Cheng-Nan Chang

Alkaline and ultrasonic pretreatment of sludge before anaerobic digestion

Pretreatment of waste activated sludge (WAS) results in an improved efficiency of the subsequent anaerobic biotransformation of the organic matter to volatile fatty acids. The pretreatment process has been carried out using alkaline treatment, ultrasonic treatment (20 KHz, 120 W) and different combination of these two methods: alkaline followed by ultrasonic, as well as the combining method in which ultrasonic treatment is applied to WAS samples dosed with alkaline. The hydrolysis efficiency was evaluated based on the quantity of soluble COD (SCOD) and organic nitrogen in the pretreated WAS as well as the production of total volatile fatty acids (TVFA) in the following biochemical acid potential (BAP) test. For WAS samples with described pretreatments, the released SCOD varied from 36% to 89% of the total COD (TCOD) and soluble organic nitrogen from 34% to 42%. The TVFA/TCOD ratio of the raw WAS used in this study was less than 10%. For the alkaline pretreated WAS, the TVFA/TCOD ratio increased to 30%, and the following ultrasonic treatment enhanced the ratio 66%. Further, WAS samples pretreated using simultaneous ultrasound and alkaline treatment in which ultrasonic was applied to WAS samples dosed with 40 meq/L NaOH for 14.4 sec/mL could achieve a maximum TVFA/TCOD ratio of 84% in 21 hours. Therefore, the combination of simultaneous alkaline and ultrasound pretreatment is efficient in enhancing the production of volatile acids in WAS in order to achieve recovery of volatile fatty acids from the WAS.

Enhancement of decomposition of 2-chlorophenol with ultrasound/H2O2 process

We investigated the effects of pH, ionic strength, catalyst, and initial concentration on both decomposition of 2-chlorophenol (2-cp) and removal of total organic carbon (TOC) in aqueous solution with ultrasonic amplitude 120 μm and H 2 O 2 (200 mg/l). When the initial concentrations of 2-cp was 100 mg/l and the pH was controlled at 3, the rate of 2-cp decomposition was enhanced up to 6.6-fold and TOC removal up to 9.8-fold over pH controlled at 11. At pH 3, the efficiency of decomposition of 2-cp was 99% but the removal of TOC was only 63%; a similar situation applied at pH 7 and 11. Hence intermediate compounds were produced and 2-cp was not completely mineralized. When the concentration of ionic strength was increased from 0.001 to 0.1 M, the rate of 2-cp decomposition was enhanced only 0.3-fold, whereas the TOC removal was not enhanced. In comparison of the effects of pH and ionic strength, pH had greater influence on both 2-cp decomposition and TOC removal than ionic strength. The effect of a catalyst (FeSO 4 ) on decomposition of 2-cp was insignificant comparing with direct addition of H 2 O 2 . The reaction rate at a smaller initial concentration of 2-cp (10 mg/l) was more rapid than at a greater one (100 mg/l). The rate of 2-cp decomposition and TOC removal appeared to follow pseudo-first-order reaction kinetics.

DRY DEPOSITION OF METAL ELEMENTS ON SURROGATE SURFACES IN THE AMBIENT AIR OF CENTRAL TAIWAN

Different surrogate surface were used to measure the atmospheric dry deposition flux of total‐particle mass and metals. Three different surrogate surface (overhead projection, T60A20 and Teflon) and two absorbent grease (Apenzion L grease and silicone grease) were compared and investigated. The results of this study indicated that using the Teflon filter coated with the silicone grease yielded the minimum background interference and high reproducibility for metal dry deposition analysis. Dry deposition and particle concentration were sampled simultaneously among three sampling sites (THU, JES and SES) with several dry deposition plates and TSP (total suspended particle) samplers from October 1994 to December 1995 at the central Taiwan. Six individual metals (Ca, Fe, Zn, Pb, Cu and Cd) were analyzed primarily with an AA‐680/G flame atomic absorption spectrophotometer. The results showed that the highest dry deposition flux, concentration of total particle‐mass and metals occurred in the SES sampling site w...

