| The DHA is a kind of unsaturated fatty acids which is very helpful for the cardiovascular system, nervous system and anti-inflammatory immune system of human and it is one of the most essential elements to human health as well. The bio-fermentation process was used to produce DHA products in a science and technology company in Jiangsu, with byproducts of a certain amount of high concentration refractory organic wastewater which features with high concentration of COD ranging from 53000 to 54000mg/L, and the ratios of BOD5/COD from 0.09 to 0.1. As the DHA wastewater is low biodegradable, we use the ferric-carbon micro-electrolysis-UASB-MBR combined process to examine each system and the combined process of COD removal efficiency and obtain the optimum operation conditions at last.The ferric-carbon micro-electrolysis was used as the pretreatment process for DHA wastewater in this study. The orthogonal experiments showed that the sequence of the factors on COD removal efficiency in ferric-carbon micro-electrolysis reaction can be given as ferric-carbon ratio> pH value> reaction time> stirring intensity. The optimum operation conditions was the influent pH of 3, 4 hours of reaction time, Fe/C volumetric ratio of 3:1 and 300 r/min of stirring intensity in the single factor experiment. The results showed that 45% of COD was removed and the B/C ratio was improved from 0.1 to 0.31 by the ferric-carbon micro-electrolysis process in the optimum operating conditions which is benefit for the latter treatment of bio-process.The UASB reactor was used as the anaerobic process for DHA wastewater in this study. The volume load in the anaerobic section had reached to 8kgCOD/(m3·d) after 67 days debugging time with about 1500mg/L of COD content in effluent and 81% of The effect of different volume load on COD removal efficiency was studied in the experiments. The results showed that when the volume load greater than 8kgCOD/(m3·d), COD removal efficiency with significantly decreased and water quality is very unstable. Moreover, by taking into account of the actual project which can be damaged by the temperature control device to reduce the interior temperature of the reactor, the effect of water temperature dips inside UASB reactor for COD removal was studied as well. The study showed that when the reactor temperature dropped to 30?, COD removal rate decreased, while in terms with the growth of the reaction time, the COD removal rate increased. When the water temperature dropped to 20?, the effluent exhibited poor water quality, and COD removal efficiency was only about 60%. Therefore, when using the UASB reactor to treat the DHA wastewater, the volume load should be controlled at 8kgCOD/(m3·d), and the water temperature should be ensured above 30?.The MBR system was adopted in the aerobic treatment. After debugging, the volume load of the aerobic biological system was up to 1.5kgCOD/(m3·d). Under the operation conditions of 1.5kgCOD/(m3·d) of volume load and 24 h of HRT, the effluent quality of MBR was better, with COD content of about 80mg/L, the removal rate of 94%, the ammonia nitrogen content lower than 5mg/L, and the removal above 96%.The ferric-carbon micro-electrolysis-UASB-MBR assembled processes was applied at the small scale in the laboratory showed that it could effectively remove the organic content in wastewater, and the effluent quality was stabled and met well with the wastewater quality standards for discharged to municipal sewers(CJ 343-2010), this can be used as a reference for DHA wastewater treatment processes. |
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