Exploration And Optimization On Pretreatment Of Molasses Alcohol Anaerobic Effluent

Molasses alcohol wastewater anaerobic effluent is a typical hard-biodegrafable industrial organic wastewater with high concentration of organic substance(COD 25301 mg/L) and high color degree(5556 times). In this study, different processes were conducted as pretreatment to improve the biodegradability, such as hydrolytic acidification-adsorption combination process, electric flocculation and electro-Fenton. The process conditions were optimized on the basis of analyses for the removal efficiency of organic substance and color degree, as well as the biodegradability. These measurements and analyses could provide theory guidance to realize the efficient treatment for molasses alcohol wastewater anaerobic effluent.Hydrolytic acidification-adsorption combined process was preliminarily employed, the result of the study showed that the COD removal was only around 7.5%, and the biodegradability didn't get any improvement after hydrolytic acidification. So the adsorption for hydrolysate was conducted as further process with different adsorbent, the adsorption effect of powder activated carbon was best, but the B/C of the effluent was 0.174, what demonstrated the effluent was still poorly biochemical. Therefore, the combined process of hydrolytic acidification-adsorption was not suitable as biological pretreatment for molasses alcohol anaerobic effluent due to the effect of the combined process was not significant on the removal of organic substance and B/C improvement.Electrolytic flocculation treatment for molasses alcohol anaerobic effluent was conducted, and based on both of the removal performance and the operating costs, optimal operating condition was proposed as follows: plate spacing 15 mm, current density 3 A/dm2, and the electrolyze time was 40 minutes. Under these conditions, COD removal was 38.27%, color degree removal was 44.87%, and B/C increased from 0.113 to 0.212. The COD removal was up to 54.66% and B/C increased to 0.250 when the wastewater diluted one times. This process was not economic due to the operation cost was 76.11 RMB/t.Due to the expensive cost of electric flocculation and no significant effect, further experiment of electro-Fenton was conducted with iron plate as anode and stainless steel as cathode. The results showed that operating at initial pH=3.00, current density 0.6 mA/cm2, H2O2 dosage 20 ml/L, plate spacing 2 cm, and electrolyze 90 minutes, and the treated wastewater regulated by sodium hydroxide to pH=8.5, great performance achieved: 75% of COD was removed and B/C was up to 0.479, the biodegradability of molasses alcohol anaerobic effluent had been improved significantly, and the costs under the best conditions was 29.94 RMB/t, lower than that of electrolytic flocculation. The electro-Fenton process was much preferred to electrolytic flocculation, because both the higher removal efficiency and the lower cost, it was the ideal pretreatment method for molasses alcohol anaerobic effluent.Through the exploration on the methods of biochemical pretreatment for molasses alcohol anaerobic effluent, it had been demonstrated that it was difficult to make the wastewater meeting the standards after biochemical treatment only with one pretreatment method, and the combination of various pretreatment methods maybe better, with the exception of costs. Therefor, it is still the difficulty to explore high efficiency and low cost process for molasses alcohol anaerobic effluent.