Modified nernst model for on-line control of the chemical oxidation decoloring process

A modified Nernst equation was used to describe the decoloring reaction using the Oxidation-reduction potential (ORP) as an on-line monitoring and control parameter of the chemical reaction. In the modified equation, an “S” term is defined to indicate the oxidative potential (or decoloring potential) of dyes being studied. The laboratory study utilizes sodium hypochlorite (NaOCl) to reduce the color of wastewater spiked with textile dyes. Five dyes were used in preparing the wastewater samples: methyl red (MR), methyl violet (MV), methyl blue (MB), malachite green (MG) and methyl orange (MO). The color was measured by use of an automatic ADMI (American Dye Manufacturer Institute) measurement system in which a visible spectrophotometer was connected to a personal computer and the samples were scanned from 400 nm to 700 nm with a 10 nm interval each step. During the batch decoloring studies, several factors including ADMI, ORP, temperature and pH were continuously monitored with the computer. In this study, the potential of the decoloring compound of the dyes studies are in the following order: MG>MV>MO>MR>MB, with numeric ratios of 2.08 : 1.78 : 1.78 : 1.28 : 1.00, respectively.

The pretreatment of acrylonitrile and styrene with the ozonation process

Acrylonitrile and styrene are used as the raw materials for manufacturing acrylic fiber, thus they are often found as pollutants in the petrochemical wastewater. This study utilizes ozone to decompose the organic nitrogen contained in acrylonitrile and styrene, and the oxidation process was monitored using on-line measurements of oxidation-reduction potential (ORP) and pH. The efficiency of organic nitrogen decomposition was also estimated based on the COD, organic nitrogen, TOC, ammonia-N, nitrite, and nitrate measurements. Both the initial pH and alkalinity are observed to affect the degradation rate of organic nitrogen. The acrylonitrile sample with the lowest initial pH value (i.e., 4.0) has a shorter t1/2 of 18.9 min and that for samples of the highest initial pH (i.e., 11) was 34 min. The alkalinity of one acrylonitrile sample was boosted by adding 500 mg/l CaCO3, to simulate the field ABS (Acrylonltrde-Butadiene-Styrene) wastewater effluent. It was observed that within a short ozone contact time, the acrylonitrile sample spiked with 500 mg/l CaCO3 had the highest COD decomposition rate of 0.411 mm−1, or 1.3 times more than that for samples without addition of CaCO3. Results of the ozonation process can be fitted with a modified Nernst equation for the various pH conditions. Additionally, the ozone treated synthetic ABS sample shows a faster COD removal rate in the subsequent biological process than those samples without ozone treatment.

The study of temple and pastureland particle-bound polycyclic aromatic hydrocarbons concentrations in central Taiwan

The concentrations of polycyclic aromatic hydrocarbons in the atmosphere were measured simultaneously at Tzu Yun Yen temple and Tung Hai University pastureland in Taichung, central Taiwan. At both sites, 24 h samplings were performed between August 2001 and December 2001. The results indicated that high molecular mass polycyclic aromatic hydrocarbons are predominant at the Tzu Yun Yen temple sampling site. Moreover, the PM2.5 (fine particulate) fraction of total polycyclic aromatic hydrocarbons was higher than that of the PM2.5-10 (coarse particulate) fraction by a factor of about 1.48 at the temple sampling site. This ratio was 1.24 for the pastureland environment.

Decoloring Mechanisms of Dye Stuff by Chemical Oxidation

This study utilizes sodium hypochlorite (NaOC1) to reduce the color of synthetic dye solutions. Five dyes including methyl red (MR), methyl violet (MV), methyl blue (MB), malachite green (MG) and methyl orange (MO) were studied. The color was measured using an automatic ADMI (American Dye Manufacturer Institute) measurement system. A visible spectrophotometer is connected to a personal computer so that samples can be scanned and the results are recorded automatically. During the batch decoloring study, several factors: ADMI, ORP, temperature and pH were also monitored continuously using the computer and makes it possible to have an automated decoloring process.

