| Chroma is an important index of wastewater quality, pharmic production wastewater is charactered with higher concentration of chroma, and it is difficult to decolourd, so the chroma in the effluent of pharmic production wastewater hardly meets the integrated wastewater discharge standard. The radical reason is short of the studies of color formation mechanism and wastewater decoloration mechanism. In this study, vitamin C wastewater was taken as the object of study to set up a method of characterics analysis of organic colourd matters in pharmic ferment product wastewater with modernized instrumental analysis, to determine chromophore, auxochrome and conjugated system, and the color formation mechanism and wastewater decoloration mechanism were studied. This study provided a good theoretical basis for development of the effective decoloration process, meanwhile, it has some meanings to take example by study on decoloration mechanism of other industrial wastewater. The study results are as follow:1. Effluent form biochemical treatment of vitamin C wastewater was taken as the object, infrared spectral analysis showed:the peak 1640-1620 cm-1 in the function group region of represent was assigned to C=O stretching vibration, and the peak 3450-3250 cm-1 was assigned to-OH (3700-3200 cm-1) or -NH2 (3500-3300 cm-1) stretching vibration,-OH/-NH2 was auxochrome. Ultraviolet spectral analysis showed:the 265-270 nm absorption peak was also assigned to C=O, and the 200-210 nm fine peaks were assigned to conjugated system. Coexistence of carbonyl, conjugated system make organics to be chromophoric matters, meanwhile, the intensity of chroma was deepen by auxochrome (hydroxyl/a mino)2. Two methods were adopted to confirm the chromophore carbonyl (C=O) existence in vitamin C production wastewater. The effluent from biochemical treatment was separated by extraction with butanol, then the separated liquor containing colourd organics was tested by gas chromatography-mass spectrograph (GC/MS), and the molecule fragments with the chromophore carbonyl (C=O) were validated, but this method needs to filter extraction method, and separate the deoclored organics, this way will cost a lot of times. "Reagent for Fructosa mine Test (NBT) can directly test acyla mino (being contained in mailard reaction products) to confirm the chromophore carbonyl (C=O) existence in wastewater. Reagent for Fructosa mine Test with charters of simpleness, easy-operation, was chosen as a perfect method for determination of chromophoric group in wastewater. And the suitable conditions for reaction, such as medicine dosage, temperature, reaction time, etc, were investigated.3. There were the same chromophoric group carbony, auxochrome and conjugated system in all vitamin C wastewater, which included raw higher-colored wastewater (multi-mother liquor, waste acid or alkali, residual methanol liquor and mixed wastewater), effluent from routine biochemical treatment (up anaerobic sludge bed (UASB), moving bed biofilm reactor (MBBR)), and effluent from every advanced treatment units (catalytic ozonation, electrolysis oxidation, integrative biochemical reactor (AF-MBBR), inner-cycle aerated biofilter and two-stage catalytic ozonation), so it can drawn this conclusion that there were the same chromophoric structure in different vitamin C wastewater. The organics with micromolecule weight (>5 kDa) in raw wastewater came from complex biochemical reactions during the vitamin C production. Coloured organics separated from multi-mother liquor by extraction with tertiary butanol, was tested by gas chromatography-mass spectrograph (GC/MS), and the molecule fragments with the chromophore carbonyl (C=O) wered validated.4. Four other typical ferment pharmic production wastewater, such as vitamin B12, terramycline, penicillin and streptomycin, had the same mechanism of chroma formation as vitamin C, had the same chromophore (C=O), auxochrome (-OH/-NH2) and conjugated system. However, absorption peaks of the chromophoric groups took a shift from the orginal region. Carbonyl group in terramycin mother liquor took an shift from 1640-1600 cm’1 to 1581 cm’1 in infrared spectral, from 265-270 nm to 249 nm in ultraviolet spectral. Micromolecule organics with little contents in vitamin B12 greatly contributed to chroma of wastewater, macromolecular organics did the opposite. Medium molecule weight organics (1-3 kDa) in terramycin had played a big part in chroma.5. Due to hydrolysis reaction took place in anaerobic treatment, some-OH was added to the colored organics, so the chroma in it got darker during routine biochemical treatment, the rate of chroma increased by 40%. Aerobic treatment has definite efficiency in wastewater decoloration, the average rate of colour remove was 26.5±8.6%. During the advanced treatment of the effluent of biochemical treatment, the catalytic ozonation and electrolysis had higher efficiency of decoloration, the rate of colour remove were 45.5%,49.9%, respectively. The biochemical treatment took a small role in decoloratio, and the rate of colour remove inner-cylce aerated biofilter just was 14.4%. Two-stage catalytic ozonatio had higher efficiency in decoloration with a rate removal of 79.4% in its own treatment unit, although it took small role in decoloration of the whole process, it can assure the final efflutent can meet the discharge standard.6. During the routine and advanced treatment of vitamin C wastewater, along the wastewater treatment process flow, the chromophore carbonyl (C=O), auxochrome (-OH/-NH2) were decrease gradually, this inlustrated they were destroyed or removed. But the fine conjugated structure weren’t completely disappeared, so the wastewater had chroma to some extent. The organic concentration in effluent from the end units of advanced treatment:nanofiltering and two-stage reverse osmosis was very lower, the chroma of them was just 0-1 times, and the adsorption peak and conjugated structure in the infrared spectral disappeared almostly, so decolourd organics and chroma were removed completely.7. Observation with SEM showed bacteria in the biochemical reactors for decoloration were mainly brevibacterium, oval-shaped bacteria and coccus. The thicker biofilm in the AF-MBBR has more gaps. On the contrary, the biofilm attaching to ceramicite granule in inner-cycle aerated biofilter was thinner, and less empty in it, so the activity and decoloration efficiency was lower. The microbial diversity (H 3.1571) at lower temperature was less than that at higher temperature (H3.2513). Glucose decreased biodiversity at higher temperature, and did the opposite at lower temperature. The bacteria system in aerated biofilter was stable. There were various functional bacteria, such as Novosphingobium aromaticivorans, Paracoccus denitrificans and Rhodococcus rhodochrous, etc. can degraded aromatic compounds, because they can destroy the conjugated structure of chromophoric compounds, they were mainly bacterial groups for decoloration in wastewater. |
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