J.N. Chen

Pretreatment of pesticide wastewater by photocatalytic oxidation

The toxic chemicals, 2,4-D (a herbicide) and propoxur (an insecticide), were used as the model compounds in these experiments. Total organic carbon analyzer was used to assess the efficiency of photocatalytic mineralization. Microtox bioassay was employed in evaluating the toxicity of solutions treated by photocatalysis. Ultraviolet absorption spectra were also used for showing the different characteristics of the compounds undergoing photocatalytic oxidation. Results show that propoxur is less degradable than 2,4-D, and the photomineralization of these pesticides follows a behavior of first-order reaction. Products of 2,4-D and propoxur are more toxic than the parent compound after partial photodegradation. This shows that complete mineralization is necessary for total detoxification of these pesticides. In other words, toxicity is an important criteria in assessing the pretreatment process.

Photocatalytic oxidation of chlorophenols in the presence of manganese ions

The decomposition of chlorophenols in aqueous solution with UV-illuminated TiO2 suspensions in the presence of manganese ions was studied. It was found that the removal rate of chlorophenols would be the highest at pH 3 in the presence of 1.18×10−4 M manganese ion. The effect of ionic strength on the 2-CP decomposition can be ignored in the range from 0.1 to 0.005 M for NaClO4. This study is also to explore the relationship between the adsorption rate and reaction rate. Results showed that the more the adsorption rate the more the decomposition rate for the three chlorophenols. Manganese ions can increase the photocatalytic oxidation of 2-chlorophenol in terms of DOC. The relationship between temperature and reaction rate for 2-CP is k = 0.0043 T - 1.2146.

Nitrification–Denitrification of Opto-electronic Industrial Wastewater by Anoxic/Aerobic Process

Abstract This research focused on the biological treatment of high-strength organic nitrogen wastewater, and presented the results from the nitrification and denitrification of an actual industrial wastewater using anoxic/aerobic process. The opto-electronic industrial wastewater often contains a significant quantity of organic nitrogen compounds and has a ratio over 95% in organic nitrogen (Org-N) to total nitrogen (T-N). In this study, a 2-stage anoxic/aerobic process was established and evaluated the efficiency of wastewater treatment. Raw wastewater from an actual TFT-LCD manufacturing plant was obtained as the sample for looking into the feasibility of opto-electronic industrial wastewater treatment. After toxicity identification evaluation (TIE) test of raw wastewater, the inhibition was related to organic nitrogen (TMAH, MEA) and unionized ammonia (free ammonia, NH3) with high pH. Therefore, pH control is important for biological treatment of high-strength organic nitrogen industrial wastewater. Besides, hydraulic retention time (HRT) and mixed liquor recycled rate (MLR) were controlled independently to distinguish between the effects of these two factors. Under suitable HRT (>1.7 d) and mixed liquor recycled rate (<4Q), effluent of NH4-N, NO3-N + NO2-N, and COD can fall below 20 mg/L, 30 mg/L, and 80 mg/L. The anoxic/aerobic process removed 92–98% of the carbon source, and approximately 80% of TKN, 70% of T-N.

Recycling and Reuse of Wastewater from a New-Developed Community Using Sand Filtration, Ultrafiltration, and Ozonation

Abstract In this study, the pilot apparatus combined with sand filtration, ozonation and ultrafiltration was established. Wastewater from the secondary treatment effluent in the new-developed community was taken as the sample for looking into the feasibility of domestic wastewater reuse and recycling. The test results by sand filtration, sand filtration/ultrafiltration, sand filtration/ozonation, and sand filtration/ultrafiltration/ozonation were compared for looking for appropriate treatment processes applied in the domestic wastewater reuse and recycling. Finally, cost analysis was carried out and sand filtration/ozonation process was suggested to be one of the best processes. The total cost is about 0.1–0.32

Heterogeneous catalytic ozonation of 2-chlorophenol queous solution with alumina as a catalyst

USD per cubic meter of produced water by considering the capital and operation cost for five years in the small domestic wastewater treatment plant (50–750 CMD).