Study of particulates and metallic elements at a farm sampling site in central Taiwan

The total suspended particle (TSP) concentration, dry deposition and wind speed were measured with a PS-1 sampler, a dry deposition plate and a Weather Monitor II (#7440), respectively, at the Experimental Farm of Thunghai University in Taiwan. Taiching Industrial Park, Taichung Cong Road (traffic) and a hospital incinerator are close to the sampling site. The sampling time was from August 2001 to December 2001. The average dry deposition flux, the TSP concentration, dry deposition velocities, average wind speed and maximum wind speed were recorded as 617.7 ± 281.4 mg/day/m², 117.5 ± 17.6 µg/m³, 5.9 ± 2.2 cm/s, 2.7 ± 1.3 m/s and 7.6 ± 2.3 m/s, respectively, at this sampling site. Good correlation coefficients (R) of the TSP concentration and the dry deposition flux with wind speed were found, with values of 0.46 and 0.50, respectively. The concentrations and dry deposition of the total metallic elements were also obtained. The results indicated that the concentrations of anthropogenic elements (Pb, Mn, Cd, Ni, Cr and Zn) were mostly higher than those obtained in other studies around the world. The average dry deposition fluxes and TSP concentrations for Zn and Pb were 0.45 and 0.42, respectively. The same phenomenon was also observed for Fe and Mg (R = 0.59 and 0.65). The results indicate that these elements were all coming from the same emission sources at the farm sampling site.

Characteristic study of particulates and metallic elements at an urban sampling site in Taichung, central Taiwan

Atmospheric total suspended particulate concentrations and metallic element concentrations were measured at three locations, characteristic of urban, suburban and rural sites. The sampling period was from July 2000 to August 2000. The results indicated that the urban sampling site had the highest total suspended particulate concentrations (average 108.61µ1m³), followed by the suburban site (average 60.11µ1m³) and the rural site (average 53.31µ1m³). The average PM2.5 concentrations (24.11µ1m³) were higher than the PM2.5-10 concentrations (12.81µ1m³) at the urban site. The average distributed ratios for PM2.5/PM2.5-10 were about 1.29, 1.53, 0.12, 1.12 and 2.31 for Pb, Zn, Fe, Ni and Cr, respectively. The average total suspended particulate mass ratios for daytime and nighttime were about 1.72. As for the elements Cu, Pb, Zn, Fe, Ni and Cr, these ratios were about 0.63, 0.97, 0.54, 1.66, 0.53 and 1.12, respectively. The total suspended particulate daytime concentrations of Pb and Zn were positively correlated (R = 0.925) at the urban sampling site. The elements Ni and Cr were positively correlated both during the daytime (R = 0.648) and the nighttime (R = 0.511), revealing that they came from the same emission source during daytime and nighttime, at the urban sampling site.

台灣地區空氣污染物多環芳香烴化合物(PAHs)之研究

This paper was to summarize all the PAHs results studied in Taiwan and then compared them with those of the other areas data obtained in the world. For total-PAHs, the averaged dry deposition flux of total-PAHs were 622, 529 and 575 µg/m^2/day in Taiwan was much higher than that in Great Lake, Siskiwit Lake and Chesapeake Bay and was the same as that of Chicago. For the traffic sampling site the total PAH composition were 7275, 839 and 2450 g/g for Taichung, Tainan and Ping Tung, respectively. Taichung traffic sampling site had the largest total-PAH composition than other two sampling site. The reason is the sampling site was located in the National Freeway Interchange and had more cars than other two sampling sites during the sampling time in the business time than that in Tainan and Ping Tung. As for rural sampling sites, the total-PAH composition were 523, 645 and 531 g/g for Taichung, Tainan and Ping Tung, separately. There were no significant difference for PAHs in the rural site of Taiwan. Atmosphere pollutants like PAHs in Taiwan were most associated with fine particles ( ＜ 2.5μm) in other words, which are strongly related to a potential health risk.