| In this study, an A2/O system was applied to treat comprehensive chemicalindustrial wastewater from a chemical industrial park in Tianjin, China. According tothe analysis of this wastewater, the removal performance of the system was evaluatedand several enhancement measures were considered to improve the removalperformance of the system. These measurements and analyses could provideeconomic and efficacious technical support to the efficacious treatment of chemicalindustrial wastewater in full-scale industrial wastewater treatment plants.The organic matter in the raw wastewater showed complex contents. Accordingto the analysis of organic matter characteristics in the wastewater, the compounds inthe wastewater were mainly in low moleculer size and hydrophobic fractions. Thecharacteristics of function groups of various faractions in wastewater were alsoconsidered by spectrum analysis, such as UV-visable, Fourier transform infraredspectroscopy, three dimensional excitation-emission fluorescence spectra. And thenthe moleculer structure of organic matter in various fractions was decided by gaschromatograph-mass spectrometer. There were various organic compounds containedin wastewater, such as alkane, BTEX, PAHs, aromatic acids, phenols and esters. Theorganic acids in wastewater were mainly in acid fractions (including HPO-A andTPI-A fractions). Alkane, PAHs and esters were mainly in HPO-N fraction. TPI-Nfraction mainly contained phenols. The aromatic compounds, which were refractoryand toxic, were mainly contained in the wastewater and difficult to remove inwastewater treatment plants.A traditional A2/O system was applied to treat this wastewater under theconditions of influent COD=190-570mg/L, HRT=20h, MLSS=3.0-4.0g/L. Theorganic matter removal in the system showed poor removal performance with theefficiencies:40%-50%of COD,40%of ammonia and20%of total nitrogen,respectively. It indicated that these complicated compounds existed in the wastewatercaused the poor removal performance of the system.To improve the system removal performance, operation conditions wereoptimized in the system. COD removal efficiency increased form45%to70%withHRT prolonged from20h to60h and MLSS increased from3.0g/L to6.0g/L. Itindicated that prolonging HRT could increase the removal of dissolved biodegradable organic pollutants and increasing MLSS could cultivate and enrich the degrader.However, TN removal was not improved because of denitrification carboninsufficiency.To improve TN removal performance, external carbon was added to the system.According to the results of external carbon added section and dosage optimization, itwas found that TN removal performance was improved when the carbon was added toanoxic reactor, and COD removal efficiency also increased slightly. However, TN andCOD removal was not improved when the carbon was added to aerobic reactor. Itillustrated that the external carbon was simply utilized by heterotrophic bacteria.To remove the refractory organic matter in the wastewater, powdered activatedcarbon (PAC) was added to the biological system. COD removal performance wasenhanced by PAC adding at2g/L. According to the analysis of organic matter removalcharacteristics in the wastewater and treated effluents, It was found that PACpreferred to adsorbed hydrophobic organic compounds, while activated sludge waslikely to removal organic matter in TPI-N and HPI fractions. In PAC-AS system, theremoval performance of various fractions showed superior to the performance inindividual AS and PAC system due to additive effect of biodegradation and PACadsorption. According to the results of spectrum analysis, the compounds containing–OH and C–O–C were removed by both activated sludge transformation and PACadsorption. However, large molecular size organic acids-like and aromatic compounds,refractory to biodegradation, could be partly removed by PAC. |
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