerobic reactor. Another important finding was that the inorganic precipitates were entrapped into facultative aerobes floc. The ash/SS ratio of aerobes floc increased from 0.17 to 0.55 after 50 days of operation, which confirms this phenomenon. Based on our investigation, the new process can control scaling effectively to extend the membrane application in anaerobic treatment.

Biodegradable dissolved organic material and ammonia present problems for conventional water treatment processes and may contribute to biological instability in the treated water. One solution may be to use a biological process upstream of the regular water treatment process. Biofiltration may be cost-effective in removing ammonia and the precursors of trihalomethanes but the characteristics of the biotreated effluent may affect to the subsequent coagulation process. A continuous flow biological filter packed with reticulated polyurethane foam markedly altered the particle size distribution and the charge density of the mixed liquor, shifting the granulometric distribution toward larger sizes. The mean and median diameter of the particles increased from 9.7 and 5.9 µm to 97.6 and 37.1 µm, respectively. The average charge density of the biofilter effluent (7.6 meq dm −3 ) was much lower than that of the raw water (12.7 meq dm −3 ). The optimum coagulant dosage for the subsequent coagulation was reduced substantially from 10 mg dm −3 to 1 mg dm −3 as Al due to the lowered charge density of the mixed liquor and the enhanced cation bridging of the extracellular polymers on the bioparticle surface.