| The combined technology of iron-carbon and Fenton is applied to pretreat high COD wastewater from a pharmaceutical factory in Jiangxi, and the wastewater with high sulfate concentration in this factory is chemically and physically treated using limestone desulphurization process in this study. This research provides technical support for the transformation of the pharmaceutical factory's original technics. The wastewater mixed up with effluent after pretreatment and comprehensive sewage with low concentrations of COD and sulfate is biochemically treated further by the ABR and A/O process. The released water meets the acceptance standard of sewage treatment plant in pharmaceutical industrial park. The results show that:(1)The optimum reaction conditions for the combined experiment of Fe-C and Fenton are: the ratio of Fe-C and solid-liquid is 30%, the reaction pH of Fe-C is 3 and the reaction time is 2 hours; the H2O2 dosage of Fenton reaction is 15ml/L, the reaction pH of Fenton technique is 3.0 and the reaction time of Fenton technique is 1hour. The degradation effect of iron-carbon and Fenton combination process in the optimum reaction conditions are: the removal rate of CODcr is 51.9%;( 2) The optimum reaction conditions for the limestone desulphurization experiment are: the adding amount of hydrated lime is 3.4g, the reaction time is 3hours. The optimum removal results of limestone desulphurization experiment under these experimental conditions are: wastewater pH increased from 1.4 to 8.0, the removal rate of sulfate ion is 80%, with the concentration of sulfate ion reduction from 42000mg/L to 8400mg/L;(3)After the wastewater with high COD concentration being treated using the combined technology of iron-carbon and Fenton, that after stable operation of iron-carbon reaction pond, Fenton reaction tank and sedimentation tank in actual operation, its removal rate of CODcr can be stabilized between 45% and 50% with the CODcr concentration being decreased from 120000~150000mg/L to 60000~80000mg/L. After the wastewater mixed up with effluent after pretreatment and comprehensive sewage being biochemically treated further by the ABR and A/Oprocess, its released water reaches the required discharge standards, with CODcr and BOD5 concentration being within 250 and 50mg/L, respectively. This shows that it is feasible to pretreat high COD wastewater using combined technology of iron-carbon and Fenton;(4)After the wastewater with high sulfate concentration stable operation of the desulfurization reaction and sedimentation tanks in actual operation, its removal rate of sulfate can be stabilized between 73% and 78%. The concentration of sulfate in released water remains between 8000 and 12000mg/L, and can be controlled under12000mg/L. Before biochemical treatment, the sulfate concentration of the sewage mixed up with other kinds of wastewater can be controlled under 1150mg/L, which can meet the requirements of biochemical treatment. This shows that it is feasible to treat high sulfate wastewater using physical and chemical desulfurization(limestone desulphurization)technology. |
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